Bochs/bochs/cpu/protect_ctrl.cc

/////////////////////////////////////////////////////////////////////////
// $Id: protect_ctrl.cc,v 1.39 2005-06-22 18:13:45 sshwarts Exp $
/////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2001  MandrakeSoft S.A.
//
//    MandrakeSoft S.A.
//    43, rue d'Aboukir
//    75002 Paris - France
//    http://www.linux-mandrake.com/
//    http://www.mandrakesoft.com/
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//
//  This library 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
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA



#define NEED_CPU_REG_SHORTCUTS 1
#include "bochs.h"
#define LOG_THIS BX_CPU_THIS_PTR


  void
BX_CPU_C::ARPL_EwGw(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("ARPL_EwRw: not supported on 8086!"));
  UndefinedOpcode(i);
#else /* 286+ */

  Bit16u op2_16, op1_16;

  if (protected_mode()) {
    /* op1_16 is a register or memory reference */
    if (i->modC0()) {
      op1_16 = BX_READ_16BIT_REG(i->rm());
    }
    else {
      /* pointer, segment address pair */
      read_RMW_virtual_word(i->seg(), RMAddr(i), &op1_16);
    }

    op2_16 = BX_READ_16BIT_REG(i->nnn());

    if ((op1_16 & 0x03) < (op2_16 & 0x03)) {
      op1_16 = (op1_16 & 0xfffc) | (op2_16 & 0x03);
      /* now write back to destination */
      if (i->modC0()) {
        if (i->os32L()) {
          // if 32bit opsize, then 0xff3f is or'd into
          // upper 16bits of register
          Bit32u op1_32 = BX_READ_32BIT_REG(i->rm());
          op1_32 = (op1_32 & 0xffff0000) | op1_16;
          op1_32 |= 0xff3f0000;
          BX_WRITE_32BIT_REGZ(i->rm(), op1_32);
        }
        else {
          BX_WRITE_16BIT_REG(i->rm(), op1_16);
        }
      }
      else {
        Write_RMW_virtual_word(op1_16);
      }
      set_ZF(1);
    }
    else {
      set_ZF(0);
    }
  }
  else {
    BX_DEBUG(("ARPL: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }
#endif
}

  void
BX_CPU_C::LAR_GvEw(bxInstruction_c *i)
{
  /* for 16 bit operand size mode */
  Bit16u raw_selector;
  bx_descriptor_t descriptor;
  bx_selector_t selector;
  Bit32u dword1, dword2;

  if (real_mode() || v8086_mode()) {
    BX_INFO(("LAR: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
    return;
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
    /* pointer, segment address pair */
    read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector null, clear ZF and done */
  if ((raw_selector & 0xfffc) == 0) {
    set_ZF(0);
    return;
  }

  parse_selector(raw_selector, &selector);

  if (!fetch_raw_descriptor2(&selector, &dword1, &dword2)) {
    /* not within descriptor table */
    set_ZF(0);
    return;
  }

  parse_descriptor(dword1, dword2, &descriptor);

  if (descriptor.valid==0) {
    set_ZF(0);
    return;
  }

  /* if source selector is visible at CPL & RPL,
   * within the descriptor table, and of type accepted by LAR instruction,
   * then load register with segment limit and set ZF
   */

  if (descriptor.segment) { /* normal segment */
    if (descriptor.u.segment.executable && descriptor.u.segment.c_ed) {
      /* ignore DPL for conforming segments */
    }
    else {
      if ((descriptor.dpl<CPL) || (descriptor.dpl<selector.rpl)) {
        set_ZF(0);
        return;
      }
    }
    set_ZF(1);
    if (i->os32L()) {
      /* masked by 00FxFF00, where x is undefined */
      BX_WRITE_32BIT_REGZ(i->nnn(), dword2 & 0x00ffff00);
    }
    else {
      BX_WRITE_16BIT_REG(i->nnn(), dword2 & 0xff00);
    }
    return;
  }
  else { /* system or gate segment */
    switch (descriptor.type) {
      case BX_SYS_SEGMENT_AVAIL_286_TSS:
      case BX_SYS_SEGMENT_LDT:
      case BX_SYS_SEGMENT_BUSY_286_TSS:
      case BX_286_CALL_GATE:
      case BX_TASK_GATE:
#if BX_CPU_LEVEL >= 3
      case BX_SYS_SEGMENT_AVAIL_386_TSS:
      case BX_SYS_SEGMENT_BUSY_386_TSS:
      case BX_386_CALL_GATE:
#endif
        break;
      default: /* rest not accepted types to LAR */
        set_ZF(0);
        BX_DEBUG(("lar(): not accepted type"));
        return;
    }

    if ((descriptor.dpl<CPL) || (descriptor.dpl<selector.rpl)) {
      set_ZF(0);
      return;
    }
    set_ZF(1);
    if (i->os32L()) {
      /* masked by 00FxFF00, where x is undefined ? */
      BX_WRITE_32BIT_REGZ(i->nnn(), dword2 & 0x00ffff00);
    }
    else {
      BX_WRITE_16BIT_REG(i->nnn(), dword2 & 0xff00);
    }
  }
}

  void
BX_CPU_C::LSL_GvEw(bxInstruction_c *i)
{
  /* for 16 bit operand size mode */
  Bit16u raw_selector;
  Bit32u limit32;
  bx_selector_t selector;
  Bit32u dword1, dword2;
  Bit32u descriptor_dpl;

  if (real_mode() || v8086_mode()) {
    BX_INFO(("LSL: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
    return;
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
    /* pointer, segment address pair */
    read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector null, clear ZF and done */
  if ((raw_selector & 0xfffc) == 0) {
    set_ZF(0);
    return;
  }

  parse_selector(raw_selector, &selector);

  if (!fetch_raw_descriptor2(&selector, &dword1, &dword2)) {
    /* not within descriptor table */
    set_ZF(0);
    return;
  }

  descriptor_dpl = (dword2 >> 13) & 0x03;

  if ((dword2 & 0x00001000) == 0) { // system segment
    Bit32u type = (dword2 >> 8) & 0x0000000f;
    switch (type) {
      case BX_SYS_SEGMENT_AVAIL_286_TSS:
      case BX_SYS_SEGMENT_BUSY_286_TSS:
      case BX_SYS_SEGMENT_LDT:
      case BX_SYS_SEGMENT_AVAIL_386_TSS:
      case BX_SYS_SEGMENT_BUSY_386_TSS:
        limit32 = (dword1 & 0x0000ffff) | (dword2 & 0x000f0000);
        if (dword2 & 0x00800000)
          limit32 = (limit32 << 12) | 0x00000fff;
        if ((descriptor_dpl<CPL) || (descriptor_dpl<selector.rpl)) {
          set_ZF(0);
          return;
        }
        goto lsl_ok;
        break;
      default:
        set_ZF(0);
        return;
    }
  }
  else { // data & code segment
    limit32 = (dword1 & 0x0000ffff) | (dword2 & 0x000f0000);
    if (dword2 & 0x00800000)
      limit32 = (limit32 << 12) | 0x00000fff;
    if ((dword2 & 0x00000c00) == 0x00000c00) {
      // conforming code segment, no check done
      goto lsl_ok;
    }

    if ((descriptor_dpl<CPL) || (descriptor_dpl<selector.rpl)) {
      set_ZF(0);
      return;
    }
    goto lsl_ok;
  }

lsl_ok:
  /* all checks pass, limit32 is now byte granular, write to op1 */
  set_ZF(1);

  if (i->os32L())
    BX_WRITE_32BIT_REGZ(i->nnn(), limit32)
  else
    // chop off upper 16 bits
    BX_WRITE_16BIT_REG(i->nnn(), (Bit16u) limit32)
}

  void
BX_CPU_C::SLDT_Ew(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("SLDT: not supported on 8086!"));
  UndefinedOpcode(i);
#else
  if (real_mode() || v8086_mode()) {
    BX_INFO(("SLDT: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }
  else {
    Bit16u val16 = BX_CPU_THIS_PTR ldtr.selector.value;
    if (i->modC0()) {
      BX_WRITE_16BIT_REG(i->rm(), val16);
    }
    else {
      write_virtual_word(i->seg(), RMAddr(i), &val16);
    }
  }
#endif
}

  void
BX_CPU_C::STR_Ew(bxInstruction_c *i)
{
  if (real_mode() || v8086_mode()) {
    BX_INFO(("STR: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }
  else {
    Bit16u val16 = BX_CPU_THIS_PTR tr.selector.value;
    if (i->modC0()) {
      BX_WRITE_16BIT_REG(i->rm(), val16);
    }
    else {
      write_virtual_word(i->seg(), RMAddr(i), &val16);
    }
  }
}

  void
BX_CPU_C::LLDT_Ew(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("LLDT_Ew: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  if (real_mode() || v8086_mode()) {
    BX_INFO(("LLDT: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }

  invalidate_prefetch_q();

  /* protected mode */
  bx_descriptor_t  descriptor;
  bx_selector_t    selector;
  Bit16u raw_selector;
  Bit32u dword1, dword2;

  /* #GP(0) if the current privilege level is not 0 */
  if (CPL != 0) {
    BX_INFO(("LLDT: The current priveledge level is not 0"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
      read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector is NULL, invalidate and done */
  if ((raw_selector & 0xfffc) == 0) {
    BX_CPU_THIS_PTR ldtr.selector.value = raw_selector;
    BX_CPU_THIS_PTR ldtr.cache.valid = 0;
    return;
  }

  /* parse fields in selector */
  parse_selector(raw_selector, &selector);

  // #GP(selector) if the selector operand does not point into GDT
  if (selector.ti != 0) {
    BX_ERROR(("LLDT: selector.ti != 0"));
    exception(BX_GP_EXCEPTION, raw_selector & 0xfffc, 0);
  }

  if ((selector.index*8 + 7) > BX_CPU_THIS_PTR gdtr.limit) {
    BX_PANIC(("LLDT: GDT: index > limit"));
    exception(BX_GP_EXCEPTION, raw_selector & 0xfffc, 0);
    return;
  }

  access_linear(BX_CPU_THIS_PTR gdtr.base + selector.index*8,     4, 0,
      BX_READ, &dword1);
  access_linear(BX_CPU_THIS_PTR gdtr.base + selector.index*8 + 4, 4, 0,
      BX_READ, &dword2);

  parse_descriptor(dword1, dword2, &descriptor);

  /* if selector doesn't point to an LDT descriptor #GP(selector) */
  if (descriptor.valid == 0 || descriptor.segment ||
         descriptor.type != BX_SYS_SEGMENT_LDT) 
  {
    BX_ERROR(("LLDT: doesn't point to an LDT descriptor!"));
    exception(BX_GP_EXCEPTION, raw_selector & 0xfffc, 0);
  }

  /* #NP(selector) if LDT descriptor is not present */
  if (descriptor.p==0) {
    BX_ERROR(("LLDT: LDT descriptor not present!"));
    exception(BX_NP_EXCEPTION, raw_selector & 0xfffc, 0);
  }

  if (descriptor.u.ldt.limit < 7) {
    BX_ERROR(("LLDT: ldtr.limit < 7"));
  }

  BX_CPU_THIS_PTR ldtr.selector = selector;
  BX_CPU_THIS_PTR ldtr.cache = descriptor;
  BX_CPU_THIS_PTR ldtr.cache.valid = 1;
#endif
}

void BX_CPU_C::LTR_Ew(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("LTR_Ew: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  if (real_mode() || v8086_mode()) {
    BX_INFO(("LTR: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }

  // protected mode
  invalidate_prefetch_q();

  bx_descriptor_t descriptor;
  bx_selector_t selector;
  Bit16u raw_selector;
  Bit32u dword1, dword2;
#if BX_SUPPORT_X86_64
  Bit32u dword3;
#endif

  /* #GP(0) if the current privilege level is not 0 */
  if (CPL != 0) {
    BX_ERROR(("LTR: The current priveledge level is not 0"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
    read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector is NULL, invalidate and done */
  if ((raw_selector & 0xfffc) == 0) {
    BX_PANIC(("LTR: loading with NULL selector!"));
    /* if this is OK, then invalidate and load selector & descriptor cache */
    /* load here */
    BX_CPU_THIS_PTR tr.selector.value = raw_selector;
    BX_CPU_THIS_PTR tr.cache.valid = 0;
    return;
  }

  /* parse fields in selector, then check for null selector */
  parse_selector(raw_selector, &selector);

  if (selector.ti) {
    BX_ERROR(("LTR: selector.ti != 0"));
    exception(BX_GP_EXCEPTION, raw_selector & 0xfffc, 0);
    return;
  }

  /* fetch 2 dwords of descriptor; call handles out of limits checks */
  fetch_raw_descriptor(&selector, &dword1, &dword2, BX_GP_EXCEPTION);
  parse_descriptor(dword1, dword2, &descriptor);

#if BX_SUPPORT_X86_64
  if (BX_CPU_THIS_PTR cpu_mode == BX_MODE_LONG_64) {
    // set upper 32 bits of tss base
    access_linear(BX_CPU_THIS_PTR gdtr.base + selector.index*8 + 8, 4, 0, BX_READ, &dword3);
    descriptor.u.tss386.base |= ((Bit64u)dword3 << 32);
    BX_INFO(("64 bit tss base = 0x%08x%08x",
       (Bit32u)(descriptor.u.tss386.base >> 32),
       (Bit32u) descriptor.u.tss386.base));
  }
#endif

  /* #GP(selector) if object is not a TSS or is already busy */
  if (descriptor.valid==0 || descriptor.segment ||
         (descriptor.type!=BX_SYS_SEGMENT_AVAIL_286_TSS && 
          descriptor.type!=BX_SYS_SEGMENT_AVAIL_386_TSS)) 
  {
    BX_ERROR(("LTR: doesn't point to an available TSS descriptor!"));
    exception(BX_GP_EXCEPTION, raw_selector & 0xfffc, 0);
    return;
  }

  /* #NP(selector) if TSS descriptor is not present */
  if (descriptor.p==0) {
    BX_ERROR(("LTR: LDT descriptor not present!"));
    exception(BX_NP_EXCEPTION, raw_selector & 0xfffc, 0);
    return;
  }

/*
  // the real hardware CPU allow loading of tss with limit < minimum
  if (descriptor.type==1 && descriptor.u.tss286.limit<43) {
    BX_PANIC(("LTR:286TSS: loading tr.limit < 43"));
  }
  else if (descriptor.type==9 && descriptor.u.tss386.limit_scaled<103) {
    BX_PANIC(("LTR:386TSS: loading tr.limit < 103"));
  }
*/

  BX_CPU_THIS_PTR tr.selector = selector;
  BX_CPU_THIS_PTR tr.cache    = descriptor;
  BX_CPU_THIS_PTR tr.cache.valid = 1;
  // tr.cache.type should not have busy bit, or it would not get 
  // through the conditions above.
  BX_ASSERT((BX_CPU_THIS_PTR tr.cache.type & 2) == 0);

  /* mark as busy */
  dword2 |= 0x00000200; /* set busy bit */
  access_linear(BX_CPU_THIS_PTR gdtr.base + selector.index*8 + 4, 4, 0,
      BX_WRITE, &dword2);
#endif
}

void BX_CPU_C::VERR_Ew(bxInstruction_c *i)
{
  /* for 16 bit operand size mode */
  Bit16u raw_selector;
  bx_descriptor_t descriptor;
  bx_selector_t selector;
  Bit32u dword1, dword2;

  if (real_mode() || v8086_mode()) {
    BX_INFO(("VERR: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
    /* pointer, segment address pair */
    read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector null, clear ZF and done */
  if ((raw_selector & 0xfffc) == 0) {
    set_ZF(0);
    BX_ERROR(("VERR: null selector"));
    return;
  }

  /* if source selector is visible at CPL & RPL,
   * within the descriptor table, and of type accepted by VERR instruction,
   * then load register with segment limit and set ZF */
  parse_selector(raw_selector, &selector);

  if (!fetch_raw_descriptor2(&selector, &dword1, &dword2)) {
    /* not within descriptor table */
    set_ZF(0);
    BX_ERROR(("VERR: not in table"));
    return;
  }

  parse_descriptor(dword1, dword2, &descriptor);

  if (descriptor.segment==0) { /* system or gate descriptor */
    set_ZF(0); /* inaccessible */
    BX_ERROR(("VERR: system descriptor"));
    return;
  }

  if (descriptor.valid==0) {
    set_ZF(0);
    BX_INFO(("VERR: valid bit cleared"));
    return;
  }

  /* normal data/code segment */
  if (descriptor.u.segment.executable) { /* code segment */
    /* ignore DPL for readable conforming segments */
    if (descriptor.u.segment.c_ed && descriptor.u.segment.r_w) {
      set_ZF(1); /* accessible */
      BX_INFO(("VERR: conforming code, OK"));
      return;
    }
    if (descriptor.u.segment.r_w==0) {
      set_ZF(0); /* inaccessible */
      BX_INFO(("VERR: code not readable"));
      return;
    }
    /* readable, non-conforming code segment */
    if ((descriptor.dpl<CPL) || (descriptor.dpl<selector.rpl)) {
      set_ZF(0); /* inaccessible */
      BX_INFO(("VERR: non-conforming code not withing priv level"));
      return;
    }

    set_ZF(1); /* accessible */
  }
  else { /* data segment */
    if ((descriptor.dpl<CPL) || (descriptor.dpl<selector.rpl)) {
      set_ZF(0); /* not accessible */
      BX_INFO(("VERR: data seg not withing priv level"));
      return;
    }
    set_ZF(1); /* accessible */
  }
}

void BX_CPU_C::VERW_Ew(bxInstruction_c *i)
{
  /* for 16 bit operand size mode */
  Bit16u raw_selector;
  bx_descriptor_t descriptor;
  bx_selector_t selector;
  Bit32u dword1, dword2;

  if (real_mode() || v8086_mode()) {
    BX_INFO(("VERW: not recognized in real or virtual-8086 mode"));
    UndefinedOpcode(i);
    return;
  }

  if (i->modC0()) {
    raw_selector = BX_READ_16BIT_REG(i->rm());
  }
  else {
    /* pointer, segment address pair */
    read_virtual_word(i->seg(), RMAddr(i), &raw_selector);
  }

  /* if selector null, clear ZF and done */
  if ((raw_selector & 0xfffc) == 0) {
    set_ZF(0);
    BX_ERROR(("VERW: null selector"));
    return;
  }

  /* if source selector is visible at CPL & RPL,
   * within the descriptor table, and of type accepted by VERW instruction,
   * then load register with segment limit and set ZF */
  parse_selector(raw_selector, &selector);

  if (!fetch_raw_descriptor2(&selector, &dword1, &dword2)) {
    /* not within descriptor table */
    set_ZF(0);
    BX_ERROR(("VERW: not in table"));
    return;
  }

  parse_descriptor(dword1, dword2, &descriptor);

  /* rule out system segments & code segments */
  if (descriptor.segment==0 || descriptor.u.segment.executable) {
    set_ZF(0);
    BX_ERROR(("VERW: system seg or code"));
    return;
  }

  if (descriptor.valid==0) {
    set_ZF(0);
    BX_INFO(("VERW: valid bit cleared"));
    return;
  }

  /* data segment */
  if (descriptor.u.segment.r_w) { /* writable */
    if ((descriptor.dpl<CPL) || (descriptor.dpl<selector.rpl)) {
      set_ZF(0); /* not accessible */
      BX_INFO(("VERW: writable data seg not within priv level"));
      return;
    }

    set_ZF(1); /* accessible */
    return;
  }

  set_ZF(0); /* not accessible */
  BX_INFO(("VERW: data seg not writable"));
}

void BX_CPU_C::SGDT_Ms(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("SGDT_Ms: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  /* op1 is a register or memory reference */
  if (i->modC0()) {
    /* undefined opcode exception */
    BX_INFO(("SGDT_Ms: use of register is undefined opcode."));
    UndefinedOpcode(i);
  }

#if BX_SUPPORT_X86_64
  if (BX_CPU_THIS_PTR cpu_mode == BX_MODE_LONG_64)
  {
    Bit16u limit_16 = BX_CPU_THIS_PTR gdtr.limit;
    Bit64u base_64  = BX_CPU_THIS_PTR gdtr.base;

    write_virtual_word(i->seg(), RMAddr(i), &limit_16);
    write_virtual_qword(i->seg(), RMAddr(i)+2, &base_64);
  }
  else
#endif
  {
    Bit16u limit_16 = BX_CPU_THIS_PTR gdtr.limit;
    Bit32u base_32  = BX_CPU_THIS_PTR gdtr.base;
#if BX_CPU_LEVEL == 2
    base_32 |= 0xff000000; /* ??? */
#else /* 386+ */
    /* 32bit processors always write 32bits of base */
#endif
    write_virtual_word(i->seg(), RMAddr(i), &limit_16);
    write_virtual_dword(i->seg(), RMAddr(i)+2, &base_32);
  }
#endif
}

void BX_CPU_C::SIDT_Ms(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("SIDT_Ms: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  /* op1 is a register or memory reference */
  if (i->modC0()) {
    /* undefined opcode exception */
    BX_INFO(("SIDT: use of register is undefined opcode."));
    UndefinedOpcode(i);
  }

#if BX_SUPPORT_X86_64
  if (BX_CPU_THIS_PTR cpu_mode == BX_MODE_LONG_64)
  {
    Bit16u limit_16 = BX_CPU_THIS_PTR idtr.limit;
    Bit64u base_64  = BX_CPU_THIS_PTR idtr.base;

    write_virtual_word(i->seg(), RMAddr(i), &limit_16);
    write_virtual_qword(i->seg(), RMAddr(i)+2, &base_64);
  }
  else
#endif
  {
    Bit16u limit_16 = BX_CPU_THIS_PTR idtr.limit;
    Bit32u base_32  = BX_CPU_THIS_PTR idtr.base;

#if BX_CPU_LEVEL == 2
    base_32 |= 0xff000000;
#else /* 386+ */
    /* regardless of operand size, all 32bits of base are stored */
#endif

    write_virtual_word(i->seg(), RMAddr(i), &limit_16);
    write_virtual_dword(i->seg(), RMAddr(i)+2, &base_32);
  }

#endif
}

void BX_CPU_C::LGDT_Ms(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("LGDT_Ms: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  if (v8086_mode()) {
    BX_INFO(("LGDT: not recognized in virtual-8086 mode"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  invalidate_prefetch_q();

  if (!real_mode() && CPL!=0) {
    BX_INFO(("LGDT: CPL!=0 in protected mode"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  /* operand might be a register or memory reference */
  if (i->modC0()) {
    BX_INFO(("LGDT: must be memory reference"));
    UndefinedOpcode(i);
  }

#if BX_CPU_LEVEL >= 3
#if BX_SUPPORT_X86_64
  if (BX_CPU_THIS_PTR cpu_mode == BX_MODE_LONG_64)
  {
    Bit16u limit_16;
    Bit64u base_64;

    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_qword(i->seg(), RMAddr(i) + 2, &base_64);

    BX_CPU_THIS_PTR gdtr.limit = limit_16;
    BX_CPU_THIS_PTR gdtr.base = base_64;
  }
  else
#endif
  if (i->os32L()) {
    Bit16u limit_16;
    Bit32u base0_31;

    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_dword(i->seg(), RMAddr(i) + 2, &base0_31);

    BX_CPU_THIS_PTR gdtr.limit = limit_16;
    BX_CPU_THIS_PTR gdtr.base = base0_31;
  }
  else
#endif
  {
    Bit16u limit_16, base0_15;
    Bit8u base16_23;

    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_word(i->seg(), RMAddr(i) + 2, &base0_15);
    read_virtual_byte(i->seg(), RMAddr(i) + 4, &base16_23);

    /* ignore high 8 bits */
    BX_CPU_THIS_PTR gdtr.limit = limit_16;
    BX_CPU_THIS_PTR gdtr.base = (base16_23 << 16) | base0_15;
  }
#endif
}

void BX_CPU_C::LIDT_Ms(bxInstruction_c *i)
{
#if BX_CPU_LEVEL < 2
  BX_PANIC(("LIDT_Ms: not supported on 8086!"));
  UndefinedOpcode(i);
#else

  Bit16u limit_16;
  Bit32u base_32;

  if (v8086_mode()) {
    BX_INFO(("LIDT: not recognized in virtual-8086 mode"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  invalidate_prefetch_q();

  if (!real_mode() && CPL!=0) {
    BX_INFO(("LIDT: CPL!=0 in protected mode"));
    exception(BX_GP_EXCEPTION, 0, 0);
  }

  /* operand might be a register or memory reference */
  if (i->modC0()) {
    BX_INFO(("LIDT: must be memory reference"));
    UndefinedOpcode(i);
  }

#if BX_CPU_LEVEL >= 3
#if BX_SUPPORT_X86_64
  if (BX_CPU_THIS_PTR cpu_mode == BX_MODE_LONG_64)
  {
    Bit64u base_64;

    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_qword(i->seg(), RMAddr(i) + 2, &base_64);

    BX_CPU_THIS_PTR idtr.limit = limit_16;
    BX_CPU_THIS_PTR idtr.base = base_64;
  }
  else 
#endif
  if (i->os32L()) {
    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_dword(i->seg(), RMAddr(i) + 2, &base_32);

    BX_CPU_THIS_PTR idtr.limit = limit_16;
    BX_CPU_THIS_PTR idtr.base = base_32;
  }
  else
#endif
  {
    read_virtual_word(i->seg(), RMAddr(i), &limit_16);
    read_virtual_dword(i->seg(), RMAddr(i) + 2, &base_32);

    BX_CPU_THIS_PTR idtr.limit = limit_16;
    BX_CPU_THIS_PTR idtr.base = base_32 & 0x00ffffff; /* ignore upper 8 bits */
  }
#endif
}