; $Id: bs3-mode-SwitchToLM32.asm 59287 2016-01-08 10:08:40Z vboxsync $
;; @file
; BS3Kit - Bs3SwitchToLM32
;

;
; Copyright (C) 2007-2016 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.
;

%include "bs3kit-template-header.mac"


;;
; Switch to 32-bit long mode from any other mode.
;
; @cproto   BS3_DECL(void) Bs3SwitchToLM32(void);
;
; @uses     Nothing (except possibly high 32-bit and/or upper 64-bit register parts).
;
; @remarks  There are no IDT or TSS differences between LM16, LM32 and LM64 (unlike
;           PE16 & PE32, PP16 & PP32, and PAE16 & PAE32).
;
; @remarks  Obviously returns to 32-bit mode, even if the caller was in 16-bit
;           or 64-bit mode.  It doesn't not preserve the callers ring, but
;           instead changes to ring-0.
;
; @remarks  Does not require 20h of parameter scratch space in 64-bit mode.
;
BS3_PROC_BEGIN_MODE Bs3SwitchToLM32
%ifdef TMPL_LM32
        ret

%elifdef TMPL_CMN_LM
        ;
        ; Already in long mode, just switch to 32-bit.
        ;
        extern  BS3_CMN_NM(Bs3SwitchTo32Bit)
        jmp     BS3_CMN_NM(Bs3SwitchTo32Bit)

%else
 %if TMPL_BITS == 16
        push    word 0                  ; save space for extending the return value.
 %endif

        ;
        ; Switch to 32-bit protected mode (for identify mapped pages).
        ;
        extern  TMPL_NM(Bs3SwitchToPE32)
        call    TMPL_NM(Bs3SwitchToPE32)
        BS3_SET_BITS 32
 %if TMPL_BITS == 16
        jmp     .thirty_two_bit_segment
BS3_BEGIN_TEXT32
.thirty_two_bit_segment:
 %endif

        push    eax
        push    ecx
        push    edx
        pushfd

        ;
        ; Make sure both PAE and PSE are enabled (requires pentium pro).
        ;
        mov     eax, cr4
        mov     ecx, eax
        or      eax, X86_CR4_PAE | X86_CR4_PSE
        cmp     eax, ecx
        je      .cr4_is_fine
        mov     cr4, eax
.cr4_is_fine:

        ;
        ; Get the page directory (returned in eax).
        ; Will lazy init page tables.
        ;
        extern NAME(Bs3PagingGetRootForLM64_pe32)
        call   NAME(Bs3PagingGetRootForLM64_pe32)

        cli
        mov     cr3, eax

        ;
        ; Enable long mode in EFER.
        ;
        mov     ecx, MSR_K6_EFER
        rdmsr
        or      eax, MSR_K6_EFER_LME
        wrmsr

        ;
        ; Enable paging and thereby activating LM64.
        ;
BS3_EXTERN_SYSTEM16 Bs3Lgdt_Gdt
BS3_BEGIN_TEXT32
        mov     eax, cr0
        or      eax, X86_CR0_PG
        mov     cr0, eax
        jmp     .in_lm32
.in_lm32:

        ;
        ; Call rountine for doing mode specific setups.
        ;
        extern  NAME(Bs3EnteredMode_lm32)
        call    NAME(Bs3EnteredMode_lm32)

        ;
        ; Restore ecx, eax and flags (IF).
        ;
 %if TMPL_BITS == 16
        movzx   eax, word [esp + 16 + 2] ; Load return address.
        add     eax, BS3_ADDR_BS3TEXT16  ; Convert it to a flat address.
        mov     [esp + 16], eax          ; Store it in the place right for 32-bit returns.
 %endif
        popfd
        pop     edx
        pop     ecx
        pop     eax
        ret

 %if TMPL_BITS != 32
TMPL_BEGIN_TEXT
 %endif
%endif
BS3_PROC_END_MODE   Bs3SwitchToLM32