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/*

 * mmu.c -- MMU simulation

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <setjmp.h>

#include "common.h"

#include "console.h"

#include "error.h"

#include "except.h"

#include "cpu.h"

#include "mmu.h"

#include "memory.h"

static Bool debugUse = false;

static Bool debugWrite = false;

static TLB_Entry tlb[TLB_SIZE];

static Word tlbIndex;

static Word tlbEntryHi;

static Word tlbEntryLo;

static Word tlbBadAddr;

static int assoc(Word page) {

  int n, i;

  n = -1;

  for (i = 0; i < TLB_SIZE; i++) {

    if (tlb[i].page == page) {

      n = i;

    }

  }

  return n;

}

static void assocDelay(void) {

  int n, i;

  /* simulate delay introduced by assoc when using mapped

     addresses but not experienced with unmapped addresses */

  n = -1;

  for (i = 0; i < TLB_SIZE; i++) {

    if (tlb[i].page == 0) {

      n = i;

    }

  }

}

static Word v2p(Word vAddr, Bool userMode, Bool writing) {

  Word pAddr;

  Word page, offset;

  int index;

  if (debugUse) {

    cPrintf("**** vAddr = 0x%08X", vAddr);

  }

  if ((vAddr & 0x80000000) != 0 && userMode) {

    /* trying to access a privileged address from user mode */

    tlbBadAddr = vAddr;

    throwException(EXC_PRV_ADDRESS);

  }

  if ((vAddr & 0xC0000000) == 0xC0000000) {

    /* unmapped address space */

    assocDelay();

    pAddr = vAddr & ~0xC0000000;

  } else {

    /* mapped address space */

    page = vAddr & PAGE_MASK;

    offset = vAddr & OFFSET_MASK;

    index = assoc(page);

    if (index == -1) {

      /* TLB miss exception */

      tlbBadAddr = vAddr;

      tlbEntryHi = page;

      throwException(EXC_TLB_MISS);

    }

    if (!tlb[index].valid) {

      /* TLB invalid exception */

      tlbBadAddr = vAddr;

      tlbEntryHi = page;

      throwException(EXC_TLB_INVALID);

    }

    if (!tlb[index].write && writing) {

      /* TLB write exception */

      tlbBadAddr = vAddr;

      tlbEntryHi = page;

      throwException(EXC_TLB_WRITE);

    }

    pAddr = tlb[index].frame | offset;

  }

  if (debugUse) {

    cPrintf(", pAddr = 0x%08X ****\n", pAddr);

  }

  return pAddr;

}

Word mmuReadWord(Word vAddr, Bool userMode) {

  if ((vAddr & 3) != 0) {

    /* throw illegal address exception */

    tlbBadAddr = vAddr;

    throwException(EXC_ILL_ADDRESS);

  }

  return memoryReadWord(v2p(vAddr, userMode, false));

}

Half mmuReadHalf(Word vAddr, Bool userMode) {

  if ((vAddr & 1) != 0) {

    /* throw illegal address exception */

    tlbBadAddr = vAddr;

    throwException(EXC_ILL_ADDRESS);

  }

  return memoryReadHalf(v2p(vAddr, userMode, false));

}

Byte mmuReadByte(Word vAddr, Bool userMode) {

  return memoryReadByte(v2p(vAddr, userMode, false));

}

void mmuWriteWord(Word vAddr, Word data, Bool userMode) {

  if ((vAddr & 3) != 0) {

    /* throw illegal address exception */

    tlbBadAddr = vAddr;

    throwException(EXC_ILL_ADDRESS);

  }

  memoryWriteWord(v2p(vAddr, userMode, true), data);

}

void mmuWriteHalf(Word vAddr, Half data, Bool userMode) {

  if ((vAddr & 1) != 0) {

    /* throw illegal address exception */

    tlbBadAddr = vAddr;

    throwException(EXC_ILL_ADDRESS);

  }

  memoryWriteHalf(v2p(vAddr, userMode, true), data);

}

void mmuWriteByte(Word vAddr, Byte data, Bool userMode) {

  memoryWriteByte(v2p(vAddr, userMode, true), data);

}

Word mmuGetIndex(void) {

  return tlbIndex;

}

void mmuSetIndex(Word value) {

  tlbIndex = value & TLB_MASK;

}

Word mmuGetEntryHi(void) {

  return tlbEntryHi;

}

void mmuSetEntryHi(Word value) {

  tlbEntryHi = value & PAGE_MASK;

}

Word mmuGetEntryLo(void) {

  return tlbEntryLo;

}

void mmuSetEntryLo(Word value) {

  tlbEntryLo = value & (PAGE_MASK | TLB_WRITE | TLB_VALID);

}

Word mmuGetBadAddr(void) {

  return tlbBadAddr;

}

void mmuSetBadAddr(Word value) {

  tlbBadAddr = value;

}

void mmuTbs(void) {

  int index;

  index = assoc(tlbEntryHi & PAGE_MASK);

  if (index == -1) {

    tlbIndex = 0x80000000;

  } else {

    tlbIndex = index;

  }

}

void mmuTbwr(void) {

  int index;

  /* choose a random index, but don't touch fixed entries */

  do {

    index = rand() & TLB_MASK;

  } while (index < TLB_FIXED);

  tlb[index].page = tlbEntryHi & PAGE_MASK;

  tlb[index].frame = tlbEntryLo & PAGE_MASK;

  tlb[index].write = tlbEntryLo & TLB_WRITE ? true : false;

  tlb[index].valid = tlbEntryLo & TLB_VALID ? true : false;

  if (debugWrite) {

    cPrintf("**** TLB[%02d] <- 0x%08X 0x%08X %c %c ****\n",

            index, tlb[index].page, tlb[index].frame,

            tlb[index].write ? 'w' : '-',

            tlb[index].valid ? 'v' : '-');

  }

}

void mmuTbri(void) {

  int index;

  index = tlbIndex & TLB_MASK;

  tlbEntryHi = tlb[index].page;

  tlbEntryLo = tlb[index].frame;

  if (tlb[index].write) {

    tlbEntryLo |= TLB_WRITE;

  }

  if (tlb[index].valid) {

    tlbEntryLo |= TLB_VALID;

  }

}

void mmuTbwi(void) {

  int index;

  index = tlbIndex & TLB_MASK;

  tlb[index].page = tlbEntryHi & PAGE_MASK;

  tlb[index].frame = tlbEntryLo & PAGE_MASK;

  tlb[index].write = tlbEntryLo & TLB_WRITE ? true : false;

  tlb[index].valid = tlbEntryLo & TLB_VALID ? true : false;

  if (debugWrite) {

    cPrintf("**** TLB[%02d] <- 0x%08X 0x%08X %c %c ****\n",

            index, tlb[index].page, tlb[index].frame,

            tlb[index].write ? 'w' : '-',

            tlb[index].valid ? 'v' : '-');

  }

}

TLB_Entry mmuGetTLB(int index) {

  return tlb[index & TLB_MASK];

}

void mmuSetTLB(int index, TLB_Entry tlbEntry) {

  index &= TLB_MASK;

  tlb[index] = tlbEntry;

  if (debugWrite) {

    cPrintf("**** TLB[%02d] <- 0x%08X 0x%08X %c %c ****\n",

            index, tlb[index].page, tlb[index].frame,

            tlb[index].write ? 'w' : '-',

            tlb[index].valid ? 'v' : '-');

  }

}

void mmuReset(void) {

  int i;

  cPrintf("Resetting MMU...\n");

  for (i = 0; i < TLB_SIZE; i++) {

    tlb[i].page = rand() & PAGE_MASK;

    tlb[i].frame = rand() & PAGE_MASK;

    tlb[i].write = rand() & 0x1000 ? true : false;

    tlb[i].valid = rand() & 0x1000 ? true : false;

    if (debugWrite) {

      cPrintf("**** TLB[%02d] <- 0x%08X 0x%08X %c %c ****\n",

              i, tlb[i].page, tlb[i].frame,

              tlb[i].write ? 'w' : '-',

              tlb[i].valid ? 'v' : '-');

    }

  }

  tlbIndex = rand() & TLB_MASK;

  tlbEntryHi = rand() & PAGE_MASK;

  tlbEntryLo = rand() & (PAGE_MASK | TLB_WRITE | TLB_VALID);

  tlbBadAddr = rand();

}

void mmuInit(void) {

  mmuReset();

}

void mmuExit(void) {

}