newlib/winsup/cygwin/fhandler_tty.cc

/* fhandler_tty.cc

   Copyright 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   2006, 2007, 2008, 2009, 2010 Red Hat, Inc.

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include <stdlib.h>
#include <cygwin/kd.h>
#include "cygerrno.h"
#include "security.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "sigproc.h"
#include "pinfo.h"
#include "ntdll.h"
#include "cygheap.h"
#include "shared_info.h"
#include "cygthread.h"
#include "child_info.h"

#define close_maybe(h) \
  do { \
    if (h && h != INVALID_HANDLE_VALUE) \
      CloseHandle (h); \
  } while (0)

/* pty master control pipe messages */
struct pipe_request {
  DWORD pid;
};

struct pipe_reply {
  HANDLE from_master;
  HANDLE to_master;
  DWORD error;
};

/* tty master stuff */

fhandler_tty_master NO_COPY *tty_master;

static void WINAPI process_input (void *) __attribute__((noreturn));		// Input queue thread
static void WINAPI process_output (void *) __attribute__((noreturn));		// Output queue thread
static void WINAPI process_ioctl (void *) __attribute__((noreturn));		// Ioctl requests thread

fhandler_tty_master::fhandler_tty_master ()
  : fhandler_pty_master (), console (NULL)
{
}

int
fhandler_tty_slave::get_unit ()
{
  return dev () == FH_TTY ? myself->ctty : dev ().minor;
}

void
fhandler_tty_master::set_winsize (bool sendSIGWINCH)
{
  winsize w;
  console->ioctl (TIOCGWINSZ, &w);
  get_ttyp ()->winsize = w;
  if (sendSIGWINCH)
    tc->kill_pgrp (SIGWINCH);
}

int
fhandler_tty_master::init ()
{
  termios_printf ("Creating master for tty%d", get_unit ());

  if (init_console ())
    {
      termios_printf ("can't create fhandler");
      return -1;
    }

  if (!setup (false))
    return 1;

  set_winsize (false);

  set_close_on_exec (true);

  new cygthread (process_input, cygself, "ttyin");
  new cygthread (process_ioctl, cygself, "ttyioctl");
  new cygthread (process_output, cygself, "ttyout");

  return 0;
}

#ifdef DEBUGGING
static class mutex_stack
{
public:
  const char *fn;
  int ln;
  const char *tname;
} ostack[100];

static int osi;
#endif /*DEBUGGING*/

DWORD
fhandler_tty_common::__acquire_output_mutex (const char *fn, int ln,
					   DWORD ms)
{
  if (strace.active ())
    strace.prntf (_STRACE_TERMIOS, fn, "(%d): tty output_mutex: waiting %d ms", ln, ms);
  DWORD res = WaitForSingleObject (output_mutex, ms);
  if (res == WAIT_OBJECT_0)
    {
#ifndef DEBUGGING
      if (strace.active ())
	strace.prntf (_STRACE_TERMIOS, fn, "(%d): tty output_mutex: acquired", ln, res);
#else
      ostack[osi].fn = fn;
      ostack[osi].ln = ln;
      ostack[osi].tname = cygthread::name ();
      termios_printf ("acquired for %s:%d, osi %d", fn, ln, osi);
      osi++;
#endif
    }
  return res;
}

void
fhandler_tty_common::__release_output_mutex (const char *fn, int ln)
{
  if (ReleaseMutex (output_mutex))
    {
#ifndef DEBUGGING
      if (strace.active ())
	strace.prntf (_STRACE_TERMIOS, fn, "(%d): tty output_mutex released", ln);
#else
      if (osi > 0)
	osi--;
      termios_printf ("released at %s:%d, osi %d", fn, ln, osi);
      termios_printf ("  for %s:%d (%s)", ostack[osi].fn, ostack[osi].ln, ostack[osi].tname);
      ostack[osi].ln = -ln;
#endif
    }
#ifdef DEBUGGING
  else if (osi > 0)
    {
      system_printf ("couldn't release output mutex but we seem to own it, %E");
      try_to_debug ();
    }
#endif
}

/* Process tty input. */

void
fhandler_pty_master::doecho (const void *str, DWORD len)
{
  acquire_output_mutex (INFINITE);
  if (!WriteFile (to_master, str, len, &len, NULL))
    termios_printf ("Write to %p failed, %E", to_master);
//  WaitForSingleObject (output_done_event, INFINITE);
  release_output_mutex ();
}

int
fhandler_pty_master::accept_input ()
{
  DWORD bytes_left;
  int ret = 1;

  WaitForSingleObject (input_mutex, INFINITE);

  bytes_left = eat_readahead (-1);

  if (!bytes_left)
    {
      termios_printf ("sending EOF to slave");
      get_ttyp ()->read_retval = 0;
    }
  else
    {
      char *p = rabuf;
      DWORD rc;
      DWORD written = 0;

      termios_printf ("about to write %d chars to slave", bytes_left);
      rc = WriteFile (get_output_handle (), p, bytes_left, &written, NULL);
      if (!rc)
	{
	  debug_printf ("error writing to pipe %E");
	  get_ttyp ()->read_retval = -1;
	  ret = -1;
	}
      else
	{
	  get_ttyp ()->read_retval = 1;
	  p += written;
	  bytes_left -= written;
	  if (bytes_left > 0)
	    {
	      debug_printf ("to_slave pipe is full");
	      puts_readahead (p, bytes_left);
	      ret = 0;
	    }
	}
    }

  SetEvent (input_available_event);
  ReleaseMutex (input_mutex);
  return ret;
}

static void WINAPI
process_input (void *)
{
  char rawbuf[INP_BUFFER_SIZE];

  while (1)
    {
      size_t nraw = INP_BUFFER_SIZE;
      tty_master->console->read ((void *) rawbuf, nraw);
      if (tty_master->line_edit (rawbuf, nraw, tty_master->get_ttyp ()->ti)
	  == line_edit_signalled)
	tty_master->console->eat_readahead (-1);
    }
}

bool
fhandler_pty_master::hit_eof ()
{
  if (get_ttyp ()->was_opened && !get_ttyp ()->slave_alive ())
    {
      /* We have the only remaining open handle to this pty, and
	 the slave pty has been opened at least once.  We treat
	 this as EOF.  */
      termios_printf ("all other handles closed");
      return 1;
    }
  return 0;
}

/* Process tty output requests */

int
fhandler_pty_master::process_slave_output (char *buf, size_t len, int pktmode_on)
{
  size_t rlen;
  char outbuf[OUT_BUFFER_SIZE + 1];
  DWORD n;
  int column = 0;
  int rc = 0;

  if (len == 0)
    goto out;

  if (need_nl)
    {
      /* We need to return a left over \n character, resulting from
	 \r\n conversion.  Note that we already checked for FLUSHO and
	 output_stopped at the time that we read the character, so we
	 don't check again here.  */
      if (buf)
	buf[0] = '\n';
      need_nl = 0;
      rc = 1;
      goto out;
    }


  for (;;)
    {
      /* Set RLEN to the number of bytes to read from the pipe.  */
      rlen = len;
      if (get_ttyp ()->ti.c_oflag & OPOST && get_ttyp ()->ti.c_oflag & ONLCR)
	{
	  /* We are going to expand \n to \r\n, so don't read more than
	     half of the number of bytes requested.  */
	  rlen /= 2;
	  if (rlen == 0)
	    rlen = 1;
	}
      if (rlen > sizeof outbuf)
	rlen = sizeof outbuf;

      HANDLE handle = get_io_handle ();

      n = 0; // get_readahead_into_buffer (outbuf, len);
      if (!n)
	{
	  /* Doing a busy wait like this is quite inefficient, but nothing
	     else seems to work completely.  Windows should provide some sort
	     of overlapped I/O for pipes, or something, but it doesn't.  */
	  while (1)
	    {
	      if (!PeekNamedPipe (handle, NULL, 0, NULL, &n, NULL))
		goto err;
	      if (n > 0)
		break;
	      if (hit_eof ())
		goto out;
	      /* DISCARD (FLUSHO) and tcflush can finish here. */
	      if (n == 0 && (get_ttyp ()->ti.c_lflag & FLUSHO || !buf))
		goto out;
	      if (n == 0 && is_nonblocking ())
		{
		  set_errno (EAGAIN);
		  rc = -1;
		  break;
		}

	      Sleep (10);
	    }

	  if (ReadFile (handle, outbuf, rlen, &n, NULL) == FALSE)
	    goto err;
	}

      termios_printf ("bytes read %u", n);
      get_ttyp ()->write_error = 0;
      if (output_done_event != NULL)
	SetEvent (output_done_event);

      if (get_ttyp ()->ti.c_lflag & FLUSHO || !buf)
	continue;

      char *optr;
      optr = buf;
      if (pktmode_on)
	*optr++ = TIOCPKT_DATA;

      if (!(get_ttyp ()->ti.c_oflag & OPOST))	// post-process output
	{
	  memcpy (optr, outbuf, n);
	  optr += n;
	}
      else					// raw output mode
	{
	  char *iptr = outbuf;

	  while (n--)
	    {
	      switch (*iptr)
		{
		case '\r':
		  if ((get_ttyp ()->ti.c_oflag & ONOCR) && column == 0)
		    {
		      iptr++;
		      continue;
		    }
		  if (get_ttyp ()->ti.c_oflag & OCRNL)
		    *iptr = '\n';
		  else
		    column = 0;
		  break;
		case '\n':
		  if (get_ttyp ()->ti.c_oflag & ONLCR)
		    {
		      *optr++ = '\r';
		      column = 0;
		    }
		  if (get_ttyp ()->ti.c_oflag & ONLRET)
		    column = 0;
		  break;
		default:
		  column++;
		  break;
		}

	      /* Don't store data past the end of the user's buffer.  This
		 can happen if the user requests a read of 1 byte when
		 doing \r\n expansion.  */
	      if (optr - buf >= (int) len)
		{
		  if (*iptr != '\n' || n != 0)
		    system_printf ("internal error: %d unexpected characters", n);
		  need_nl = 1;
		  break;
		}

	      *optr++ = *iptr++;
	    }
	}
      rc = optr - buf;
      break;

    err:
      if (GetLastError () == ERROR_BROKEN_PIPE)
	rc = 0;
      else
	{
	  __seterrno ();
	  rc = -1;
	}
      break;
    }

out:
  termios_printf ("returning %d", rc);
  return rc;
}

static void WINAPI
process_output (void *)
{
  char buf[OUT_BUFFER_SIZE * 2];

  for (;;)
    {
      int n = tty_master->process_slave_output (buf, OUT_BUFFER_SIZE, 0);
      if (n <= 0)
	{
	  if (n < 0)
	    termios_printf ("ReadFile %E");
	  ExitThread (0);
	}
      n = tty_master->console->write ((void *) buf, (size_t) n);
      tty_master->get_ttyp ()->write_error = n == -1 ? get_errno () : 0;
    }
}


/* Process tty ioctl requests */

static void WINAPI
process_ioctl (void *)
{
  while (1)
    {
      WaitForSingleObject (tty_master->ioctl_request_event, INFINITE);
      termios_printf ("ioctl() request");
      tty *ttyp = tty_master->get_ttyp ();
      ttyp->ioctl_retval =
      tty_master->console->ioctl (ttyp->cmd,
				  (ttyp->cmd == KDSKBMETA)
				  ? (void *) ttyp->arg.value
				  : (void *) &ttyp->arg);
      SetEvent (tty_master->ioctl_done_event);
    }
}

/**********************************************************************/
/* Tty slave stuff */

fhandler_tty_slave::fhandler_tty_slave ()
  : fhandler_tty_common (), inuse (NULL)
{
  uninterruptible_io (true);
}

/* FIXME: This function needs to close handles when it has
   a failing condition. */
int
fhandler_tty_slave::open (int flags, mode_t)
{
  HANDLE tty_owner, from_master_local, to_master_local;
  HANDLE *handles[] =
  {
    &from_master_local, &input_available_event, &input_mutex, &inuse,
    &ioctl_done_event, &ioctl_request_event, &output_done_event,
    &output_mutex, &to_master_local, &tty_owner,
    NULL
  };

  const char *errmsg = NULL;

  for (HANDLE **h = handles; *h; h++)
    **h = NULL;

  if (get_device () == FH_TTY)
    dev().tty_to_real_device ();
  fhandler_tty_slave *arch = (fhandler_tty_slave *) cygheap->fdtab.find_archetype (pc.dev);
  if (arch)
    {
      *this = *(fhandler_tty_slave *) arch;
      termios_printf ("copied fhandler_tty_slave archetype");
      set_flags ((flags & ~O_TEXT) | O_BINARY);
      cygheap->manage_console_count ("fhandler_tty_slave::open<arch>", 1);
      goto out;
    }

  tcinit (cygwin_shared->tty[get_unit ()], false);

  cygwin_shared->tty.attach (get_unit ());

  set_flags ((flags & ~O_TEXT) | O_BINARY);
  /* Create synchronisation events */
  char buf[MAX_PATH];

  /* output_done_event may or may not exist.  It will exist if the tty
     was opened by fhandler_tty_master::init, normally called at
     startup if use_tty is non-zero.  It will not exist if this is a
     pty opened by fhandler_pty_master::open.  In the former case, tty
     output is handled by a separate thread which controls output.  */
  shared_name (buf, OUTPUT_DONE_EVENT, get_unit ());
  output_done_event = OpenEvent (MAXIMUM_ALLOWED, TRUE, buf);

  if (!(output_mutex = get_ttyp ()->open_output_mutex (MAXIMUM_ALLOWED)))
    {
      errmsg = "open output mutex failed, %E";
      goto err;
    }
  if (!(input_mutex = get_ttyp ()->open_input_mutex (MAXIMUM_ALLOWED)))
    {
      errmsg = "open input mutex failed, %E";
      goto err;
    }
  shared_name (buf, INPUT_AVAILABLE_EVENT, get_unit ());
  if (!(input_available_event = OpenEvent (MAXIMUM_ALLOWED, TRUE, buf)))
    {
      errmsg = "open input event failed, %E";
      goto err;
    }

  /* The ioctl events may or may not exist.  See output_done_event,
     above.  */
  shared_name (buf, IOCTL_REQUEST_EVENT, get_unit ());
  ioctl_request_event = OpenEvent (MAXIMUM_ALLOWED, TRUE, buf);
  shared_name (buf, IOCTL_DONE_EVENT, get_unit ());
  ioctl_done_event = OpenEvent (MAXIMUM_ALLOWED, TRUE, buf);

  /* FIXME: Needs a method to eliminate tty races */
  {
    /* Create security attribute.  Default permissions are 0620. */
    security_descriptor sd;
    sd.malloc (sizeof (SECURITY_DESCRIPTOR));
    InitializeSecurityDescriptor (sd, SECURITY_DESCRIPTOR_REVISION);
    SECURITY_ATTRIBUTES sa = { sizeof (SECURITY_ATTRIBUTES), NULL, TRUE };
    if (!create_object_sd_from_attribute (NULL, myself->uid, myself->gid,
					  S_IFCHR | S_IRUSR | S_IWUSR | S_IWGRP,
					  sd))
      sa.lpSecurityDescriptor = (PSECURITY_DESCRIPTOR) sd;
    acquire_output_mutex (500);
    inuse = get_ttyp ()->create_inuse (&sa);
    get_ttyp ()->was_opened = true;
    release_output_mutex ();
  }

  if (!get_ttyp ()->from_master || !get_ttyp ()->to_master)
    {
      errmsg = "tty handles have been closed";
      set_errno (EACCES);
      goto err_no_errno;
    }

  if (get_ttyp ()->master_pid < 0)
    {
      errmsg = "*** master is closed";
      set_errno (EAGAIN);
      goto err_no_errno;
    }
  /* Three case for duplicating the pipe handles:
     - Either we're the master.  In this case, just duplicate the handles.
     - Or, we have the right to open the master process for handle duplication.
       In this case, just duplicate the handles.
     - Or, we have to ask the master process itself.  In this case, send our
       pid to the master process and check the reply.  The reply contains
       either the handles, or an error code which tells us why we didn't
       get the handles. */
  if (myself->pid == get_ttyp ()->master_pid)
    {
      /* This is the most common case, just calling openpty. */
      termios_printf ("dup handles within myself.");
      tty_owner = GetCurrentProcess ();
    }
  else
    {
      pinfo p (get_ttyp ()->master_pid);
      if (!p)
	termios_printf ("*** couldn't find tty master");
      else
	{
	  tty_owner = OpenProcess (PROCESS_DUP_HANDLE, FALSE, p->dwProcessId);
	  if (tty_owner)
	    termios_printf ("dup handles directly since I'm allmighty.");
	}
    }
  if (tty_owner)
    {
      if (!DuplicateHandle (tty_owner, get_ttyp ()->from_master,
			    GetCurrentProcess (), &from_master_local, 0, TRUE,
			    DUPLICATE_SAME_ACCESS))
	{
	  termios_printf ("can't duplicate input from %u/%p, %E",
			  get_ttyp ()->master_pid, get_ttyp ()->from_master);
	  __seterrno ();
	  goto err_no_msg;
	}
      if (!DuplicateHandle (tty_owner, get_ttyp ()->to_master,
			  GetCurrentProcess (), &to_master_local, 0, TRUE,
			  DUPLICATE_SAME_ACCESS))
	{
	  errmsg = "can't duplicate output, %E";
	  goto err;
	}
      if (tty_owner != GetCurrentProcess ())
	CloseHandle (tty_owner);
    }
  else
    {
      pipe_request req = { GetCurrentProcessId () };
      pipe_reply repl;
      DWORD len;

      __small_sprintf (buf, "\\\\.\\pipe\\cygwin-%S-tty%d-master-ctl",
		       &installation_key, get_unit ());
      termios_printf ("dup handles via master control pipe %s", buf);
      if (!CallNamedPipe (buf, &req, sizeof req, &repl, sizeof repl,
			  &len, 500))
	{
	  errmsg = "can't call master, %E";
	  goto err;
	}
      from_master_local = repl.from_master;
      to_master_local = repl.to_master;
      if (!from_master_local || !to_master_local)
	{
	  SetLastError (repl.error);
	  errmsg = "error duplicating pipes, %E";
	  goto err;
	}
    }
  VerifyHandle (from_master_local);
  VerifyHandle (to_master_local);

  termios_printf ("duplicated from_master %p->%p from tty_owner",
		  get_ttyp ()->from_master, from_master_local);
  termios_printf ("duplicated to_master %p->%p from tty_owner",
		  get_ttyp ()->to_master, to_master_local);

  set_io_handle (from_master_local);
  set_output_handle (to_master_local);
  set_close_on_exec (!!(flags & O_CLOEXEC));

  set_open_status ();
  if (cygheap->manage_console_count ("fhandler_tty_slave::open", 1) == 1
      && !output_done_event)
    fhandler_console::need_invisible ();

  // FIXME: Do this better someday
  arch = (fhandler_tty_slave *) cmalloc_abort (HEAP_ARCHETYPES, sizeof (*this));
  *((fhandler_tty_slave **) cygheap->fdtab.add_archetype ()) = arch;
  archetype = arch;
  *arch = *this;

out:
  usecount = 0;
  arch->usecount++;
  report_tty_counts (this, "opened", "");
  myself->set_ctty (get_ttyp (), flags, arch);

  return 1;

err:
  __seterrno ();
err_no_errno:
  termios_printf (errmsg);
err_no_msg:
  for (HANDLE **h = handles; *h; h++)
    if (**h && **h != INVALID_HANDLE_VALUE)
      CloseHandle (**h);
  return 0;
}

int
fhandler_tty_slave::close ()
{
  /* This used to always call fhandler_tty_common::close when hExeced but that
     caused multiple closes of the handles associated with this tty.  Since
     close_all_files is not called until after the cygwin process has synced
     or before a non-cygwin process has exited, it should be safe to just
     close this normally.  cgf 2006-05-20 */
  cygheap->manage_console_count ("fhandler_tty_slave::close", -1);

  archetype->usecount--;
  report_tty_counts (this, "closed", "");

  if (archetype->usecount)
    {
#ifdef DEBUGGING
      if (archetype->usecount < 0)
	system_printf ("error: usecount %d", archetype->usecount);
#endif
      termios_printf ("just returning because archetype usecount is != 0");
      return 0;
    }

  termios_printf ("closing last open %s handle", ttyname ());
  if (inuse && !CloseHandle (inuse))
    termios_printf ("CloseHandle (inuse), %E");
  return fhandler_tty_common::close ();
}

int
fhandler_tty_slave::init (HANDLE f, DWORD a, mode_t)
{
  int flags = 0;

  a &= GENERIC_READ | GENERIC_WRITE;
  if (a == GENERIC_READ)
    flags = O_RDONLY;
  if (a == GENERIC_WRITE)
    flags = O_WRONLY;
  if (a == (GENERIC_READ | GENERIC_WRITE))
    flags = O_RDWR;

  int ret = open (flags);

  if (ret && !cygwin_finished_initializing && !being_debugged ())
    {
      /* This only occurs when called from dtable::init_std_file_from_handle
	 We have been started from a non-Cygwin process.  So we should become
	 tty process group leader.
	 TODO: Investigate how SIGTTIN should be handled with pure-windows
	 programs. */
      pinfo p (tc->getpgid ());
      /* We should only grab this when the process group owner for this
	 tty is a non-cygwin process or we've been started directly
	 from a non-Cygwin process with no Cygwin ancestry.  */
      if (!p || ISSTATE (p, PID_NOTCYGWIN))
	{
	  termios_printf ("Setting process group leader to %d since %W(%d) is not a cygwin process",
			  myself->pgid, p->progname, p->pid);
	  tc->setpgid (myself->pgid);
	}
    }

  if (f != INVALID_HANDLE_VALUE)
    CloseHandle (f);	/* Reopened by open */

  return ret;
}

ssize_t __stdcall
fhandler_tty_slave::write (const void *ptr, size_t len)
{
  DWORD n, towrite = len;

  termios_printf ("tty%d, write(%x, %d)", get_unit (), ptr, len);

  acquire_output_mutex (INFINITE);

  while (len)
    {
      n = min (OUT_BUFFER_SIZE, len);
      char *buf = (char *)ptr;
      ptr = (char *) ptr + n;
      len -= n;

      /* Previous write may have set write_error to != 0.  Check it here.
	 This is less than optimal, but the alternative slows down tty
	 writes enormously. */
      if (get_ttyp ()->write_error)
	{
	  set_errno (get_ttyp ()->write_error);
	  towrite = (DWORD) -1;
	  break;
	}

      if (WriteFile (get_output_handle (), buf, n, &n, NULL) == FALSE)
	{
	  DWORD err = GetLastError ();
	  termios_printf ("WriteFile failed, %E");
	  switch (err)
	    {
	    case ERROR_NO_DATA:
	      err = ERROR_IO_DEVICE;
	    default:
	      __seterrno_from_win_error (err);
	    }
	  raise (SIGHUP);		/* FIXME: Should this be SIGTTOU? */
	  towrite = (DWORD) -1;
	  break;
	}

      if (output_done_event != NULL)
	{
	  DWORD rc;
	  DWORD x = n * 1000;
	  rc = WaitForSingleObject (output_done_event, x);
	  termios_printf ("waited %d ms for output_done_event, WFSO %d", x, rc);
	}
    }
  release_output_mutex ();
  return towrite;
}

void __stdcall
fhandler_tty_slave::read (void *ptr, size_t& len)
{
  int totalread = 0;
  int vmin = 0;
  int vtime = 0;	/* Initialized to prevent -Wuninitialized warning */
  size_t readlen;
  DWORD bytes_in_pipe;
  char buf[INP_BUFFER_SIZE];
  char peek_buf[INP_BUFFER_SIZE];
  DWORD time_to_wait;
  DWORD rc;
  HANDLE w4[2];

  termios_printf ("read(%x, %d) handle %p", ptr, len, get_handle ());

  if (!ptr) /* Indicating tcflush(). */
    time_to_wait = 0;
  else if ((get_ttyp ()->ti.c_lflag & ICANON))
    time_to_wait = INFINITE;
  else
    {
      vmin = get_ttyp ()->ti.c_cc[VMIN];
      if (vmin > INP_BUFFER_SIZE)
	vmin = INP_BUFFER_SIZE;
      vtime = get_ttyp ()->ti.c_cc[VTIME];
      if (vmin < 0)
	vmin = 0;
      if (vtime < 0)
	vtime = 0;
      if (!vmin && !vtime)
	time_to_wait = 0;
      else
	time_to_wait = !vtime ? INFINITE : 100 * vtime;
    }

  w4[0] = signal_arrived;
  w4[1] = input_available_event;

  DWORD waiter = time_to_wait;
  while (len)
    {
      rc = WaitForMultipleObjects (2, w4, FALSE, waiter);

      if (rc == WAIT_TIMEOUT)
	{
	  termios_printf ("wait timed out, waiter %u", waiter);
	  break;
	}

      if (rc == WAIT_FAILED)
	{
	  termios_printf ("wait for input event failed, %E");
	  break;
	}

      if (rc == WAIT_OBJECT_0)
	{
	  /* if we've received signal after successfully reading some data,
	     just return all data successfully read */
	  if (totalread > 0)
	    break;
	  set_sig_errno (EINTR);
	  len = (size_t) -1;
	  return;
	}

      rc = WaitForSingleObject (input_mutex, 1000);
      if (rc == WAIT_FAILED)
	{
	  termios_printf ("wait for input mutex failed, %E");
	  break;
	}
      else if (rc == WAIT_TIMEOUT)
	{
	  termios_printf ("failed to acquire input mutex after input event arrived");
	  break;
	}
      if (!PeekNamedPipe (get_handle (), peek_buf, sizeof (peek_buf), &bytes_in_pipe, NULL, NULL))
	{
	  termios_printf ("PeekNamedPipe failed, %E");
	  raise (SIGHUP);
	  bytes_in_pipe = 0;
	}

      /* On first peek determine no. of bytes to flush. */
      if (!ptr && len == UINT_MAX)
	len = (size_t) bytes_in_pipe;

      if (ptr && !bytes_in_pipe && !vmin && !time_to_wait)
	{
	  ReleaseMutex (input_mutex);
	  len = (size_t) bytes_in_pipe;
	  return;
	}

      readlen = min (bytes_in_pipe, min (len, sizeof (buf)));

      if (ptr && vmin && readlen > (unsigned) vmin)
	readlen = vmin;

      DWORD n = 0;
      if (readlen)
	{
	  termios_printf ("reading %d bytes (vtime %d)", readlen, vtime);
	  if (ReadFile (get_handle (), buf, readlen, &n, NULL) == FALSE)
	    {
	      termios_printf ("read failed, %E");
	      raise (SIGHUP);
	    }
	  /* MSDN states that 5th prameter can be used to determine total
	     number of bytes in pipe, but for some reason this number doesn't
	     change after successful read. So we have to peek into the pipe
	     again to see if input is still available */
	  if (!PeekNamedPipe (get_handle (), peek_buf, 1, &bytes_in_pipe, NULL, NULL))
	    {
	      termios_printf ("PeekNamedPipe failed, %E");
	      raise (SIGHUP);
	      bytes_in_pipe = 0;
	    }
	  if (n)
	    {
	      len -= n;
	      totalread += n;
	      if (ptr)
		{
		  memcpy (ptr, buf, n);
		  ptr = (char *) ptr + n;
		}
	    }
	}

      if (!bytes_in_pipe)
	ResetEvent (input_available_event);

      ReleaseMutex (input_mutex);

      if (!ptr)
	{
	  if (!bytes_in_pipe)
	    break;
	  continue;
	}

      if (get_ttyp ()->read_retval < 0)	// read error
	{
	  set_errno (-get_ttyp ()->read_retval);
	  totalread = -1;
	  break;
	}
      if (get_ttyp ()->read_retval == 0)	//EOF
	{
	  termios_printf ("saw EOF");
	  break;
	}
      if (get_ttyp ()->ti.c_lflag & ICANON || is_nonblocking ())
	break;
      if (vmin && totalread >= vmin)
	break;

      /* vmin == 0 && vtime == 0:
       *   we've already read all input, if any, so return immediately
       * vmin == 0 && vtime > 0:
       *   we've waited for input 10*vtime ms in WFSO(input_available_event),
       *   no matter whether any input arrived, we shouldn't wait any longer,
       *   so return immediately
       * vmin > 0 && vtime == 0:
       *   here, totalread < vmin, so continue waiting until more data
       *   arrive
       * vmin > 0 && vtime > 0:
       *   similar to the previous here, totalread < vmin, and timer
       *   hadn't expired -- WFSO(input_available_event) != WAIT_TIMEOUT,
       *   so "restart timer" and wait until more data arrive
       */

      if (vmin == 0)
	break;

      if (n)
	waiter = time_to_wait;
    }
  termios_printf ("%d=read(%x, %d)", totalread, ptr, len);
  len = (size_t) totalread;
}

int
fhandler_tty_slave::dup (fhandler_base *child)
{
  fhandler_tty_slave *arch = (fhandler_tty_slave *) archetype;
  *(fhandler_tty_slave *) child = *arch;
  child->set_flags (get_flags ());
  child->usecount = 0;
  arch->usecount++;
  cygheap->manage_console_count ("fhandler_tty_slave::dup", 1);
  report_tty_counts (child, "duped", "");
  return 0;
}

int
fhandler_pty_master::dup (fhandler_base *child)
{
  fhandler_tty_master *arch = (fhandler_tty_master *) archetype;
  *(fhandler_tty_master *) child = *arch;
  child->set_flags (get_flags ());
  child->usecount = 0;
  arch->usecount++;
  report_tty_counts (child, "duped master", "");
  return 0;
}

int
fhandler_tty_slave::tcgetattr (struct termios *t)
{
  *t = get_ttyp ()->ti;
  return 0;
}

int
fhandler_tty_slave::tcsetattr (int, const struct termios *t)
{
  acquire_output_mutex (INFINITE);
  get_ttyp ()->ti = *t;
  release_output_mutex ();
  return 0;
}

int
fhandler_tty_slave::tcflush (int queue)
{
  int ret = 0;

  termios_printf ("tcflush(%d) handle %p", queue, get_handle ());

  if (queue == TCIFLUSH || queue == TCIOFLUSH)
    {
      size_t len = UINT_MAX;
      read (NULL, len);
      ret = ((int) len) >= 0 ? 0 : -1;
    }
  if (queue == TCOFLUSH || queue == TCIOFLUSH)
    {
      /* do nothing for now. */
    }

  termios_printf ("%d=tcflush(%d)", ret, queue);
  return ret;
}

int
fhandler_tty_slave::ioctl (unsigned int cmd, void *arg)
{
  termios_printf ("ioctl (%x)", cmd);

  if (myself->pgid && get_ttyp ()->getpgid () != myself->pgid
      && myself->ctty == get_unit () && (get_ttyp ()->ti.c_lflag & TOSTOP))
    {
      /* background process */
      termios_printf ("bg ioctl pgid %d, tpgid %d, %s", myself->pgid,
		      get_ttyp ()->getpgid (), myctty ());
      raise (SIGTTOU);
    }

  int retval;
  switch (cmd)
    {
    case TIOCGWINSZ:
    case TIOCSWINSZ:
    case TIOCLINUX:
    case KDGKBMETA:
    case KDSKBMETA:
      break;
    case FIONBIO:
      set_nonblocking (*(int *) arg);
      retval = 0;
      goto out;
    case TIOCGPGRP:
      {
	pid_t pid = this->tcgetpgrp ();
	if (pid < 0)
	  retval = -1;
	else
	  {
	    *((pid_t *) arg) = pid;
	    retval = 0;
	  }
      }
      goto out;
    case TIOCSPGRP:
      retval = this->tcsetpgrp ((pid_t) arg);
      goto out;
    default:
      set_errno (EINVAL);
      return -1;
    }

  acquire_output_mutex (INFINITE);

  get_ttyp ()->cmd = cmd;
  get_ttyp ()->ioctl_retval = 0;
  int val;
  switch (cmd)
    {
    case TIOCGWINSZ:
      get_ttyp ()->arg.winsize = get_ttyp ()->winsize;
      if (ioctl_request_event)
	SetEvent (ioctl_request_event);
      *(struct winsize *) arg = get_ttyp ()->arg.winsize;
      if (ioctl_done_event)
	WaitForSingleObject (ioctl_done_event, INFINITE);
      get_ttyp ()->winsize = get_ttyp ()->arg.winsize;
      break;
    case TIOCSWINSZ:
      if (get_ttyp ()->winsize.ws_row != ((struct winsize *) arg)->ws_row
	  || get_ttyp ()->winsize.ws_col != ((struct winsize *) arg)->ws_col)
	{
	  get_ttyp ()->arg.winsize = *(struct winsize *) arg;
	  if (ioctl_request_event)
	    {
	      get_ttyp ()->ioctl_retval = -EINVAL;
	      SetEvent (ioctl_request_event);
	    }
	  else
	    {
	      get_ttyp ()->winsize = *(struct winsize *) arg;
	      killsys (-get_ttyp ()->getpgid (), SIGWINCH);
	    }
	  if (ioctl_done_event)
	    WaitForSingleObject (ioctl_done_event, INFINITE);
	}
      break;
    case TIOCLINUX:
      val = *(unsigned char *) arg;
      if (val != 6 || !ioctl_request_event || !ioctl_done_event)
	  get_ttyp ()->ioctl_retval = -EINVAL;
      else
	{
	  get_ttyp ()->arg.value = val;
	  SetEvent (ioctl_request_event);
	  WaitForSingleObject (ioctl_done_event, INFINITE);
	  *(unsigned char *) arg = (unsigned char) (get_ttyp ()->arg.value);
	}
      break;
    case KDGKBMETA:
      if (ioctl_request_event)
	{
	  SetEvent (ioctl_request_event);
	  if (ioctl_done_event)
	    WaitForSingleObject (ioctl_done_event, INFINITE);
	  *(int *) arg = get_ttyp ()->arg.value;
	}
      else
	get_ttyp ()->ioctl_retval = -EINVAL;
      break;
    case KDSKBMETA:
      if (ioctl_request_event)
	{
	  get_ttyp ()->arg.value = (int) arg;
	  SetEvent (ioctl_request_event);
	  if (ioctl_done_event)
	    WaitForSingleObject (ioctl_done_event, INFINITE);
	}
      else
	get_ttyp ()->ioctl_retval = -EINVAL;
      break;
    }

  release_output_mutex ();
  retval = get_ttyp ()->ioctl_retval;
  if (retval < 0)
    {
      set_errno (-retval);
      retval = -1;
    }

out:
  termios_printf ("%d = ioctl (%x)", retval, cmd);
  return retval;
}

int __stdcall
fhandler_tty_slave::fstat (struct __stat64 *st)
{
  fhandler_base::fstat (st);

  bool to_close = false;
  if (!input_available_event)
    {
      char buf[MAX_PATH];
      shared_name (buf, INPUT_AVAILABLE_EVENT, get_unit ());
      input_available_event = OpenEvent (READ_CONTROL, TRUE, buf);
      if (input_available_event)
	to_close = true;
    }
  if (!input_available_event
      || get_object_attribute (input_available_event, &st->st_uid, &st->st_gid,
			       &st->st_mode))
    {
      /* If we can't access the ACL, or if the tty doesn't actually exist,
         then fake uid and gid to strict, system-like values. */
      st->st_mode = S_IFCHR | S_IRUSR | S_IWUSR;
      st->st_uid = 18;
      st->st_gid = 544;
    }
  if (to_close)
    CloseHandle (input_available_event);
  return 0;
}

/* Helper function for fchmod and fchown, which just opens all handles
   and signals success via bool return. */
bool
fhandler_tty_slave::fch_open_handles ()
{
  char buf[MAX_PATH];

  tc = cygwin_shared->tty[get_unit ()];
  shared_name (buf, INPUT_AVAILABLE_EVENT, get_unit ());
  input_available_event = OpenEvent (READ_CONTROL | WRITE_DAC | WRITE_OWNER,
				     TRUE, buf);
  output_mutex = get_ttyp ()->open_output_mutex (WRITE_DAC | WRITE_OWNER);
  input_mutex = get_ttyp ()->open_input_mutex (WRITE_DAC | WRITE_OWNER);
  inuse = get_ttyp ()->open_inuse (WRITE_DAC | WRITE_OWNER);
  if (!input_available_event || !output_mutex || !input_mutex || !inuse)
    {
      __seterrno ();
      return false;
    }
  /* These members are optional, no error checking */
  shared_name (buf, OUTPUT_DONE_EVENT, get_unit ());
  output_done_event = OpenEvent (WRITE_DAC | WRITE_OWNER, TRUE, buf);
  shared_name (buf, IOCTL_REQUEST_EVENT, get_unit ());
  ioctl_request_event = OpenEvent (WRITE_DAC | WRITE_OWNER, TRUE, buf);
  shared_name (buf, IOCTL_DONE_EVENT, get_unit ());
  ioctl_done_event = OpenEvent (WRITE_DAC | WRITE_OWNER, TRUE, buf);
  return true;
}

/* Helper function for fchmod and fchown, which sets the new security
   descriptor on all objects representing the tty. */
int
fhandler_tty_slave::fch_set_sd (security_descriptor &sd, bool chown)
{
  security_descriptor sd_old;

  get_object_sd (input_available_event, sd_old);
  if (!set_object_sd (input_available_event, sd, chown)
      && !set_object_sd (output_mutex, sd, chown)
      && !set_object_sd (input_mutex, sd, chown)
      && !set_object_sd (inuse, sd, chown)
      && (!output_done_event
	  || !set_object_sd (output_done_event, sd, chown))
      && (!ioctl_request_event
	  || !set_object_sd (ioctl_request_event, sd, chown))
      && (!ioctl_done_event
	  || !set_object_sd (ioctl_done_event, sd, chown)))
    return 0;
  set_object_sd (input_available_event, sd_old, chown);
  set_object_sd (output_mutex, sd_old, chown);
  set_object_sd (input_mutex, sd_old, chown);
  set_object_sd (inuse, sd_old, chown);
  if (!output_done_event)
      set_object_sd (output_done_event, sd_old, chown);
  if (!ioctl_request_event)
      set_object_sd (ioctl_request_event, sd_old, chown);
  if (!ioctl_done_event)
      set_object_sd (ioctl_done_event, sd_old, chown);
  return -1;
}

/* Helper function for fchmod and fchown, which closes all object handles in
   the tty. */
void
fhandler_tty_slave::fch_close_handles ()
{
  close_maybe (get_io_handle ());
  close_maybe (get_output_handle ());
  close_maybe (output_done_event);
  close_maybe (ioctl_done_event);
  close_maybe (ioctl_request_event);
  close_maybe (input_available_event);
  close_maybe (output_mutex);
  close_maybe (input_mutex);
  close_maybe (inuse);
}

int __stdcall
fhandler_tty_slave::fchmod (mode_t mode)
{
  int ret = -1;
  bool to_close = false;
  security_descriptor sd;
  __uid32_t uid;
  __gid32_t gid;

  if (!input_available_event)
    {
      to_close = true;
      if (!fch_open_handles ())
	goto errout;
    }
  sd.malloc (sizeof (SECURITY_DESCRIPTOR));
  InitializeSecurityDescriptor (sd, SECURITY_DESCRIPTOR_REVISION);
  if (!get_object_attribute (input_available_event, &uid, &gid, NULL)
      && !create_object_sd_from_attribute (NULL, uid, gid, S_IFCHR | mode, sd))
    ret = fch_set_sd (sd, false);
errout:
  if (to_close)
    fch_close_handles ();
  return ret;
}

int __stdcall
fhandler_tty_slave::fchown (__uid32_t uid, __gid32_t gid)
{
  int ret = -1;
  bool to_close = false;
  mode_t mode;
  __uid32_t o_uid;
  __gid32_t o_gid;
  security_descriptor sd;

  if (uid == ILLEGAL_UID && gid == ILLEGAL_GID)
    return 0;
  if (!input_available_event)
    {
      to_close = true;
      if (!fch_open_handles ())
	goto errout;
    }
  sd.malloc (sizeof (SECURITY_DESCRIPTOR));
  InitializeSecurityDescriptor (sd, SECURITY_DESCRIPTOR_REVISION);
  if (!get_object_attribute (input_available_event, &o_uid, &o_gid, &mode))
    {
      if ((uid == ILLEGAL_UID || uid == o_uid)
	  && (gid == ILLEGAL_GID || gid == o_gid))
	ret = 0;
      else if (!create_object_sd_from_attribute (input_available_event,
						 uid, gid, S_IFCHR | mode, sd))
	ret = fch_set_sd (sd, true);
    }
errout:
  if (to_close)
    fch_close_handles ();
  return ret;
}

/*******************************************************
 fhandler_pty_master
*/
fhandler_pty_master::fhandler_pty_master ()
  : fhandler_tty_common (), pktmode (0), need_nl (0), dwProcessId (0)
{
}

int
fhandler_pty_master::open (int flags, mode_t)
{
  /* Note that allocate returns with the tty lock set if it was successful. */
  int ntty = cygwin_shared->tty.allocate (false);
  if (ntty < 0)
    return 0;

  dev().devn = FHDEV (DEV_TTYM_MAJOR, ntty);
  if (!setup (true))
    {
      lock_ttys::release ();
      return 0;
    }
  lock_ttys::release ();
  set_flags ((flags & ~O_TEXT) | O_BINARY);
  set_open_status ();

  /* FIXME: Do this better someday */
  fhandler_pty_master *arch = (fhandler_tty_master *) cmalloc_abort (HEAP_ARCHETYPES, sizeof (*this));
  *((fhandler_pty_master **) cygheap->fdtab.add_archetype ()) = arch;
  archetype = arch;
  *arch = *this;
  arch->dwProcessId = GetCurrentProcessId ();

  usecount = 0;
  arch->usecount++;
  char buf[sizeof ("opened pty master for ttyNNNNNNNNNNN")];
  __small_sprintf (buf, "opened pty master for tty%d", get_unit ());
  report_tty_counts (this, buf, "");
  return 1;
}

_off64_t
fhandler_tty_common::lseek (_off64_t, int)
{
  set_errno (ESPIPE);
  return -1;
}

int
fhandler_tty_common::close ()
{
  termios_printf ("tty%d <%p,%p> closing", get_unit (), get_handle (), get_output_handle ());
  if (output_done_event && !CloseHandle (output_done_event))
    termios_printf ("CloseHandle (output_done_event), %E");
  if (ioctl_done_event && !CloseHandle (ioctl_done_event))
    termios_printf ("CloseHandle (ioctl_done_event), %E");
  if (ioctl_request_event && !CloseHandle (ioctl_request_event))
    termios_printf ("CloseHandle (ioctl_request_event), %E");
  if (!ForceCloseHandle (input_mutex))
    termios_printf ("CloseHandle (input_mutex<%p>), %E", input_mutex);
  if (!ForceCloseHandle (output_mutex))
    termios_printf ("CloseHandle (output_mutex<%p>), %E", output_mutex);
  if (!ForceCloseHandle1 (get_handle (), from_pty))
    termios_printf ("CloseHandle (get_handle ()<%p>), %E", get_handle ());
  if (!ForceCloseHandle1 (get_output_handle (), to_pty))
    termios_printf ("CloseHandle (get_output_handle ()<%p>), %E", get_output_handle ());

  if (!ForceCloseHandle (input_available_event))
    termios_printf ("CloseHandle (input_available_event<%p>), %E", input_available_event);

  return 0;
}

int
fhandler_pty_master::close ()
{
#if 0
  while (accept_input () > 0)
    continue;
#endif
  archetype->usecount--;
  report_tty_counts (this, "closing master", "");

  if (archetype->usecount)
    {
#ifdef DEBUGGING
      if (archetype->usecount < 0)
	system_printf ("error: usecount %d", archetype->usecount);
#endif
      termios_printf ("just returning because archetype usecount is != 0");
      return 0;
    }

  fhandler_tty_master *arch = (fhandler_tty_master *) archetype;
  termios_printf ("closing from_master(%p)/to_master(%p) since we own them(%d)",
		  arch->from_master, arch->to_master, arch->dwProcessId);
  if (cygwin_finished_initializing)
    {
      if (arch->master_ctl && get_ttyp ()->master_pid == myself->pid)
	{
	  char buf[MAX_PATH];
	  pipe_request req = { (DWORD) -1 };
	  pipe_reply repl;
	  DWORD len;

	  __small_sprintf (buf, "\\\\.\\pipe\\cygwin-%S-tty%d-master-ctl",
			   &installation_key, get_unit ());
	  CallNamedPipe (buf, &req, sizeof req, &repl, sizeof repl, &len, 500);
	  CloseHandle (arch->master_ctl);
	  arch->master_thread->detach ();
	}
      if (!ForceCloseHandle (arch->from_master))
	termios_printf ("error closing from_master %p, %E", arch->from_master);
      if (!ForceCloseHandle (arch->to_master))
	termios_printf ("error closing from_master %p, %E", arch->to_master);
    }
  fhandler_tty_common::close ();

  if (hExeced || get_ttyp ()->master_pid != myself->pid)
    termios_printf ("not clearing: %d, master_pid %d", hExeced, get_ttyp ()->master_pid);
  else
    get_ttyp ()->set_master_closed ();

  return 0;
}

ssize_t __stdcall
fhandler_pty_master::write (const void *ptr, size_t len)
{
  int i;
  char *p = (char *) ptr;
  termios ti = tc->ti;

  for (i = 0; i < (int) len; i++)
    {
      line_edit_status status = line_edit (p++, 1, ti);
      if (status > line_edit_signalled)
	{
	  if (status != line_edit_pipe_full)
	    i = -1;
	  break;
	}
    }
  return i;
}

void __stdcall
fhandler_pty_master::read (void *ptr, size_t& len)
{
  len = (size_t) process_slave_output ((char *) ptr, len, pktmode);
}

int
fhandler_pty_master::tcgetattr (struct termios *t)
{
  *t = cygwin_shared->tty[get_unit ()]->ti;
  return 0;
}

int
fhandler_pty_master::tcsetattr (int, const struct termios *t)
{
  cygwin_shared->tty[get_unit ()]->ti = *t;
  return 0;
}

int
fhandler_pty_master::tcflush (int queue)
{
  int ret = 0;

  termios_printf ("tcflush(%d) handle %p", queue, get_handle ());

  if (queue == TCIFLUSH || queue == TCIOFLUSH)
    ret = process_slave_output (NULL, OUT_BUFFER_SIZE, 0);
  else if (queue == TCIFLUSH || queue == TCIOFLUSH)
    {
      /* do nothing for now. */
    }

  termios_printf ("%d=tcflush(%d)", ret, queue);
  return ret;
}

int
fhandler_pty_master::ioctl (unsigned int cmd, void *arg)
{
  switch (cmd)
    {
    case TIOCPKT:
      pktmode = *(int *) arg;
      break;
    case TIOCGWINSZ:
      *(struct winsize *) arg = get_ttyp ()->winsize;
      break;
    case TIOCSWINSZ:
      if (get_ttyp ()->winsize.ws_row != ((struct winsize *) arg)->ws_row
	  || get_ttyp ()->winsize.ws_col != ((struct winsize *) arg)->ws_col)
	{
	  get_ttyp ()->winsize = *(struct winsize *) arg;
	  killsys (-get_ttyp ()->getpgid (), SIGWINCH);
	}
      break;
    case TIOCGPGRP:
      *((pid_t *) arg) = this->tcgetpgrp ();
      break;
    case TIOCSPGRP:
      return this->tcsetpgrp ((pid_t) arg);
    case FIONBIO:
      set_nonblocking (*(int *) arg);
      break;
    default:
      set_errno (EINVAL);
      return -1;
    }
  return 0;
}

char *
fhandler_pty_master::ptsname ()
{
  static char buf[TTY_NAME_MAX];

  __small_sprintf (buf, "/dev/tty%d", get_unit ());
  return buf;
}

void
fhandler_tty_common::set_close_on_exec (bool val)
{
  // Cygwin processes will handle this specially on exec.
  close_on_exec (val);
}

void
fhandler_tty_slave::fixup_after_fork (HANDLE parent)
{
  // fork_fixup (parent, inuse, "inuse");
  // fhandler_tty_common::fixup_after_fork (parent);
  report_tty_counts (this, "inherited", "");
}

void
fhandler_tty_slave::fixup_after_exec ()
{
  if (!close_on_exec ())
    fixup_after_fork (NULL);
}

int
fhandler_tty_master::init_console ()
{
  console = (fhandler_console *) build_fh_dev (*console_dev, "/dev/ttym");
  if (console == NULL)
    return -1;

  console->init (INVALID_HANDLE_VALUE, GENERIC_READ | GENERIC_WRITE, O_BINARY);
  cygheap->manage_console_count ("fhandler_tty_master::init_console", -1, true);
  console->uninterruptible_io (true);
  return 0;
}

extern "C" BOOL WINAPI GetNamedPipeClientProcessId (HANDLE, PULONG);

/* This thread function handles the master control pipe.  It waits for a
   client to connect.  Then it checks if the client process has permissions
   to access the tty handles.  If so, it opens the client process and
   duplicates the handles into that process.  If that fails, it sends a reply
   with at least one handle set to NULL and an error code.  Last but not
   least, the client is disconnected and the thread waits for the next client.

   A special case is when the master side of the tty is about to be closed.
   The client side is the fhandler_pty_master::close function and it sends
   a PID -1 in that case.  On Vista and later a check is performed that the
   request to leave really comes from the master process itself.  On earlier
   OSes there's no function to check for the PID of the client process so
   we have to trust the client side.

   Since there's always only one pipe instance, there's a chance that clients
   have to wait to connect to the master control pipe.  Therefore the client
   calls to CallNamedPipe should have a big enough timeout value.  For now this
   is 500ms.  Hope that's enough. */

DWORD
fhandler_pty_master::pty_master_thread ()
{
  bool exit = false;
  GENERIC_MAPPING map = { EVENT_QUERY_STATE, EVENT_MODIFY_STATE, 0,
			  EVENT_QUERY_STATE | EVENT_MODIFY_STATE };
  pipe_request req;
  DWORD len;
  security_descriptor sd;
  HANDLE token;
  PRIVILEGE_SET ps;
  BOOL ret;
  DWORD pid;

  termios_printf ("Entered");
  while (!exit && (ConnectNamedPipe (master_ctl, NULL) || GetLastError () == ERROR_PIPE_CONNECTED))
    {
      pipe_reply repl = { NULL, NULL, 0 };
      bool deimp = false;
      BOOL allow = FALSE;
      ACCESS_MASK access = EVENT_MODIFY_STATE;
      HANDLE client = NULL;

      if (!ReadFile (master_ctl, &req, sizeof req, &len, NULL))
      	{
	  termios_printf ("ReadFile, %E");
	  goto reply;
	}
      /* This function is only available since Vista, unfortunately.
	 In earlier OSes we simply have to believe that the client
	 has no malicious intent (== sends arbitrary PIDs). */
      if (!GetNamedPipeClientProcessId (master_ctl, &pid))
	pid = req.pid;
      if (get_object_sd (input_available_event, sd))
	{
	  termios_printf ("get_object_sd, %E");
	  goto reply;
	}
      cygheap->user.deimpersonate ();
      deimp = true;
      if (!ImpersonateNamedPipeClient (master_ctl))
	{
	  termios_printf ("ImpersonateNamedPipeClient, %E");
	  goto reply;
	}
      if (!OpenThreadToken (GetCurrentThread (), TOKEN_QUERY, TRUE, &token))
	{
	  termios_printf ("OpenThreadToken, %E");
	  goto reply;
	}
      len = sizeof ps;
      ret = AccessCheck (sd, token, access, &map, &ps, &len, &access, &allow);
      CloseHandle (token);
      if (!ret)
	{
	  termios_printf ("AccessCheck, %E");
	  goto reply;
	}
      if (!RevertToSelf ())
	{
	  termios_printf ("RevertToSelf, %E");
	  goto reply;
	}
      if (req.pid == (DWORD) -1)	/* Request to finish thread. */
	{
	  /* Pre-Vista: Just believe in the good of the client process.
	     Post-Vista: Check if the requesting process is the master
	     process itself. */
	  if (pid == (DWORD) -1 || pid == GetCurrentProcessId ())
	    exit = true;
	  goto reply;
	}
      if (allow)
	{
	  client = OpenProcess (PROCESS_DUP_HANDLE, FALSE, pid);
	  if (!client)
	    {
	      termios_printf ("OpenProcess, %E");
	      goto reply;
	    }
	  if (!DuplicateHandle (GetCurrentProcess (), from_master,
			       client, &repl.from_master,
			       0, TRUE, DUPLICATE_SAME_ACCESS))
	    {
	      termios_printf ("DuplicateHandle (from_master), %E");
	      goto reply;
	    }
	  if (!DuplicateHandle (GetCurrentProcess (), to_master,
				client, &repl.to_master,
				0, TRUE, DUPLICATE_SAME_ACCESS))
	    {
	      termios_printf ("DuplicateHandle (to_master), %E");
	      goto reply;
	    }
	}
reply:
      repl.error = GetLastError ();
      if (client)
	CloseHandle (client);
      if (deimp)
	cygheap->user.reimpersonate ();
      sd.free ();
      termios_printf ("Reply: from %p, to %p, error %lu",
		      repl.from_master, repl.to_master, repl.error );
      if (!WriteFile (master_ctl, &repl, sizeof repl, &len, NULL))
	termios_printf ("WriteFile, %E");
      if (!DisconnectNamedPipe (master_ctl))
	termios_printf ("DisconnectNamedPipe, %E");
    }
  termios_printf ("Leaving");
  return 0;
}

static DWORD WINAPI
pty_master_thread (VOID *arg)           
{ 
  return ((fhandler_pty_master *) arg)->pty_master_thread ();
} 

bool
fhandler_pty_master::setup (bool ispty)
{
  int res;
  security_descriptor sd;
  SECURITY_ATTRIBUTES sa = { sizeof (SECURITY_ATTRIBUTES), NULL, TRUE };

  tty& t = *cygwin_shared->tty[get_unit ()];

  tcinit (&t, true);		/* Set termios information.  Force initialization. */

  const char *errstr = NULL;
  DWORD pipe_mode = PIPE_NOWAIT;

  /* Create communication pipes */
  char pipename[sizeof("ttyNNNN-from-master")];
  __small_sprintf (pipename, "tty%d-from-master", get_unit ());
  res = fhandler_pipe::create_selectable (ispty ? &sec_none : &sec_none_nih,
					  from_master, get_output_handle (),
					  128 * 1024, pipename);
  if (res)
    {
      errstr = "input pipe";
      goto err;
    }

  if (!SetNamedPipeHandleState (get_output_handle (), &pipe_mode, NULL, NULL))
    termios_printf ("can't set output_handle(%p) to non-blocking mode",
		    get_output_handle ());

  __small_sprintf (pipename, "tty%d-to-master", get_unit ());
  res = fhandler_pipe::create_selectable (ispty ? &sec_none : &sec_none_nih,
					  get_io_handle (), to_master,
					  128 * 1024, pipename);
  if (res)
    {
      errstr = "output pipe";
      goto err;
    }

  need_nl = 0;

  /* Create security attribute.  Default permissions are 0620. */
  sd.malloc (sizeof (SECURITY_DESCRIPTOR));
  InitializeSecurityDescriptor (sd, SECURITY_DESCRIPTOR_REVISION);
  if (!create_object_sd_from_attribute (NULL, myself->uid, myself->gid,
					S_IFCHR | S_IRUSR | S_IWUSR | S_IWGRP,
					sd))
    sa.lpSecurityDescriptor = (PSECURITY_DESCRIPTOR) sd;

  /* Create synchronisation events */

  if (!ispty)
    {
      if (!(output_done_event = t.get_event (errstr = OUTPUT_DONE_EVENT, &sa)))
	goto err;
      if (!(ioctl_done_event = t.get_event (errstr = IOCTL_DONE_EVENT, &sa)))
	goto err;
      if (!(ioctl_request_event = t.get_event (errstr = IOCTL_REQUEST_EVENT,
					       &sa)))
	goto err;
    }

  /* Carefully check that the input_available_event didn't already exist.
     This is a measure to make sure that the event security descriptor
     isn't occupied by a malicious process.  We must make sure that the
     event's security descriptor is what we expect it to be. */
  if (!(input_available_event = t.get_event (errstr = INPUT_AVAILABLE_EVENT,
					     &sa, TRUE))
      || GetLastError () == ERROR_ALREADY_EXISTS)
    goto err;

  char buf[MAX_PATH];
  errstr = shared_name (buf, OUTPUT_MUTEX, t.ntty);
  if (!(output_mutex = CreateMutex (&sa, FALSE, buf)))
    goto err;

  errstr = shared_name (buf, INPUT_MUTEX, t.ntty);
  if (!(input_mutex = CreateMutex (&sa, FALSE, buf)))
    goto err;

  /* Create master control pipe which allows the master to duplicate
     the pty pipe handles to processes which deserve it. */
  __small_sprintf (buf, "\\\\.\\pipe\\cygwin-%S-tty%d-master-ctl",
		   &installation_key, get_unit ());
  master_ctl = CreateNamedPipe (buf, PIPE_ACCESS_DUPLEX,
				PIPE_WAIT | PIPE_TYPE_MESSAGE
				| PIPE_READMODE_MESSAGE, 1, 4096, 4096,
				0, &sec_all_nih);
  if (master_ctl == INVALID_HANDLE_VALUE)
    {
      errstr = "pty master control pipe";
      goto err;
    }
  master_thread = new cygthread (::pty_master_thread, this, "pty_master");
  if (!master_thread)
    {
      errstr = "pty master control thread";
      goto err;
    }

  t.from_master = from_master;
  t.to_master = to_master;
  // /* screws up tty master */ ProtectHandle1INH (output_mutex, output_mutex);
  // /* screws up tty master */ ProtectHandle1INH (input_mutex, input_mutex);
  t.winsize.ws_col = 80;
  t.winsize.ws_row = 25;
  t.master_pid = myself->pid;

  termios_printf ("tty%d opened - from_slave %p, to_slave %p", t.ntty,
		  get_io_handle (), get_output_handle ());
  return true;

err:
  __seterrno ();
  close_maybe (get_io_handle ());
  close_maybe (get_output_handle ());
  close_maybe (output_done_event);
  close_maybe (ioctl_done_event);
  close_maybe (ioctl_request_event);
  close_maybe (input_available_event);
  close_maybe (output_mutex);
  close_maybe (input_mutex);
  close_maybe (from_master);
  close_maybe (to_master);
  close_maybe (master_ctl);
  termios_printf ("tty%d open failed - failed to create %s", errstr);
  return false;
}

void
fhandler_pty_master::fixup_after_fork (HANDLE parent)
{
  DWORD wpid = GetCurrentProcessId ();
  fhandler_tty_master *arch = (fhandler_tty_master *) archetype;
  if (arch->dwProcessId != wpid)
    {
      tty& t = *get_ttyp ();
      if (!DuplicateHandle (parent, arch->from_master, GetCurrentProcess (),
			    &arch->from_master, 0, false, DUPLICATE_SAME_ACCESS))
	system_printf ("couldn't duplicate from_parent(%p), %E", arch->from_master);
      if (!DuplicateHandle (parent, arch->to_master, GetCurrentProcess (),
			    &arch->to_master, 0, false, DUPLICATE_SAME_ACCESS))
	system_printf ("couldn't duplicate to_parent(%p), %E", arch->from_master);
      if (myself->pid == t.master_pid)
	{
	  t.from_master = arch->from_master;
	  t.to_master = arch->to_master;
	}
      arch->dwProcessId = wpid;
    }
  from_master = arch->from_master;
  to_master = arch->to_master;
  report_tty_counts (this, "inherited master", "");
}

void
fhandler_pty_master::fixup_after_exec ()
{
  if (!close_on_exec ())
    fixup_after_fork (spawn_info->parent);
  else
    from_master = to_master = NULL;
}