dlls/winedos/module.c

   1 /*
   2  * DOS (MZ) loader
   3  *
   4  * Copyright 1998 Ove Kåven
   5  *
   6  * This code hasn't been completely cleaned up yet.
   7  */
   8
   9 #include "config.h"
  10
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <errno.h>
  15 #include <fcntl.h>
  16 #include <signal.h>
  17 #include <unistd.h>
  18 #include <sys/types.h>
  19 #include <sys/stat.h>
  20 #include <sys/time.h>
  21 #include "windef.h"
  22 #include "wine/winbase16.h"
  23 #include "winerror.h"
  24 #include "module.h"
  25 #include "task.h"
  26 #include "file.h"
  27 #include "miscemu.h"
  28 #include "debugtools.h"
  29 #include "dosexe.h"
  30 #include "../../loader/dos/dosmod.h"
  31 #include "options.h"
  32 #include "vga.h"
  33
  34 DEFAULT_DEBUG_CHANNEL(module);
  35
  36 static LPDOSTASK dos_current;
  37
  38 #ifdef MZ_SUPPORTED
  39
  40 #ifdef HAVE_SYS_MMAN_H
  41 # include <sys/mman.h>
  42 #endif
  43
  44 /* define this to try mapping through /proc/pid/mem instead of a temp file,
  45    but Linus doesn't like mmapping /proc/pid/mem, so it doesn't work for me */
  46 #undef MZ_MAPSELF
  47
  48 #define BIOS_DATA_SEGMENT 0x40
  49 #define PSP_SIZE 0x10
  50
  51 #define SEG16(ptr,seg) ((LPVOID)((BYTE*)ptr+((DWORD)(seg)<<4)))
  52 #define SEGPTR16(ptr,segptr) ((LPVOID)((BYTE*)ptr+((DWORD)SELECTOROF(segptr)<<4)+OFFSETOF(segptr)))
  53
  54 /* structures for EXEC */
  55
  56 typedef struct {
  57   WORD env_seg;
  58   DWORD cmdline WINE_PACKED;
  59   DWORD fcb1 WINE_PACKED;
  60   DWORD fcb2 WINE_PACKED;
  61   WORD init_sp;
  62   WORD init_ss;
  63   WORD init_ip;
  64   WORD init_cs;
  65 } ExecBlock;
  66
  67 typedef struct {
  68   WORD load_seg;
  69   WORD rel_seg;
  70 } OverlayBlock;
  71
  72 /* global variables */
  73
  74 static WORD init_cs,init_ip,init_ss,init_sp;
  75 static char mm_name[128];
  76
  77 int read_pipe, write_pipe;
  78 HANDLE hReadPipe, hWritePipe;
  79 pid_t dosmod_pid;
  80
  81 static void MZ_Launch(void);
  82 static BOOL MZ_InitTask(void);
  83 static void MZ_KillTask(void);
  84
  85 static void MZ_CreatePSP( LPVOID lpPSP, WORD env, WORD par )
  86 {
  87   PDB16*psp=lpPSP;
  88
  89   psp->int20=0x20CD; /* int 20 */
  90   /* some programs use this to calculate how much memory they need */
  91   psp->nextParagraph=0x9FFF; /* FIXME: use a real value */
  92   /* FIXME: dispatcher */
  93   psp->savedint22 = INT_GetRMHandler(0x22);
  94   psp->savedint23 = INT_GetRMHandler(0x23);
  95   psp->savedint24 = INT_GetRMHandler(0x24);
  96   psp->parentPSP=par;
  97   psp->environment=env;
  98   /* FIXME: more PSP stuff */
  99 }
 100
 101 static void MZ_FillPSP( LPVOID lpPSP, LPCSTR cmdline )
 102 {
 103  PDB16*psp=lpPSP;
 104  const char*cmd=cmdline?strchr(cmdline,' '):NULL;
 105
 106  /* copy parameters */
 107  if (cmd) {
 108 #if 0
 109   /* command.com doesn't do this */
 110   while (*cmd == ' ') cmd++;
 111 #endif
 112   psp->cmdLine[0]=strlen(cmd);
 113   strcpy(psp->cmdLine+1,cmd);
 114   psp->cmdLine[psp->cmdLine[0]+1]='\r';
 115  } else psp->cmdLine[1]='\r';
 116  /* FIXME: more PSP stuff */
 117 }
 118
 119 /* default INT 08 handler: increases timer tick counter but not much more */
 120 static char int08[]={
 121  0xCD,0x1C,           /* int $0x1c */
 122  0x50,                /* pushw %ax */
 123  0x1E,                /* pushw %ds */
 124  0xB8,0x40,0x00,      /* movw $0x40,%ax */
 125  0x8E,0xD8,           /* movw %ax,%ds */
 126 #if 0
 127  0x83,0x06,0x6C,0x00,0x01, /* addw $1,(0x6c) */
 128  0x83,0x16,0x6E,0x00,0x00, /* adcw $0,(0x6e) */
 129 #else
 130  0x66,0xFF,0x06,0x6C,0x00, /* incl (0x6c) */
 131 #endif
 132  0xB0,0x20,           /* movb $0x20,%al */
 133  0xE6,0x20,           /* outb %al,$0x20 */
 134  0x1F,                /* popw %ax */
 135  0x58,                /* popw %ax */
 136  0xCF                 /* iret */
 137 };
 138
 139 static void MZ_InitHandlers(void)
 140 {
 141  WORD seg;
 142  LPBYTE start=DOSMEM_GetBlock(sizeof(int08),&seg);
 143  memcpy(start,int08,sizeof(int08));
 144 /* INT 08: point it at our tick-incrementing handler */
 145  ((SEGPTR*)0)[0x08]=MAKESEGPTR(seg,0);
 146 /* INT 1C: just point it to IRET, we don't want to handle it ourselves */
 147  ((SEGPTR*)0)[0x1C]=MAKESEGPTR(seg,sizeof(int08)-1);
 148 }
 149
 150 static WORD MZ_InitEnvironment( LPCSTR env, LPCSTR name )
 151 {
 152  unsigned sz=0;
 153  WORD seg;
 154  LPSTR envblk;
 155
 156  if (env) {
 157   /* get size of environment block */
 158   while (env[sz++]) sz+=strlen(env+sz)+1;
 159  } else sz++;
 160  /* allocate it */
 161  envblk=DOSMEM_GetBlock(sz+sizeof(WORD)+strlen(name)+1,&seg);
 162  /* fill it */
 163  if (env) {
 164   memcpy(envblk,env,sz);
 165  } else envblk[0]=0;
 166  /* DOS 3.x: the block contains 1 additional string */
 167  *(WORD*)(envblk+sz)=1;
 168  /* being the program name itself */
 169  strcpy(envblk+sz+sizeof(WORD),name);
 170  return seg;
 171 }
 172
 173 static BOOL MZ_InitMemory(void)
 174 {
 175     int mm_fd;
 176     void *img_base;
 177
 178     /* initialize the memory */
 179     TRACE("Initializing DOS memory structures\n");
 180     DOSMEM_Init(TRUE);
 181
 182     /* allocate 1MB+64K shared memory */
 183     tmpnam(mm_name);
 184     /* strcpy(mm_name,"/tmp/mydosimage"); */
 185     mm_fd = open(mm_name,O_RDWR|O_CREAT /* |O_TRUNC */,S_IRUSR|S_IWUSR);
 186     if (mm_fd < 0) ERR("file %s could not be opened\n",mm_name);
 187     /* fill the file with the DOS memory */
 188     if (write( mm_fd, NULL, 0x110000 ) != 0x110000) ERR("cannot write DOS mem\n");
 189     /* map it in */
 190     img_base = mmap(NULL,0x110000,PROT_READ|PROT_WRITE|PROT_EXEC,MAP_SHARED|MAP_FIXED,mm_fd,0);
 191     close( mm_fd );
 192
 193     if (img_base)
 194     {
 195         ERR("could not map shared memory, error=%s\n",strerror(errno));
 196         return FALSE;
 197     }
 198     MZ_InitHandlers();
 199     return TRUE;
 200 }
 201
 202 static BOOL MZ_DoLoadImage( HANDLE hFile, LPCSTR filename, OverlayBlock *oblk )
 203 {
 204   LPDOSTASK lpDosTask = dos_current;
 205   IMAGE_DOS_HEADER mz_header;
 206   DWORD image_start,image_size,min_size,max_size,avail;
 207   BYTE*psp_start,*load_start,*oldenv;
 208   int x, old_com=0, alloc;
 209   SEGPTR reloc;
 210   WORD env_seg, load_seg, rel_seg, oldpsp_seg;
 211   DWORD len;
 212
 213   if (lpDosTask) {
 214     /* DOS process already running, inherit from it */
 215     PDB16* par_psp = (PDB16*)((DWORD)lpDosTask->psp_seg << 4);
 216     alloc=0;
 217     oldenv = (LPBYTE)((DWORD)par_psp->environment << 4);
 218     oldpsp_seg = lpDosTask->psp_seg;
 219   } else {
 220     /* allocate new DOS process, inheriting from Wine environment */
 221     alloc=1;
 222     lpDosTask = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(DOSTASK));
 223     dos_current = lpDosTask;
 224     oldenv = GetEnvironmentStringsA();
 225     oldpsp_seg = 0;
 226   }
 227
 228  SetFilePointer(hFile,0,NULL,FILE_BEGIN);
 229  if (   !ReadFile(hFile,&mz_header,sizeof(mz_header),&len,NULL)
 230      || len != sizeof(mz_header)
 231      || mz_header.e_magic != IMAGE_DOS_SIGNATURE) {
 232   char *p = strrchr( filename, '.' );
 233   if (!p || strcasecmp( p, ".com" ))  /* check for .COM extension */
 234   {
 235       SetLastError(ERROR_BAD_FORMAT);
 236       goto load_error;
 237   }
 238   old_com=1; /* assume .COM file */
 239   image_start=0;
 240   image_size=GetFileSize(hFile,NULL);
 241   min_size=0x10000; max_size=0x100000;
 242   mz_header.e_crlc=0;
 243   mz_header.e_ss=0; mz_header.e_sp=0xFFFE;
 244   mz_header.e_cs=0; mz_header.e_ip=0x100;
 245  } else {
 246   /* calculate load size */
 247   image_start=mz_header.e_cparhdr<<4;
 248   image_size=mz_header.e_cp<<9; /* pages are 512 bytes */
 249   if ((mz_header.e_cblp!=0)&&(mz_header.e_cblp!=4)) image_size-=512-mz_header.e_cblp;
 250   image_size-=image_start;
 251   min_size=image_size+((DWORD)mz_header.e_minalloc<<4)+(PSP_SIZE<<4);
 252   max_size=image_size+((DWORD)mz_header.e_maxalloc<<4)+(PSP_SIZE<<4);
 253  }
 254
 255   if (alloc) MZ_InitMemory();
 256
 257   if (oblk) {
 258     /* load overlay into preallocated memory */
 259     load_seg=oblk->load_seg;
 260     rel_seg=oblk->rel_seg;
 261     load_start=(LPBYTE)((DWORD)load_seg<<4);
 262   } else {
 263     /* allocate environment block */
 264     env_seg=MZ_InitEnvironment(oldenv, filename);
 265
 266     /* allocate memory for the executable */
 267     TRACE("Allocating DOS memory (min=%ld, max=%ld)\n",min_size,max_size);
 268     avail=DOSMEM_Available();
 269     if (avail<min_size) {
 270       ERR("insufficient DOS memory\n");
 271       SetLastError(ERROR_NOT_ENOUGH_MEMORY);
 272       goto load_error;
 273     }
 274     if (avail>max_size) avail=max_size;
 275     psp_start=DOSMEM_GetBlock(avail,&lpDosTask->psp_seg);
 276     if (!psp_start) {
 277       ERR("error allocating DOS memory\n");
 278       SetLastError(ERROR_NOT_ENOUGH_MEMORY);
 279       goto load_error;
 280     }
 281     load_seg=lpDosTask->psp_seg+(old_com?0:PSP_SIZE);
 282     rel_seg=load_seg;
 283     load_start=psp_start+(PSP_SIZE<<4);
 284     MZ_CreatePSP(psp_start, env_seg, oldpsp_seg);
 285   }
 286
 287  /* load executable image */
 288  TRACE("loading DOS %s image, %08lx bytes\n",old_com?"COM":"EXE",image_size);
 289  SetFilePointer(hFile,image_start,NULL,FILE_BEGIN);
 290  if (!ReadFile(hFile,load_start,image_size,&len,NULL) || len != image_size) {
 291   SetLastError(ERROR_BAD_FORMAT);
 292   goto load_error;
 293  }
 294
 295  if (mz_header.e_crlc) {
 296   /* load relocation table */
 297   TRACE("loading DOS EXE relocation table, %d entries\n",mz_header.e_crlc);
 298   /* FIXME: is this too slow without read buffering? */
 299   SetFilePointer(hFile,mz_header.e_lfarlc,NULL,FILE_BEGIN);
 300   for (x=0; x<mz_header.e_crlc; x++) {
 301    if (!ReadFile(hFile,&reloc,sizeof(reloc),&len,NULL) || len != sizeof(reloc)) {
 302     SetLastError(ERROR_BAD_FORMAT);
 303     goto load_error;
 304    }
 305    *(WORD*)SEGPTR16(load_start,reloc)+=rel_seg;
 306   }
 307  }
 308
 309   if (!oblk) {
 310     init_cs = load_seg+mz_header.e_cs;
 311     init_ip = mz_header.e_ip;
 312     init_ss = load_seg+mz_header.e_ss;
 313     init_sp = mz_header.e_sp;
 314
 315     TRACE("entry point: %04x:%04x\n",init_cs,init_ip);
 316   }
 317
 318   if (alloc && !MZ_InitTask()) {
 319     MZ_KillTask();
 320     SetLastError(ERROR_GEN_FAILURE);
 321     return FALSE;
 322   }
 323
 324   return TRUE;
 325
 326 load_error:
 327   lpDosTask->psp_seg = oldpsp_seg;
 328   if (alloc) {
 329     dos_current = NULL;
 330     if (mm_name[0]!=0) unlink(mm_name);
 331   }
 332
 333   return FALSE;
 334 }
 335
 336 BOOL WINAPI MZ_LoadImage( LPCSTR cmdline )
 337 {
 338     HFILE hFile;
 339     char *name, buffer[MAX_PATH];
 340     LPCSTR p = strchr( cmdline, ' ' );
 341
 342     if (p)
 343     {
 344         if (!(name = HeapAlloc( GetProcessHeap(), 0, p - cmdline + 1 ))) return FALSE;
 345         memcpy( name, cmdline, p - cmdline );
 346         name[p - cmdline] = 0;
 347     }
 348     else name = (char *)cmdline;
 349
 350     if (!SearchPathA( NULL, name, ".exe", sizeof(buffer), buffer, NULL )) goto error;
 351     if ((hFile = CreateFileA( buffer, GENERIC_READ, FILE_SHARE_READ,
 352                               NULL, OPEN_EXISTING, 0, -1 )) == INVALID_HANDLE_VALUE)
 353         goto error;
 354     if (!MZ_DoLoadImage( hFile, buffer, NULL ))
 355     {
 356         CloseHandle( hFile );
 357         goto error;
 358     }
 359     MZ_Launch();
 360  error:
 361     if (name != cmdline) HeapFree( GetProcessHeap(), 0, name );
 362     return FALSE;
 363 }
 364
 365 BOOL WINAPI MZ_Exec( CONTEXT86 *context, LPCSTR filename, BYTE func, LPVOID paramblk )
 366 {
 367   /* this may only be called from existing DOS processes
 368    * (i.e. one DOS app spawning another) */
 369   /* FIXME: do we want to check binary type first, to check
 370    * whether it's a NE/PE executable? */
 371   LPDOSTASK lpDosTask = MZ_Current();
 372   HFILE hFile = CreateFileA( filename, GENERIC_READ, FILE_SHARE_READ,
 373                              NULL, OPEN_EXISTING, 0, -1);
 374   BOOL ret = FALSE;
 375   if (hFile == INVALID_HANDLE_VALUE) return FALSE;
 376   switch (func) {
 377   case 0: /* load and execute */
 378   case 1: /* load but don't execute */
 379     {
 380       /* save current process's return SS:SP now */
 381       LPBYTE psp_start = (LPBYTE)((DWORD)lpDosTask->psp_seg << 4);
 382       PDB16 *psp = (PDB16 *)psp_start;
 383       psp->saveStack = (DWORD)MAKESEGPTR(context->SegSs, LOWORD(context->Esp));
 384     }
 385     ret = MZ_DoLoadImage( hFile, filename, NULL );
 386     if (ret) {
 387       /* MZ_LoadImage created a new PSP and loaded new values into lpDosTask,
 388        * let's work on the new values now */
 389       LPBYTE psp_start = (LPBYTE)((DWORD)lpDosTask->psp_seg << 4);
 390       ExecBlock *blk = (ExecBlock *)paramblk;
 391       MZ_FillPSP(psp_start, DOSMEM_MapRealToLinear(blk->cmdline));
 392       /* the lame MS-DOS engineers decided that the return address should be in int22 */
 393       INT_SetRMHandler(0x22, (FARPROC16)MAKESEGPTR(context->SegCs, LOWORD(context->Eip)));
 394       if (func) {
 395         /* don't execute, just return startup state */
 396         blk->init_cs = init_cs;
 397         blk->init_ip = init_ip;
 398         blk->init_ss = init_ss;
 399         blk->init_sp = init_sp;
 400       } else {
 401         /* execute by making us return to new process */
 402         context->SegCs = init_cs;
 403         context->Eip   = init_ip;
 404         context->SegSs = init_ss;
 405         context->Esp   = init_sp;
 406         context->SegDs = lpDosTask->psp_seg;
 407         context->SegEs = lpDosTask->psp_seg;
 408         context->Eax   = 0;
 409       }
 410     }
 411     break;
 412   case 3: /* load overlay */
 413     {
 414       OverlayBlock *blk = (OverlayBlock *)paramblk;
 415       ret = MZ_DoLoadImage( hFile, filename, blk );
 416     }
 417     break;
 418   default:
 419     FIXME("EXEC load type %d not implemented\n", func);
 420     SetLastError(ERROR_INVALID_FUNCTION);
 421     break;
 422   }
 423   CloseHandle(hFile);
 424   return ret;
 425 }
 426
 427 LPDOSTASK WINAPI MZ_AllocDPMITask( void )
 428 {
 429   LPDOSTASK lpDosTask = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(DOSTASK));
 430
 431   if (lpDosTask) {
 432     dos_current = lpDosTask;
 433     MZ_InitMemory();
 434     MZ_InitTask();
 435   }
 436   return lpDosTask;
 437 }
 438
 439 static void MZ_InitTimer( int ver )
 440 {
 441  if (ver<1) {
 442   /* can't make timer ticks */
 443  } else {
 444   int func;
 445   struct timeval tim;
 446
 447   /* start dosmod timer at 55ms (18.2Hz) */
 448   func=DOSMOD_SET_TIMER;
 449   tim.tv_sec=0; tim.tv_usec=54925;
 450   write(write_pipe,&func,sizeof(func));
 451   write(write_pipe,&tim,sizeof(tim));
 452  }
 453 }
 454
 455 static BOOL MZ_InitTask(void)
 456 {
 457   int write_fd[2],x_fd;
 458   pid_t child;
 459   char path[256],*fpath;
 460
 461   /* create pipes */
 462   if (!CreatePipe(&hReadPipe,&hWritePipe,NULL,0)) return FALSE;
 463   if (pipe(write_fd)<0) {
 464     CloseHandle(hReadPipe);
 465     CloseHandle(hWritePipe);
 466     return FALSE;
 467   }
 468
 469   read_pipe = FILE_GetUnixHandle( hReadPipe, GENERIC_READ );
 470   x_fd = FILE_GetUnixHandle( hWritePipe, GENERIC_WRITE );
 471
 472   TRACE("win32 pipe: read=%d, write=%d, unix pipe: read=%d, write=%d\n",
 473         hReadPipe,hWritePipe,read_pipe,x_fd);
 474   TRACE("outbound unix pipe: read=%d, write=%d, pid=%d\n",write_fd[0],write_fd[1],getpid());
 475
 476   write_pipe=write_fd[1];
 477
 478   TRACE("Loading DOS VM support module\n");
 479   if ((child=fork())<0) {
 480     close(write_fd[0]);
 481     close(read_pipe);
 482     close(write_pipe);
 483     close(x_fd);
 484     CloseHandle(hReadPipe);
 485     CloseHandle(hWritePipe);
 486     return FALSE;
 487   }
 488  if (child!=0) {
 489   /* parent process */
 490   int ret;
 491
 492   close(write_fd[0]);
 493   close(x_fd);
 494   dosmod_pid = child;
 495   /* wait for child process to signal readiness */
 496   while (1) {
 497     if (read(read_pipe,&ret,sizeof(ret))==sizeof(ret)) break;
 498     if ((errno==EINTR)||(errno==EAGAIN)) continue;
 499     /* failure */
 500     ERR("dosmod has failed to initialize\n");
 501     if (mm_name[0]!=0) unlink(mm_name);
 502     return FALSE;
 503   }
 504   /* the child has now mmaped the temp file, it's now safe to unlink.
 505    * do it here to avoid leaving a mess in /tmp if/when Wine crashes... */
 506   if (mm_name[0]!=0) unlink(mm_name);
 507   /* start simulated system timer */
 508   MZ_InitTimer(ret);
 509   if (ret<2) {
 510     ERR("dosmod version too old! Please install newer dosmod properly\n");
 511     ERR("If you don't, the new dosmod event handling system will not work\n");
 512   }
 513   /* all systems are now go */
 514  } else {
 515   /* child process */
 516   close(read_pipe);
 517   close(write_pipe);
 518   /* put our pipes somewhere dosmod can find them */
 519   dup2(write_fd[0],0); /* stdin */
 520   dup2(x_fd,1);        /* stdout */
 521   /* now load dosmod */
 522   /* check argv[0]-derived paths first, since the newest dosmod is most likely there
 523    * (at least it was once for Andreas Mohr, so I decided to make it easier for him) */
 524   fpath=strrchr(strcpy(path,full_argv0),'/');
 525   if (fpath) {
 526    strcpy(fpath,"/dosmod");
 527    execl(path,mm_name,NULL);
 528    strcpy(fpath,"/loader/dos/dosmod");
 529    execl(path,mm_name,NULL);
 530   }
 531   /* okay, it wasn't there, try in the path */
 532   execlp("dosmod",mm_name,NULL);
 533   /* last desperate attempts: current directory */
 534   execl("dosmod",mm_name,NULL);
 535   /* and, just for completeness... */
 536   execl("loader/dos/dosmod",mm_name,NULL);
 537   /* if failure, exit */
 538   ERR("Failed to spawn dosmod, error=%s\n",strerror(errno));
 539   exit(1);
 540  }
 541  return TRUE;
 542 }
 543
 544 static void MZ_Launch(void)
 545 {
 546   LPDOSTASK lpDosTask = MZ_Current();
 547   CONTEXT context;
 548   TDB *pTask = (TDB *)GlobalLock16( GetCurrentTask() );
 549   BYTE *psp_start = PTR_REAL_TO_LIN( lpDosTask->psp_seg, 0 );
 550
 551   MZ_FillPSP(psp_start, GetCommandLineA());
 552   pTask->flags |= TDBF_WINOLDAP;
 553
 554   memset( &context, 0, sizeof(context) );
 555   context.SegCs  = init_cs;
 556   context.Eip    = init_ip;
 557   context.SegSs  = init_ss;
 558   context.Esp    = init_sp;
 559   context.SegDs  = lpDosTask->psp_seg;
 560   context.SegEs  = lpDosTask->psp_seg;
 561   context.EFlags = 0x00080000;  /* virtual interrupt flag */
 562   DOSVM_Enter( &context );
 563 }
 564
 565 static void MZ_KillTask(void)
 566 {
 567   TRACE("killing DOS task\n");
 568   VGA_Clean();
 569   kill(dosmod_pid,SIGTERM);
 570 }
 571
 572 void WINAPI MZ_Exit( CONTEXT86 *context, BOOL cs_psp, WORD retval )
 573 {
 574   LPDOSTASK lpDosTask = MZ_Current();
 575   if (lpDosTask) {
 576     WORD psp_seg = cs_psp ? context->SegCs : lpDosTask->psp_seg;
 577     LPBYTE psp_start = (LPBYTE)((DWORD)psp_seg << 4);
 578     PDB16 *psp = (PDB16 *)psp_start;
 579     WORD parpsp = psp->parentPSP; /* check for parent DOS process */
 580     if (parpsp) {
 581       /* retrieve parent's return address */
 582       FARPROC16 retaddr = INT_GetRMHandler(0x22);
 583       /* restore interrupts */
 584       INT_SetRMHandler(0x22, psp->savedint22);
 585       INT_SetRMHandler(0x23, psp->savedint23);
 586       INT_SetRMHandler(0x24, psp->savedint24);
 587       /* FIXME: deallocate file handles etc */
 588       /* free process's associated memory
 589        * FIXME: walk memory and deallocate all blocks owned by process */
 590       DOSMEM_FreeBlock(DOSMEM_MapRealToLinear(MAKELONG(0,psp->environment)));
 591       DOSMEM_FreeBlock(DOSMEM_MapRealToLinear(MAKELONG(0,lpDosTask->psp_seg)));
 592       /* switch to parent's PSP */
 593       lpDosTask->psp_seg = parpsp;
 594       psp_start = (LPBYTE)((DWORD)parpsp << 4);
 595       psp = (PDB16 *)psp_start;
 596       /* now return to parent */
 597       lpDosTask->retval = retval;
 598       context->SegCs = SELECTOROF(retaddr);
 599       context->Eip   = OFFSETOF(retaddr);
 600       context->SegSs = SELECTOROF(psp->saveStack);
 601       context->Esp   = OFFSETOF(psp->saveStack);
 602       return;
 603     } else
 604       MZ_KillTask();
 605   }
 606   ExitThread( retval );
 607 }
 608
 609 #else /* !MZ_SUPPORTED */
 610
 611 BOOL WINAPI MZ_LoadImage( LPCSTR cmdline )
 612 {
 613   WARN("DOS executables not supported on this platform\n");
 614   SetLastError(ERROR_BAD_FORMAT);
 615   return FALSE;
 616 }
 617
 618 BOOL WINAPI MZ_Exec( CONTEXT86 *context, LPCSTR filename, BYTE func, LPVOID paramblk )
 619 {
 620   /* can't happen */
 621   SetLastError(ERROR_BAD_FORMAT);
 622   return FALSE;
 623 }
 624
 625 LPDOSTASK WINAPI MZ_AllocDPMITask( void )
 626 {
 627     ERR("Actual real-mode calls not supported on this platform!\n");
 628     return NULL;
 629 }
 630
 631 void WINAPI MZ_Exit( CONTEXT86 *context, BOOL cs_psp, WORD retval )
 632 {
 633   ExitThread( retval );
 634 }
 635
 636 #endif /* !MZ_SUPPORTED */
 637
 638 LPDOSTASK WINAPI MZ_Current( void )
 639 {
 640   return dos_current;
 641 }