miscemu/instr.c

   1 /*
   2  * Emulation of priviledged instructions
   3  *
   4  * Copyright 1995 Alexandre Julliard
   5  */
   6
   7 #include <stdio.h>
   8 #include "windows.h"
   9 #include "ldt.h"
  10 #include "miscemu.h"
  11 #include "registers.h"
  12
  13
  14 #define STACK_reg(context) \
  15    ((GET_SEL_FLAGS(SS_reg(context)) & LDT_FLAGS_32BIT) ? \
  16                    ESP_reg(context) : SP_reg(context))
  17
  18 #define STACK_PTR(context) \
  19     (PTR_SEG_OFF_TO_LIN(SS_reg(context),STACK_reg(context)))
  20
  21 /***********************************************************************
  22  *           INSTR_ReplaceSelector
  23  *
  24  * Try to replace an invalid selector by a valid one.
  25  * For now, only selector 0x40 is handled here.
  26  */
  27 static WORD INSTR_ReplaceSelector( struct sigcontext_struct *context, WORD sel)
  28 {
  29     if (sel == 0x40)
  30     {
  31         fprintf( stderr, "Direct access to segment 0x40 (cs:ip=%04x:%04lx).\n",
  32                  CS_reg(context), EIP_reg(context) );
  33         return DOSMEM_BiosSeg;
  34     }
  35     return 0;  /* Can't replace selector */
  36 }
  37
  38
  39 /***********************************************************************
  40  *           INSTR_GetOperandAddr
  41  *
  42  * Return the address of an instruction operand (from the mod/rm byte).
  43  */
  44 static BYTE *INSTR_GetOperandAddr( struct sigcontext_struct *context,
  45                                    BYTE *instr, int long_addr,
  46                                    int segprefix, int *len )
  47 {
  48     int mod, rm, base, index = 0, ss = 0, seg = 0, off;
  49
  50 #define GET_VAL(val,type) \
  51     { *val = *(type *)instr; instr += sizeof(type); *len += sizeof(type); }
  52
  53     *len = 0;
  54     GET_VAL( &mod, BYTE );
  55     rm = mod & 7;
  56     mod >>= 6;
  57
  58     if (mod == 3)
  59     {
  60         switch(rm)
  61         {
  62         case 0: return (BYTE *)&EAX_reg(context);
  63         case 1: return (BYTE *)&ECX_reg(context);
  64         case 2: return (BYTE *)&EDX_reg(context);
  65         case 3: return (BYTE *)&EBX_reg(context);
  66         case 4: return (BYTE *)&ESP_reg(context);
  67         case 5: return (BYTE *)&EBP_reg(context);
  68         case 6: return (BYTE *)&ESI_reg(context);
  69         case 7: return (BYTE *)&EDI_reg(context);
  70         }
  71     }
  72
  73     if (long_addr)
  74     {
  75         if (rm == 4)
  76         {
  77             BYTE sib;
  78             GET_VAL( &sib, BYTE );
  79             rm = sib & 7;
  80             ss = sib >> 6;
  81             switch(sib >> 3)
  82             {
  83             case 0: index = EAX_reg(context); break;
  84             case 1: index = ECX_reg(context); break;
  85             case 2: index = EDX_reg(context); break;
  86             case 3: index = EBX_reg(context); break;
  87             case 4: index = 0; break;
  88             case 5: index = EBP_reg(context); break;
  89             case 6: index = ESI_reg(context); break;
  90             case 7: index = EDI_reg(context); break;
  91             }
  92         }
  93
  94         switch(rm)
  95         {
  96         case 0: base = EAX_reg(context); seg = DS_reg(context); break;
  97         case 1: base = ECX_reg(context); seg = DS_reg(context); break;
  98         case 2: base = EDX_reg(context); seg = DS_reg(context); break;
  99         case 3: base = EBX_reg(context); seg = DS_reg(context); break;
 100         case 4: base = ESP_reg(context); seg = SS_reg(context); break;
 101         case 5: base = EBP_reg(context); seg = SS_reg(context); break;
 102         case 6: base = ESI_reg(context); seg = DS_reg(context); break;
 103         case 7: base = EDI_reg(context); seg = DS_reg(context); break;
 104         }
 105         switch (mod)
 106         {
 107         case 0:
 108             if (rm == 5)  /* special case: ds:(disp32) */
 109             {
 110                 GET_VAL( &base, DWORD );
 111                 seg = DS_reg(context);
 112             }
 113             break;
 114
 115         case 1:  /* 8-bit disp */
 116             GET_VAL( &off, BYTE );
 117             base += (signed char)off;
 118             break;
 119
 120         case 2:  /* 32-bit disp */
 121             GET_VAL( &off, DWORD );
 122             base += (signed long)off;
 123             break;
 124         }
 125     }
 126     else  /* short address */
 127     {
 128         switch(rm)
 129         {
 130         case 0:  /* ds:(bx,si) */
 131             base = BX_reg(context) + SI_reg(context);
 132             seg  = DS_reg(context);
 133             break;
 134         case 1:  /* ds:(bx,di) */
 135             base = BX_reg(context) + DI_reg(context);
 136             seg  = DS_reg(context);
 137             break;
 138         case 2:  /* ss:(bp,si) */
 139             base = BP_reg(context) + SI_reg(context);
 140             seg  = SS_reg(context);
 141             break;
 142         case 3:  /* ss:(bp,di) */
 143             base = BP_reg(context) + DI_reg(context);
 144             seg  = SS_reg(context);
 145             break;
 146         case 4:  /* ds:(si) */
 147             base = SI_reg(context);
 148             seg  = DS_reg(context);
 149             break;
 150         case 5:  /* ds:(di) */
 151             base = DI_reg(context);
 152             seg  = DS_reg(context);
 153             break;
 154         case 6:  /* ss:(bp) */
 155             base = BP_reg(context);
 156             seg  = SS_reg(context);
 157             break;
 158         case 7:  /* ds:(bx) */
 159             base = BX_reg(context);
 160             seg  = DS_reg(context);
 161             break;
 162         }
 163
 164         switch(mod)
 165         {
 166         case 0:
 167             if (rm == 6)  /* special case: ds:(disp16) */
 168             {
 169                 GET_VAL( &base, WORD );
 170                 seg  = DS_reg(context);
 171             }
 172             break;
 173
 174         case 1:  /* 8-bit disp */
 175             GET_VAL( &off, BYTE );
 176             base += (signed char)off;
 177             break;
 178
 179         case 2:  /* 16-bit disp */
 180             GET_VAL( &off, WORD );
 181             base += (signed short)off;
 182             break;
 183         }
 184         base &= 0xffff;
 185     }
 186     if (segprefix != -1) seg = segprefix;
 187
 188     /* FIXME: should check limit of the segment here */
 189     return (BYTE *)PTR_SEG_OFF_TO_LIN( seg, (base + (index << ss)) );
 190 }
 191
 192
 193 /***********************************************************************
 194  *           INSTR_EmulateLDS
 195  *
 196  * Emulate the LDS (and LES,LFS,etc.) instruction.
 197  */
 198 static BOOL INSTR_EmulateLDS( struct sigcontext_struct *context,
 199                               BYTE *instr, int long_op, int long_addr,
 200                               int segprefix, int *len )
 201 {
 202     BYTE *regmodrm = instr + 1 + (*instr == 0x0f);
 203     BYTE *addr = INSTR_GetOperandAddr( context, regmodrm,
 204                                        long_addr, segprefix, len );
 205     WORD seg = *(WORD *)(addr + (long_op ? 4 : 2));
 206
 207     if (!(seg = INSTR_ReplaceSelector( context, seg )))
 208         return FALSE;  /* Unable to emulate it */
 209
 210     /* Now store the offset in the correct register */
 211
 212     switch((*regmodrm >> 3) & 7)
 213     {
 214     case 0:
 215         if (long_op) EAX_reg(context) = *(DWORD *)addr;
 216         else AX_reg(context) = *(WORD *)addr;
 217         break;
 218     case 1:
 219         if (long_op) ECX_reg(context) = *(DWORD *)addr;
 220         else CX_reg(context) = *(WORD *)addr;
 221         break;
 222     case 2:
 223         if (long_op) EDX_reg(context) = *(DWORD *)addr;
 224         else DX_reg(context) = *(WORD *)addr;
 225         break;
 226     case 3:
 227         if (long_op) EBX_reg(context) = *(DWORD *)addr;
 228         else BX_reg(context) = *(WORD *)addr;
 229         break;
 230     case 4:
 231         if (long_op) ESP_reg(context) = *(DWORD *)addr;
 232         else SP_reg(context) = *(WORD *)addr;
 233         break;
 234     case 5:
 235         if (long_op) EBP_reg(context) = *(DWORD *)addr;
 236         else BP_reg(context) = *(WORD *)addr;
 237         break;
 238     case 6:
 239         if (long_op) ESI_reg(context) = *(DWORD *)addr;
 240         else SI_reg(context) = *(WORD *)addr;
 241         break;
 242     case 7:
 243         if (long_op) EDI_reg(context) = *(DWORD *)addr;
 244         else DI_reg(context) = *(WORD *)addr;
 245         break;
 246     }
 247
 248     /* Store the correct segment in the segment register */
 249
 250     switch(*instr)
 251     {
 252     case 0xc4: ES_reg(context) = seg; break;  /* les */
 253     case 0xc5: DS_reg(context) = seg; break;  /* lds */
 254     case 0x0f: switch(instr[1])
 255                {
 256                case 0xb2: SS_reg(context) = seg; break;  /* lss */
 257 #ifdef FS_reg
 258                case 0xb4: FS_reg(context) = seg; break;  /* lfs */
 259 #endif
 260 #ifdef GS_reg
 261                case 0xb5: GS_reg(context) = seg; break;  /* lgs */
 262 #endif
 263                }
 264                break;
 265     }
 266
 267     /* Add the opcode size to the total length */
 268
 269     *len += 1 + (*instr == 0x0f);
 270     return TRUE;
 271 }
 272
 273
 274 /***********************************************************************
 275  *           INSTR_EmulateInstruction
 276  *
 277  * Emulate a priviledged instruction. Returns TRUE if emulation successful.
 278  */
 279 BOOL INSTR_EmulateInstruction( struct sigcontext_struct *context )
 280 {
 281     int prefix, segprefix, prefixlen, len, repX, long_op, long_addr;
 282     BYTE *instr;
 283
 284     long_op = long_addr = (GET_SEL_FLAGS(CS_reg(context)) & LDT_FLAGS_32BIT) != 0;
 285     instr = (BYTE *) PTR_SEG_OFF_TO_LIN( CS_reg(context), EIP_reg(context) );
 286
 287     /* First handle any possible prefix */
 288
 289     segprefix = -1;  /* no prefix */
 290     prefix = 1;
 291     repX = 0;
 292     prefixlen = 0;
 293     while(prefix)
 294     {
 295         switch(*instr)
 296         {
 297         case 0x2e:
 298             segprefix = CS_reg(context);
 299             break;
 300         case 0x36:
 301             segprefix = SS_reg(context);
 302             break;
 303         case 0x3e:
 304             segprefix = DS_reg(context);
 305             break;
 306         case 0x26:
 307             segprefix = ES_reg(context);
 308             break;
 309 #ifdef FS_reg
 310         case 0x64:
 311             segprefix = FS_reg(context);
 312             break;
 313 #endif
 314 #ifdef GS_reg
 315         case 0x65:
 316             segprefix = GS_reg(context);
 317             break;
 318 #endif
 319         case 0x66:
 320             long_op = !long_op;  /* opcode size prefix */
 321             break;
 322         case 0x67:
 323             long_addr = !long_addr;  /* addr size prefix */
 324             break;
 325         case 0xf0:  /* lock */
 326             break;
 327         case 0xf2:  /* repne */
 328             repX = 1;
 329             break;
 330         case 0xf3:  /* repe */
 331             repX = 2;
 332             break;
 333         default:
 334             prefix = 0;  /* no more prefixes */
 335             break;
 336         }
 337         if (prefix)
 338         {
 339             instr++;
 340             prefixlen++;
 341         }
 342     }
 343
 344     /* Now look at the actual instruction */
 345
 346     switch(*instr)
 347     {
 348         case 0x07: /* pop es */
 349         case 0x17: /* pop ss */
 350         case 0x1f: /* pop ds */
 351             {
 352                 WORD seg = *(WORD *)STACK_PTR( context );
 353                 if ((seg = INSTR_ReplaceSelector( context, seg )) != 0)
 354                 {
 355                     switch(*instr)
 356                     {
 357                     case 0x07: ES_reg(context) = seg; break;
 358                     case 0x17: SS_reg(context) = seg; break;
 359                     case 0x1f: DS_reg(context) = seg; break;
 360                     }
 361                     STACK_reg(context) += long_op ? 4 : 2;
 362                     EIP_reg(context) += prefixlen + 1;
 363                     return TRUE;
 364                 }
 365             }
 366             break;  /* Unable to emulate it */
 367
 368         case 0x0f: /* extended instruction */
 369             switch(instr[1])
 370             {
 371 #ifdef FS_reg
 372             case 0xa1: /* pop fs */
 373                 {
 374                     WORD seg = *(WORD *)STACK_PTR( context );
 375                     if ((seg = INSTR_ReplaceSelector( context, seg )) != 0)
 376                     {
 377                         FS_reg(context) = seg;
 378                         STACK_reg(context) += long_op ? 4 : 2;
 379                         EIP_reg(context) += prefixlen + 2;
 380                         return TRUE;
 381                     }
 382                 }
 383                 break;
 384 #endif  /* FS_reg */
 385
 386 #ifdef GS_reg
 387             case 0xa9: /* pop gs */
 388                 {
 389                     WORD seg = *(WORD *)STACK_PTR( context );
 390                     if ((seg = INSTR_ReplaceSelector( context, seg )) != 0)
 391                     {
 392                         GS_reg(context) = seg;
 393                         STACK_reg(context) += long_op ? 4 : 2;
 394                         EIP_reg(context) += prefixlen + 2;
 395                         return TRUE;
 396                     }
 397                 }
 398                 break;
 399 #endif  /* GS_reg */
 400
 401             case 0xb2: /* lss addr,reg */
 402 #ifdef FS_reg
 403             case 0xb4: /* lfs addr,reg */
 404 #endif
 405 #ifdef GS_reg
 406             case 0xb5: /* lgs addr,reg */
 407 #endif
 408                 if (INSTR_EmulateLDS( context, instr, long_op,
 409                                       long_addr, segprefix, &len ))
 410                 {
 411                     EIP_reg(context) += prefixlen + len;
 412                     return TRUE;
 413                 }
 414                 break;
 415             }
 416             break;  /* Unable to emulate it */
 417
 418         case 0x6c: /* insb     */
 419         case 0x6d: /* insw/d   */
 420         case 0x6e: /* outsb    */
 421         case 0x6f: /* outsw/d  */
 422             {
 423               int typ = *instr;  /* Just in case it's overwritten.  */
 424               int outp = (typ >= 0x6e);
 425               unsigned long count = repX ?
 426                           (long_addr ? ECX_reg(context) : CX_reg(context)) : 1;
 427               int opsize = (typ & 1) ? (long_op ? 4 : 2) : 1;
 428               int step = (EFL_reg(context) & 0x400) ? -opsize : +opsize;
 429               int seg = outp ? (segprefix >= 0 ? segprefix : DS_reg(context))
 430                              : ES_reg(context);  /* FIXME: is this right? */
 431
 432               if (outp)
 433                 /* FIXME: Check segment readable.  */
 434                 (void)0;
 435               else
 436                 /* FIXME: Check segment writeable.  */
 437                 (void)0;
 438
 439               if (repX)
 440                 if (long_addr)
 441                   ECX_reg(context) = 0;
 442                 else
 443                   CX_reg(context) = 0;
 444
 445               while (count-- > 0)
 446                 {
 447                   void *data;
 448                   if (outp)
 449                   {
 450                       data = PTR_SEG_OFF_TO_LIN (seg,
 451                                long_addr ? ESI_reg(context) : SI_reg(context));
 452                       if (long_addr) ESI_reg(context) += step;
 453                       else SI_reg(context) += step;
 454                   }
 455                   else
 456                   {
 457                       data = PTR_SEG_OFF_TO_LIN (seg,
 458                                long_addr ? EDI_reg(context) : DI_reg(context));
 459                       if (long_addr) EDI_reg(context) += step;
 460                       else DI_reg(context) += step;
 461                   }
 462
 463                   switch (typ)
 464                   {
 465                     case 0x6c:
 466                       *((BYTE *)data) = inport( DX_reg(context), 1);
 467                       break;
 468                     case 0x6d:
 469                       if (long_op)
 470                         *((DWORD *)data) = inport( DX_reg(context), 4);
 471                       else
 472                         *((WORD *)data) = inport( DX_reg(context), 2);
 473                       break;
 474                     case 0x6e:
 475                       outport( DX_reg(context), 1, *((BYTE *)data));
 476                       break;
 477                     case 0x6f:
 478                       if (long_op)
 479                         outport( DX_reg(context), 4, *((DWORD *)data));
 480                       else
 481                         outport( DX_reg(context), 2, *((WORD *)data));
 482                       break;
 483                     }
 484                 }
 485               EIP_reg(context) += prefixlen + 1;
 486             }
 487             return TRUE;
 488
 489         case 0x8e: /* mov XX,segment_reg */
 490             {
 491                 WORD seg = *(WORD *)INSTR_GetOperandAddr( context, instr + 1,
 492                                                   long_addr, segprefix, &len );
 493                 if (!(seg = INSTR_ReplaceSelector( context, seg )))
 494                     break;  /* Unable to emulate it */
 495
 496                 switch((instr[1] >> 3) & 7)
 497                 {
 498                 case 0:
 499                     ES_reg(context) = seg;
 500                     EIP_reg(context) += prefixlen + len + 1;
 501                     return TRUE;
 502                 case 1:  /* cs */
 503                     break;
 504                 case 2:
 505                     SS_reg(context) = seg;
 506                     EIP_reg(context) += prefixlen + len + 1;
 507                     return TRUE;
 508                 case 3:
 509                     DS_reg(context) = seg;
 510                     EIP_reg(context) += prefixlen + len + 1;
 511                     return TRUE;
 512                 case 4:
 513 #ifdef FS_reg
 514                     FS_reg(context) = seg;
 515                     EIP_reg(context) += prefixlen + len + 1;
 516                     return TRUE;
 517 #endif
 518                 case 5:
 519 #ifdef GS_reg
 520                     GS_reg(context) = seg;
 521                     EIP_reg(context) += prefixlen + len + 1;
 522                     return TRUE;
 523 #endif
 524                 case 6:  /* unused */
 525                 case 7:  /* unused */
 526                     break;
 527                 }
 528             }
 529             break;  /* Unable to emulate it */
 530
 531         case 0xc4: /* les addr,reg */
 532         case 0xc5: /* lds addr,reg */
 533             if (INSTR_EmulateLDS( context, instr, long_op,
 534                                   long_addr, segprefix, &len ))
 535             {
 536                 EIP_reg(context) += prefixlen + len;
 537                 return TRUE;
 538             }
 539             break;  /* Unable to emulate it */
 540
 541         case 0xcd: /* int <XX> */
 542             if (long_op)
 543             {
 544                 fprintf(stderr, "int xx from 32-bit code is not supported.\n");
 545                 break;  /* Unable to emulate it */
 546             }
 547             else
 548             {
 549                 SEGPTR addr = INT_GetHandler( instr[1] );
 550                 WORD *stack = (WORD *)STACK_PTR( context );
 551                 /* Push the flags and return address on the stack */
 552                 *(--stack) = FL_reg(context);
 553                 *(--stack) = CS_reg(context);
 554                 *(--stack) = IP_reg(context) + prefixlen + 2;
 555                 STACK_reg(context) -= 3 * sizeof(WORD);
 556                 /* Jump to the interrupt handler */
 557                 CS_reg(context)  = HIWORD(addr);
 558                 EIP_reg(context) = LOWORD(addr);
 559             }
 560             return TRUE;
 561
 562         case 0xcf: /* iret */
 563             if (long_op)
 564             {
 565                 DWORD *stack = (DWORD *)STACK_PTR( context );
 566                 EIP_reg(context) = *stack++;
 567                 CS_reg(context)  = *stack++;
 568                 EFL_reg(context) = *stack;
 569                 STACK_reg(context) += 3*sizeof(DWORD);  /* Pop the return address and flags */
 570             }
 571             else
 572             {
 573                 WORD *stack = (WORD *)STACK_PTR( context );
 574                 EIP_reg(context) = *stack++;
 575                 CS_reg(context)  = *stack++;
 576                 FL_reg(context)  = *stack;
 577                 STACK_reg(context) += 3*sizeof(WORD);  /* Pop the return address and flags */
 578             }
 579             return TRUE;
 580
 581         case 0xe4: /* inb al,XX */
 582             AL_reg(context) = inport( instr[1], 1 );
 583             EIP_reg(context) += prefixlen + 2;
 584             return TRUE;
 585
 586         case 0xe5: /* in (e)ax,XX */
 587             if (long_op) EAX_reg(context) = inport( instr[1], 4 );
 588             else AX_reg(context) = inport( instr[1], 2 );
 589             EIP_reg(context) += prefixlen + 2;
 590             return TRUE;
 591
 592         case 0xe6: /* outb XX,al */
 593             outport( instr[1], 1, AL_reg(context) );
 594             EIP_reg(context) += prefixlen + 2;
 595             return TRUE;
 596
 597         case 0xe7: /* out XX,(e)ax */
 598             if (long_op) outport( instr[1], 4, EAX_reg(context) );
 599             else outport( instr[1], 2, AX_reg(context) );
 600             EIP_reg(context) += prefixlen + 2;
 601             return TRUE;
 602
 603         case 0xec: /* inb al,dx */
 604             AL_reg(context) = inport( DX_reg(context), 1 );
 605             EIP_reg(context) += prefixlen + 1;
 606             return TRUE;
 607
 608         case 0xed: /* in (e)ax,dx */
 609             if (long_op) EAX_reg(context) = inport( DX_reg(context), 4 );
 610             else AX_reg(context) = inport( DX_reg(context), 2 );
 611             EIP_reg(context) += prefixlen + 1;
 612             return TRUE;
 613
 614         case 0xee: /* outb dx,al */
 615             outport( DX_reg(context), 1, AL_reg(context) );
 616             EIP_reg(context) += prefixlen + 1;
 617             return TRUE;
 618
 619         case 0xef: /* out dx,(e)ax */
 620             if (long_op) outport( DX_reg(context), 4, EAX_reg(context) );
 621             else outport( DX_reg(context), 2, AX_reg(context) );
 622             EIP_reg(context) += prefixlen + 1;
 623             return TRUE;
 624
 625         case 0xfa: /* cli, ignored */
 626             EIP_reg(context) += prefixlen + 1;
 627             return TRUE;
 628
 629         case 0xfb: /* sti, ignored */
 630             EIP_reg(context) += prefixlen + 1;
 631             return TRUE;
 632     }
 633     fprintf(stderr, "Unexpected Windows program segfault"
 634                     " - opcode = %x\n", *instr);
 635     return FALSE;  /* Unable to emulate it */
 636 }