src/arch/x86/predecoder.cc

   1 /*
   2  * Copyright (c) 2007 The Hewlett-Packard Development Company
   3  * All rights reserved.
   4  *
   5  * Redistribution and use of this software in source and binary forms,
   6  * with or without modification, are permitted provided that the
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   8  *
   9  * The software must be used only for Non-Commercial Use which means any
  10  * use which is NOT directed to receiving any direct monetary
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  12  * examples of non-commercial use are academic research, personal study,
  13  * teaching, education and corporate research & development.
  14  * Illustrative examples of commercial use are distributing products for
  15  * commercial advantage and providing services using the software for
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  17  *
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  19  * covered by patents for commercial use, please contact:
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  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  44  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  45  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  46  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  47  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  48  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  49  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  50  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  51  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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  53  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  54  *
  55  * Authors: Gabe Black
  56  */
  57
  58 #include "arch/x86/predecoder.hh"
  59 #include "base/misc.hh"
  60 #include "base/trace.hh"
  61 #include "sim/host.hh"
  62
  63 namespace X86ISA
  64 {
  65     void Predecoder::reset()
  66     {
  67         origPC = basePC + offset;
  68         DPRINTF(Predecoder, "Setting origPC to %#x\n", origPC);
  69         emi.rex = 0;
  70         emi.legacy = 0;
  71         emi.opcode.num = 0;
  72
  73         immediateCollected = 0;
  74         emi.immediate = 0;
  75         displacementCollected = 0;
  76         emi.displacement = 0;
  77
  78         emi.modRM = 0;
  79         emi.sib = 0;
  80     }
  81
  82     void Predecoder::process()
  83     {
  84         //This function drives the predecoder state machine.
  85
  86         //Some sanity checks. You shouldn't try to process more bytes if
  87         //there aren't any, and you shouldn't overwrite an already
  88         //predecoder ExtMachInst.
  89         assert(!outOfBytes);
  90         assert(!emiIsReady);
  91
  92         //While there's still something to do...
  93         while(!emiIsReady && !outOfBytes)
  94         {
  95             uint8_t nextByte = getNextByte();
  96             switch(state)
  97             {
  98               case ResetState:
  99                 reset();
 100                 state = PrefixState;
 101               case PrefixState:
 102                 state = doPrefixState(nextByte);
 103                 break;
 104               case OpcodeState:
 105                 state = doOpcodeState(nextByte);
 106                 break;
 107               case ModRMState:
 108                 state = doModRMState(nextByte);
 109                 break;
 110               case SIBState:
 111                 state = doSIBState(nextByte);
 112                 break;
 113               case DisplacementState:
 114                 state = doDisplacementState();
 115                 break;
 116               case ImmediateState:
 117                 state = doImmediateState();
 118                 break;
 119               case ErrorState:
 120                 panic("Went to the error state in the predecoder.\n");
 121               default:
 122                 panic("Unrecognized state! %d\n", state);
 123             }
 124         }
 125     }
 126
 127     //Either get a prefix and record it in the ExtMachInst, or send the
 128     //state machine on to get the opcode(s).
 129     Predecoder::State Predecoder::doPrefixState(uint8_t nextByte)
 130     {
 131         uint8_t prefix = Prefixes[nextByte];
 132         State nextState = PrefixState;
 133         if(prefix)
 134             consumeByte();
 135         switch(prefix)
 136         {
 137             //Operand size override prefixes
 138           case OperandSizeOverride:
 139             DPRINTF(Predecoder, "Found operand size override prefix.\n");
 140             emi.legacy.op = true;
 141             break;
 142           case AddressSizeOverride:
 143             DPRINTF(Predecoder, "Found address size override prefix.\n");
 144             emi.legacy.addr = true;
 145             break;
 146             //Segment override prefixes
 147           case CSOverride:
 148           case DSOverride:
 149           case ESOverride:
 150           case FSOverride:
 151           case GSOverride:
 152           case SSOverride:
 153             DPRINTF(Predecoder, "Found segment override.\n");
 154             emi.legacy.seg = prefix;
 155             break;
 156           case Lock:
 157             DPRINTF(Predecoder, "Found lock prefix.\n");
 158             emi.legacy.lock = true;
 159             break;
 160           case Rep:
 161             DPRINTF(Predecoder, "Found rep prefix.\n");
 162             emi.legacy.rep = true;
 163             break;
 164           case Repne:
 165             DPRINTF(Predecoder, "Found repne prefix.\n");
 166             emi.legacy.repne = true;
 167             break;
 168           case RexPrefix:
 169             DPRINTF(Predecoder, "Found Rex prefix %#x.\n", nextByte);
 170             emi.rex = nextByte;
 171             break;
 172           case 0:
 173             nextState = OpcodeState;
 174             break;
 175           default:
 176             panic("Unrecognized prefix %#x\n", nextByte);
 177         }
 178         return nextState;
 179     }
 180
 181     //Load all the opcodes (currently up to 2) and then figure out
 182     //what immediate and/or ModRM is needed.
 183     Predecoder::State Predecoder::doOpcodeState(uint8_t nextByte)
 184     {
 185         State nextState = ErrorState;
 186         emi.opcode.num++;
 187         //We can't handle 3+ byte opcodes right now
 188         assert(emi.opcode.num < 3);
 189         consumeByte();
 190         if(emi.opcode.num == 1 && nextByte == 0x0f)
 191         {
 192             nextState = OpcodeState;
 193             DPRINTF(Predecoder, "Found two byte opcode.\n");
 194             emi.opcode.prefixA = nextByte;
 195         }
 196         else if(emi.opcode.num == 2 &&
 197                 (nextByte == 0x0f ||
 198                  (nextByte & 0xf8) == 0x38))
 199         {
 200             panic("Three byte opcodes aren't yet supported!\n");
 201             nextState = OpcodeState;
 202             DPRINTF(Predecoder, "Found three byte opcode.\n");
 203             emi.opcode.prefixB = nextByte;
 204         }
 205         else
 206         {
 207             DPRINTF(Predecoder, "Found opcode %#x.\n", nextByte);
 208             emi.opcode.op = nextByte;
 209
 210             //Figure out the effective operand size. This can be overriden to
 211             //a fixed value at the decoder level.
 212             if(/*FIXME long mode*/1)
 213             {
 214                 if(emi.rex && emi.rex.w)
 215                     emi.opSize = 3; // 64 bit operand size
 216                 else if(emi.legacy.op)
 217                     emi.opSize = 1; // 16 bit operand size
 218                 else
 219                     emi.opSize = 2; // 32 bit operand size
 220             }
 221             else if(/*FIXME default 32*/1)
 222             {
 223                 if(emi.legacy.op)
 224                     emi.opSize = 1; // 16 bit operand size
 225                 else
 226                     emi.opSize = 2; // 32 bit operand size
 227             }
 228             else // 16 bit default operand size
 229             {
 230                 if(emi.legacy.op)
 231                     emi.opSize = 2; // 32 bit operand size
 232                 else
 233                     emi.opSize = 1; // 16 bit operand size
 234             }
 235
 236             //Figure out how big of an immediate we'll retreive based
 237             //on the opcode.
 238             int immType = ImmediateType[emi.opcode.num - 1][nextByte];
 239             immediateSize = SizeTypeToSize[emi.opSize - 1][immType];
 240
 241             //Determine what to expect next
 242             if (UsesModRM[emi.opcode.num - 1][nextByte]) {
 243                 nextState = ModRMState;
 244             } else {
 245                 if(immediateSize) {
 246                     nextState = ImmediateState;
 247                 } else {
 248                     emiIsReady = true;
 249                     nextState = ResetState;
 250                 }
 251             }
 252         }
 253         return nextState;
 254     }
 255
 256     //Get the ModRM byte and determine what displacement, if any, there is.
 257     //Also determine whether or not to get the SIB byte, displacement, or
 258     //immediate next.
 259     Predecoder::State Predecoder::doModRMState(uint8_t nextByte)
 260     {
 261         State nextState = ErrorState;
 262         emi.modRM = nextByte;
 263         DPRINTF(Predecoder, "Found modrm byte %#x.\n", nextByte);
 264         if (0) {//FIXME in 16 bit mode
 265             //figure out 16 bit displacement size
 266             if(nextByte & 0xC7 == 0x06 ||
 267                     nextByte & 0xC0 == 0x80)
 268                 displacementSize = 2;
 269             else if(nextByte & 0xC0 == 0x40)
 270                 displacementSize = 1;
 271             else
 272                 displacementSize = 0;
 273         } else {
 274             //figure out 32/64 bit displacement size
 275             if(nextByte & 0xC6 == 0x04 ||
 276                     nextByte & 0xC0 == 0x80)
 277                 displacementSize = 4;
 278             else if(nextByte & 0xC0 == 0x40)
 279                 displacementSize = 1;
 280             else
 281                 displacementSize = 0;
 282         }
 283         //If there's an SIB, get that next.
 284         //There is no SIB in 16 bit mode.
 285         if(nextByte & 0x7 == 4 &&
 286                 nextByte & 0xC0 != 0xC0) {
 287                 // && in 32/64 bit mode)
 288             nextState = SIBState;
 289         } else if(displacementSize) {
 290             nextState = DisplacementState;
 291         } else if(immediateSize) {
 292             nextState = ImmediateState;
 293         } else {
 294             emiIsReady = true;
 295             nextState = ResetState;
 296         }
 297         //The ModRM byte is consumed no matter what
 298         consumeByte();
 299         return nextState;
 300     }
 301
 302     //Get the SIB byte. We don't do anything with it at this point, other
 303     //than storing it in the ExtMachInst. Determine if we need to get a
 304     //displacement or immediate next.
 305     Predecoder::State Predecoder::doSIBState(uint8_t nextByte)
 306     {
 307         State nextState = ErrorState;
 308         emi.sib = nextByte;
 309         DPRINTF(Predecoder, "Found SIB byte %#x.\n", nextByte);
 310         consumeByte();
 311         if(displacementSize) {
 312             nextState = DisplacementState;
 313         } else if(immediateSize) {
 314             nextState = ImmediateState;
 315         } else {
 316             emiIsReady = true;
 317             nextState = ResetState;
 318         }
 319         return nextState;
 320     }
 321
 322     //Gather up the displacement, or at least as much of it
 323     //as we can get.
 324     Predecoder::State Predecoder::doDisplacementState()
 325     {
 326         State nextState = ErrorState;
 327
 328         getImmediate(displacementCollected,
 329                 emi.displacement,
 330                 displacementSize);
 331
 332         DPRINTF(Predecoder, "Collecting %d byte displacement, got %d bytes.\n",
 333                 displacementSize, displacementCollected);
 334
 335         if(displacementSize == displacementCollected) {
 336             //Sign extend the displacement
 337             switch(displacementSize)
 338             {
 339               case 1:
 340                 emi.displacement = sext<8>(emi.displacement);
 341                 break;
 342               case 2:
 343                 emi.displacement = sext<16>(emi.displacement);
 344                 break;
 345               case 4:
 346                 emi.displacement = sext<32>(emi.displacement);
 347                 break;
 348               default:
 349                 panic("Undefined displacement size!\n");
 350             }
 351             DPRINTF(Predecoder, "Collected displacement %#x.\n",
 352                     emi.displacement);
 353             if(immediateSize) {
 354                 nextState = ImmediateState;
 355             } else {
 356                 emiIsReady = true;
 357                 nextState = ResetState;
 358             }
 359         }
 360         else
 361             nextState = DisplacementState;
 362         return nextState;
 363     }
 364
 365     //Gather up the immediate, or at least as much of it
 366     //as we can get
 367     Predecoder::State Predecoder::doImmediateState()
 368     {
 369         State nextState = ErrorState;
 370
 371         getImmediate(immediateCollected,
 372                 emi.immediate,
 373                 immediateSize);
 374
 375         DPRINTF(Predecoder, "Collecting %d byte immediate, got %d bytes.\n",
 376                 immediateSize, immediateCollected);
 377
 378         if(immediateSize == immediateCollected)
 379         {
 380             //XXX Warning! The following is an observed pattern and might
 381             //not always be true!
 382
 383             //Instructions which use 64 bit operands but 32 bit immediates
 384             //need to have the immediate sign extended to 64 bits.
 385             //Instructions which use true 64 bit immediates won't be
 386             //affected, and instructions that use true 32 bit immediates
 387             //won't notice.
 388             if(immediateSize == 4)
 389                 emi.immediate = sext<32>(emi.immediate);
 390             DPRINTF(Predecoder, "Collected immediate %#x.\n",
 391                     emi.immediate);
 392             emiIsReady = true;
 393             nextState = ResetState;
 394         }
 395         else
 396             nextState = ImmediateState;
 397         return nextState;
 398     }
 399 }