dosexe.c

/*
 * DOS (MZ) loader
 *
 * Copyright 1998 Ove Kåven
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 *
 * Note: This code hasn't been completely cleaned up yet.
 */

#include "config.h"
#include "wine/port.h"

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <sys/types.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include "windef.h"
#include "winbase.h"
#include "wine/winbase16.h"
#include "wingdi.h"
#include "winuser.h"
#include "winerror.h"
#include "wine/debug.h"
#include "kernel16_private.h"
#include "dosexe.h"
#include "vga.h"
#include "../toolhelp/toolhelp.h"

WINE_DEFAULT_DEBUG_CHANNEL(module);

static BOOL DOSVM_isdosexe;

/**********************************************************************
 *          DOSVM_IsWin16
 * 
 * Return TRUE if we are in Windows process.
 */
BOOL DOSVM_IsWin16(void)
{
  return !DOSVM_isdosexe;
}

/**********************************************************************
 *          DOSVM_Exit
 */
void DOSVM_Exit( WORD retval )
{
    DWORD count;

    TOOLHELP_CallNotify(NFY_EXITTASK, retval);
    ReleaseThunkLock( &count );
    ExitThread( retval );
}


#ifdef MZ_SUPPORTED

#define BIOS_DATA_SEGMENT 0x40
#define PSP_SIZE 0x10

#define SEG16(ptr,seg) ((LPVOID)((BYTE*)ptr+((DWORD)(seg)<<4)))
#define SEGPTR16(ptr,segptr) ((LPVOID)((BYTE*)ptr+((DWORD)SELECTOROF(segptr)<<4)+OFFSETOF(segptr)))

/* structures for EXEC */

#include "pshpack1.h"

typedef struct {
  WORD env_seg;
  DWORD cmdline;
  DWORD fcb1;
  DWORD fcb2;
  WORD init_sp;
  WORD init_ss;
  WORD init_ip;
  WORD init_cs;
} ExecBlock;

typedef struct {
  WORD load_seg;
  WORD rel_seg;
} OverlayBlock;

#include "poppack.h"

/* global variables */

pid_t dosvm_pid;

static WORD init_cs,init_ip,init_ss,init_sp;
static HANDLE dosvm_thread, loop_thread;
static DWORD dosvm_tid, loop_tid;

static DWORD MZ_Launch( LPCSTR cmdtail, int length );
static BOOL MZ_InitTask(void);

static void MZ_CreatePSP( LPVOID lpPSP, WORD env, WORD par )
{
  PDB16*psp=lpPSP;

  psp->int20=0x20CD; /* int 20 */
  /* some programs use this to calculate how much memory they need */
  psp->nextParagraph=0x9FFF; /* FIXME: use a real value */
  /* FIXME: dispatcher */
  psp->savedint22 = DOSVM_GetRMHandler(0x22);
  psp->savedint23 = DOSVM_GetRMHandler(0x23);
  psp->savedint24 = DOSVM_GetRMHandler(0x24);
  psp->parentPSP=par;
  psp->environment=env;
  /* FIXME: more PSP stuff */
}

extern char *DOSMEM_dosmem;
static void MZ_FillPSP( LPVOID lpPSP, LPCSTR cmdtail, int length )
{
    PDB16 *psp = (PDB16*)lpPSP;

    if(length > 127) 
    {
        WARN( "Command tail truncated! (length %d)\n", length );
        length = 126;
    }

    psp->cmdLine[0] = length;

    /*
     * Length of exactly 127 bytes means that full command line is 
     * stored in environment variable CMDLINE and PSP contains 
     * command tail truncated to 126 bytes.
     */
    if(length == 127)
        length = 126;

    if(length > 0)
        memmove(psp->cmdLine+1, cmdtail, length);

    psp->cmdLine[length+1] = '\r';

    /* FIXME: more PSP stuff */
}

static WORD MZ_InitEnvironment( LPCSTR env, LPCSTR name )
{
 unsigned sz=0;
 unsigned i=0;
 WORD seg;
 LPSTR envblk;

 if (env) {
  /* get size of environment block */
  while (env[sz++]) sz+=strlen(env+sz)+1;
 } else sz++;
 /* allocate it */
 envblk=DOSMEM_AllocBlock(sz+sizeof(WORD)+strlen(name)+1,&seg);
 /* fill it */
 if (env) {
  memcpy(envblk,env,sz);
 } else envblk[0]=0;
 /* DOS environment variables are uppercase */
 while (envblk[i]){
  while (envblk[i] != '='){
   if (envblk[i]>='a' && envblk[i] <= 'z'){
    envblk[i] -= 32;
   }
   i++;
  }
  i += strlen(envblk+i) + 1;
 }
 /* DOS 3.x: the block contains 1 additional string */
 *(WORD*)(envblk+sz)=1;
 /* being the program name itself */
 strcpy(envblk+sz+sizeof(WORD),name);
 return seg;
}

static BOOL MZ_InitMemory(void)
{
    /* initialize the memory */
    TRACE("Initializing DOS memory structures\n");
    DOSMEM_MapDosLayout();
    DOSDEV_InstallDOSDevices();
    MSCDEX_InstallCDROM();

    return TRUE;
}

static BOOL MZ_DoLoadImage( HANDLE hFile, LPCSTR filename, OverlayBlock *oblk, WORD par_env_seg )
{
  IMAGE_DOS_HEADER mz_header;
  DWORD image_start,image_size,min_size,max_size,avail;
  BYTE*psp_start,*load_start;
  LPSTR oldenv = 0;
  int x, old_com=0, alloc;
  SEGPTR reloc;
  WORD env_seg, load_seg, rel_seg, oldpsp_seg;
  DWORD len;

  if (DOSVM_psp) {
    /* DOS process already running, inherit from it */
    PDB16* par_psp;
    alloc=0;
    oldpsp_seg = DOSVM_psp;
    if( !par_env_seg) {  
        par_psp = (PDB16*)PTR_REAL_TO_LIN(DOSVM_psp, 0);
        oldenv = (LPSTR)((DWORD)PTR_REAL_TO_LIN(par_psp->environment, 0));
    }
  } else {
    /* allocate new DOS process, inheriting from Wine environment */
    alloc=1;
    oldpsp_seg = 0;
    if( !par_env_seg)
        oldenv = GetEnvironmentStringsA();
  }

 SetFilePointer(hFile,0,NULL,FILE_BEGIN);
 if (   !ReadFile(hFile,&mz_header,sizeof(mz_header),&len,NULL)
     || len != sizeof(mz_header)
     || mz_header.e_magic != IMAGE_DOS_SIGNATURE) {
  const char *p = strrchr( filename, '.' );
  if (!p || strcasecmp( p, ".com" ))  /* check for .COM extension */
  {
      SetLastError(ERROR_BAD_FORMAT);
      goto load_error;
  }
  old_com=1; /* assume .COM file */
  image_start=0;
  image_size=GetFileSize(hFile,NULL);
  min_size=0x10000; max_size=0x100000;
  mz_header.e_crlc=0;
  mz_header.e_ss=0; mz_header.e_sp=0xFFFE;
  mz_header.e_cs=0; mz_header.e_ip=0x100;
 } else {
  /* calculate load size */
  image_start=mz_header.e_cparhdr<<4;
  image_size=mz_header.e_cp<<9; /* pages are 512 bytes */
  /* From Ralf Brown Interrupt List: If the word at offset 02h is 4, it should
   * be treated as 00h, since pre-1.10 versions of the MS linker set it that
   * way. */
  if ((mz_header.e_cblp!=0)&&(mz_header.e_cblp!=4)) image_size-=512-mz_header.e_cblp;
  image_size-=image_start;
  min_size=image_size+((DWORD)mz_header.e_minalloc<<4)+(PSP_SIZE<<4);
  max_size=image_size+((DWORD)mz_header.e_maxalloc<<4)+(PSP_SIZE<<4);
 }

  if (alloc) MZ_InitMemory();

  if (oblk) {
    /* load overlay into preallocated memory */
    load_seg=oblk->load_seg;
    rel_seg=oblk->rel_seg;
    load_start=(LPBYTE)((DWORD)load_seg<<4);
  } else {
    /* allocate environment block */
    if( par_env_seg)
        env_seg = par_env_seg;
    else
        env_seg=MZ_InitEnvironment(oldenv, filename);
    if (alloc)
        FreeEnvironmentStringsA( oldenv);

    /* allocate memory for the executable */
    TRACE("Allocating DOS memory (min=%d, max=%d)\n",min_size,max_size);
    avail=DOSMEM_Available();
    if (avail<min_size) {
      ERR("insufficient DOS memory\n");
      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
      goto load_error;
    }
    if (avail>max_size) avail=max_size;
    psp_start=DOSMEM_AllocBlock(avail,&DOSVM_psp);
    if (!psp_start) {
      ERR("error allocating DOS memory\n");
      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
      goto load_error;
    }
    load_seg=DOSVM_psp+(old_com?0:PSP_SIZE);
    rel_seg=load_seg;
    load_start=psp_start+(PSP_SIZE<<4);
    MZ_CreatePSP(psp_start, env_seg, oldpsp_seg);
  }

 /* load executable image */
 TRACE("loading DOS %s image, %08x bytes\n",old_com?"COM":"EXE",image_size);
 SetFilePointer(hFile,image_start,NULL,FILE_BEGIN);
 if (!ReadFile(hFile,load_start,image_size,&len,NULL) || len != image_size) {
  /* check if this is due to the workaround for the pre-1.10 MS linker and we
     really had only 4 bytes on the last page */
  if (mz_header.e_cblp != 4 || image_size - len != 512 - 4) {
    SetLastError(ERROR_BAD_FORMAT);
    goto load_error;
  }
 }

 if (mz_header.e_crlc) {
  /* load relocation table */
  TRACE("loading DOS EXE relocation table, %d entries\n",mz_header.e_crlc);
  /* FIXME: is this too slow without read buffering? */
  SetFilePointer(hFile,mz_header.e_lfarlc,NULL,FILE_BEGIN);
  for (x=0; x<mz_header.e_crlc; x++) {
   if (!ReadFile(hFile,&reloc,sizeof(reloc),&len,NULL) || len != sizeof(reloc)) {
    SetLastError(ERROR_BAD_FORMAT);
    goto load_error;
   }
   *(WORD*)SEGPTR16(load_start,reloc)+=rel_seg;
  }
 }

  if (!oblk) {
    init_cs = load_seg+mz_header.e_cs;
    init_ip = mz_header.e_ip;
    init_ss = load_seg+mz_header.e_ss;
    init_sp = mz_header.e_sp;
    if (old_com){
      /* .COM files exit with ret. Make sure they jump to psp start (=int 20) */
      WORD* stack = PTR_REAL_TO_LIN(init_ss, init_sp);
      *stack = 0;
    }

    TRACE("entry point: %04x:%04x\n",init_cs,init_ip);
  }

  if (alloc && !MZ_InitTask()) {
    SetLastError(ERROR_GEN_FAILURE);
    return FALSE;
  }

  return TRUE;

load_error:
  DOSVM_psp = oldpsp_seg;

  return FALSE;
}

/***********************************************************************
 *		__wine_load_dos_exe (KERNEL.@)
 *
 * Called from WineVDM when a new real-mode DOS process is started.
 * Loads DOS program into memory and executes the program.
 */
void __wine_load_dos_exe( LPCSTR filename, LPCSTR cmdline )
{
    char dos_cmdtail[126];
    int  dos_length = 0;

    HANDLE hFile = CreateFileA( filename, GENERIC_READ, FILE_SHARE_READ, 
                                NULL, OPEN_EXISTING, 0, 0 );
    if (hFile == INVALID_HANDLE_VALUE) return;
    DOSVM_isdosexe = TRUE;
    DOSMEM_InitDosMemory();

    if(cmdline && *cmdline)
    {
        dos_length = strlen(cmdline);
        memmove( dos_cmdtail + 1, cmdline, 
                 (dos_length < 125) ? dos_length : 125 );

        /* Non-empty command tail always starts with at least one space. */
        dos_cmdtail[0] = ' ';
        dos_length++;

        /*
         * If command tail is longer than 126 characters,
         * set tail length to 127 and fill CMDLINE environment variable 
         * with full command line (this includes filename).
         */
        if (dos_length > 126)
        {
            char *cmd = HeapAlloc( GetProcessHeap(), 0, 
                                   dos_length + strlen(filename) + 4 );
            char *ptr = cmd;

            if (!cmd)
                return;

            /*
             * Append filename. If path includes spaces, quote the path.
             */
            if (strchr(filename, ' '))
            {
                *ptr++ = '\"';
                strcpy( ptr, filename );
                ptr += strlen(filename);                   
                *ptr++ = '\"';
            }
            else
            {
                strcpy( ptr, filename );
                ptr += strlen(filename);  
            }

            /*
             * Append command tail.
             */
            if (cmdline[0] != ' ')
                *ptr++ = ' ';
            strcpy( ptr, cmdline );

            /*
             * Set environment variable. This will be passed to
             * new DOS process.
             */
            if (!SetEnvironmentVariableA( "CMDLINE", cmd ))
            {
                HeapFree(GetProcessHeap(), 0, cmd );
                return;
            }

            HeapFree(GetProcessHeap(), 0, cmd );
            dos_length = 127;
        }
    }

    AllocConsole();
    SetConsoleTitleA(filename);

    if (MZ_DoLoadImage( hFile, filename, NULL, 0 ))
    {
        DWORD err = MZ_Launch( dos_cmdtail, dos_length );
        /* if we get back here it failed */
        SetLastError( err );
    }
}

/***********************************************************************
 *		MZ_Exec
 *
 * this may only be called from existing DOS processes
 */
BOOL MZ_Exec( CONTEXT *context, LPCSTR filename, BYTE func, LPVOID paramblk )
{
  DWORD binType;
  STARTUPINFOA st;
  PROCESS_INFORMATION pe;
  HANDLE hFile;

  BOOL ret = FALSE;

  if(!GetBinaryTypeA(filename, &binType))   /* determine what kind of binary this is */
  {
    return FALSE; /* binary is not an executable */
  }

  /* handle non-dos executables */
  if(binType != SCS_DOS_BINARY)
  {
    if(func == 0) /* load and execute */
    {
      LPSTR fullCmdLine;
      WORD fullCmdLength;
      LPBYTE psp_start = (LPBYTE)PTR_REAL_TO_LIN(DOSVM_psp, 0);
      PDB16 *psp = (PDB16 *)psp_start;
      ExecBlock *blk = paramblk;
      LPBYTE cmdline = PTR_REAL_TO_LIN(SELECTOROF(blk->cmdline),OFFSETOF(blk->cmdline));
      LPBYTE envblock = PTR_REAL_TO_LIN(psp->environment, 0);
      int    cmdLength = cmdline[0];

      /*
       * If cmdLength is 127, command tail is truncated and environment 
       * variable CMDLINE should contain full command line 
       * (this includes filename).
       */
      if (cmdLength == 127)
      {
          FIXME( "CMDLINE argument passing is unimplemented.\n" );
          cmdLength = 126; /* FIXME */
      }

      fullCmdLength = (strlen(filename) + 1) + cmdLength + 1; /* filename + space + cmdline + terminating null character */

      fullCmdLine = HeapAlloc(GetProcessHeap(), 0, fullCmdLength);
      if(!fullCmdLine) return FALSE; /* return false on memory alloc failure */

      /* build the full command line from the executable file and the command line being passed in */
      snprintf(fullCmdLine, fullCmdLength, "%s ", filename); /* start off with the executable filename and a space */
      memcpy(fullCmdLine + strlen(fullCmdLine), cmdline + 1, cmdLength); /* append cmdline onto the end */
      fullCmdLine[fullCmdLength - 1] = 0; /* null terminate string */

      ZeroMemory (&st, sizeof(STARTUPINFOA));
      st.cb = sizeof(STARTUPINFOA);
      ret = CreateProcessA (NULL, fullCmdLine, NULL, NULL, TRUE, 0, envblock, NULL, &st, &pe);

      /* wait for the app to finish and clean up PROCESS_INFORMATION handles */
      if(ret)
      {
        WaitForSingleObject(pe.hProcess, INFINITE);  /* wait here until the child process is complete */
        CloseHandle(pe.hProcess);
        CloseHandle(pe.hThread);
      }

      HeapFree(GetProcessHeap(), 0, fullCmdLine);  /* free the memory we allocated */
    }
    else
    {
      FIXME("EXEC type of %d not implemented for non-dos executables\n", func);
      ret = FALSE;
    }

    return ret;
  } /* if(binType != SCS_DOS_BINARY) */


  /* handle dos executables */

  hFile = CreateFileA( filename, GENERIC_READ, FILE_SHARE_READ,
			     NULL, OPEN_EXISTING, 0, 0);
  if (hFile == INVALID_HANDLE_VALUE) return FALSE;

  switch (func) {
  case 0: /* load and execute */
  case 1: /* load but don't execute */
    {
      /* save current process's return SS:SP now */
      LPBYTE psp_start = (LPBYTE)PTR_REAL_TO_LIN(DOSVM_psp, 0);
      PDB16 *psp = (PDB16 *)psp_start;
      psp->saveStack = (DWORD)MAKESEGPTR(context->SegSs, LOWORD(context->Esp));
    }
    ret = MZ_DoLoadImage( hFile, filename, NULL, ((ExecBlock *)paramblk)->env_seg );
    if (ret) {
      /* MZ_LoadImage created a new PSP and loaded new values into it,
       * let's work on the new values now */
      LPBYTE psp_start = (LPBYTE)PTR_REAL_TO_LIN(DOSVM_psp, 0);
      ExecBlock *blk = paramblk;
      LPBYTE cmdline = PTR_REAL_TO_LIN(SELECTOROF(blk->cmdline),OFFSETOF(blk->cmdline));

      /* First character contains the length of the command line. */
      MZ_FillPSP(psp_start, (LPSTR)cmdline + 1, cmdline[0]);

      /* the lame MS-DOS engineers decided that the return address should be in int22 */
      DOSVM_SetRMHandler(0x22, (FARPROC16)MAKESEGPTR(context->SegCs, LOWORD(context->Eip)));
      if (func) {
	/* don't execute, just return startup state */
        /*
         * From Ralph Brown:
         *  For function 01h, the AX value to be passed to the child program 
         *  is put on top of the child's stack
         */
        LPBYTE stack;
        init_sp -= 2;
        stack = CTX_SEG_OFF_TO_LIN(context, init_ss, init_sp);
        /* FIXME: push AX correctly */
        stack[0] = 0x00;    /* push AL */
        stack[1] = 0x00;    /* push AH */
	
	blk->init_cs = init_cs;
	blk->init_ip = init_ip;
	blk->init_ss = init_ss;
	blk->init_sp = init_sp;
      } else {
	/* execute by making us return to new process */
	context->SegCs = init_cs;
	context->Eip   = init_ip;
	context->SegSs = init_ss;
	context->Esp   = init_sp;
	context->SegDs = DOSVM_psp;
	context->SegEs = DOSVM_psp;
	context->Eax   = 0;
      }
    }
    break;
  case 3: /* load overlay */
    {
      OverlayBlock *blk = paramblk;
      ret = MZ_DoLoadImage( hFile, filename, blk, 0);
    }
    break;
  default:
    FIXME("EXEC load type %d not implemented\n", func);
    SetLastError(ERROR_INVALID_FUNCTION);
    break;
  }
  CloseHandle(hFile);
  return ret;
}

/***********************************************************************
 *		MZ_AllocDPMITask
 */
void MZ_AllocDPMITask( void )
{
  MZ_InitMemory();
  MZ_InitTask();
}

/***********************************************************************
 *		MZ_RunInThread
 */
void MZ_RunInThread( PAPCFUNC proc, ULONG_PTR arg )
{
  if (loop_thread) {
    DOS_SPC spc;
    HANDLE event;

    spc.proc = proc;
    spc.arg = arg;
    event = CreateEventW(NULL, TRUE, FALSE, NULL);
    PostThreadMessageA(loop_tid, WM_USER + 1, (WPARAM)event, (LPARAM)&spc);
    WaitForSingleObject(event, INFINITE);
    CloseHandle(event);
  } else
    proc(arg);
}
void *dosvm_vm86_teb_info;
static DWORD WINAPI MZ_DOSVM( LPVOID lpExtra )
{
  CONTEXT context;
  INT ret;

  dosvm_pid = getpid();

  memset( &context, 0, sizeof(context) );
  context.SegCs  = init_cs;
  context.Eip    = init_ip;
  context.SegSs  = init_ss;
  context.Esp    = init_sp;
  context.SegDs  = DOSVM_psp;
  context.SegEs  = DOSVM_psp;
  context.EFlags = V86_FLAG | VIF_MASK;
  DOSVM_SetTimer(0x10000);
  dosvm_vm86_teb_info = get_vm86_teb_info();
  ret = DOSVM_Enter( &context );
  if (ret == -1) ret = GetLastError();
  dosvm_pid = 0;
  return ret;
}

static BOOL MZ_InitTask(void)
{
  if (!DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
                       GetCurrentProcess(), &loop_thread,
                       0, FALSE, DUPLICATE_SAME_ACCESS))
    return FALSE;
  dosvm_thread = CreateThread(NULL, 0, MZ_DOSVM, NULL, CREATE_SUSPENDED, &dosvm_tid);
  if (!dosvm_thread) {
    CloseHandle(loop_thread);
    loop_thread = 0;
    return FALSE;
  }
  loop_tid = GetCurrentThreadId();
  return TRUE;
}

static DWORD MZ_Launch( LPCSTR cmdtail, int length )
{
  TDB *pTask = GlobalLock16( GetCurrentTask() );
  BYTE *psp_start = PTR_REAL_TO_LIN( DOSVM_psp, 0 );
  DWORD rv;
  SYSLEVEL *lock;
  MSG msg;

  MZ_FillPSP(psp_start, cmdtail, length);
  pTask->flags |= TDBF_WINOLDAP;

  /* DTA is set to PSP:0080h when a program is started. */
  pTask->dta = MAKESEGPTR( DOSVM_psp, 0x80 );

  GetpWin16Lock( &lock );
  _LeaveSysLevel( lock );

  /* force the message queue to be created */
  PeekMessageW(&msg, NULL, WM_USER + 1, WM_USER + 1, PM_NOREMOVE);

  ResumeThread(dosvm_thread);
  rv = DOSVM_Loop(dosvm_thread);

  CloseHandle(dosvm_thread);
  dosvm_thread = 0; dosvm_tid = 0;
  CloseHandle(loop_thread);
  loop_thread = 0; loop_tid = 0;
  if (rv) return rv;

  VGA_Clean();
  ExitProcess(0);
}

/***********************************************************************
 *		MZ_Exit
 */
void MZ_Exit( CONTEXT *context, BOOL cs_psp, WORD retval )
{
  if (DOSVM_psp) {
    WORD psp_seg = cs_psp ? context->SegCs : DOSVM_psp;
    LPBYTE psp_start = (LPBYTE)PTR_REAL_TO_LIN(psp_seg, 0);
    PDB16 *psp = (PDB16 *)psp_start;
    WORD parpsp = psp->parentPSP; /* check for parent DOS process */
    if (parpsp) {
      /* retrieve parent's return address */
      FARPROC16 retaddr = DOSVM_GetRMHandler(0x22);
      /* restore interrupts */
      DOSVM_SetRMHandler(0x22, psp->savedint22);
      DOSVM_SetRMHandler(0x23, psp->savedint23);
      DOSVM_SetRMHandler(0x24, psp->savedint24);
      /* FIXME: deallocate file handles etc */
      /* free process's associated memory
       * FIXME: walk memory and deallocate all blocks owned by process */
      DOSMEM_FreeBlock( PTR_REAL_TO_LIN(psp->environment,0) );
      DOSMEM_FreeBlock( PTR_REAL_TO_LIN(DOSVM_psp,0) );
      /* switch to parent's PSP */
      DOSVM_psp = parpsp;
      psp_start = (LPBYTE)((DWORD)PTR_REAL_TO_LIN(parpsp, 0));
      psp = (PDB16 *)psp_start;
      /* now return to parent */
      DOSVM_retval = retval;
      context->SegCs = SELECTOROF(retaddr);
      context->Eip   = OFFSETOF(retaddr);
      context->SegSs = SELECTOROF(psp->saveStack);
      context->Esp   = OFFSETOF(psp->saveStack);
      return;
    } else
      TRACE("killing DOS task\n");
  }
  DOSVM_Exit( retval );
}


/***********************************************************************
 *		MZ_Current
 */
BOOL MZ_Current( void )
{
  return (dosvm_pid != 0); /* FIXME: do a better check */
}

#else /* !MZ_SUPPORTED */

/***********************************************************************
 *		__wine_load_dos_exe (KERNEL.@)
 */
void __wine_load_dos_exe( LPCSTR filename, LPCSTR cmdline )
{
    SetLastError( ERROR_NOT_SUPPORTED );
}

/***********************************************************************
 *		MZ_Exec
 */
BOOL MZ_Exec( CONTEXT *context, LPCSTR filename, BYTE func, LPVOID paramblk )
{
  /* can't happen */
  SetLastError(ERROR_BAD_FORMAT);
  return FALSE;
}

/***********************************************************************
 *		MZ_AllocDPMITask
 */
void MZ_AllocDPMITask( void )
{
    FIXME("Actual real-mode calls not supported on this platform!\n");
}

/***********************************************************************
 *		MZ_RunInThread
 */
void MZ_RunInThread( PAPCFUNC proc, ULONG_PTR arg )
{
    proc(arg);
}

/***********************************************************************
 *		MZ_Exit
 */
void MZ_Exit( CONTEXT *context, BOOL cs_psp, WORD retval )
{
  DOSVM_Exit( retval );
}

/***********************************************************************
 *		MZ_Current
 */
BOOL MZ_Current( void )
{
    return FALSE;
}

#endif /* !MZ_SUPPORTED */