Make a better guess to find the top of the initial stack.
[wine.git] / loader / dos / module.c
blob8acf083a707b5eea18852808c43078437c555a4c
1 /*
2 * DOS (MZ) loader
4 * Copyright 1998 Ove Kåven
6 * This code hasn't been completely cleaned up yet.
7 */
9 #include "config.h"
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 "neexe.h"
26 #include "task.h"
27 #include "selectors.h"
28 #include "file.h"
29 #include "ldt.h"
30 #include "process.h"
31 #include "miscemu.h"
32 #include "debugtools.h"
33 #include "dosexe.h"
34 #include "dosmod.h"
35 #include "options.h"
36 #include "server.h"
37 #include "vga.h"
39 DEFAULT_DEBUG_CHANNEL(module)
41 #ifdef MZ_SUPPORTED
43 #ifdef HAVE_SYS_MMAN_H
44 # include <sys/mman.h>
45 #endif
47 /* define this to try mapping through /proc/pid/mem instead of a temp file,
48 but Linus doesn't like mmapping /proc/pid/mem, so it doesn't work for me */
49 #undef MZ_MAPSELF
51 #define BIOS_DATA_SEGMENT 0x40
52 #define START_OFFSET 0
53 #define PSP_SIZE 0x10
55 #define SEG16(ptr,seg) ((LPVOID)((BYTE*)ptr+((DWORD)(seg)<<4)))
56 #define SEGPTR16(ptr,segptr) ((LPVOID)((BYTE*)ptr+((DWORD)SELECTOROF(segptr)<<4)+OFFSETOF(segptr)))
58 static void MZ_InitPSP( LPVOID lpPSP, LPCSTR cmdline, WORD env )
60 PDB16*psp=lpPSP;
61 const char*cmd=cmdline?strchr(cmdline,' '):NULL;
63 psp->int20=0x20CD; /* int 20 */
64 /* some programs use this to calculate how much memory they need */
65 psp->nextParagraph=0x9FFF;
66 psp->environment=env;
67 /* copy parameters */
68 if (cmd) {
69 #if 0
70 /* command.com doesn't do this */
71 while (*cmd == ' ') cmd++;
72 #endif
73 psp->cmdLine[0]=strlen(cmd);
74 strcpy(psp->cmdLine+1,cmd);
75 psp->cmdLine[psp->cmdLine[0]+1]='\r';
76 } else psp->cmdLine[1]='\r';
77 /* FIXME: integrate the memory stuff from Wine (msdos/dosmem.c) */
78 /* FIXME: integrate the PDB stuff from Wine (loader/task.c) */
81 /* default INT 08 handler: increases timer tick counter but not much more */
82 static char int08[]={
83 0xCD,0x1C, /* int $0x1c */
84 0x50, /* pushw %ax */
85 0x1E, /* pushw %ds */
86 0xB8,0x40,0x00, /* movw $0x40,%ax */
87 0x8E,0xD8, /* movw %ax,%ds */
88 #if 0
89 0x83,0x06,0x6C,0x00,0x01, /* addw $1,(0x6c) */
90 0x83,0x16,0x6E,0x00,0x00, /* adcw $0,(0x6e) */
91 #else
92 0x66,0xFF,0x06,0x6C,0x00, /* incl (0x6c) */
93 #endif
94 0xB0,0x20, /* movb $0x20,%al */
95 0xE6,0x20, /* outb %al,$0x20 */
96 0x1F, /* popw %ax */
97 0x58, /* popw %ax */
98 0xCF /* iret */
101 static void MZ_InitHandlers( LPDOSTASK lpDosTask )
103 WORD seg;
104 LPBYTE start=DOSMEM_GetBlock(lpDosTask->hModule,sizeof(int08),&seg);
105 memcpy(start,int08,sizeof(int08));
106 /* INT 08: point it at our tick-incrementing handler */
107 ((SEGPTR*)(lpDosTask->img))[0x08]=PTR_SEG_OFF_TO_SEGPTR(seg,0);
108 /* INT 1C: just point it to IRET, we don't want to handle it ourselves */
109 ((SEGPTR*)(lpDosTask->img))[0x1C]=PTR_SEG_OFF_TO_SEGPTR(seg,sizeof(int08)-1);
112 static char enter_xms[]={
113 /* XMS hookable entry point */
114 0xEB,0x03, /* jmp entry */
115 0x90,0x90,0x90, /* nop;nop;nop */
116 /* entry: */
117 /* real entry point */
118 /* for simplicity, we'll just use the same hook as DPMI below */
119 0xCD,0x31, /* int $0x31 */
120 0xCB /* lret */
123 static void MZ_InitXMS( LPDOSTASK lpDosTask )
125 LPBYTE start=DOSMEM_GetBlock(lpDosTask->hModule,sizeof(enter_xms),&(lpDosTask->xms_seg));
126 memcpy(start,enter_xms,sizeof(enter_xms));
129 static char enter_pm[]={
130 0x50, /* pushw %ax */
131 0x52, /* pushw %dx */
132 0x55, /* pushw %bp */
133 0x89,0xE5, /* movw %sp,%bp */
134 /* get return CS */
135 0x8B,0x56,0x08, /* movw 8(%bp),%dx */
136 /* just call int 31 here to get into protected mode... */
137 /* it'll check whether it was called from dpmi_seg... */
138 0xCD,0x31, /* int $0x31 */
139 /* we are now in the context of a 16-bit relay call */
140 /* need to fixup our stack;
141 * 16-bit relay return address will be lost, but we won't worry quite yet */
142 0x8E,0xD0, /* movw %ax,%ss */
143 0x66,0x0F,0xB7,0xE5, /* movzwl %bp,%esp */
144 /* set return CS */
145 0x89,0x56,0x08, /* movw %dx,8(%bp) */
146 0x5D, /* popw %bp */
147 0x5A, /* popw %dx */
148 0x58, /* popw %ax */
149 0xCB /* lret */
152 static void MZ_InitDPMI( LPDOSTASK lpDosTask )
154 unsigned size=sizeof(enter_pm);
155 LPBYTE start=DOSMEM_GetBlock(lpDosTask->hModule,size,&(lpDosTask->dpmi_seg));
157 lpDosTask->dpmi_sel = SELECTOR_AllocBlock( start, size, SEGMENT_CODE, FALSE, FALSE );
159 memcpy(start,enter_pm,sizeof(enter_pm));
162 static WORD MZ_InitEnvironment( LPDOSTASK lpDosTask, LPCSTR env, LPCSTR name )
164 unsigned sz=0;
165 WORD seg;
166 LPSTR envblk;
168 if (env) {
169 /* get size of environment block */
170 while (env[sz++]) sz+=strlen(env+sz)+1;
171 } else sz++;
172 /* allocate it */
173 envblk=DOSMEM_GetBlock(lpDosTask->hModule,sz+sizeof(WORD)+strlen(name)+1,&seg);
174 /* fill it */
175 if (env) {
176 memcpy(envblk,env,sz);
177 } else envblk[0]=0;
178 /* DOS 3.x: the block contains 1 additional string */
179 *(WORD*)(envblk+sz)=1;
180 /* being the program name itself */
181 strcpy(envblk+sz+sizeof(WORD),name);
182 return seg;
185 static BOOL MZ_InitMemory( LPDOSTASK lpDosTask, NE_MODULE *pModule )
187 int x;
189 if (lpDosTask->img) return TRUE; /* already allocated */
191 /* allocate 1MB+64K shared memory */
192 lpDosTask->img_ofs=START_OFFSET;
193 #ifdef MZ_MAPSELF
194 lpDosTask->img=VirtualAlloc(NULL,0x110000,MEM_COMMIT,PAGE_READWRITE);
195 /* make sure mmap accepts it */
196 ((char*)lpDosTask->img)[0x10FFFF]=0;
197 #else
198 tmpnam(lpDosTask->mm_name);
199 /* strcpy(lpDosTask->mm_name,"/tmp/mydosimage"); */
200 lpDosTask->mm_fd=open(lpDosTask->mm_name,O_RDWR|O_CREAT /* |O_TRUNC */,S_IRUSR|S_IWUSR);
201 if (lpDosTask->mm_fd<0) ERR("file %s could not be opened\n",lpDosTask->mm_name);
202 /* expand file to 1MB+64K */
203 lseek(lpDosTask->mm_fd,0x110000-1,SEEK_SET);
204 x=0; write(lpDosTask->mm_fd,&x,1);
205 /* map it in */
206 lpDosTask->img=mmap(NULL,0x110000-START_OFFSET,PROT_READ|PROT_WRITE,MAP_SHARED,lpDosTask->mm_fd,0);
207 #endif
208 if (lpDosTask->img==(LPVOID)-1) {
209 ERR("could not map shared memory, error=%s\n",strerror(errno));
210 return FALSE;
212 TRACE("DOS VM86 image mapped at %08lx\n",(DWORD)lpDosTask->img);
213 pModule->dos_image=lpDosTask->img;
215 /* initialize the memory */
216 TRACE("Initializing DOS memory structures\n");
217 DOSMEM_Init(lpDosTask->hModule);
218 MZ_InitHandlers(lpDosTask);
219 MZ_InitXMS(lpDosTask);
220 MZ_InitDPMI(lpDosTask);
221 return TRUE;
224 static BOOL MZ_LoadImage( HANDLE hFile, LPCSTR filename, LPCSTR cmdline,
225 LPCSTR env, LPDOSTASK lpDosTask, NE_MODULE *pModule )
227 IMAGE_DOS_HEADER mz_header;
228 DWORD image_start,image_size,min_size,max_size,avail;
229 BYTE*psp_start,*load_start;
230 int x,old_com=0;
231 SEGPTR reloc;
232 WORD env_seg;
233 DWORD len;
235 SetFilePointer(hFile,0,NULL,FILE_BEGIN);
236 if ( !ReadFile(hFile,&mz_header,sizeof(mz_header),&len,NULL)
237 || len != sizeof(mz_header)
238 || mz_header.e_magic != IMAGE_DOS_SIGNATURE) {
239 old_com=1; /* assume .COM file */
240 image_start=0;
241 image_size=GetFileSize(hFile,NULL);
242 min_size=0x10000; max_size=0x100000;
243 mz_header.e_crlc=0;
244 mz_header.e_ss=0; mz_header.e_sp=0xFFFE;
245 mz_header.e_cs=0; mz_header.e_ip=0x100;
246 } else {
247 /* calculate load size */
248 image_start=mz_header.e_cparhdr<<4;
249 image_size=mz_header.e_cp<<9; /* pages are 512 bytes */
250 if ((mz_header.e_cblp!=0)&&(mz_header.e_cblp!=4)) image_size-=512-mz_header.e_cblp;
251 image_size-=image_start;
252 min_size=image_size+((DWORD)mz_header.e_minalloc<<4)+(PSP_SIZE<<4);
253 max_size=image_size+((DWORD)mz_header.e_maxalloc<<4)+(PSP_SIZE<<4);
256 MZ_InitMemory(lpDosTask,pModule);
258 /* allocate environment block */
259 env_seg=MZ_InitEnvironment(lpDosTask,env,filename);
261 /* allocate memory for the executable */
262 TRACE("Allocating DOS memory (min=%ld, max=%ld)\n",min_size,max_size);
263 avail=DOSMEM_Available(lpDosTask->hModule);
264 if (avail<min_size) {
265 ERR("insufficient DOS memory\n");
266 SetLastError(ERROR_NOT_ENOUGH_MEMORY);
267 return FALSE;
269 if (avail>max_size) avail=max_size;
270 psp_start=DOSMEM_GetBlock(lpDosTask->hModule,avail,&lpDosTask->psp_seg);
271 if (!psp_start) {
272 ERR("error allocating DOS memory\n");
273 SetLastError(ERROR_NOT_ENOUGH_MEMORY);
274 return FALSE;
276 lpDosTask->load_seg=lpDosTask->psp_seg+(old_com?0:PSP_SIZE);
277 load_start=psp_start+(PSP_SIZE<<4);
278 MZ_InitPSP(psp_start, cmdline, env_seg);
280 /* load executable image */
281 TRACE("loading DOS %s image, %08lx bytes\n",old_com?"COM":"EXE",image_size);
282 SetFilePointer(hFile,image_start,NULL,FILE_BEGIN);
283 if (!ReadFile(hFile,load_start,image_size,&len,NULL) || len != image_size) {
284 SetLastError(ERROR_BAD_FORMAT);
285 return FALSE;
288 if (mz_header.e_crlc) {
289 /* load relocation table */
290 TRACE("loading DOS EXE relocation table, %d entries\n",mz_header.e_crlc);
291 /* FIXME: is this too slow without read buffering? */
292 SetFilePointer(hFile,mz_header.e_lfarlc,NULL,FILE_BEGIN);
293 for (x=0; x<mz_header.e_crlc; x++) {
294 if (!ReadFile(hFile,&reloc,sizeof(reloc),&len,NULL) || len != sizeof(reloc)) {
295 SetLastError(ERROR_BAD_FORMAT);
296 return FALSE;
298 *(WORD*)SEGPTR16(load_start,reloc)+=lpDosTask->load_seg;
302 lpDosTask->init_cs=lpDosTask->load_seg+mz_header.e_cs;
303 lpDosTask->init_ip=mz_header.e_ip;
304 lpDosTask->init_ss=lpDosTask->load_seg+mz_header.e_ss;
305 lpDosTask->init_sp=mz_header.e_sp;
307 TRACE("entry point: %04x:%04x\n",lpDosTask->init_cs,lpDosTask->init_ip);
308 return TRUE;
311 LPDOSTASK MZ_AllocDPMITask( HMODULE16 hModule )
313 LPDOSTASK lpDosTask = calloc(1, sizeof(DOSTASK));
314 NE_MODULE *pModule;
316 if (lpDosTask) {
317 lpDosTask->hModule = hModule;
319 pModule = (NE_MODULE *)GlobalLock16(hModule);
320 pModule->lpDosTask = lpDosTask;
322 lpDosTask->img=NULL; lpDosTask->mm_name[0]=0; lpDosTask->mm_fd=-1;
324 MZ_InitMemory(lpDosTask, pModule);
326 GlobalUnlock16(hModule);
328 return lpDosTask;
331 static void MZ_InitTimer( LPDOSTASK lpDosTask, int ver )
333 if (ver<1) {
334 /* can't make timer ticks */
335 } else {
336 int func;
337 struct timeval tim;
339 /* start dosmod timer at 55ms (18.2Hz) */
340 func=DOSMOD_SET_TIMER;
341 tim.tv_sec=0; tim.tv_usec=54925;
342 write(lpDosTask->write_pipe,&func,sizeof(func));
343 write(lpDosTask->write_pipe,&tim,sizeof(tim));
347 BOOL MZ_InitTask( LPDOSTASK lpDosTask )
349 int write_fd[2],x_fd;
350 pid_t child;
351 char *fname,*farg,arg[16],fproc[64],path[256],*fpath;
352 SECURITY_ATTRIBUTES attr={sizeof(attr),NULL,TRUE};
353 struct get_read_fd_request *r_req = get_req_buffer();
354 struct get_write_fd_request *w_req = get_req_buffer();
356 if (!lpDosTask) return FALSE;
357 /* create pipes */
358 /* this happens in the wrong process context, so we have to let the new process
359 inherit it... (FIXME: call MZ_InitTask in the right process context) */
360 if (!CreatePipe(&(lpDosTask->hReadPipe),&(lpDosTask->hXPipe),&attr,0)) return FALSE;
361 if (pipe(write_fd)<0) {
362 CloseHandle(lpDosTask->hReadPipe);
363 CloseHandle(lpDosTask->hXPipe);
364 return FALSE;
366 r_req->handle = lpDosTask->hReadPipe;
367 server_call_fd( REQ_GET_READ_FD, -1, &lpDosTask->read_pipe );
368 w_req->handle = lpDosTask->hXPipe;
369 server_call_fd( REQ_GET_WRITE_FD, -1, &x_fd );
371 TRACE("win32 pipe: read=%d, write=%d, unix pipe: read=%d, write=%d\n",
372 lpDosTask->hReadPipe,lpDosTask->hXPipe,lpDosTask->read_pipe,x_fd);
373 TRACE("outbound unix pipe: read=%d, write=%d, pid=%d\n",write_fd[0],write_fd[1],getpid());
375 lpDosTask->write_pipe=write_fd[1];
377 lpDosTask->hConInput=GetStdHandle(STD_INPUT_HANDLE);
378 lpDosTask->hConOutput=GetStdHandle(STD_OUTPUT_HANDLE);
380 /* if we have a mapping file, use it */
381 fname=lpDosTask->mm_name; farg=NULL;
382 if (!fname[0]) {
383 /* otherwise, map our own memory image */
384 sprintf(fproc,"/proc/%d/mem",getpid());
385 sprintf(arg,"%ld",(unsigned long)lpDosTask->img);
386 fname=fproc; farg=arg;
389 TRACE("Loading DOS VM support module (hmodule=%04x)\n",lpDosTask->hModule);
390 if ((child=fork())<0) {
391 close(write_fd[0]);
392 close(lpDosTask->read_pipe);
393 close(lpDosTask->write_pipe);
394 close(x_fd);
395 CloseHandle(lpDosTask->hReadPipe);
396 CloseHandle(lpDosTask->hXPipe);
397 return FALSE;
399 if (child!=0) {
400 /* parent process */
401 int ret;
403 close(write_fd[0]);
404 close(x_fd);
405 lpDosTask->task=child;
406 /* wait for child process to signal readiness */
407 while (1) {
408 if (read(lpDosTask->read_pipe,&ret,sizeof(ret))==sizeof(ret)) break;
409 if ((errno==EINTR)||(errno==EAGAIN)) continue;
410 /* failure */
411 ERR("dosmod has failed to initialize\n");
412 if (lpDosTask->mm_name[0]!=0) unlink(lpDosTask->mm_name);
413 return FALSE;
415 /* the child has now mmaped the temp file, it's now safe to unlink.
416 * do it here to avoid leaving a mess in /tmp if/when Wine crashes... */
417 if (lpDosTask->mm_name[0]!=0) unlink(lpDosTask->mm_name);
418 /* start simulated system timer */
419 MZ_InitTimer(lpDosTask,ret);
420 if (ret<2) {
421 ERR("dosmod version too old! Please install newer dosmod properly\n");
422 ERR("If you don't, the new dosmod event handling system will not work\n");
424 /* all systems are now go */
425 } else {
426 /* child process */
427 close(lpDosTask->read_pipe);
428 close(lpDosTask->write_pipe);
429 /* put our pipes somewhere dosmod can find them */
430 dup2(write_fd[0],0); /* stdin */
431 dup2(x_fd,1); /* stdout */
432 /* now load dosmod */
433 /* check argv[0]-derived paths first, since the newest dosmod is most likely there
434 * (at least it was once for Andreas Mohr, so I decided to make it easier for him) */
435 fpath=strrchr(strcpy(path,argv0),'/');
436 if (fpath) {
437 strcpy(fpath,"/dosmod");
438 execl(path,fname,farg,NULL);
439 strcpy(fpath,"/loader/dos/dosmod");
440 execl(path,fname,farg,NULL);
442 /* okay, it wasn't there, try in the path */
443 execlp("dosmod",fname,farg,NULL);
444 /* last desperate attempts: current directory */
445 execl("dosmod",fname,farg,NULL);
446 /* and, just for completeness... */
447 execl("loader/dos/dosmod",fname,farg,NULL);
448 /* if failure, exit */
449 ERR("Failed to spawn dosmod, error=%s\n",strerror(errno));
450 exit(1);
452 return TRUE;
455 #if 0
456 BOOL MZ_CreateProcess( HANDLE hFile, LPCSTR filename, LPCSTR cmdline, LPCSTR env,
457 LPSECURITY_ATTRIBUTES psa, LPSECURITY_ATTRIBUTES tsa,
458 BOOL inherit, DWORD flags, LPSTARTUPINFOA startup,
459 LPPROCESS_INFORMATION info )
461 LPDOSTASK lpDosTask = NULL; /* keep gcc from complaining */
462 HMODULE16 hModule;
463 PDB *pdb = PROCESS_Current();
464 TDB *pTask = (TDB*)GlobalLock16( GetCurrentTask() );
465 NE_MODULE *pModule = pTask ? NE_GetPtr( pTask->hModule ) : NULL;
466 int alloc = !(pModule && pModule->dos_image);
468 if (alloc && (lpDosTask = calloc(1, sizeof(DOSTASK))) == NULL) {
469 SetLastError(ERROR_NOT_ENOUGH_MEMORY);
470 return FALSE;
473 if ((!env)&&pdb) env = pdb->env_db->environ;
474 if (alloc) {
475 if ((hModule = MODULE_CreateDummyModule(filename, 0)) < 32) {
476 SetLastError(hModule);
477 return FALSE;
479 lpDosTask->hModule = hModule;
481 pModule = (NE_MODULE *)GlobalLock16(hModule);
482 pModule->lpDosTask = lpDosTask;
484 lpDosTask->img=NULL; lpDosTask->mm_name[0]=0; lpDosTask->mm_fd=-1;
485 } else lpDosTask=pModule->lpDosTask;
486 if (!MZ_LoadImage( hFile, filename, cmdline, env, lpDosTask, pModule )) {
487 if (alloc) {
488 if (lpDosTask->mm_name[0]!=0) {
489 if (lpDosTask->img!=NULL) munmap(lpDosTask->img,0x110000-START_OFFSET);
490 if (lpDosTask->mm_fd>=0) close(lpDosTask->mm_fd);
491 unlink(lpDosTask->mm_name);
492 } else
493 if (lpDosTask->img!=NULL) VirtualFree(lpDosTask->img,0x110000,MEM_RELEASE);
495 return FALSE;
497 if (alloc) {
498 pModule->dos_image = lpDosTask->img;
499 if (!MZ_InitTask( lpDosTask )) {
500 MZ_KillModule( lpDosTask );
501 /* FIXME: cleanup hModule */
502 SetLastError(ERROR_GEN_FAILURE);
503 return FALSE;
505 inherit = TRUE; /* bad hack for inheriting the CreatePipe... */
506 if (!PROCESS_Create( pModule, hFile, cmdline, env,
507 psa, tsa, inherit, flags, startup, info ))
508 return FALSE;
510 return TRUE;
512 #endif
514 void MZ_KillModule( LPDOSTASK lpDosTask )
516 DOSEVENT *event,*p_event;
517 DOSSYSTEM *sys,*p_sys;
519 TRACE("killing DOS task\n");
520 VGA_Clean();
521 if (lpDosTask->mm_name[0]!=0) {
522 munmap(lpDosTask->img,0x110000-START_OFFSET);
523 close(lpDosTask->mm_fd);
524 } else VirtualFree(lpDosTask->img,0x110000,MEM_RELEASE);
525 close(lpDosTask->read_pipe);
526 close(lpDosTask->write_pipe);
527 CloseHandle(lpDosTask->hReadPipe);
528 CloseHandle(lpDosTask->hXPipe);
529 kill(lpDosTask->task,SIGTERM);
530 /* free memory allocated for events and systems */
531 #define DFREE(var,pvar,svar) \
532 var = lpDosTask->svar; \
533 while (var) { \
534 if (var->data) free(var->data); \
535 pvar = var->next; free(var); var = pvar; \
538 DFREE(event,p_event,pending)
539 DFREE(event,p_event,current)
540 DFREE(sys,p_sys,sys)
542 #undef DFREE
544 #if 0
545 /* FIXME: this seems to crash */
546 if (lpDosTask->dpmi_sel)
547 SELECTOR_FreeBlock(lpDosTask->dpmi_sel, 1);
548 #endif
551 LPDOSTASK MZ_Current( void )
553 TDB *pTask = (TDB *)GlobalLock16( GetCurrentTask() );
554 NE_MODULE *pModule = pTask ? NE_GetPtr( pTask->hModule ) : NULL;
556 GlobalUnlock16( GetCurrentTask() );
558 if (pModule)
559 return pModule->lpDosTask;
561 return NULL;
564 #else /* !MZ_SUPPORTED */
566 BOOL MZ_CreateProcess( HANDLE hFile, LPCSTR filename, LPCSTR cmdline, LPCSTR env,
567 LPSECURITY_ATTRIBUTES psa, LPSECURITY_ATTRIBUTES tsa,
568 BOOL inherit, DWORD flags, LPSTARTUPINFOA startup,
569 LPPROCESS_INFORMATION info )
571 WARN("DOS executables not supported on this architecture\n");
572 SetLastError(ERROR_BAD_FORMAT);
573 return FALSE;
576 LPDOSTASK MZ_Current( void )
578 return NULL;
581 #endif