miscemu/instr.c

   1 /*
   2  * Emulation of priviledged instructions
   3  *
   4  * Copyright 1995 Alexandre Julliard
   5  */
   6
   7 #include "windows.h"
   8 #include "ldt.h"
   9 #include "global.h"
  10 #include "module.h"
  11 #include "dosexe.h"
  12 #include "miscemu.h"
  13 #include "sig_context.h"
  14 #include "selectors.h"
  15 #include "debug.h"
  16
  17
  18 #define IS_V86(context) (EFL_sig(context)&V86_FLAG)
  19 #define IS_SEL_32(context,seg) \
  20    (IS_V86(context) ? FALSE : IS_SELECTOR_32BIT(seg))
  21
  22 #define STACK_sig(context) \
  23    (IS_SEL_32(context,SS_sig(context)) ? ESP_sig(context) : SP_sig(context))
  24
  25 #define MAKE_PTR(seg,off) \
  26    (IS_SELECTOR_SYSTEM(seg) ? (void *)(off) : PTR_SEG_OFF_TO_LIN(seg,off))
  27
  28 #define MK_PTR(context,seg,off) \
  29    (IS_V86(context) ? DOSMEM_MapRealToLinear(MAKELONG(off,seg)) \
  30                     : MAKE_PTR(seg,off))
  31
  32 #define STACK_PTR(context) \
  33    (IS_V86(context) ? DOSMEM_MapRealToLinear(MAKELONG(SP_sig(context),SS_sig(context))) : \
  34     (IS_SELECTOR_SYSTEM(SS_sig(context)) ? (void *)ESP_sig(context) : \
  35      (PTR_SEG_OFF_TO_LIN(SS_sig(context),STACK_sig(context)))))
  36
  37 /* For invalid registers fixup */
  38 extern DWORD CallFrom16_Start,CallFrom16_End;
  39
  40
  41 /***********************************************************************
  42  *           INSTR_ReplaceSelector
  43  *
  44  * Try to replace an invalid selector by a valid one.
  45  * The only selector where it is allowed to do "mov ax,40;mov es,ax"
  46  * is the so called 'bimodal' selector 0x40, which points to the BIOS
  47  * data segment. Used by (at least) Borland products (and programs compiled
  48  * using Borland products).
  49  *
  50  * See Undocumented Windows, Chapter 5, __0040.
  51  */
  52 static BOOL32 INSTR_ReplaceSelector( SIGCONTEXT *context, WORD *sel )
  53 {
  54     if (IS_SELECTOR_SYSTEM(CS_sig(context)) &&
  55         (EIP_sig(context) >= (DWORD)&CallFrom16_Start) &&
  56         (EIP_sig(context) < (DWORD)&CallFrom16_End))
  57     {
  58         /* Saved selector may have become invalid when the relay code */
  59         /* tries to restore it. We simply clear it. */
  60         *sel = 0;
  61         return TRUE;
  62     }
  63     if (*sel == 0x40)
  64     {
  65         static WORD sys_timer = 0;
  66         if (!sys_timer)
  67             sys_timer = CreateSystemTimer( 55, (FARPROC16)DOSMEM_Tick );
  68         *sel = DOSMEM_BiosSeg;
  69         return TRUE;
  70     }
  71     return FALSE;  /* Can't replace selector, crashdump */
  72 }
  73
  74
  75 /***********************************************************************
  76  *           INSTR_GetOperandAddr
  77  *
  78  * Return the address of an instruction operand (from the mod/rm byte).
  79  */
  80 static BYTE *INSTR_GetOperandAddr( SIGCONTEXT *context, BYTE *instr,
  81                                    int long_addr, int segprefix, int *len )
  82 {
  83     int mod, rm, base, index = 0, ss = 0, seg = 0, off;
  84
  85 #define GET_VAL(val,type) \
  86     { *val = *(type *)instr; instr += sizeof(type); *len += sizeof(type); }
  87
  88     *len = 0;
  89     GET_VAL( &mod, BYTE );
  90     rm = mod & 7;
  91     mod >>= 6;
  92
  93     if (mod == 3)
  94     {
  95         switch(rm)
  96         {
  97         case 0: return (BYTE *)&EAX_sig(context);
  98         case 1: return (BYTE *)&ECX_sig(context);
  99         case 2: return (BYTE *)&EDX_sig(context);
 100         case 3: return (BYTE *)&EBX_sig(context);
 101         case 4: return (BYTE *)&ESP_sig(context);
 102         case 5: return (BYTE *)&EBP_sig(context);
 103         case 6: return (BYTE *)&ESI_sig(context);
 104         case 7: return (BYTE *)&EDI_sig(context);
 105         }
 106     }
 107
 108     if (long_addr)
 109     {
 110         if (rm == 4)
 111         {
 112             BYTE sib;
 113             GET_VAL( &sib, BYTE );
 114             rm = sib & 7;
 115             ss = sib >> 6;
 116             switch(sib >> 3)
 117             {
 118             case 0: index = EAX_sig(context); break;
 119             case 1: index = ECX_sig(context); break;
 120             case 2: index = EDX_sig(context); break;
 121             case 3: index = EBX_sig(context); break;
 122             case 4: index = 0; break;
 123             case 5: index = EBP_sig(context); break;
 124             case 6: index = ESI_sig(context); break;
 125             case 7: index = EDI_sig(context); break;
 126             }
 127         }
 128
 129         switch(rm)
 130         {
 131         case 0: base = EAX_sig(context); seg = DS_sig(context); break;
 132         case 1: base = ECX_sig(context); seg = DS_sig(context); break;
 133         case 2: base = EDX_sig(context); seg = DS_sig(context); break;
 134         case 3: base = EBX_sig(context); seg = DS_sig(context); break;
 135         case 4: base = ESP_sig(context); seg = SS_sig(context); break;
 136         case 5: base = EBP_sig(context); seg = SS_sig(context); break;
 137         case 6: base = ESI_sig(context); seg = DS_sig(context); break;
 138         case 7: base = EDI_sig(context); seg = DS_sig(context); break;
 139         }
 140         switch (mod)
 141         {
 142         case 0:
 143             if (rm == 5)  /* special case: ds:(disp32) */
 144             {
 145                 GET_VAL( &base, DWORD );
 146                 seg = DS_sig(context);
 147             }
 148             break;
 149
 150         case 1:  /* 8-bit disp */
 151             GET_VAL( &off, BYTE );
 152             base += (signed char)off;
 153             break;
 154
 155         case 2:  /* 32-bit disp */
 156             GET_VAL( &off, DWORD );
 157             base += (signed long)off;
 158             break;
 159         }
 160     }
 161     else  /* short address */
 162     {
 163         switch(rm)
 164         {
 165         case 0:  /* ds:(bx,si) */
 166             base = BX_sig(context) + SI_sig(context);
 167             seg  = DS_sig(context);
 168             break;
 169         case 1:  /* ds:(bx,di) */
 170             base = BX_sig(context) + DI_sig(context);
 171             seg  = DS_sig(context);
 172             break;
 173         case 2:  /* ss:(bp,si) */
 174             base = BP_sig(context) + SI_sig(context);
 175             seg  = SS_sig(context);
 176             break;
 177         case 3:  /* ss:(bp,di) */
 178             base = BP_sig(context) + DI_sig(context);
 179             seg  = SS_sig(context);
 180             break;
 181         case 4:  /* ds:(si) */
 182             base = SI_sig(context);
 183             seg  = DS_sig(context);
 184             break;
 185         case 5:  /* ds:(di) */
 186             base = DI_sig(context);
 187             seg  = DS_sig(context);
 188             break;
 189         case 6:  /* ss:(bp) */
 190             base = BP_sig(context);
 191             seg  = SS_sig(context);
 192             break;
 193         case 7:  /* ds:(bx) */
 194             base = BX_sig(context);
 195             seg  = DS_sig(context);
 196             break;
 197         }
 198
 199         switch(mod)
 200         {
 201         case 0:
 202             if (rm == 6)  /* special case: ds:(disp16) */
 203             {
 204                 GET_VAL( &base, WORD );
 205                 seg  = DS_sig(context);
 206             }
 207             break;
 208
 209         case 1:  /* 8-bit disp */
 210             GET_VAL( &off, BYTE );
 211             base += (signed char)off;
 212             break;
 213
 214         case 2:  /* 16-bit disp */
 215             GET_VAL( &off, WORD );
 216             base += (signed short)off;
 217             break;
 218         }
 219         base &= 0xffff;
 220     }
 221     if (segprefix != -1) seg = segprefix;
 222
 223     /* Make sure the segment and offset are valid */
 224     if (IS_SELECTOR_SYSTEM(seg)) return (BYTE *)(base + (index << ss));
 225     if (((seg & 7) != 7) || IS_SELECTOR_FREE(seg)) return NULL;
 226     if (GET_SEL_LIMIT(seg) < (base + (index << ss))) return NULL;
 227     return (BYTE *)PTR_SEG_OFF_TO_LIN( seg, (base + (index << ss)) );
 228 #undef GET_VAL
 229 }
 230
 231
 232 /***********************************************************************
 233  *           INSTR_EmulateLDS
 234  *
 235  * Emulate the LDS (and LES,LFS,etc.) instruction.
 236  */
 237 static BOOL32 INSTR_EmulateLDS( SIGCONTEXT *context, BYTE *instr, int long_op,
 238                                 int long_addr, int segprefix, int *len )
 239 {
 240     WORD seg;
 241     BYTE *regmodrm = instr + 1 + (*instr == 0x0f);
 242     BYTE *addr = INSTR_GetOperandAddr( context, regmodrm,
 243                                        long_addr, segprefix, len );
 244     if (!addr)
 245         return FALSE;  /* Unable to emulate it */
 246     seg = *(WORD *)(addr + (long_op ? 4 : 2));
 247
 248     if (!INSTR_ReplaceSelector( context, &seg ))
 249         return FALSE;  /* Unable to emulate it */
 250
 251     /* Now store the offset in the correct register */
 252
 253     switch((*regmodrm >> 3) & 7)
 254     {
 255     case 0:
 256         if (long_op) EAX_sig(context) = *(DWORD *)addr;
 257         else AX_sig(context) = *(WORD *)addr;
 258         break;
 259     case 1:
 260         if (long_op) ECX_sig(context) = *(DWORD *)addr;
 261         else CX_sig(context) = *(WORD *)addr;
 262         break;
 263     case 2:
 264         if (long_op) EDX_sig(context) = *(DWORD *)addr;
 265         else DX_sig(context) = *(WORD *)addr;
 266         break;
 267     case 3:
 268         if (long_op) EBX_sig(context) = *(DWORD *)addr;
 269         else BX_sig(context) = *(WORD *)addr;
 270         break;
 271     case 4:
 272         if (long_op) ESP_sig(context) = *(DWORD *)addr;
 273         else SP_sig(context) = *(WORD *)addr;
 274         break;
 275     case 5:
 276         if (long_op) EBP_sig(context) = *(DWORD *)addr;
 277         else BP_sig(context) = *(WORD *)addr;
 278         break;
 279     case 6:
 280         if (long_op) ESI_sig(context) = *(DWORD *)addr;
 281         else SI_sig(context) = *(WORD *)addr;
 282         break;
 283     case 7:
 284         if (long_op) EDI_sig(context) = *(DWORD *)addr;
 285         else DI_sig(context) = *(WORD *)addr;
 286         break;
 287     }
 288
 289     /* Store the correct segment in the segment register */
 290
 291     switch(*instr)
 292     {
 293     case 0xc4: ES_sig(context) = seg; break;  /* les */
 294     case 0xc5: DS_sig(context) = seg; break;  /* lds */
 295     case 0x0f: switch(instr[1])
 296                {
 297                case 0xb2: SS_sig(context) = seg; break;  /* lss */
 298 #ifdef FS_sig
 299                case 0xb4: FS_sig(context) = seg; break;  /* lfs */
 300 #endif
 301 #ifdef GS_sig
 302                case 0xb5: GS_sig(context) = seg; break;  /* lgs */
 303 #endif
 304                }
 305                break;
 306     }
 307
 308     /* Add the opcode size to the total length */
 309
 310     *len += 1 + (*instr == 0x0f);
 311     return TRUE;
 312 }
 313
 314
 315 /***********************************************************************
 316  *           INSTR_EmulateInstruction
 317  *
 318  * Emulate a priviledged instruction. Returns TRUE if emulation successful.
 319  */
 320 BOOL32 INSTR_EmulateInstruction( SIGCONTEXT *context )
 321 {
 322     int prefix, segprefix, prefixlen, len, repX, long_op, long_addr;
 323     SEGPTR gpHandler;
 324     BYTE *instr;
 325
 326     /* Check for page-fault */
 327
 328 #if defined(TRAP_sig) && defined(CR2_sig)
 329     if (TRAP_sig(context) == 0x0e
 330         && VIRTUAL_HandleFault( (LPVOID)CR2_sig(context) )) return TRUE;
 331 #endif
 332
 333     long_op = long_addr = IS_SEL_32(context,CS_sig(context));
 334     instr = (BYTE *)MK_PTR(context,CS_sig(context),EIP_sig(context));
 335     if (!instr) return FALSE;
 336
 337     /* First handle any possible prefix */
 338
 339     segprefix = -1;  /* no prefix */
 340     prefix = 1;
 341     repX = 0;
 342     prefixlen = 0;
 343     while(prefix)
 344     {
 345         switch(*instr)
 346         {
 347         case 0x2e:
 348             segprefix = CS_sig(context);
 349             break;
 350         case 0x36:
 351             segprefix = SS_sig(context);
 352             break;
 353         case 0x3e:
 354             segprefix = DS_sig(context);
 355             break;
 356         case 0x26:
 357             segprefix = ES_sig(context);
 358             break;
 359 #ifdef FS_sig
 360         case 0x64:
 361             segprefix = FS_sig(context);
 362             break;
 363 #endif
 364 #ifdef GS_sig
 365         case 0x65:
 366             segprefix = GS_sig(context);
 367             break;
 368 #endif
 369         case 0x66:
 370             long_op = !long_op;  /* opcode size prefix */
 371             break;
 372         case 0x67:
 373             long_addr = !long_addr;  /* addr size prefix */
 374             break;
 375         case 0xf0:  /* lock */
 376             break;
 377         case 0xf2:  /* repne */
 378             repX = 1;
 379             break;
 380         case 0xf3:  /* repe */
 381             repX = 2;
 382             break;
 383         default:
 384             prefix = 0;  /* no more prefixes */
 385             break;
 386         }
 387         if (prefix)
 388         {
 389             instr++;
 390             prefixlen++;
 391         }
 392     }
 393
 394     /* Now look at the actual instruction */
 395
 396     switch(*instr)
 397     {
 398         case 0x07: /* pop es */
 399         case 0x17: /* pop ss */
 400         case 0x1f: /* pop ds */
 401             {
 402                 WORD seg = *(WORD *)STACK_PTR( context );
 403                 if (INSTR_ReplaceSelector( context, &seg ))
 404                 {
 405                     switch(*instr)
 406                     {
 407                     case 0x07: ES_sig(context) = seg; break;
 408                     case 0x17: SS_sig(context) = seg; break;
 409                     case 0x1f: DS_sig(context) = seg; break;
 410                     }
 411                     STACK_sig(context) += long_op ? 4 : 2;
 412                     EIP_sig(context) += prefixlen + 1;
 413                     return TRUE;
 414                 }
 415             }
 416             break;  /* Unable to emulate it */
 417
 418         case 0x0f: /* extended instruction */
 419             switch(instr[1])
 420             {
 421             case 0x20: /* mov cr4, eax */
 422                 if (instr[2]!=0xe0)
 423                         break;
 424                 /* CR4 register . See linux/arch/i386/mm/init.c, X86_CR4_ defs
 425                  * bit 0: VME   Virtual Mode Exception ?
 426                  * bit 1: PVI   Protected mode Virtual Interrupt
 427                  * bit 2: TSD   Timestamp disable
 428                  * bit 3: DE    Debugging extensions
 429                  * bit 4: PSE   Page size extensions
 430                  * bit 5: PAE   Physical address extension
 431                  * bit 6: MCE   Machine check enable
 432                  * bit 7: PGE   Enable global pages
 433                  * bit 8: PCE   Enable performance counters at IPL3
 434                  */
 435                 fprintf(stderr,"mov cr4,eax at 0x%08lx\n",EIP_sig(context));
 436                 EAX_sig(context) = 0;
 437                 EIP_sig(context) += prefixlen+3;
 438                 return TRUE;
 439 #ifdef FS_sig
 440             case 0xa1: /* pop fs */
 441                 {
 442                     WORD seg = *(WORD *)STACK_PTR( context );
 443                     if (INSTR_ReplaceSelector( context, &seg ))
 444                     {
 445                         FS_sig(context) = seg;
 446                         STACK_sig(context) += long_op ? 4 : 2;
 447                         EIP_sig(context) += prefixlen + 2;
 448                         return TRUE;
 449                     }
 450                 }
 451                 break;
 452 #endif  /* FS_sig */
 453
 454 #ifdef GS_sig
 455             case 0xa9: /* pop gs */
 456                 {
 457                     WORD seg = *(WORD *)STACK_PTR( context );
 458                     if (INSTR_ReplaceSelector( context, &seg ))
 459                     {
 460                         GS_sig(context) = seg;
 461                         STACK_sig(context) += long_op ? 4 : 2;
 462                         EIP_sig(context) += prefixlen + 2;
 463                         return TRUE;
 464                     }
 465                 }
 466                 break;
 467 #endif  /* GS_sig */
 468
 469             case 0xb2: /* lss addr,reg */
 470 #ifdef FS_sig
 471             case 0xb4: /* lfs addr,reg */
 472 #endif
 473 #ifdef GS_sig
 474             case 0xb5: /* lgs addr,reg */
 475 #endif
 476                 if (INSTR_EmulateLDS( context, instr, long_op,
 477                                       long_addr, segprefix, &len ))
 478                 {
 479                     EIP_sig(context) += prefixlen + len;
 480                     return TRUE;
 481                 }
 482                 break;
 483             }
 484             break;  /* Unable to emulate it */
 485
 486         case 0x6c: /* insb     */
 487         case 0x6d: /* insw/d   */
 488         case 0x6e: /* outsb    */
 489         case 0x6f: /* outsw/d  */
 490             {
 491               int typ = *instr;  /* Just in case it's overwritten.  */
 492               int outp = (typ >= 0x6e);
 493               unsigned long count = repX ?
 494                           (long_addr ? ECX_sig(context) : CX_sig(context)) : 1;
 495               int opsize = (typ & 1) ? (long_op ? 4 : 2) : 1;
 496               int step = (EFL_sig(context) & 0x400) ? -opsize : +opsize;
 497               int seg = outp ? DS_sig(context) : ES_sig(context);  /* FIXME: is this right? */
 498
 499               if (outp)
 500                 /* FIXME: Check segment readable.  */
 501                 (void)0;
 502               else
 503                 /* FIXME: Check segment writeable.  */
 504                 (void)0;
 505
 506               if (repX)
 507               {
 508                 if (long_addr)
 509                   ECX_sig(context) = 0;
 510                 else
 511                   CX_sig(context) = 0;
 512               }
 513
 514               while (count-- > 0)
 515                 {
 516                   void *data;
 517                   if (outp)
 518                   {
 519                       data = MAKE_PTR(seg,
 520                                long_addr ? ESI_sig(context) : SI_sig(context));
 521                       if (long_addr) ESI_sig(context) += step;
 522                       else SI_sig(context) += step;
 523                   }
 524                   else
 525                   {
 526                       data = MAKE_PTR(seg,
 527                                long_addr ? EDI_sig(context) : DI_sig(context));
 528                       if (long_addr) EDI_sig(context) += step;
 529                       else DI_sig(context) += step;
 530                   }
 531
 532                   switch (typ)
 533                   {
 534                     case 0x6c:
 535                       *((BYTE *)data) = IO_inport( DX_sig(context), 1);
 536                       TRACE(io, "0x%x < %02x @ %04x:%04x\n", DX_sig(context),
 537                         *((BYTE *)data), CS_sig(context), IP_sig(context));
 538                       break;
 539                     case 0x6d:
 540                       if (long_op)
 541                       {
 542                         *((DWORD *)data) = IO_inport( DX_sig(context), 4);
 543                         TRACE(io, "0x%x < %08lx @ %04x:%04x\n", DX_sig(context),
 544                           *((DWORD *)data), CS_sig(context), IP_sig(context));
 545                       }
 546                       else
 547                       {
 548                         *((WORD *)data) = IO_inport( DX_sig(context), 2);
 549                         TRACE(io, "0x%x < %04x @ %04x:%04x\n", DX_sig(context),
 550                           *((WORD *)data), CS_sig(context), IP_sig(context));
 551                       }
 552                       break;
 553                     case 0x6e:
 554                         IO_outport( DX_sig(context), 1, *((BYTE *)data));
 555                         TRACE(io, "0x%x > %02x @ %04x:%04x\n", DX_sig(context),
 556                           *((BYTE *)data), CS_sig(context), IP_sig(context));
 557                         break;
 558                     case 0x6f:
 559                         if (long_op)
 560                         {
 561                             IO_outport( DX_sig(context), 4, *((DWORD *)data));
 562                             TRACE(io, "0x%x > %08lx @ %04x:%04x\n", DX_sig(context),
 563                               *((DWORD *)data), CS_sig(context), IP_sig(context));
 564                         }
 565                         else
 566                         {
 567                             IO_outport( DX_sig(context), 2, *((WORD *)data));
 568                             TRACE(io, "0x%x > %04x @ %04x:%04x\n", DX_sig(context),
 569                               *((WORD *)data), CS_sig(context), IP_sig(context));
 570                         }
 571                         break;
 572                     }
 573                 }
 574               EIP_sig(context) += prefixlen + 1;
 575             }
 576             return TRUE;
 577
 578         case 0x8e: /* mov XX,segment_reg */
 579             {
 580                 WORD seg;
 581                 BYTE *addr = INSTR_GetOperandAddr(context, instr + 1,
 582                                                   long_addr, segprefix, &len );
 583                 if (!addr)
 584                     break;  /* Unable to emulate it */
 585                 seg = *(WORD *)addr;
 586                 if (!INSTR_ReplaceSelector( context, &seg ))
 587                     break;  /* Unable to emulate it */
 588
 589                 switch((instr[1] >> 3) & 7)
 590                 {
 591                 case 0:
 592                     ES_sig(context) = seg;
 593                     EIP_sig(context) += prefixlen + len + 1;
 594                     return TRUE;
 595                 case 1:  /* cs */
 596                     break;
 597                 case 2:
 598                     SS_sig(context) = seg;
 599                     EIP_sig(context) += prefixlen + len + 1;
 600                     return TRUE;
 601                 case 3:
 602                     DS_sig(context) = seg;
 603                     EIP_sig(context) += prefixlen + len + 1;
 604                     return TRUE;
 605                 case 4:
 606 #ifdef FS_sig
 607                     FS_sig(context) = seg;
 608                     EIP_sig(context) += prefixlen + len + 1;
 609                     return TRUE;
 610 #endif
 611                 case 5:
 612 #ifdef GS_sig
 613                     GS_sig(context) = seg;
 614                     EIP_sig(context) += prefixlen + len + 1;
 615                     return TRUE;
 616 #endif
 617                 case 6:  /* unused */
 618                 case 7:  /* unused */
 619                     break;
 620                 }
 621             }
 622             break;  /* Unable to emulate it */
 623
 624         case 0xc4: /* les addr,reg */
 625         case 0xc5: /* lds addr,reg */
 626             if (INSTR_EmulateLDS( context, instr, long_op,
 627                                   long_addr, segprefix, &len ))
 628             {
 629                 EIP_sig(context) += prefixlen + len;
 630                 return TRUE;
 631             }
 632             break;  /* Unable to emulate it */
 633
 634         case 0xcd: /* int <XX> */
 635             if (long_op)
 636             {
 637                 ERR(int, "int xx from 32-bit code is not supported.\n");
 638                 break;  /* Unable to emulate it */
 639             }
 640             else
 641             {
 642                 FARPROC16 addr = INT_GetPMHandler( instr[1] );
 643                 WORD *stack = (WORD *)STACK_PTR( context );
 644                 /* Push the flags and return address on the stack */
 645                 *(--stack) = FL_sig(context);
 646                 *(--stack) = CS_sig(context);
 647                 *(--stack) = IP_sig(context) + prefixlen + 2;
 648                 STACK_sig(context) -= 3 * sizeof(WORD);
 649                 /* Jump to the interrupt handler */
 650                 CS_sig(context)  = HIWORD(addr);
 651                 EIP_sig(context) = LOWORD(addr);
 652             }
 653             return TRUE;
 654
 655         case 0xcf: /* iret */
 656             if (long_op)
 657             {
 658                 DWORD *stack = (DWORD *)STACK_PTR( context );
 659                 EIP_sig(context) = *stack++;
 660                 CS_sig(context)  = *stack++;
 661                 EFL_sig(context) = *stack;
 662                 STACK_sig(context) += 3*sizeof(DWORD);  /* Pop the return address and flags */
 663             }
 664             else
 665             {
 666                 WORD *stack = (WORD *)STACK_PTR( context );
 667                 EIP_sig(context) = *stack++;
 668                 CS_sig(context)  = *stack++;
 669                 FL_sig(context)  = *stack;
 670                 STACK_sig(context) += 3*sizeof(WORD);  /* Pop the return address and flags */
 671             }
 672             return TRUE;
 673
 674         case 0xe4: /* inb al,XX */
 675             AL_sig(context) = IO_inport( instr[1], 1 );
 676             TRACE(io, "0x%x < %02x @ %04x:%04x\n", instr[1],
 677                 AL_sig(context), CS_sig(context), IP_sig(context));
 678             EIP_sig(context) += prefixlen + 2;
 679             return TRUE;
 680
 681         case 0xe5: /* in (e)ax,XX */
 682             if (long_op)
 683             {
 684                 EAX_sig(context) = IO_inport( instr[1], 4 );
 685                 TRACE(io, "0x%x < %08lx @ %04x:%04x\n", instr[1],
 686                     EAX_sig(context), CS_sig(context), IP_sig(context));
 687             }
 688             else
 689             {
 690                 AX_sig(context) = IO_inport( instr[1], 2 );
 691                 TRACE(io, "0x%x < %04x @ %04x:%04x\n", instr[1],
 692                     AX_sig(context), CS_sig(context), IP_sig(context));
 693             }
 694             EIP_sig(context) += prefixlen + 2;
 695             return TRUE;
 696
 697         case 0xe6: /* outb XX,al */
 698             IO_outport( instr[1], 1, AL_sig(context) );
 699             TRACE(io, "0x%x > %02x @ %04x:%04x\n", instr[1],
 700                 AL_sig(context), CS_sig(context), IP_sig(context));
 701             EIP_sig(context) += prefixlen + 2;
 702             return TRUE;
 703
 704         case 0xe7: /* out XX,(e)ax */
 705             if (long_op)
 706             {
 707                 IO_outport( instr[1], 4, EAX_sig(context) );
 708                 TRACE(io, "0x%x > %08lx @ %04x:%04x\n", instr[1],
 709                     EAX_sig(context), CS_sig(context), IP_sig(context));
 710             }
 711             else
 712             {
 713                 IO_outport( instr[1], 2, AX_sig(context) );
 714                 TRACE(io, "0x%x > %04x @ %04x:%04x\n", instr[1],
 715                     AX_sig(context), CS_sig(context), IP_sig(context));
 716             }
 717             EIP_sig(context) += prefixlen + 2;
 718             return TRUE;
 719
 720         case 0xec: /* inb al,dx */
 721             AL_sig(context) = IO_inport( DX_sig(context), 1 );
 722             TRACE(io, "0x%x < %02x @ %04x:%04x\n", DX_sig(context),
 723                 AL_sig(context), CS_sig(context), IP_sig(context));
 724             EIP_sig(context) += prefixlen + 1;
 725             return TRUE;
 726
 727         case 0xed: /* in (e)ax,dx */
 728             if (long_op)
 729             {
 730                 EAX_sig(context) = IO_inport( DX_sig(context), 4 );
 731                 TRACE(io, "0x%x < %08lx @ %04x:%04x\n", DX_sig(context),
 732                     EAX_sig(context), CS_sig(context), IP_sig(context));
 733             }
 734             else
 735             {
 736                 AX_sig(context) = IO_inport( DX_sig(context), 2 );
 737                 TRACE(io, "0x%x < %04x @ %04x:%04x\n", DX_sig(context),
 738                     AX_sig(context), CS_sig(context), IP_sig(context));
 739             }
 740             EIP_sig(context) += prefixlen + 1;
 741             return TRUE;
 742
 743         case 0xee: /* outb dx,al */
 744             IO_outport( DX_sig(context), 1, AL_sig(context) );
 745             TRACE(io, "0x%x > %02x @ %04x:%04x\n", DX_sig(context),
 746                 AL_sig(context), CS_sig(context), IP_sig(context));
 747             EIP_sig(context) += prefixlen + 1;
 748             return TRUE;
 749
 750         case 0xef: /* out dx,(e)ax */
 751             if (long_op)
 752             {
 753                 IO_outport( DX_sig(context), 4, EAX_sig(context) );
 754                 TRACE(io, "0x%x > %08lx @ %04x:%04x\n", DX_sig(context),
 755                     EAX_sig(context), CS_sig(context), IP_sig(context));
 756             }
 757             else
 758             {
 759                 IO_outport( DX_sig(context), 2, AX_sig(context) );
 760                 TRACE(io, "0x%x > %04x @ %04x:%04x\n", DX_sig(context),
 761                     AX_sig(context), CS_sig(context), IP_sig(context));
 762             }
 763             EIP_sig(context) += prefixlen + 1;
 764             return TRUE;
 765
 766         case 0xfa: /* cli, ignored */
 767             EIP_sig(context) += prefixlen + 1;
 768             return TRUE;
 769
 770         case 0xfb: /* sti, ignored */
 771             EIP_sig(context) += prefixlen + 1;
 772             return TRUE;
 773     }
 774
 775
 776     /* Check for Win16 __GP handler */
 777     gpHandler = HasGPHandler( PTR_SEG_OFF_TO_SEGPTR( CS_sig(context),
 778                                                      EIP_sig(context) ) );
 779     if (gpHandler)
 780     {
 781         WORD *stack = (WORD *)STACK_PTR( context );
 782         *--stack = CS_sig(context);
 783         *--stack = EIP_sig(context);
 784         STACK_sig(context) -= 2*sizeof(WORD);
 785
 786         CS_sig(context) = SELECTOROF( gpHandler );
 787         EIP_sig(context) = OFFSETOF( gpHandler );
 788         return TRUE;
 789     }
 790
 791     MSG("Unexpected Windows program segfault"
 792                     " - opcode = %x\n", *instr);
 793     return FALSE;  /* Unable to emulate it */
 794 }