src/org/xwt/mips/Interpreter.java

   1 // Copyright 2003 Brian Alliet
   2 // Based on org.xwt.imp.MIPS by Adam Megacz
   3 // Portions Copyright 2003 Adam Megacz
   4
   5 package org.xwt.mips;
   6
   7 import org.xwt.mips.util.*;
   8 import java.io.*;
   9
  10 public class Interpreter extends UnixRuntime {
  11     // Registers
  12     private int[] registers = new int[32];
  13     private int hi,lo;
  14
  15     // Floating Point Registers
  16     private int[] fpregs = new int[32];
  17     // 24-31 - unused
  18     // 23 - conditional bit
  19     // 18-22 - unused
  20     // 12-17 - cause bits (unimplemented)
  21     // 7-11  - enables bits (unimplemented)
  22     // 2-6   - flags (unimplemented)
  23     // 0-1   - rounding mode (only implemented for fixed point conversions)
  24     private int fcsr;
  25
  26     private int pc;
  27
  28     // The filename if the binary we're running
  29     public String image;
  30     private ELF.Symtab symtab;
  31
  32     // Register Operations
  33     private final void setFC(boolean b) { fcsr = (fcsr&~0x800000) | (b ? 0x800000 : 0x000000); }
  34     private final int roundingMode() { return fcsr & 3; /* bits 0-1 */ }
  35     private final double getDouble(int r) {
  36         return Double.longBitsToDouble(((fpregs[r+1]&0xffffffffL) << 32) | (fpregs[r]&0xffffffffL));
  37     }
  38     private final void setDouble(int r, double d) {
  39         long l = Double.doubleToLongBits(d);
  40         fpregs[r+1] = (int)(l >>> 32); fpregs[r] = (int)l;
  41     }
  42     private final float getFloat(int r) { return Float.intBitsToFloat(fpregs[r]); }
  43     private final void setFloat(int r, float f) { fpregs[r] = Float.floatToRawIntBits(f); }
  44
  45     protected void _execute() throws ExecutionException {
  46         try {
  47             runSome();
  48         } catch(ExecutionException e) {
  49             e.setLocation(toHex(pc) + ": " + sourceLine(pc));
  50             throw e;
  51         }
  52     }
  53
  54     // Main interpretor
  55     // the return value is meaningless, its just to catch people typing "return" by accident
  56     private final int runSome() throws FaultException,ExecutionException {
  57         int[] r = registers;
  58         int[] f = fpregs;
  59         int pc = this.pc;
  60         int nextPC = pc + 4;
  61     try {
  62     OUTER: for(;;) {
  63         int insn;
  64         try {
  65             insn = readPages[pc>>>PAGE_SHIFT][(pc>>>2)&PAGE_WORDS-1];
  66         } catch (RuntimeException e) {
  67             insn = memRead(pc);
  68         }
  69
  70         int op = (insn >>> 26) & 0xff;                 // bits 26-31
  71         int rs = (insn >>> 21) & 0x1f;                 // bits 21-25
  72         int rt = (insn >>> 16) & 0x1f;                 // bits 16-20
  73         int ft = (insn >>> 16) & 0x1f;
  74         int rd = (insn >>> 11) & 0x1f;                 // bits 11-15
  75         int fs = (insn >>> 11) & 0x1f;
  76         int shamt = (insn >>> 6) & 0x1f;               // bits 6-10
  77         int fd = (insn >>> 6) & 0x1f;
  78         int subcode = insn & 0x3f;                     // bits 0-5
  79
  80         int jumpTarget = (insn & 0x03ffffff);          // bits 0-25
  81         int unsignedImmediate = insn & 0xffff;
  82         int signedImmediate = (insn << 16) >> 16;
  83         int branchTarget = signedImmediate;
  84
  85         int tmp, addr; // temporaries
  86
  87         r[ZERO] = 0;
  88
  89         switch(op) {
  90             case 0: {
  91                 switch(subcode) {
  92                     case 0: // SLL
  93                         if(insn == 0) break;
  94                         r[rd] = r[rt] << shamt;
  95                         break;
  96                     case 2: // SRL
  97                         r[rd] = r[rt] >>> shamt;
  98                         break;
  99                     case 3: // SRA
 100                         r[rd] = r[rt] >> shamt;
 101                         break;
 102                     case 4: // SLLV
 103                         r[rd] = r[rt] << (r[rs]&0x1f);
 104                         break;
 105                     case 6: // SRLV
 106                         r[rd] = r[rt] >>> (r[rs]&0x1f);
 107                         break;
 108                     case 7: // SRAV
 109                         r[rd] = r[rt] >> (r[rs]&0x1f);
 110                         break;
 111                     case 8: // JR
 112                         tmp = r[rs]; pc += 4; nextPC = tmp;
 113                         continue OUTER;
 114                     case 9: // JALR
 115                         tmp = r[rs]; pc += 4; r[rd] = pc+4; nextPC = tmp;
 116                         continue OUTER;
 117                     case 12: // SYSCALL
 118                         this.pc = pc;
 119                         r[V0] = syscall(r[V0],r[A0],r[A1],r[A2],r[A3]);
 120                         if(state != RUNNING) { this.pc = nextPC; break OUTER; }
 121                         break;
 122                     case 13: // BREAK
 123                         throw new ExecutionException("Break");
 124                     case 16: // MFHI
 125                         r[rd] = hi;
 126                         break;
 127                     case 17: // MTHI
 128                         hi = r[rs];
 129                         break;
 130                     case 18: // MFLO
 131                         r[rd] = lo;
 132                         break;
 133                     case 19: // MTLO
 134                         lo = r[rs];
 135                         break;
 136                     case 24: { // MULT
 137                         long hilo = (long)(r[rs]) * ((long)r[rt]);
 138                         hi = (int) (hilo >>> 32);
 139                         lo = (int) hilo;
 140                         break;
 141                     }
 142                     case 25: { // MULTU
 143                         long hilo = (r[rs] & 0xffffffffL) * (r[rt] & 0xffffffffL);
 144                         hi = (int) (hilo >>> 32);
 145                         lo = (int) hilo;
 146                         break;
 147                     }
 148                     case 26: // DIV
 149                         hi = r[rs]%r[rt];
 150                         lo = r[rs]/r[rt];
 151                         break;
 152                     case 27: // DIVU
 153                         if(rt != 0) {
 154                             hi = (int)((r[rs] & 0xffffffffL) % (r[rt] & 0xffffffffL));
 155                             lo = (int)((r[rs] & 0xffffffffL) / (r[rt] & 0xffffffffL));
 156                         }
 157                         break;
 158                     case 32: // ADD
 159                         throw new ExecutionException("ADD (add with oveflow trap) not suported");
 160                         /*This must trap on overflow
 161                         r[rd] = r[rs] + r[rt];
 162                         break;*/
 163                     case 33: // ADDU
 164                         r[rd] = r[rs] + r[rt];
 165                         break;
 166                     case 34: // SUB
 167                         throw new ExecutionException("SUB (sub with oveflow trap) not suported");
 168                         /*This must trap on overflow
 169                         r[rd] = r[rs] - r[rt];
 170                         break;*/
 171                     case 35: // SUBU
 172                         r[rd] = r[rs] - r[rt];
 173                         break;
 174                     case 36: // AND
 175                         r[rd] = r[rs] & r[rt];
 176                         break;
 177                     case 37: // OR
 178                         r[rd] = r[rs] | r[rt];
 179                         break;
 180                     case 38: // XOR
 181                         r[rd] = r[rs] ^ r[rt];
 182                         break;
 183                     case 39: // NOR
 184                         r[rd] = ~(r[rs] | r[rt]);
 185                         break;
 186                     case 42: // SLT
 187                         r[rd] = r[rs] < r[rt] ? 1 : 0;
 188                         break;
 189                     case 43: // SLTU
 190                         r[rd] = ((r[rs] & 0xffffffffL) < (r[rt] & 0xffffffffL)) ? 1 : 0;
 191                         break;
 192                     default:
 193                         throw new ExecutionException("Illegal instruction 0/" + subcode);
 194                 }
 195                 break;
 196             }
 197             case 1: {
 198                 switch(rt) {
 199                     case 0: // BLTZ
 200                         if(r[rs] < 0) {
 201                             pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 202                             continue OUTER;
 203                         }
 204                         break;
 205                     case 1: // BGEZ
 206                         if(r[rs] >= 0) {
 207                             pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 208                             continue OUTER;
 209                         }
 210                         break;
 211                     case 16: // BLTZAL
 212                         if(r[rs] < 0) {
 213                             pc += 4; r[RA] = pc+4; tmp = pc + branchTarget*4; nextPC = tmp;
 214                             continue OUTER;
 215                         }
 216                         break;
 217                     case 17: // BGEZAL
 218                         if(r[rs] >= 0) {
 219                             pc += 4; r[RA] = pc+4; tmp = pc + branchTarget*4; nextPC = tmp;
 220                             continue OUTER;
 221                         }
 222                         break;
 223                     default:
 224                         throw new ExecutionException("Illegal Instruction");
 225                 }
 226                 break;
 227             }
 228             case 2: { // J
 229                 tmp = (pc&0xf0000000) | (jumpTarget << 2);
 230                 pc+=4; nextPC = tmp;
 231                 continue OUTER;
 232             }
 233             case 3: { // JAL
 234                 tmp = (pc&0xf0000000) | (jumpTarget << 2);
 235                 pc+=4; r[RA] = pc+4; nextPC = tmp;
 236                 continue OUTER;
 237             }
 238             case 4: // BEQ
 239                 if(r[rs] == r[rt]) {
 240                     pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 241                     continue OUTER;
 242                 }
 243                 break;
 244             case 5: // BNE
 245                 if(r[rs] != r[rt]) {
 246                     pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 247                     continue OUTER;
 248                 }
 249                 break;
 250             case 6: //BLEZ
 251                 if(r[rs] <= 0) {
 252                     pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 253                     continue OUTER;
 254                 }
 255                 break;
 256             case 7: //BGTZ
 257                 if(r[rs] > 0) {
 258                     pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 259                     continue OUTER;
 260                 }
 261                 break;
 262             case 8: // ADDI
 263                 r[rt] = r[rs] + signedImmediate;
 264                 break;
 265             case 9: // ADDIU
 266                 r[rt] = r[rs] + signedImmediate;
 267                 break;
 268             case 10: // SLTI
 269                 r[rt] = r[rs] < signedImmediate ? 1 : 0;
 270                 break;
 271             case 11: // SLTIU
 272                 r[rt] = (r[rs]&0xffffffffL) < (unsignedImmediate&0xffffffffL) ? 1 : 0;
 273                 break;
 274             case 12: // ANDI
 275                 r[rt] = r[rs] & unsignedImmediate;
 276                 break;
 277             case 13: // ORI
 278                 r[rt] = r[rs] | unsignedImmediate;
 279                 break;
 280             case 14: // XORI
 281                 r[rt] = r[rs] ^ unsignedImmediate;
 282                 break;
 283             case 15: // LUI
 284                 r[rt] = unsignedImmediate << 16;
 285                 break;
 286             case 16:
 287                 throw new ExecutionException("TLB/Exception support not implemented");
 288             case 17: { // FPU
 289                 boolean debug = false;
 290                 String line = debug ? sourceLine(pc) : "";
 291                 boolean debugon = debug && (line.indexOf("dtoa.c:51") >= 0 || line.indexOf("dtoa.c:52") >= 0 || line.indexOf("test.c") >= 0);
 292                 if(rs > 8 && debugon)
 293                     System.out.println("               FP Op: " + op + "/" + rs + "/" + subcode + " " + line);
 294                 if(roundingMode() != 0 && rs != 6 /*CTC.1*/ && !((rs==16 || rs==17) && subcode == 36 /* CVT.W.Z */))
 295                     throw new ExecutionException("Non-cvt.w.z operation attempted with roundingMode != round to nearest");
 296                 switch(rs) {
 297                     case 0: // MFC.1
 298                         r[rt] = f[rd];
 299                         break;
 300                     case 2: // CFC.1
 301                         if(fs != 31) throw new ExecutionException("FCR " + fs + " unavailable");
 302                         r[rt] = fcsr;
 303                         break;
 304                     case 4: // MTC.1
 305                         f[rd] = r[rt];
 306                         break;
 307                     case 6: // CTC.1
 308                         if(fs != 31) throw new ExecutionException("FCR " + fs + " unavailable");
 309                         fcsr = r[rt];
 310                         break;
 311                     case 8: // BC1F, BC1T
 312                         if(((fcsr&0x800000)!=0) == (((insn>>>16)&1)!=0)) {
 313                             pc += 4; tmp = pc + branchTarget*4; nextPC = tmp;
 314                             continue OUTER;
 315                         }
 316                         break;
 317                     case 16: {  // Single
 318                         switch(subcode) {
 319                             case 0: // ADD.S
 320                                 setFloat(fd,getFloat(fs)+getFloat(ft));
 321                                 break;
 322                             case 1: // SUB.S
 323                                 setFloat(fd,getFloat(fs)-getFloat(ft));
 324                                 break;
 325                             case 2: // MUL.S
 326                                 setFloat(fd,getFloat(fs)*getFloat(ft));
 327                                 break;
 328                             case 3: // DIV.S
 329                                 setFloat(fd,getFloat(fs)/getFloat(ft));
 330                                 break;
 331                             case 5: // ABS.S
 332                                 setFloat(fd,Math.abs(getFloat(fs)));
 333                                 break;
 334                             case 6: // MOV.S
 335                                 f[fd] = f[fs];
 336                                 break;
 337                             case 7: // NEG.S
 338                                 setFloat(fd,-getFloat(fs));
 339                                 break;
 340                             case 33: // CVT.D.S
 341                                 setDouble(fd,getFloat(fs));
 342                                 break;
 343                             case 36: // CVT.W.S
 344                                 switch(roundingMode()) {
 345                                     case 0: f[fd] = (int)Math.floor(getFloat(fs)+0.5f); break; // Round to nearest
 346                                     case 1: f[fd] = (int)getFloat(fs); break; // Round towards zero
 347                                     case 2: f[fd] = (int)Math.ceil(getFloat(fs)); break; // Round towards plus infinity
 348                                     case 3: f[fd] = (int)Math.floor(getFloat(fs)); break; // Round towards minus infinity
 349                                 }
 350                                 break;
 351                             case 50: // C.EQ.S
 352                                 setFC(getFloat(fs) == getFloat(ft));
 353                                 break;
 354                             case 60: // C.LT.S
 355                                 setFC(getFloat(fs) < getFloat(ft));
 356                                 break;
 357                             default: throw new ExecutionException("Invalid Instruction 17/" + rs + "/" + subcode + " at " + sourceLine(pc));
 358                         }
 359                         break;
 360                     }
 361                     case 17: { // Double
 362                         switch(subcode) {
 363                             case 0: // ADD.D
 364                                 setDouble(fd,getDouble(fs)+getDouble(ft));
 365                                 break;
 366                             case 1: // SUB.D
 367                                 if(debugon) System.out.println("f" + fd + " = f" + fs + " (" + getDouble(fs) + ") - f" + ft + " (" + getDouble(ft) + ")");
 368                                 setDouble(fd,getDouble(fs)-getDouble(ft));
 369                                 break;
 370                             case 2: // MUL.D
 371                                 if(debugon) System.out.println("f" + fd + " = f" + fs + " (" + getDouble(fs) + ") * f" + ft + " (" + getDouble(ft) + ")");
 372                                 setDouble(fd,getDouble(fs)*getDouble(ft));
 373                                 if(debugon) System.out.println("f" + fd + " = " + getDouble(fd));
 374                                 break;
 375                             case 3: // DIV.D
 376                                 setDouble(fd,getDouble(fs)/getDouble(ft));
 377                                 break;
 378                             case 5: // ABS.D
 379                                 setDouble(fd,Math.abs(getDouble(fs)));
 380                                 break;
 381                             case 6: // MOV.D
 382                                 f[fd] = f[fs];
 383                                 f[fd+1] = f[fs+1];
 384                                 break;
 385                             case 7: // NEG.D
 386                                 setDouble(fd,-getDouble(fs));
 387                                 break;
 388                             case 32: // CVT.S.D
 389                                 setFloat(fd,(float)getDouble(fs));
 390                                 break;
 391                             case 36: // CVT.W.D
 392                                 if(debugon) System.out.println("CVT.W.D rm: " + roundingMode() + " f" + fs + ":" + getDouble(fs));
 393                                 switch(roundingMode()) {
 394                                     case 0: f[fd] = (int)Math.floor(getDouble(fs)+0.5); break; // Round to nearest
 395                                     case 1: f[fd] = (int)getDouble(fs); break; // Round towards zero
 396                                     case 2: f[fd] = (int)Math.ceil(getDouble(fs)); break; // Round towards plus infinity
 397                                     case 3: f[fd] = (int)Math.floor(getDouble(fs)); break; // Round towards minus infinity
 398                                 }
 399                                 if(debugon) System.out.println("CVT.W.D: f" + fd + ":" + f[fd]);
 400                                 break;
 401                             case 50: // C.EQ.D
 402                                 setFC(getDouble(fs) == getDouble(ft));
 403                                 break;
 404                             case 60: // C.LT.D
 405                                 setFC(getDouble(fs) < getDouble(ft));
 406                                 break;
 407                             case 62: // C.LE.D
 408                                 setFC(getDouble(fs) <= getDouble(ft));
 409                                 break;
 410                             default: throw new ExecutionException("Invalid Instruction 17/" + rs + "/" + subcode + " at " + sourceLine(pc));
 411                         }
 412                         break;
 413                     }
 414                     case 20: { // Integer
 415                         switch(subcode) {
 416                             case 33: // CVT.D.W
 417                                 setDouble(fd,f[fs]);
 418                                 break;
 419                             default: throw new ExecutionException("Invalid Instruction 17/" + rs + "/" + subcode + " at " + sourceLine(pc));
 420                         }
 421                         break;
 422                     }
 423                     default:
 424                         throw new ExecutionException("Invalid Instruction 17/" + rs);
 425                 }
 426                 break;
 427             }
 428             case 18: case 19:
 429                 throw new ExecutionException("No coprocessor installed");
 430             case 32: { // LB
 431                 addr = r[rs] + signedImmediate;
 432                 try {
 433                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 434                 } catch(RuntimeException e) {
 435                     tmp = memRead(addr&~3);
 436                 }
 437                 switch(addr&3) {
 438                     case 0: tmp = (tmp>>>24)&0xff; break;
 439                     case 1: tmp = (tmp>>>16)&0xff; break;
 440                     case 2: tmp = (tmp>>> 8)&0xff; break;
 441                     case 3: tmp = (tmp>>> 0)&0xff; break;
 442                 }
 443                 if((tmp&0x80)!=0) tmp |= 0xffffff00; // sign extend
 444                 r[rt] = tmp;
 445                 break;
 446             }
 447             case 33: { // LH
 448                 addr = r[rs] + signedImmediate;
 449                 try {
 450                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 451                 } catch(RuntimeException e) {
 452                     tmp = memRead(addr&~3);
 453                 }
 454                 switch(addr&2) {
 455                     case 0: tmp = (tmp>>>16)&0xffff; break;
 456                     case 2: tmp = (tmp>>> 0)&0xffff; break;
 457                 }
 458                 if((tmp&0x8000)!=0) tmp |= 0xffff0000; // sign extend
 459                 r[rt] = tmp;
 460                 break;
 461             }
 462             case 34: { // LWL;
 463                 addr = r[rs] + signedImmediate;
 464                 try {
 465                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 466                 } catch(RuntimeException e) {
 467                     tmp = memRead(addr&~3);
 468                 }
 469                 switch(addr&3) {
 470                     case 0: r[rt] = (r[rt]&0x00000000)|(tmp<< 0); break;
 471                     case 1: r[rt] = (r[rt]&0x000000ff)|(tmp<< 8); break;
 472                     case 2: r[rt] = (r[rt]&0x0000ffff)|(tmp<<16); break;
 473                     case 3: r[rt] = (r[rt]&0x00ffffff)|(tmp<<24); break;
 474                 }
 475                 break;
 476             }
 477             case 35: // LW
 478                 addr = r[rs] + signedImmediate;
 479                 try {
 480                     r[rt] = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 481                 } catch(RuntimeException e) {
 482                     r[rt] = memRead(addr);
 483                 }
 484                 break;
 485             case 36: { // LBU
 486                 addr = r[rs] + signedImmediate;
 487                 try {
 488                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 489                 } catch(RuntimeException e) {
 490                     tmp = memRead(addr);
 491                 }
 492                 switch(addr&3) {
 493                     case 0: r[rt] = (tmp>>>24)&0xff; break;
 494                     case 1: r[rt] = (tmp>>>16)&0xff; break;
 495                     case 2: r[rt] = (tmp>>> 8)&0xff; break;
 496                     case 3: r[rt] = (tmp>>> 0)&0xff; break;
 497                 }
 498                 break;
 499             }
 500             case 37: { // LHU
 501                 addr = r[rs] + signedImmediate;
 502                 try {
 503                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 504                 } catch(RuntimeException e) {
 505                     tmp = memRead(addr&~3);
 506                 }
 507                 switch(addr&2) {
 508                     case 0: r[rt] = (tmp>>>16)&0xffff; break;
 509                     case 2: r[rt] = (tmp>>> 0)&0xffff; break;
 510                 }
 511                 break;
 512             }
 513             case 38: { // LWR
 514                 addr = r[rs] + signedImmediate;
 515                 try {
 516                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 517                 } catch(RuntimeException e) {
 518                     tmp = memRead(addr&~3);
 519                 }
 520                 switch(addr&3) {
 521                     case 0: r[rt] = (r[rt]&0xffffff00)|(tmp>>>24); break;
 522                     case 1: r[rt] = (r[rt]&0xffff0000)|(tmp>>>16); break;
 523                     case 2: r[rt] = (r[rt]&0xff000000)|(tmp>>> 8); break;
 524                     case 3: r[rt] = (r[rt]&0x00000000)|(tmp>>> 0); break;
 525                 }
 526                 break;
 527             }
 528             case 40: { // SB
 529                 addr = r[rs] + signedImmediate;
 530                 try {
 531                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 532                 } catch(RuntimeException e) {
 533                     tmp = memRead(addr&~3);
 534                 }
 535                 switch(addr&3) {
 536                     case 0: tmp = (tmp&0x00ffffff) | ((r[rt]&0xff)<<24); break;
 537                     case 1: tmp = (tmp&0xff00ffff) | ((r[rt]&0xff)<<16); break;
 538                     case 2: tmp = (tmp&0xffff00ff) | ((r[rt]&0xff)<< 8); break;
 539                     case 3: tmp = (tmp&0xffffff00) | ((r[rt]&0xff)<< 0); break;
 540                 }
 541                 try {
 542                     writePages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)] = tmp;
 543                 } catch(RuntimeException e) {
 544                     memWrite(addr&~3,tmp);
 545                 }
 546                 break;
 547             }
 548             case 41: { // SH
 549                 addr = r[rs] + signedImmediate;
 550                 try {
 551                     tmp = readPages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)];
 552                 } catch(RuntimeException e) {
 553                     tmp = memRead(addr&~3);
 554                 }
 555                 switch(addr&2) {
 556                     case 0: tmp = (tmp&0x0000ffff) | ((r[rt]&0xffff)<<16); break;
 557                     case 2: tmp = (tmp&0xffff0000) | ((r[rt]&0xffff)<< 0); break;
 558                 }
 559                 try {
 560                     writePages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)] = tmp;
 561                 } catch(RuntimeException e) {
 562                     memWrite(addr&~3,tmp);
 563                 }
 564                 break;
 565             }
 566             case 42: { // SWL
 567                 addr = r[rs] + signedImmediate;
 568                 tmp = memRead(addr&~3);
 569                 switch(addr&3) {
 570                     case 0: tmp=(tmp&0x00000000)|(r[rt]>>> 0); break;
 571                     case 1: tmp=(tmp&0xff000000)|(r[rt]>>> 8); break;
 572                     case 2: tmp=(tmp&0xffff0000)|(r[rt]>>>16); break;
 573                     case 3: tmp=(tmp&0xffffff00)|(r[rt]>>>24); break;
 574                 }
 575                 try {
 576                     writePages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)] = tmp;
 577                 } catch(RuntimeException e) {
 578                     memWrite(addr&~3,tmp);
 579                 }
 580                 break;
 581             }
 582             case 43: // SW
 583                 addr = r[rs] + signedImmediate;
 584                 try {
 585                     writePages[addr>>>PAGE_SHIFT][(addr>>>2)&(PAGE_WORDS-1)] = r[rt];
 586                 } catch(RuntimeException e) {
 587                     memWrite(addr&~3,r[rt]);
 588                 }
 589                 break;
 590             case 46: { // SWR
 591                 addr = r[rs] + signedImmediate;
 592                 tmp = memRead(addr&~3);
 593                 switch(addr&3) {
 594                     case 0: tmp=(tmp&0x00ffffff)|(r[rt]<<24); break;
 595                     case 1: tmp=(tmp&0x0000ffff)|(r[rt]<<16); break;
 596                     case 2: tmp=(tmp&0x000000ff)|(r[rt]<< 8); break;
 597                     case 3: tmp=(tmp&0x00000000)|(r[rt]<< 0); break;
 598                 }
 599                 memWrite(addr&~3,tmp);
 600                 break;
 601             }
 602             // FEATURE: Needs to be atomic w/ threads
 603             case 48: // LWC0/LL
 604                 r[rt] = memRead(r[rs] + signedImmediate);
 605                 break;
 606             case 49: // LWC1
 607                 f[rt] = memRead(r[rs] + signedImmediate);
 608                 break;
 609             // FEATURE: Needs to be atomic w/ threads
 610             case 56:
 611                 memWrite(r[rs] + signedImmediate,r[rt]);
 612                 r[rt] = 1;
 613                 break;
 614             case 57: // SWC1
 615                 memWrite(r[rs] + signedImmediate,f[rt]);
 616                 break;
 617             default:
 618                 throw new ExecutionException("Invalid Instruction: " + op);
 619         }
 620         pc = nextPC;
 621         nextPC = pc + 4;
 622     } // for(;;)
 623     } catch(ExecutionException e) {
 624         this.pc = pc;
 625         throw e;
 626     }
 627         return 0;
 628     }
 629
 630     public int lookupSymbol(String name) {
 631         ELF.Symbol sym = symtab.getGlobalSymbol(name);
 632         return sym == null ? -1 : sym.addr;
 633     }
 634
 635     // Image loading function
 636     private void loadImage(SeekableData data) throws IOException {
 637         if(state != UNINITIALIZED) throw new IllegalStateException("loadImage called on initialized runtime");
 638
 639         ELF elf = new ELF(data);
 640         symtab = elf.getSymtab();
 641
 642         if(elf.header.type != ELF.ELFHeader.ET_EXEC) throw new IOException("Binary is not an executable");
 643         if(elf.header.machine != ELF.ELFHeader.EM_MIPS) throw new IOException("Binary is not for the MIPS I Architecture");
 644         if(elf.ident.data != ELF.ELFIdent.ELFDATA2MSB) throw new IOException("Binary is not big endian");
 645
 646         entryPoint = elf.header.entry;
 647
 648         ELF.Symtab symtab = elf.getSymtab();
 649         if(symtab == null) throw new IOException("No symtab in binary (did you strip it?)");
 650         ELF.Symbol userInfo = symtab.getGlobalSymbol("user_info");
 651         ELF.Symbol gpsym = symtab.getGlobalSymbol("_gp");
 652
 653         if(gpsym == null) throw new IOException("NO _gp symbol!");
 654         gp = gpsym.addr;
 655
 656         if(userInfo != null) {
 657             userInfoBase = userInfo.addr;
 658             userInfoSize = userInfo.size;
 659         }
 660
 661         ELF.PHeader[] pheaders = elf.pheaders;
 662         int brk = 0;
 663         for(int i=0;i<pheaders.length;i++) {
 664             ELF.PHeader ph = pheaders[i];
 665             if(ph.type != ELF.PHeader.PT_LOAD) continue;
 666             int memsize = ph.memsz;
 667             int filesize = ph.filesz;
 668             if(memsize == 0) continue;
 669             if(memsize < 0) throw new IOException("pheader size too large");
 670             int addr = ph.vaddr;
 671             if(addr == 0x0) throw new IOException("pheader vaddr == 0x0");
 672             brk = max(addr+memsize,brk);
 673
 674             for(int j=0;j<memsize+PAGE_SIZE-1;j+=PAGE_SIZE) {
 675                 int page = (j+addr) >>> PAGE_SHIFT;
 676                 if(readPages[page] == null)
 677                     readPages[page] = new int[PAGE_WORDS];
 678                 if(ph.writable()) writePages[page] = readPages[page];
 679             }
 680             if(filesize != 0) {
 681                 filesize = filesize & ~3;
 682                 DataInputStream dis = new DataInputStream(ph.getInputStream());
 683                 do {
 684                     readPages[addr >>> PAGE_SHIFT][(addr >>> 2)&(PAGE_WORDS-1)] = dis.readInt();
 685                     addr+=4;
 686                     filesize-=4;
 687                 } while(filesize > 0);
 688                 dis.close();
 689             }
 690         }
 691         brkAddr = (brk+PAGE_SIZE-1)&~(PAGE_SIZE-1);
 692         state = INITIALIZED;
 693     }
 694
 695     protected void setCPUState(CPUState state) {
 696         for(int i=1;i<32;i++) registers[i] = state.r[i];
 697         for(int i=0;i<32;i++) fpregs[i] = state.f[i];
 698         hi=state.hi; lo=state.lo; fcsr=state.fcsr;
 699         pc=state.pc;
 700     }
 701
 702     protected CPUState getCPUState() {
 703         CPUState state = new CPUState();
 704         for(int i=1;i<32;i++) state.r[i] = registers[i];
 705         for(int i=0;i<32;i++) state.f[i] = fpregs[i];
 706         state.hi=hi; state.lo=lo; state.fcsr=fcsr;
 707         state.pc=pc;
 708         return state;
 709     }
 710
 711     // This is package private for fork() which does all kinds of ugly things behind the scenes
 712     Interpreter() { super(4096,65536,true); }
 713     public Interpreter(SeekableData data) throws IOException { this(); loadImage(data); }
 714     public Interpreter(String filename) throws IOException {
 715         this(new SeekableFile(filename,false));
 716         image = filename;
 717     }
 718     public Interpreter(InputStream is) throws IOException { this(new SeekableInputStream(is)); }
 719
 720     // Debug functions
 721     // NOTE: This probably requires a jdk > 1.1, however, it is only used for debugging
 722     private java.util.HashMap sourceLineCache;
 723     public String sourceLine(int pc) {
 724         final String addr2line = "mips-unknown-elf-addr2line";
 725         String line = (String) (sourceLineCache == null ? null : sourceLineCache.get(new Integer(pc)));
 726         if(line != null) return line;
 727         if(image==null) return null;
 728         try {
 729             Process p = java.lang.Runtime.getRuntime().exec(new String[]{addr2line,"-e",image,toHex(pc)});
 730             line = new BufferedReader(new InputStreamReader(p.getInputStream())).readLine();
 731             if(line == null) return null;
 732             while(line.startsWith("../")) line = line.substring(3);
 733             if(sourceLineCache == null) sourceLineCache = new java.util.HashMap();
 734             sourceLineCache.put(new Integer(pc),line);
 735             return line;
 736         } catch(IOException e) {
 737             return null;
 738         }
 739     }
 740
 741     public class DebugShutdownHook implements Runnable {
 742         public void run() {
 743             int pc = Interpreter.this.pc;
 744             if(getState() == RUNNING)
 745                 System.err.print("\nCPU Executing " + toHex(pc) + ": " + sourceLine(pc) + "\n");
 746         }
 747     }
 748
 749     public static void main(String[] argv) throws Exception {
 750         String image = argv[0];
 751         Interpreter emu = new Interpreter(image);
 752         java.lang.Runtime.getRuntime().addShutdownHook(new Thread(emu.new DebugShutdownHook()));
 753         int status = emu.run(argv);
 754         System.err.println("Exit status: " + status);
 755         System.exit(status);
 756     }
 757 }