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/////////////////////////////////////////////////////////////////////////

// $Id: cpu.cc,v 1.2 2009-01-11 03:22:15 zeus 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"

#include "cpu.h"

#define LOG_THIS BX_CPU_THIS_PTR

#include "iodev/iodev.h"

#if BX_EXTERNAL_DEBUGGER

#include "extdb.h"

#endif

// Make code more tidy with a few macros.

#if BX_SUPPORT_X86_64==0

#define RIP EIP

#define RCX ECX

#endif

// ICACHE instrumentation code

#if BX_SUPPORT_ICACHE

#define InstrumentICACHE 0

#if InstrumentICACHE

static unsigned iCacheLookups=0;

static unsigned iCacheMisses=0;

#define InstrICache_StatsMask 0xffffff

#define InstrICache_Stats() {\

  if ((iCacheLookups & InstrICache_StatsMask) == 0) { \

    BX_INFO(("ICACHE lookups: %u, misses: %u, hit rate = %6.2f%% ", \

          iCacheLookups, \

          iCacheMisses,  \

          (iCacheLookups-iCacheMisses) * 100.0 / iCacheLookups)); \

    iCacheLookups = iCacheMisses = 0; \

  } \

}

#define InstrICache_Increment(v) (v)++

#else

#define InstrICache_Stats()

#define InstrICache_Increment(v)

#endif

#endif // BX_SUPPORT_ICACHE

// The CHECK_MAX_INSTRUCTIONS macro allows cpu_loop to execute a few

// instructions and then return so that the other processors have a chance to

// run.  This is used by bochs internal debugger or when simulating

// multiple processors.

//

// If maximum instructions have been executed, return. The zero-count

// means run forever.

#if BX_SUPPORT_SMP || BX_DEBUGGER

  #define CHECK_MAX_INSTRUCTIONS(count) \

    if ((count) > 0) {                  \

      (count)--;                        \

      if ((count) == 0) return;         \

    }

#else

  #define CHECK_MAX_INSTRUCTIONS(count)

#endif

void BX_CPU_C::cpu_loop(Bit32u max_instr_count)

{

#if BX_DEBUGGER

  BX_CPU_THIS_PTR break_point = 0;

  BX_CPU_THIS_PTR magic_break = 0;

  BX_CPU_THIS_PTR stop_reason = STOP_NO_REASON;

#endif

  if (setjmp(BX_CPU_THIS_PTR jmp_buf_env)) {

    // only from exception function we can get here ...

    BX_INSTR_NEW_INSTRUCTION(BX_CPU_ID);

    BX_TICK1_IF_SINGLE_PROCESSOR();

#if BX_DEBUGGER || BX_EXTERNAL_DEBUGGER || BX_GDBSTUB

    if (dbg_instruction_epilog()) return;

#endif

    CHECK_MAX_INSTRUCTIONS(max_instr_count);

#if BX_GDBSTUB

    if (bx_dbg.gdbstub_enabled) return;

#endif

  }

  // If the exception() routine has encountered a nasty fault scenario,

  // the debugger may request that control is returned to it so that

  // the situation may be examined.

#if BX_DEBUGGER

  if (bx_guard.interrupt_requested) return;

#endif

  // We get here either by a normal function call, or by a longjmp

  // back from an exception() call.  In either case, commit the

  // new EIP/ESP, and set up other environmental fields.  This code

  // mirrors similar code below, after the interrupt() call.

  BX_CPU_THIS_PTR prev_rip = RIP; // commit new EIP

  BX_CPU_THIS_PTR speculative_rsp = 0;

  BX_CPU_THIS_PTR EXT = 0;

  BX_CPU_THIS_PTR errorno = 0;

  while (1) {

    // check on events which occurred for previous instructions (traps)

    // and ones which are asynchronous to the CPU (hardware interrupts)

/*

 * Zet: we don't handle external interrupts

 *

    if (BX_CPU_THIS_PTR async_event) {

      if (handleAsyncEvent()) {

        // If request to return to caller ASAP.

        return;

      }

    }

 */

no_async_event:

    Bit32u eipBiased = RIP + BX_CPU_THIS_PTR eipPageBias;

    if (eipBiased >= BX_CPU_THIS_PTR eipPageWindowSize) {

      prefetch();

      eipBiased = RIP + BX_CPU_THIS_PTR eipPageBias;

    }

#if BX_SUPPORT_ICACHE

    bx_phy_address pAddr = BX_CPU_THIS_PTR pAddrA20Page + eipBiased;

    bxICacheEntry_c *entry = BX_CPU_THIS_PTR iCache.get_entry(pAddr);

    bxInstruction_c *i = entry->i;

    InstrICache_Increment(iCacheLookups);

    InstrICache_Stats();

    if ((entry->pAddr == pAddr) &&

        (entry->writeStamp == *(BX_CPU_THIS_PTR currPageWriteStampPtr)))

    {

      // iCache hit. An instruction was found in the iCache.

#if BX_INSTRUMENTATION

      BX_INSTR_OPCODE(BX_CPU_ID, BX_CPU_THIS_PTR eipFetchPtr + eipBiased,

         i->ilen(), BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].cache.u.segment.d_b, Is64BitMode());

#endif

    }

    else {

      // iCache miss. No validated instruction with matching fetch parameters

      // is in the iCache.

      InstrICache_Increment(iCacheMisses);

      serveICacheMiss(entry, eipBiased, pAddr);

      i = entry->i;

    }

#else

    bxInstruction_c iStorage, *i = &iStorage;

    unsigned remainingInPage = BX_CPU_THIS_PTR eipPageWindowSize - eipBiased;

    const Bit8u *fetchPtr = BX_CPU_THIS_PTR eipFetchPtr + eipBiased;

    fetchInstruction(i, fetchPtr, remainingInPage);

#endif

#if BX_SUPPORT_TRACE_CACHE

    unsigned length = entry->ilen;

    for(;;i++) {

#endif

      // An instruction will have been fetched using either the normal case,

      // or the boundary fetch (across pages), by this point.

      BX_INSTR_FETCH_DECODE_COMPLETED(BX_CPU_ID, i);

#if BX_DEBUGGER || BX_EXTERNAL_DEBUGGER || BX_GDBSTUB

      if (dbg_instruction_prolog()) return;

#endif

#if BX_DISASM

      if (BX_CPU_THIS_PTR trace) {

        // print the instruction that is about to be executed

        debug_disasm_instruction(BX_CPU_THIS_PTR prev_rip);

      }

#endif

      // decoding instruction compeleted -> continue with execution

      BX_INSTR_BEFORE_EXECUTION(BX_CPU_ID, i);

      RIP += i->ilen();

      BX_CPU_CALL_METHOD(i->execute, (i)); // might iterate repeat instruction

      BX_CPU_THIS_PTR prev_rip = RIP; // commit new RIP

      BX_INSTR_AFTER_EXECUTION(BX_CPU_ID, i);

      BX_TICK1_IF_SINGLE_PROCESSOR();

      // inform instrumentation about new instruction

      BX_INSTR_NEW_INSTRUCTION(BX_CPU_ID);

      // note instructions generating exceptions never reach this point

#if BX_DEBUGGER || BX_EXTERNAL_DEBUGGER || BX_GDBSTUB

      if (dbg_instruction_epilog()) return;

#endif

      CHECK_MAX_INSTRUCTIONS(max_instr_count);

#if BX_SUPPORT_TRACE_CACHE

      if (BX_CPU_THIS_PTR async_event) {

        // clear stop trace magic indication that probably was set by repeat or branch32/64

        BX_CPU_THIS_PTR async_event &= ~BX_ASYNC_EVENT_STOP_TRACE;

        break;

      }

      if (--length == 0) goto no_async_event;

    }

#endif

  }  // while (1)

}

void BX_CPP_AttrRegparmN(2) BX_CPU_C::repeat(bxInstruction_c *i, BxExecutePtr_tR execute)

{

  // non repeated instruction

  if (! i->repUsedL()) {

    BX_CPU_CALL_METHOD(execute, (i));

    return;

  }

#if BX_SUPPORT_X86_64

  if (i->as64L()) {

    while(1) {

      if (RCX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        RCX --;

      }

      if (RCX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  else

#endif

  if (i->as32L()) {

    while(1) {

      if (ECX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        RCX = ECX - 1;

      }

      if (ECX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  else  // 16bit addrsize

  {

    while(1) {

      if (CX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        CX --;

      }

      if (CX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  RIP = BX_CPU_THIS_PTR prev_rip; // repeat loop not done, restore RIP

#if BX_SUPPORT_TRACE_CACHE

  // assert magic async_event to stop trace execution

  BX_CPU_THIS_PTR async_event |= BX_ASYNC_EVENT_STOP_TRACE;

#endif

}

void BX_CPP_AttrRegparmN(2) BX_CPU_C::repeat_ZFL(bxInstruction_c *i, BxExecutePtr_tR execute)

{

  // non repeated instruction

  if (! i->repUsedL()) {

    BX_CPU_CALL_METHOD(execute, (i));

    return;

  }

  unsigned rep = i->repUsedValue();

#if BX_SUPPORT_X86_64

  if (i->as64L()) {

    while(1) {

      if (RCX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        RCX --;

      }

      if (rep==3 && get_ZF()==0) return;

      if (rep==2 && get_ZF()!=0) return;

      if (RCX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  else

#endif

  if (i->as32L()) {

    while(1) {

      if (ECX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        RCX = ECX - 1;

      }

      if (rep==3 && get_ZF()==0) return;

      if (rep==2 && get_ZF()!=0) return;

      if (ECX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  else  // 16bit addrsize

  {

    while(1) {

      if (CX != 0) {

        BX_CPU_CALL_METHOD(execute, (i));

        BX_INSTR_REPEAT_ITERATION(BX_CPU_ID, i);

        CX --;

      }

      if (rep==3 && get_ZF()==0) return;

      if (rep==2 && get_ZF()!=0) return;

      if (CX == 0) return;

#if BX_DEBUGGER == 0

      if (BX_CPU_THIS_PTR async_event)

#endif

        break; // exit always if debugger enabled

      BX_TICK1_IF_SINGLE_PROCESSOR();

    }

  }

  RIP = BX_CPU_THIS_PTR prev_rip; // repeat loop not done, restore RIP

#if BX_SUPPORT_TRACE_CACHE

  // assert magic async_event to stop trace execution

  BX_CPU_THIS_PTR async_event |= BX_ASYNC_EVENT_STOP_TRACE;

#endif

}

unsigned BX_CPU_C::handleAsyncEvent(void)

{

  //

  // This area is where we process special conditions and events.

  //

  if (BX_CPU_THIS_PTR debug_trap & BX_DEBUG_TRAP_SPECIAL) {

    // I made up the bitmask above to mean HALT state.

    // for one processor, pass the time as quickly as possible until

    // an interrupt wakes up the CPU.

    while (1)

    {

      if ((BX_CPU_INTR && (BX_CPU_THIS_PTR get_IF() || (BX_CPU_THIS_PTR debug_trap & BX_DEBUG_TRAP_MWAIT_IF))) ||

           BX_CPU_THIS_PTR nmi_pending || BX_CPU_THIS_PTR smi_pending)

      {

        // interrupt ends the HALT condition

#if BX_SUPPORT_MONITOR_MWAIT

        if (BX_CPU_THIS_PTR debug_trap & BX_DEBUG_TRAP_MWAIT)

          BX_MEM(0)->clear_monitor(BX_CPU_THIS_PTR bx_cpuid);

#endif

        BX_CPU_THIS_PTR debug_trap = 0; // clear traps for after resume

        BX_CPU_THIS_PTR inhibit_mask = 0; // clear inhibits for after resume

        break;

      }

      if ((BX_CPU_THIS_PTR debug_trap & BX_DEBUG_TRAP_SPECIAL) == 0) {

        BX_INFO(("handleAsyncEvent: reset detected in HLT state"));

        break;

      }

      // for multiprocessor simulation, even if this CPU is halted we still

      // must give the others a chance to simulate.  If an interrupt has

      // arrived, then clear the HALT condition; otherwise just return from

      // the CPU loop with stop_reason STOP_CPU_HALTED.

#if BX_SUPPORT_SMP

      if (BX_SMP_PROCESSORS > 1) {

        // HALT condition remains, return so other CPUs have a chance

#if BX_DEBUGGER

        BX_CPU_THIS_PTR stop_reason = STOP_CPU_HALTED;

#endif

        return 1; // Return to caller of cpu_loop.

      }

#endif

#if BX_DEBUGGER

      if (bx_guard.interrupt_requested)

        return 1; // Return to caller of cpu_loop.

#endif

      BX_TICK1();

    }

  } else if (bx_pc_system.kill_bochs_request) {

    // setting kill_bochs_request causes the cpu loop to return ASAP.

    return 1; // Return to caller of cpu_loop.

  }

  // Priority 1: Hardware Reset and Machine Checks

  //   RESET

  //   Machine Check

  // (bochs doesn't support these)

  // Priority 2: Trap on Task Switch

  //   T flag in TSS is set

  if (BX_CPU_THIS_PTR debug_trap & 0x00008000) {

    BX_CPU_THIS_PTR dr6 |= BX_CPU_THIS_PTR debug_trap;

    exception(BX_DB_EXCEPTION, 0, 0); // no error, not interrupt

  }

  // Priority 3: External Hardware Interventions

  //   FLUSH

  //   STOPCLK

  //   SMI

  //   INIT

  // (bochs doesn't support these)

  if (BX_CPU_THIS_PTR smi_pending && ! BX_CPU_THIS_PTR smm_mode())

  {

    // clear SMI pending flag and disable NMI when SMM was accepted

    BX_CPU_THIS_PTR smi_pending = 0;

    BX_CPU_THIS_PTR nmi_disable = 1;

    enter_system_management_mode();

  }

  // Priority 4: Traps on Previous Instruction

  //   Breakpoints

  //   Debug Trap Exceptions (TF flag set or data/IO breakpoint)

  if (BX_CPU_THIS_PTR debug_trap &&

       !(BX_CPU_THIS_PTR inhibit_mask & BX_INHIBIT_DEBUG))

  {

    // A trap may be inhibited on this boundary due to an instruction

    // which loaded SS.  If so we clear the inhibit_mask below

    // and don't execute this code until the next boundary.

    // Commit debug events to DR6

    BX_CPU_THIS_PTR dr6 |= BX_CPU_THIS_PTR debug_trap;

    exception(BX_DB_EXCEPTION, 0, 0); // no error, not interrupt

  }

  // Priority 5: External Interrupts

  //   NMI Interrupts

  //   Maskable Hardware Interrupts

  if (BX_CPU_THIS_PTR inhibit_mask & BX_INHIBIT_INTERRUPTS) {

    // Processing external interrupts is inhibited on this

    // boundary because of certain instructions like STI.

    // inhibit_mask is cleared below, in which case we will have

    // an opportunity to check interrupts on the next instruction

    // boundary.

  }

  else if (BX_CPU_THIS_PTR nmi_pending) {

    BX_CPU_THIS_PTR nmi_pending = 0;

    BX_CPU_THIS_PTR nmi_disable = 1;

    BX_CPU_THIS_PTR errorno = 0;

    BX_CPU_THIS_PTR EXT = 1; /* external event */

    BX_INSTR_HWINTERRUPT(BX_CPU_ID, 2, BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value, RIP);

    interrupt(2, 0, 0, 0);

  }

  else if (BX_CPU_INTR && BX_CPU_THIS_PTR get_IF() && BX_DBG_ASYNC_INTR)

  {

    Bit8u vector;

    // NOTE: similar code in ::take_irq()

#if BX_SUPPORT_APIC

    if (BX_CPU_THIS_PTR local_apic.INTR)

      vector = BX_CPU_THIS_PTR local_apic.acknowledge_int();

    else

#endif

      // if no local APIC, always acknowledge the PIC.

      vector = DEV_pic_iac(); // may set INTR with next interrupt

    BX_CPU_THIS_PTR errorno = 0;

    BX_CPU_THIS_PTR EXT = 1; /* external event */

    BX_INSTR_HWINTERRUPT(BX_CPU_ID, vector,

        BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].selector.value, RIP);

    interrupt(vector, 0, 0, 0);

    // Set up environment, as would be when this main cpu loop gets

    // invoked.  At the end of normal instructions, we always commmit

    // the new EIP/ESP values.  But here, we call interrupt() much like

    // it was a sofware interrupt instruction, and need to effect the

    // commit here.  This code mirrors similar code above.

    BX_CPU_THIS_PTR prev_rip = RIP; // commit new RIP

    BX_CPU_THIS_PTR speculative_rsp = 0;

    BX_CPU_THIS_PTR EXT = 0;

    BX_CPU_THIS_PTR errorno = 0;

  }

  else if (BX_HRQ && BX_DBG_ASYNC_DMA) {

    // NOTE: similar code in ::take_dma()

    // assert Hold Acknowledge (HLDA) and go into a bus hold state

    DEV_dma_raise_hlda();

  }

  // Priority 6: Faults from fetching next instruction

  //   Code breakpoint fault

  //   Code segment limit violation (priority 7 on 486/Pentium)

  //   Code page fault (priority 7 on 486/Pentium)

  // (handled in main decode loop)

  // Priority 7: Faults from decoding next instruction

  //   Instruction length > 15 bytes

  //   Illegal opcode

  //   Coprocessor not available

  // (handled in main decode loop etc)

  // Priority 8: Faults on executing an instruction

  //   Floating point execution

  //   Overflow

  //   Bound error

  //   Invalid TSS

  //   Segment not present

  //   Stack fault

  //   General protection

  //   Data page fault

  //   Alignment check

  // (handled by rest of the code)

  if (BX_CPU_THIS_PTR get_TF())

  {

    // TF is set before execution of next instruction.  Schedule

    // a debug trap (#DB) after execution.  After completion of

    // next instruction, the code above will invoke the trap.

    BX_CPU_THIS_PTR debug_trap |= 0x00004000; // BS flag in DR6

  }

  // Now we can handle things which are synchronous to instruction

  // execution.

  if (BX_CPU_THIS_PTR get_RF()) {

    BX_CPU_THIS_PTR clear_RF();

  }

#if BX_X86_DEBUGGER

  else {

    // only bother comparing if any breakpoints enabled

    if (BX_CPU_THIS_PTR dr7 & 0x000000ff) {

      bx_address iaddr = get_laddr(BX_SEG_REG_CS, BX_CPU_THIS_PTR prev_rip);

      Bit32u dr6_bits = hwdebug_compare(iaddr, 1, BX_HWDebugInstruction, BX_HWDebugInstruction);

      if (dr6_bits)

      {

        // Add to the list of debug events thus far.

        BX_CPU_THIS_PTR async_event = 1;

        BX_CPU_THIS_PTR debug_trap |= dr6_bits;

        // If debug events are not inhibited on this boundary,

        // fire off a debug fault.  Otherwise handle it on the next

        // boundary. (becomes a trap)

        if (! (BX_CPU_THIS_PTR inhibit_mask & BX_INHIBIT_DEBUG)) {

          // Commit debug events to DR6

          BX_CPU_THIS_PTR dr6 = BX_CPU_THIS_PTR debug_trap;

          exception(BX_DB_EXCEPTION, 0, 0); // no error, not interrupt

        }

      }

    }

  }

#endif

  // We have ignored processing of external interrupts and

  // debug events on this boundary.  Reset the mask so they

  // will be processed on the next boundary.

  BX_CPU_THIS_PTR inhibit_mask = 0;

  if (!(BX_CPU_INTR ||

        BX_CPU_THIS_PTR debug_trap ||

        BX_HRQ ||

        BX_CPU_THIS_PTR get_TF()

#if BX_X86_DEBUGGER

        || (BX_CPU_THIS_PTR dr7 & 0xff)

#endif

        ))

    BX_CPU_THIS_PTR async_event = 0;

  return 0; // Continue executing cpu_loop.

}

// boundaries of consideration:

//

//  * physical memory boundary: 1024k (1Megabyte) (increments of...)

//  * A20 boundary:             1024k (1Megabyte)

//  * page boundary:            4k

//  * ROM boundary:             2k (dont care since we are only reading)

//  * segment boundary:         any

void BX_CPU_C::prefetch(void)

{

  bx_address temp_rip = RIP;

  bx_address laddr = BX_CPU_THIS_PTR get_laddr(BX_SEG_REG_CS, temp_rip);

  bx_phy_address pAddr;

  unsigned pageOffset = PAGE_OFFSET(laddr);

  // Calculate RIP at the beginning of the page.

  BX_CPU_THIS_PTR eipPageBias = pageOffset - RIP;

  BX_CPU_THIS_PTR eipPageWindowSize = 4096;

#if BX_SUPPORT_X86_64

  if (Is64BitMode()) {

    if (! IsCanonical(RIP)) {

      BX_ERROR(("prefetch: #GP(0): RIP crossed canonical boundary"));

      exception(BX_GP_EXCEPTION, 0, 0);

    }

  }

  else

#endif

  {

    Bit32u temp_limit = BX_CPU_THIS_PTR sregs[BX_SEG_REG_CS].cache.u.segment.limit_scaled;

    if (((Bit32u) temp_rip) > temp_limit) {

      BX_ERROR(("prefetch: EIP [%08x] > CS.limit [%08x]", (Bit32u) temp_rip, temp_limit));

      exception(BX_GP_EXCEPTION, 0, 0);

    }

    if (temp_limit + BX_CPU_THIS_PTR eipPageBias < 4096) {

      BX_CPU_THIS_PTR eipPageWindowSize = temp_limit + BX_CPU_THIS_PTR eipPageBias + 1;

    }

  }

  bx_address lpf = LPFOf(laddr);

  unsigned TLB_index = BX_TLB_INDEX_OF(lpf, 0);

  bx_TLB_entry *tlbEntry = &BX_CPU_THIS_PTR TLB.entry[TLB_index];

  Bit8u *fetchPtr = 0;

  if (tlbEntry->lpf == lpf && (tlbEntry->accessBits & (0x01 << CPL))) {

    pAddr = A20ADDR(tlbEntry->ppf | pageOffset);

#if BX_SupportGuest2HostTLB

    fetchPtr = (Bit8u*) (tlbEntry->hostPageAddr);

#endif

  }

  else {

    if (BX_CPU_THIS_PTR cr0.get_PG()) {

      pAddr = translate_linear(laddr, CPL, BX_READ, CODE_ACCESS);

      pAddr = A20ADDR(pAddr);

    }

    else {

      pAddr = A20ADDR(laddr);

    }

  }

  BX_CPU_THIS_PTR pAddrA20Page = LPFOf(pAddr);

  if (fetchPtr) {

    BX_CPU_THIS_PTR eipFetchPtr = fetchPtr;

  }

  else {

    BX_CPU_THIS_PTR eipFetchPtr = BX_MEM(0)->getHostMemAddr(BX_CPU_THIS,

        BX_CPU_THIS_PTR pAddrA20Page, BX_READ, CODE_ACCESS);

  }

  // Sanity checks

  if (! BX_CPU_THIS_PTR eipFetchPtr) {

    if (pAddr >= BX_MEM(0)->get_memory_len()) {

      BX_PANIC(("prefetch: running in bogus memory, pAddr=0x" FMT_PHY_ADDRX, pAddr));

    }

    else {

      BX_PANIC(("prefetch: getHostMemAddr vetoed direct read, pAddr=0x" FMT_PHY_ADDRX, pAddr));

    }

  }

#if BX_SUPPORT_ICACHE

  BX_CPU_THIS_PTR currPageWriteStampPtr = pageWriteStampTable.getPageWriteStampPtr(pAddr);

  Bit32u pageWriteStamp = *(BX_CPU_THIS_PTR currPageWriteStampPtr);

  pageWriteStamp &= ~ICacheWriteStampFetchModeMask; // Clear out old fetch mode bits

  pageWriteStamp |=  BX_CPU_THIS_PTR fetchModeMask; // And add new ones

  pageWriteStampTable.setPageWriteStamp(pAddr, pageWriteStamp);

#endif

}

void BX_CPU_C::boundaryFetch(const Bit8u *fetchPtr, unsigned remainingInPage, bxInstruction_c *i)

{

  unsigned j;

  Bit8u fetchBuffer[16]; // Really only need 15

  unsigned ret;