diff options
Diffstat (limited to 'src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPE16.asm')
| -rw-r--r-- | src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPE16.asm | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPE16.asm b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPE16.asm new file mode 100644 index 00000000..696ead0c --- /dev/null +++ b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPE16.asm @@ -0,0 +1,198 @@ +; $Id: bs3-mode-SwitchToPE16.asm $ +;; @file +; BS3Kit - Bs3SwitchToPE16 +; + +; +; Copyright (C) 2007-2022 Oracle and/or its affiliates. +; +; This file is part of VirtualBox base platform packages, as +; available from https://www.virtualbox.org. +; +; This program is free software; you can redistribute it and/or +; modify it under the terms of the GNU General Public License +; as published by the Free Software Foundation, in version 3 of the +; License. +; +; This program is distributed in the hope that it will be useful, but +; WITHOUT ANY WARRANTY; without even the implied warranty of +; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +; General Public License for more details. +; +; You should have received a copy of the GNU General Public License +; along with this program; if not, see <https://www.gnu.org/licenses>. +; +; The contents of this file may alternatively be used under the terms +; of the Common Development and Distribution License Version 1.0 +; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included +; in the VirtualBox 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. +; +; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0 +; + +%include "bs3kit-template-header.mac" + + +;; +; Switch to 16-bit unpaged protected mode from any other mode. +; +; @cproto BS3_DECL(void) Bs3SwitchToPE16(void); +; +; @uses Nothing (except high 32-bit register parts). +; +; @remarks Obviously returns to 16-bit mode, even if the caller was +; in 32-bit or 64-bit mode. +; +; @remarks Does not require 20h of parameter scratch space in 64-bit mode. +; +%if TMPL_BITS == 16 +BS3_GLOBAL_NAME_EX TMPL_NM(Bs3SwitchToPE16_Safe), function , 0 +%endif +BS3_PROC_BEGIN_MODE Bs3SwitchToPE16, BS3_PBC_NEAR +%ifdef TMPL_PE16 + extern BS3_CMN_NM(Bs3SwitchToRing0) + call BS3_CMN_NM(Bs3SwitchToRing0) + push ax + mov ax, BS3_SEL_R0_DS16 + mov ds, ax + mov es, ax + pop ax + ret + +%elif BS3_MODE_IS_V86(TMPL_MODE) + ; + ; V8086 - Switch to 16-bit ring-0 and call worker for that mode. + ; + extern BS3_CMN_NM(Bs3SwitchToRing0) + call BS3_CMN_NM(Bs3SwitchToRing0) + extern %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToPE16) + jmp %[BS3_MODE_R0_NM_ %+ TMPL_MODE](Bs3SwitchToPE16) + +%else + ; + ; Switch to 16-bit mode and prepare for returning in 16-bit mode. + ; + %if TMPL_BITS != 16 + shl xPRE [xSP], TMPL_BITS - 16 ; Adjust the return address. + add xSP, xCB - 2 + + ; Must be in 16-bit segment when calling Bs3SwitchTo16Bit. + jmp .sixteen_bit_segment +BS3_BEGIN_TEXT16 + BS3_SET_BITS TMPL_BITS +BS3_GLOBAL_LOCAL_LABEL .sixteen_bit_segment + %endif + + ; + ; Switch to real mode. + ; + extern TMPL_NM(Bs3SwitchToRM) + call TMPL_NM(Bs3SwitchToRM) + BS3_SET_BITS 16 + + push ax + push cx + pushf + cli + + ; + ; Load the GDT and enable PE16. + ; +BS3_EXTERN_SYSTEM16 Bs3Lgdt_Gdt +BS3_EXTERN_SYSTEM16 Bs3LgdtDef_Gdt +BS3_BEGIN_TEXT16 + mov ax, BS3SYSTEM16 + mov ds, ax + lgdt [Bs3LgdtDef_Gdt] ; Will only load 24-bit base! + + smsw ax + or ax, X86_CR0_PE + lmsw ax + + ; + ; Convert from real mode stack to protected mode stack. + ; + mov ax, .p16_stack + extern NAME(Bs3ConvertRMStackToP16UsingCxReturnToAx_c16) + jmp NAME(Bs3ConvertRMStackToP16UsingCxReturnToAx_c16) +.p16_stack: + + ; + ; Call routine for doing mode specific setups. + ; + extern NAME(Bs3EnteredMode_pe16) + call NAME(Bs3EnteredMode_pe16) + + ; + ; Load full 32-bit GDT base address from 32-bit segment, if 386+ CPU. + ; + BS3_EXTERN_DATA16 g_uBs3CpuDetected + BS3_BEGIN_TEXT16 + cmp byte [g_uBs3CpuDetected], BS3CPU_80386 + jb .old_cpu_skip_32bit_lgdt + push ds + mov ax, BS3_SEL_SYSTEM16 + mov ds, ax + jmp dword BS3_SEL_R0_CS32:.load_full_gdt_base wrt FLAT +.load_full_gdt_base: + BS3_SET_BITS 32 + lgdt [Bs3Lgdt_Gdt wrt BS3SYSTEM16] + jmp BS3_SEL_R0_CS16:.back_to_16bit +.back_to_16bit: + BS3_SET_BITS 16 + pop ds +.old_cpu_skip_32bit_lgdt: + + popf + pop cx + pop ax + ret + + %if TMPL_BITS != 16 +TMPL_BEGIN_TEXT + %endif +%endif +BS3_PROC_END_MODE Bs3SwitchToPE16 + + +%if TMPL_BITS == 16 +;; +; Custom far stub. +BS3_BEGIN_TEXT16_FARSTUBS +BS3_PROC_BEGIN_MODE Bs3SwitchToPE16, BS3_PBC_FAR + inc bp + push bp + mov bp, sp + + ; Call the real thing. + call TMPL_NM(Bs3SwitchToPE16) + + %if BS3_MODE_IS_RM_OR_V86(TMPL_MODE) + ; Jmp to common code for the tedious conversion. + BS3_EXTERN_CMN Bs3SwitchHlpConvRealModeRetfPopBpDecBpAndReturn + jmp Bs3SwitchHlpConvRealModeRetfPopBpDecBpAndReturn + %else + pop bp + dec bp + retf + %endif +BS3_PROC_END_MODE Bs3SwitchToPE16 + +%else +;; +; Safe far return to non-BS3TEXT16 code. +BS3_EXTERN_CMN Bs3SwitchHlpConvFlatRetToRetfProtMode +BS3_BEGIN_TEXT16 +BS3_SET_BITS TMPL_BITS +BS3_PROC_BEGIN_MODE Bs3SwitchToPE16_Safe, BS3_PBC_NEAR + call Bs3SwitchHlpConvFlatRetToRetfProtMode ; Special internal function. Uses nothing, but modifies the stack. + call TMPL_NM(Bs3SwitchToPE16) + BS3_SET_BITS 16 + retf +BS3_PROC_END_MODE Bs3SwitchToPE16_Safe +%endif + |