dlls/winedos/int31.c

   1 /*
   2  * DPMI 0.9 emulation
   3  *
   4  * Copyright 1995 Alexandre Julliard
   5  */
   6
   7 #include "config.h"
   8
   9 #include "windef.h"
  10 #include "wine/winbase16.h"
  11 #include "miscemu.h"
  12 #include "task.h"
  13 #include "msdos.h"
  14 #include "dosexe.h"
  15
  16 #include "debugtools.h"
  17
  18 DEFAULT_DEBUG_CHANNEL(int31);
  19
  20 /* Structure for real-mode callbacks */
  21 typedef struct
  22 {
  23     DWORD edi;
  24     DWORD esi;
  25     DWORD ebp;
  26     DWORD reserved;
  27     DWORD ebx;
  28     DWORD edx;
  29     DWORD ecx;
  30     DWORD eax;
  31     WORD  fl;
  32     WORD  es;
  33     WORD  ds;
  34     WORD  fs;
  35     WORD  gs;
  36     WORD  ip;
  37     WORD  cs;
  38     WORD  sp;
  39     WORD  ss;
  40 } REALMODECALL;
  41
  42 typedef struct tagRMCB {
  43     DWORD address;
  44     DWORD proc_ofs,proc_sel;
  45     DWORD regs_ofs,regs_sel;
  46     struct tagRMCB *next;
  47 } RMCB;
  48
  49 static RMCB *FirstRMCB = NULL;
  50 static WORD dpmi_flag;
  51
  52 /**********************************************************************
  53  *          INT_GetRealModeContext
  54  */
  55 static void INT_GetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
  56 {
  57     context->Eax    = call->eax;
  58     context->Ebx    = call->ebx;
  59     context->Ecx    = call->ecx;
  60     context->Edx    = call->edx;
  61     context->Esi    = call->esi;
  62     context->Edi    = call->edi;
  63     context->Ebp    = call->ebp;
  64     context->EFlags = call->fl | V86_FLAG;
  65     context->Eip    = call->ip;
  66     context->Esp    = call->sp;
  67     context->SegCs  = call->cs;
  68     context->SegDs  = call->ds;
  69     context->SegEs  = call->es;
  70     context->SegFs  = call->fs;
  71     context->SegGs  = call->gs;
  72     context->SegSs  = call->ss;
  73 }
  74
  75
  76 /**********************************************************************
  77  *          INT_SetRealModeContext
  78  */
  79 static void INT_SetRealModeContext( REALMODECALL *call, CONTEXT86 *context )
  80 {
  81     call->eax = context->Eax;
  82     call->ebx = context->Ebx;
  83     call->ecx = context->Ecx;
  84     call->edx = context->Edx;
  85     call->esi = context->Esi;
  86     call->edi = context->Edi;
  87     call->ebp = context->Ebp;
  88     call->fl  = LOWORD(context->EFlags);
  89     call->ip  = LOWORD(context->Eip);
  90     call->sp  = LOWORD(context->Esp);
  91     call->cs  = context->SegCs;
  92     call->ds  = context->SegDs;
  93     call->es  = context->SegEs;
  94     call->fs  = context->SegFs;
  95     call->gs  = context->SegGs;
  96     call->ss  = context->SegSs;
  97 }
  98
  99
 100 #ifdef __i386__
 101
 102 void DPMI_CallRMCB32(RMCB *rmcb, UINT16 ss, DWORD esp, UINT16*es, DWORD*edi)
 103 #if 0 /* original code, which early gccs puke on */
 104 {
 105     int _clobber;
 106     __asm__ __volatile__(
 107         "pushl %%ebp\n"
 108         "pushl %%ebx\n"
 109         "pushl %%es\n"
 110         "pushl %%ds\n"
 111         "pushfl\n"
 112         "mov %7,%%es\n"
 113         "mov %5,%%ds\n"
 114         ".byte 0x36, 0xff, 0x18\n" /* lcall *%ss:(%eax) */
 115         "popl %%ds\n"
 116         "mov %%es,%0\n"
 117         "popl %%es\n"
 118         "popl %%ebx\n"
 119         "popl %%ebp\n"
 120     : "=d" (*es), "=D" (*edi), "=S" (_clobber), "=a" (_clobber), "=c" (_clobber)
 121     : "0" (ss), "2" (esp),
 122       "4" (rmcb->regs_sel), "1" (rmcb->regs_ofs),
 123       "3" (&rmcb->proc_ofs) );
 124 }
 125 #else /* code generated by a gcc new enough */
 126 ;
 127 __ASM_GLOBAL_FUNC(DPMI_CallRMCB32,
 128     "pushl %ebp\n\t"
 129     "movl %esp,%ebp\n\t"
 130     "pushl %edi\n\t"
 131     "pushl %esi\n\t"
 132     "movl 0x8(%ebp),%eax\n\t"
 133     "movl 0x10(%ebp),%esi\n\t"
 134     "movl 0xc(%ebp),%edx\n\t"
 135     "movl 0x10(%eax),%ecx\n\t"
 136     "movl 0xc(%eax),%edi\n\t"
 137     "addl $0x4,%eax\n\t"
 138     "pushl %ebp\n\t"
 139     "pushl %ebx\n\t"
 140     "pushl %es\n\t"
 141     "pushl %ds\n\t"
 142     "pushfl\n\t"
 143     "mov %cx,%es\n\t"
 144     "mov %dx,%ds\n\t"
 145     ".byte 0x36, 0xff, 0x18\n\t" /* lcall *%ss:(%eax) */
 146     "popl %ds\n\t"
 147     "mov %es,%dx\n\t"
 148     "popl %es\n\t"
 149     "popl %ebx\n\t"
 150     "popl %ebp\n\t"
 151     "movl 0x14(%ebp),%eax\n\t"
 152     "movw %dx,(%eax)\n\t"
 153     "movl 0x18(%ebp),%edx\n\t"
 154     "movl %edi,(%edx)\n\t"
 155     "popl %esi\n\t"
 156     "popl %edi\n\t"
 157     "leave\n\t"
 158     "ret")
 159 #endif
 160
 161 #endif /* __i386__ */
 162
 163 /**********************************************************************
 164  *          DPMI_CallRMCBProc
 165  *
 166  * This routine does the hard work of calling a callback procedure.
 167  */
 168 static void DPMI_CallRMCBProc( CONTEXT86 *context, RMCB *rmcb, WORD flag )
 169 {
 170     if (IS_SELECTOR_SYSTEM( rmcb->proc_sel )) {
 171         /* Wine-internal RMCB, call directly */
 172         ((RMCBPROC)rmcb->proc_ofs)(context);
 173     } else {
 174 #ifdef __i386__
 175         UINT16 ss,es;
 176         DWORD esp,edi;
 177
 178         INT_SetRealModeContext(MapSL(MAKESEGPTR( rmcb->regs_sel, rmcb->regs_ofs )), context);
 179         ss = SELECTOR_AllocBlock( (void *)(context->SegSs<<4), 0x10000, WINE_LDT_FLAGS_DATA );
 180         esp = context->Esp;
 181
 182         FIXME("untested!\n");
 183
 184         /* The called proc ends with an IRET, and takes these parameters:
 185          * DS:ESI = pointer to real-mode SS:SP
 186          * ES:EDI = pointer to real-mode call structure
 187          * It returns:
 188          * ES:EDI = pointer to real-mode call structure (may be a copy)
 189          * It is the proc's responsibility to change the return CS:IP in the
 190          * real-mode call structure. */
 191         if (flag & 1) {
 192             /* 32-bit DPMI client */
 193             DPMI_CallRMCB32(rmcb, ss, esp, &es, &edi);
 194         } else {
 195             /* 16-bit DPMI client */
 196             CONTEXT86 ctx = *context;
 197             ctx.SegCs = rmcb->proc_sel;
 198             ctx.Eip   = rmcb->proc_ofs;
 199             ctx.SegDs = ss;
 200             ctx.Esi   = esp;
 201             ctx.SegEs = rmcb->regs_sel;
 202             ctx.Edi   = rmcb->regs_ofs;
 203             /* FIXME: I'm pretty sure this isn't right - should push flags first */
 204             wine_call_to_16_regs_short(&ctx, 0);
 205             es = ctx.SegEs;
 206             edi = ctx.Edi;
 207         }
 208         FreeSelector16(ss);
 209         INT_GetRealModeContext( MapSL( MAKESEGPTR( es, edi )), context);
 210 #else
 211         ERR("RMCBs only implemented for i386\n");
 212 #endif
 213     }
 214 }
 215
 216
 217 /**********************************************************************
 218  *          DPMI_CallRMProc
 219  *
 220  * This routine does the hard work of calling a real mode procedure.
 221  */
 222 int DPMI_CallRMProc( CONTEXT86 *context, LPWORD stack, int args, int iret )
 223 {
 224     LPWORD stack16;
 225     LPVOID addr = NULL; /* avoid gcc warning */
 226     RMCB *CurrRMCB;
 227     int alloc = 0, already = 0;
 228     BYTE *code;
 229
 230     TRACE("EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
 231                  context->Eax, context->Ebx, context->Ecx, context->Edx );
 232     TRACE("ESI=%08lx EDI=%08lx ES=%04lx DS=%04lx CS:IP=%04lx:%04x, %d WORD arguments, %s\n",
 233                  context->Esi, context->Edi, context->SegEs, context->SegDs,
 234                  context->SegCs, LOWORD(context->Eip), args, iret?"IRET":"FAR" );
 235
 236 callrmproc_again:
 237
 238 /* there might be some code that just jumps to RMCBs or the like,
 239    in which case following the jumps here might get us to a shortcut */
 240     code = CTX_SEG_OFF_TO_LIN(context, context->SegCs, context->Eip);
 241     switch (*code) {
 242     case 0xe9: /* JMP NEAR */
 243       context->Eip += 3 + *(WORD *)(code+1);
 244       /* yeah, I know these gotos don't look good... */
 245       goto callrmproc_again;
 246     case 0xea: /* JMP FAR */
 247       context->Eip = *(WORD *)(code+1);
 248       context->SegCs = *(WORD *)(code+3);
 249       /* ...but since the label is there anyway... */
 250       goto callrmproc_again;
 251     case 0xeb: /* JMP SHORT */
 252       context->Eip += 2 + *(signed char *)(code+1);
 253       /* ...because of other gotos below, so... */
 254       goto callrmproc_again;
 255     }
 256
 257 /* shortcut for chaining to internal interrupt handlers */
 258     if ((context->SegCs == 0xF000) && iret)
 259     {
 260         DOSVM_RealModeInterrupt( LOWORD(context->Eip)/4, context);
 261         return 0;
 262     }
 263
 264 /* shortcut for RMCBs */
 265     CurrRMCB = FirstRMCB;
 266
 267     while (CurrRMCB && (HIWORD(CurrRMCB->address) != context->SegCs))
 268         CurrRMCB = CurrRMCB->next;
 269
 270     if (!CurrRMCB && !MZ_Current())
 271     {
 272         FIXME("DPMI real-mode call using DOS VM task system, not fully tested!\n");
 273         TRACE("creating VM86 task\n");
 274         MZ_AllocDPMITask();
 275     }
 276     if (!already) {
 277         if (!context->SegSs) {
 278             alloc = 1; /* allocate default stack */
 279             stack16 = addr = DOSMEM_GetBlock( 64, (UINT16 *)&(context->SegSs) );
 280             context->Esp = 64-2;
 281             stack16 += 32-1;
 282             if (!addr) {
 283                 ERR("could not allocate default stack\n");
 284                 return 1;
 285             }
 286         } else {
 287             stack16 = CTX_SEG_OFF_TO_LIN(context, context->SegSs, context->Esp);
 288         }
 289         context->Esp -= (args + (iret?1:0)) * sizeof(WORD);
 290         stack16 -= args;
 291         if (args) memcpy(stack16, stack, args*sizeof(WORD) );
 292         /* push flags if iret */
 293         if (iret) {
 294             stack16--; args++;
 295             *stack16 = LOWORD(context->EFlags);
 296         }
 297         /* push return address (return to interrupt wrapper) */
 298         *(--stack16) = DOSMEM_wrap_seg;
 299         *(--stack16) = 0;
 300         /* adjust stack */
 301         context->Esp -= 2*sizeof(WORD);
 302         already = 1;
 303     }
 304
 305     if (CurrRMCB) {
 306         /* RMCB call, invoke protected-mode handler directly */
 307         DPMI_CallRMCBProc(context, CurrRMCB, dpmi_flag);
 308         /* check if we returned to where we thought we would */
 309         if ((context->SegCs != DOSMEM_wrap_seg) ||
 310             (LOWORD(context->Eip) != 0)) {
 311             /* we need to continue at different address in real-mode space,
 312                so we need to set it all up for real mode again */
 313             goto callrmproc_again;
 314         }
 315     } else {
 316         TRACE("entering real mode...\n");
 317         DOSVM_Enter( context );
 318         TRACE("returned from real-mode call\n");
 319     }
 320     if (alloc) DOSMEM_FreeBlock( addr );
 321     return 0;
 322 }
 323
 324
 325 /**********************************************************************
 326  *          DOSVM_CallRMInt   (WINEDOS.@)
 327  */
 328 void WINAPI DOSVM_CallRMInt( CONTEXT86 *context )
 329 {
 330     CONTEXT86 realmode_ctx;
 331     FARPROC16 rm_int = DOSVM_GetRMHandler( BL_reg(context) );
 332     REALMODECALL *call = MapSL( MAKESEGPTR( context->SegEs, DI_reg(context) ));
 333     INT_GetRealModeContext( call, &realmode_ctx );
 334
 335     /* we need to check if a real-mode program has hooked the interrupt */
 336     if (HIWORD(rm_int)!=0xF000) {
 337         /* yup, which means we need to switch to real mode... */
 338         realmode_ctx.SegCs = HIWORD(rm_int);
 339         realmode_ctx.Eip   = LOWORD(rm_int);
 340         if (DPMI_CallRMProc( &realmode_ctx, NULL, 0, TRUE))
 341           SET_CFLAG(context);
 342     } else {
 343         RESET_CFLAG(context);
 344         /* use the IP we have instead of BL_reg, in case some apps
 345            decide to move interrupts around for whatever reason... */
 346         DOSVM_RealModeInterrupt( LOWORD(rm_int)/4, &realmode_ctx );
 347     }
 348     INT_SetRealModeContext( call, &realmode_ctx );
 349 }
 350
 351
 352 /**********************************************************************
 353  *          DOSVM_CallRMProc   (WINEDOS.@)
 354  */
 355 void WINAPI DOSVM_CallRMProc( CONTEXT86 *context, int iret )
 356 {
 357     REALMODECALL *p = MapSL( MAKESEGPTR( context->SegEs, DI_reg(context) ));
 358     CONTEXT86 context16;
 359
 360     TRACE("RealModeCall: EAX=%08lx EBX=%08lx ECX=%08lx EDX=%08lx\n",
 361           p->eax, p->ebx, p->ecx, p->edx);
 362     TRACE("              ESI=%08lx EDI=%08lx ES=%04x DS=%04x CS:IP=%04x:%04x, %d WORD arguments, %s\n",
 363           p->esi, p->edi, p->es, p->ds, p->cs, p->ip, CX_reg(context), iret?"IRET":"FAR" );
 364
 365     if (!(p->cs) && !(p->ip)) { /* remove this check
 366                                    if Int21/6501 case map function
 367                                    has been implemented */
 368         SET_CFLAG(context);
 369         return;
 370      }
 371     INT_GetRealModeContext(p, &context16);
 372     DPMI_CallRMProc( &context16, ((LPWORD)MapSL(MAKESEGPTR(context->SegSs, LOWORD(context->Esp))))+3,
 373                      CX_reg(context), iret );
 374     INT_SetRealModeContext(p, &context16);
 375 }
 376
 377
 378 /* (see dosmem.c, function DOSMEM_InitDPMI) */
 379 static void StartPM( CONTEXT86 *context )
 380 {
 381     UINT16 cs, ss, ds, es;
 382     CONTEXT86 pm_ctx;
 383     DWORD psp_ofs = (DWORD)(DOSVM_psp<<4);
 384     PDB16 *psp = (PDB16 *)psp_ofs;
 385     HANDLE16 env_seg = psp->environment;
 386     unsigned char selflags = WINE_LDT_FLAGS_DATA;
 387
 388     RESET_CFLAG(context);
 389     dpmi_flag = AX_reg(context);
 390 /* our mode switch wrapper have placed the desired CS into DX */
 391     cs = SELECTOR_AllocBlock( (void *)(DX_reg(context)<<4), 0x10000, WINE_LDT_FLAGS_CODE );
 392 /* due to a flaw in some CPUs (at least mine), it is best to mark stack segments as 32-bit if they
 393    can be used in 32-bit code. Otherwise, these CPUs may not set the high word of esp during a
 394    ring transition (from kernel code) to the 16-bit stack, and this causes trouble if executing
 395    32-bit code using this stack. */
 396     if (dpmi_flag & 1) selflags |= WINE_LDT_FLAGS_32BIT;
 397     ss = SELECTOR_AllocBlock( (void *)(context->SegSs<<4), 0x10000, selflags );
 398 /* do the same for the data segments, just in case */
 399     if (context->SegDs == context->SegSs) ds = ss;
 400     else ds = SELECTOR_AllocBlock( (void *)(context->SegDs<<4), 0x10000, selflags );
 401     es = SELECTOR_AllocBlock( psp, 0x100, selflags );
 402 /* convert environment pointer, as the spec says, but we're a bit lazy about the size here... */
 403     psp->environment = SELECTOR_AllocBlock( (void *)(env_seg<<4), 0x10000, WINE_LDT_FLAGS_DATA );
 404
 405     pm_ctx = *context;
 406     pm_ctx.SegCs = DOSMEM_dpmi_sel;
 407 /* our mode switch wrapper expects the new CS in DX, and the new SS in AX */
 408     pm_ctx.Eax   = ss;
 409     pm_ctx.Edx   = cs;
 410     pm_ctx.SegDs = ds;
 411     pm_ctx.SegEs = es;
 412     pm_ctx.SegFs = 0;
 413     pm_ctx.SegGs = 0;
 414
 415     TRACE("DOS program is now entering protected mode\n");
 416     wine_call_to_16_regs_short(&pm_ctx, 0);
 417
 418     /* in the current state of affairs, we won't ever actually return here... */
 419     /* we should have int21/ah=4c do it someday, though... */
 420
 421     FreeSelector16(psp->environment);
 422     psp->environment = env_seg;
 423     FreeSelector16(es);
 424     if (ds != ss) FreeSelector16(ds);
 425     FreeSelector16(ss);
 426     FreeSelector16(cs);
 427 }
 428
 429 static RMCB *DPMI_AllocRMCB( void )
 430 {
 431     RMCB *NewRMCB = HeapAlloc(GetProcessHeap(), 0, sizeof(RMCB));
 432     UINT16 uParagraph;
 433
 434     if (NewRMCB)
 435     {
 436         LPVOID RMCBmem = DOSMEM_GetBlock(4, &uParagraph);
 437         LPBYTE p = RMCBmem;
 438
 439         *p++ = 0xcd; /* RMCB: */
 440         *p++ = 0x31; /* int $0x31 */
 441 /* it is the called procedure's task to change the return CS:EIP
 442    the DPMI 0.9 spec states that if it doesn't, it will be called again */
 443         *p++ = 0xeb;
 444         *p++ = 0xfc; /* jmp RMCB */
 445         NewRMCB->address = MAKELONG(0, uParagraph);
 446         NewRMCB->next = FirstRMCB;
 447         FirstRMCB = NewRMCB;
 448     }
 449     return NewRMCB;
 450 }
 451
 452
 453 FARPROC16 WINAPI DPMI_AllocInternalRMCB( RMCBPROC proc )
 454 {
 455     RMCB *NewRMCB = DPMI_AllocRMCB();
 456
 457     if (NewRMCB) {
 458         NewRMCB->proc_ofs = (DWORD)proc;
 459         NewRMCB->proc_sel = 0;
 460         NewRMCB->regs_ofs = 0;
 461         NewRMCB->regs_sel = 0;
 462         return (FARPROC16)(NewRMCB->address);
 463     }
 464     return NULL;
 465 }
 466
 467
 468 static int DPMI_FreeRMCB( DWORD address )
 469 {
 470     RMCB *CurrRMCB = FirstRMCB;
 471     RMCB *PrevRMCB = NULL;
 472
 473     while (CurrRMCB && (CurrRMCB->address != address))
 474     {
 475         PrevRMCB = CurrRMCB;
 476         CurrRMCB = CurrRMCB->next;
 477     }
 478     if (CurrRMCB)
 479     {
 480         if (PrevRMCB)
 481         PrevRMCB->next = CurrRMCB->next;
 482             else
 483         FirstRMCB = CurrRMCB->next;
 484         DOSMEM_FreeBlock(DOSMEM_MapRealToLinear(CurrRMCB->address));
 485         HeapFree(GetProcessHeap(), 0, CurrRMCB);
 486         return 0;
 487     }
 488     return 1;
 489 }
 490
 491
 492 void WINAPI DPMI_FreeInternalRMCB( FARPROC16 proc )
 493 {
 494     DPMI_FreeRMCB( (DWORD)proc );
 495 }
 496
 497
 498 /* DPMI Raw Mode Switch handler */
 499
 500 #if 0
 501 void WINAPI DPMI_RawModeSwitch( SIGCONTEXT *context )
 502 {
 503   LPDOSTASK lpDosTask = MZ_Current();
 504   CONTEXT86 rm_ctx;
 505   int ret;
 506
 507   if (!lpDosTask) {
 508     /* we could probably start a DPMI-only dosmod task here, but I doubt
 509        anything other than real DOS apps want to call raw mode switch */
 510     ERR("attempting raw mode switch without DOS task!\n");
 511     ExitProcess(1);
 512   }
 513   /* initialize real-mode context as per spec */
 514   memset(&rm_ctx, 0, sizeof(rm_ctx));
 515   rm_ctx.SegDs  = AX_sig(context);
 516   rm_ctx.SegEs  = CX_sig(context);
 517   rm_ctx.SegSs  = DX_sig(context);
 518   rm_ctx.Esp    = EBX_sig(context);
 519   rm_ctx.SegCs  = SI_sig(context);
 520   rm_ctx.Eip    = EDI_sig(context);
 521   rm_ctx.Ebp    = EBP_sig(context);
 522   rm_ctx.SegFs  = 0;
 523   rm_ctx.SegGs  = 0;
 524   rm_ctx.EFlags = EFL_sig(context); /* at least we need the IF flag */
 525
 526   /* enter real mode again */
 527   TRACE("re-entering real mode at %04lx:%04lx\n",rm_ctx.SegCs,rm_ctx.Eip);
 528   ret = DOSVM_Enter( &rm_ctx );
 529   /* when the real-mode stuff call its mode switch address,
 530      DOSVM_Enter will return and we will continue here */
 531
 532   if (ret<0) {
 533     /* if the sync was lost, there's no way to recover */
 534     ExitProcess(1);
 535   }
 536
 537   /* alter protected-mode context as per spec */
 538   DS_sig(context)  = LOWORD(rm_ctx.Eax);
 539   ES_sig(context)  = LOWORD(rm_ctx.Ecx);
 540   SS_sig(context)  = LOWORD(rm_ctx.Edx);
 541   ESP_sig(context) = rm_ctx.Ebx;
 542   CS_sig(context)  = LOWORD(rm_ctx.Esi);
 543   EIP_sig(context) = rm_ctx.Edi;
 544   EBP_sig(context) = rm_ctx.Ebp;
 545   FS_sig(context) = 0;
 546   GS_sig(context) = 0;
 547
 548   /* Return to new address and hope that we didn't mess up */
 549   TRACE("re-entering protected mode at %04x:%08lx\n",
 550         CS_sig(context), EIP_sig(context));
 551 }
 552 #endif
 553
 554
 555 /**********************************************************************
 556  *          DOSVM_AllocRMCB   (WINEDOS.@)
 557  */
 558 void WINAPI DOSVM_AllocRMCB( CONTEXT86 *context )
 559 {
 560     RMCB *NewRMCB = DPMI_AllocRMCB();
 561
 562     TRACE("Function to call: %04x:%04x\n", (WORD)context->SegDs, SI_reg(context) );
 563
 564     if (NewRMCB)
 565     {
 566         /* FIXME: if 32-bit DPMI client, use ESI and EDI */
 567         NewRMCB->proc_ofs = LOWORD(context->Esi);
 568         NewRMCB->proc_sel = context->SegDs;
 569         NewRMCB->regs_ofs = LOWORD(context->Edi);
 570         NewRMCB->regs_sel = context->SegEs;
 571         SET_LOWORD( context->Ecx, HIWORD(NewRMCB->address) );
 572         SET_LOWORD( context->Edx, LOWORD(NewRMCB->address) );
 573     }
 574     else
 575     {
 576         SET_LOWORD( context->Eax, 0x8015 ); /* callback unavailable */
 577         SET_CFLAG(context);
 578     }
 579 }
 580
 581
 582 /**********************************************************************
 583  *          DOSVM_FreeRMCB   (WINEDOS.@)
 584  */
 585 void WINAPI DOSVM_FreeRMCB( CONTEXT86 *context )
 586 {
 587     FIXME("callback address: %04x:%04x\n",
 588           CX_reg(context), DX_reg(context));
 589
 590     if (DPMI_FreeRMCB(MAKELONG(DX_reg(context), CX_reg(context)))) {
 591         SET_LOWORD( context->Eax, 0x8024 ); /* invalid callback address */
 592         SET_CFLAG(context);
 593     }
 594 }
 595
 596
 597 /**********************************************************************
 598  *          DOSVM_Int31Handler
 599  *
 600  * Handler for real-mode int 31h (DPMI).
 601  */
 602 void WINAPI DOSVM_Int31Handler( CONTEXT86 *context )
 603 {
 604     /* check if it's our wrapper */
 605     TRACE("called from real mode\n");
 606     if (context->SegCs==DOSMEM_dpmi_seg) {
 607         /* This is the protected mode switch */
 608         StartPM(context);
 609         return;
 610     }
 611     else if (context->SegCs==DOSMEM_xms_seg)
 612     {
 613         /* This is the XMS driver entry point */
 614         XMS_Handler(context);
 615         return;
 616     }
 617     else
 618     {
 619         /* Check for RMCB */
 620         RMCB *CurrRMCB = FirstRMCB;
 621
 622         while (CurrRMCB && (HIWORD(CurrRMCB->address) != context->SegCs))
 623             CurrRMCB = CurrRMCB->next;
 624
 625         if (CurrRMCB) {
 626             /* RMCB call, propagate to protected-mode handler */
 627             DPMI_CallRMCBProc(context, CurrRMCB, dpmi_flag);
 628             return;
 629         }
 630     }
 631
 632     /* chain to protected mode handler */
 633     INT_Int31Handler( context );
 634 }