newlib/winsup/cygwin/pinfo.cc

/* pinfo.cc: process table support

   Copyright 1996, 1997, 1998, 2000, 2001, 2002, 2003, 2004, 2005,
   2006 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 <time.h>
#include <limits.h>
#include <stdarg.h>
#include "cygerrno.h"
#include "security.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "sigproc.h"
#include "pinfo.h"
#include "cygwin_version.h"
#include "perprocess.h"
#include "environ.h"
#include <assert.h>
#include <sys/wait.h>
#include <ntdef.h>
#include "ntdll.h"
#include "shared_info.h"
#include "cygheap.h"
#include "fhandler.h"
#include "cygmalloc.h"
#include "cygtls.h"
#include "child_info.h"

static char NO_COPY pinfo_dummy[sizeof (_pinfo)] = {0};

pinfo NO_COPY myself ((_pinfo *)&pinfo_dummy);	// Avoid myself != NULL checks

bool is_toplevel_proc;

/* Setup the pinfo structure for this process.  There may already be a
   _pinfo for this "pid" if h != NULL. */

void __stdcall
set_myself (HANDLE h)
{
  if (!h)
    cygheap->pid = cygwin_pid (GetCurrentProcessId ());
  myself.init (cygheap->pid, PID_IN_USE, h ?: INVALID_HANDLE_VALUE);
  myself->process_state |= PID_IN_USE;
  myself->dwProcessId = GetCurrentProcessId ();

  GetModuleFileName (NULL, myself->progname, sizeof (myself->progname));
  strace.hello ();
  debug_printf ("myself->dwProcessId %u", myself->dwProcessId);
  if (h)
    {
      /* here if execed */
      static pinfo NO_COPY myself_identity;
      myself_identity.init (cygwin_pid (myself->dwProcessId), PID_EXECED, NULL);
      myself->exec_sendsig = NULL;
      myself->exec_dwProcessId = 0;
    }
  else if (!myself->wr_proc_pipe)
    myself->start_time = time (NULL); /* Register our starting time. */
  else if (cygheap->pid_handle)
    {
      ForceCloseHandle (cygheap->pid_handle);
      cygheap->pid_handle = NULL;
    }
}

/* Initialize the process table entry for the current task.
   This is not called for forked tasks, only execed ones.  */
void __stdcall
pinfo_init (char **envp, int envc)
{
  if (envp)
    {
      environ_init (envp, envc);
      /* spawn has already set up a pid structure for us so we'll use that */
      myself->process_state |= PID_CYGPARENT;
    }
  else
    {
      /* Invent our own pid.  */

      set_myself (NULL);
      myself->ppid = 1;
      myself->pgid = myself->sid = myself->pid;
      myself->ctty = -1;
      myself->uid = ILLEGAL_UID;
      myself->gid = UNKNOWN_GID;
      environ_init (NULL, 0);	/* call after myself has been set up */
      myself->nice = winprio_to_nice (GetPriorityClass (hMainProc));
      debug_printf ("Set nice to %d", myself->nice);
    }

  debug_printf ("pid %d, pgid %d", myself->pid, myself->pgid);
}

# define self (*this)
void
pinfo::maybe_set_exit_code_from_windows ()
{
  DWORD x = 0xdeadbeef;
  DWORD oexitcode = self->exitcode;
  extern int sigExeced;

  if (hProcess && !(self->exitcode & EXITCODE_SET))
    {
      WaitForSingleObject (hProcess, INFINITE);	// just to be safe, in case
						// process hasn't quite exited
						// after closing pipe
      GetExitCodeProcess (hProcess, &x);
      self->exitcode = EXITCODE_SET | (sigExeced ?: (x & 0xff) << 8);
    }
  sigproc_printf ("pid %d, exit value - old %p, windows %p, cygwin %p",
		  self->pid, oexitcode, x, self->exitcode);
}

void
pinfo::zap_cwd ()
{
  extern char windows_system_directory[];
  /* Move to an innocuous location to avoid a race with other processes
     that may want to manipulate the current directory before this
     process has completely exited.  */
  SetCurrentDirectory (windows_system_directory);
}

void
pinfo::exit (DWORD n)
{
  minimal_printf ("winpid %d, exit %d", GetCurrentProcessId (), n);
  lock_process until_exit ();
  cygthread::terminate ();

  if (n != EXITCODE_NOSET)
    self->exitcode = EXITCODE_SET | n;/* We're really exiting.  Record the UNIX exit code. */
  else
    {
      exit_state = ES_EXEC_EXIT;
      maybe_set_exit_code_from_windows ();
    }

  sigproc_terminate (ES_FINAL);
  zap_cwd ();

  /* FIXME:  There is a potential race between an execed process and its
     parent here.  I hated to add a mutex just for that, though.  */
  struct rusage r;
  fill_rusage (&r, hMainProc);
  add_rusage (&self->rusage_self, &r);
  int exitcode = self->exitcode & 0xffff;
  if (!self->cygstarted)
    exitcode = ((exitcode & 0xff) << 8) | ((exitcode >> 8) & 0xff);
  sigproc_printf ("Calling ExitProcess n %p, exitcode %p", n, exitcode);
  ExitProcess (exitcode);
}
# undef self

void
pinfo::init (pid_t n, DWORD flag, HANDLE h0)
{
  shared_locations shloc;
  h = NULL;
  if (myself && !(flag & PID_EXECED)
      && (n == myself->pid || (DWORD) n == myself->dwProcessId))
    {
      procinfo = myself;
      destroy = 0;
      return;
    }

  void *mapaddr;
  int createit = flag & (PID_IN_USE | PID_EXECED);
  DWORD access = FILE_MAP_READ
		 | (flag & (PID_IN_USE | PID_EXECED | PID_MAP_RW)
		    ? FILE_MAP_WRITE : 0);
  if (!h0)
    shloc = (flag & (PID_IN_USE | PID_EXECED)) ? SH_JUSTCREATE : SH_JUSTOPEN;
  else
    {
      shloc = SH_MYSELF;
      if (h0 == INVALID_HANDLE_VALUE)
	h0 = NULL;
    }

  procinfo = NULL;
  PSECURITY_ATTRIBUTES sa_buf = (PSECURITY_ATTRIBUTES) alloca (1024);
  PSECURITY_ATTRIBUTES sec_attribs = sec_user_nih (sa_buf, cygheap->user.sid(),
						   well_known_world_sid,
						   FILE_MAP_READ);

  for (int i = 0; i < 20; i++)
    {
      DWORD mapsize;
      if (flag & PID_EXECED)
	mapsize = PINFO_REDIR_SIZE;
      else
	mapsize = sizeof (_pinfo);

      procinfo = (_pinfo *) open_shared ("cygpid", n, h0, mapsize, shloc,
					 sec_attribs, access);
      if (!h0)
	{
	  if (createit)
	    __seterrno ();
	  return;
	}

      if (!procinfo)
	{
	  if (exit_state)
	    return;

	  switch (GetLastError ())
	    {
	    case ERROR_INVALID_HANDLE:
	      api_fatal ("MapViewOfFileEx h0 %p, i %d failed, %E", h0, i);
	    case ERROR_INVALID_ADDRESS:
	      mapaddr = NULL;
	    }
	  debug_printf ("MapViewOfFileEx h0 %p, i %d failed, %E", h0, i);
	  low_priority_sleep (0);
	  continue;
	}

      bool created = shloc != SH_JUSTOPEN;

      if ((procinfo->process_state & PID_INITIALIZING) && (flag & PID_NOREDIR)
	  && cygwin_pid (procinfo->dwProcessId) != procinfo->pid)
	{
	  set_errno (ESRCH);
	  break;
	}

      if (procinfo->process_state & PID_EXECED)
	{
	  assert (i == 0);
	  pid_t realpid = procinfo->pid;
	  debug_printf ("execed process windows pid %d, cygwin pid %d", n, realpid);
	  if (realpid == n)
	    api_fatal ("retrieval of execed process info for pid %d failed due to recursion.", n);

	  n = realpid;
	  CloseHandle (h0);
	  h0 = NULL;
	  goto loop;
	}

      /* In certain pathological cases, it is possible for the shared memory
	 region to exist for a while after a process has exited.  This should
	 only be a brief occurrence, so rather than introduce some kind of
	 locking mechanism, just loop.  */
      if (!created && createit && (procinfo->process_state & PID_EXITED))
	{
	  debug_printf ("looping because pid %d, procinfo->pid %d, "
			"procinfo->dwProcessid %u has PID_EXITED set",
			n, procinfo->pid, procinfo->dwProcessId);
	  goto loop;
	}

      if (!created)
	/* nothing */;
      else if (!(flag & PID_EXECED))
	procinfo->pid = n;
      else
	{
	  procinfo->process_state |= PID_IN_USE | PID_EXECED;
	  procinfo->pid = myself->pid;
	}

      h = h0;	/* Success! */
      break;

    loop:
      release ();
      if (h0)
	low_priority_sleep (0);
    }

  if (h)
    {
      destroy = 1;
      ProtectHandle1 (h, pinfo_shared_handle);
    }
  else
    {
      h = h0;
      release ();
    }
}

void
pinfo::set_acl()
{
  PACL acl_buf = (PACL) alloca (1024);
  SECURITY_DESCRIPTOR sd;

  sec_acl (acl_buf, true, true, cygheap->user.sid (),
	   well_known_world_sid, FILE_MAP_READ);
  if (!InitializeSecurityDescriptor (&sd, SECURITY_DESCRIPTOR_REVISION))
    debug_printf ("InitializeSecurityDescriptor %E");
  else if (!SetSecurityDescriptorDacl (&sd, TRUE, acl_buf, FALSE))
    debug_printf ("SetSecurityDescriptorDacl %E");
  else if (!SetKernelObjectSecurity (h, DACL_SECURITY_INFORMATION, &sd))
    debug_printf ("SetKernelObjectSecurity %E");
}

const char *
_pinfo::_ctty (char *buf)
{
  if (ctty == TTY_CONSOLE)
    strcpy (buf, "ctty /dev/console");
  else if (ctty < 0)
    strcpy (buf, "no ctty");
  else
    __small_sprintf (buf, "ctty /dev/tty%d", ctty);
  return buf;
}

void
_pinfo::set_ctty (tty_min *tc, int flags, fhandler_tty_slave *arch)
{
  debug_printf ("old %s", __ctty ());
  if ((ctty < 0 || ctty == tc->ntty) && !(flags & O_NOCTTY))
    {
      ctty = tc->ntty;
      syscall_printf ("attached %s sid %d, pid %d, tty->pgid %d, tty->sid %d",
		      __ctty (), sid, pid, pgid, tc->getsid ());

      pinfo p (tc->getsid ());
      if (sid == pid && (!p || p->pid == pid || !p->exists ()))
	{
	  paranoid_printf ("resetting %s sid.  Was %d, now %d.  pgid was %d, now %d.",
			   __ctty (), tc->getsid (), sid, tc->getpgid (), pgid);
	  /* We are the session leader */
	  tc->setsid (sid);
	  tc->setpgid (pgid);
	}
      else
	sid = tc->getsid ();
      if (tc->getpgid () == 0)
	tc->setpgid (pgid);
      if (cygheap->ctty != arch)
	{
	  debug_printf ("cygheap->ctty %p, arch %p", cygheap->ctty, arch);
	  if (!cygheap->ctty)
	    syscall_printf ("ctty NULL");
	  else
	    {
	      syscall_printf ("ctty %p, usecount %d", cygheap->ctty,
			      cygheap->ctty->usecount);
	      cygheap->ctty->close ();
	    }
	  cygheap->ctty = arch;
	  if (arch)
	    {
	      arch->usecount++;
	      /* guard ctty arch */
	      cygheap->manage_console_count ("_pinfo::set_ctty", 1);
	      report_tty_counts (cygheap->ctty, "ctty", "");
	    }
	}
    }
}

/* Test to determine if a process really exists and is processing signals.
 */
bool __stdcall
_pinfo::exists ()
{
  return this && !(process_state & PID_EXITED);
}

bool
_pinfo::alive ()
{
  HANDLE h = OpenProcess (PROCESS_QUERY_INFORMATION, false, dwProcessId);
  if (h)
    CloseHandle (h);
  return !!h;
}

extern char **__argv;

DWORD WINAPI
commune_process (void *arg)
{
  siginfo_t& si = *((siginfo_t *) arg);
  char path[CYG_MAX_PATH];
  DWORD nr;
  HANDLE& tothem = si._si_commune._si_write_handle;
  HANDLE process_sync =
    OpenSemaphore (SYNCHRONIZE, false, shared_name (path, "commune", si.si_pid));
  if (process_sync)		// FIXME: this test shouldn't be necessary
    ProtectHandle (process_sync);

  lock_process now (false);
  if (si._si_commune._si_code & PICOM_EXTRASTR)
    si._si_commune._si_str = (char *) (&si + 1);

  switch (si._si_commune._si_code)
    {
    case PICOM_CMDLINE:
      {
	sigproc_printf ("processing PICOM_CMDLINE");
	unsigned n = 1;
	extern int __argc_safe;
	const char *argv[__argc_safe + 1];

	for (int i = 0; i < __argc_safe; i++)
	  {
	    if (IsBadStringPtr (__argv[i], INT32_MAX))
	      argv[i] = "";
	    else
	      argv[i] = __argv[i];
	    n += strlen (argv[i]) + 1;
	  }
	argv[__argc_safe] = NULL;
	if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  {
	    /*__seterrno ();*/	// this is run from the signal thread, so don't set errno
	    sigproc_printf ("WriteFile sizeof argv failed, %E");
	  }
	else
	  for (const char **a = argv; *a; a++)
	    if (!WriteFile (tothem, *a, strlen (*a) + 1, &nr, NULL))
	      {
		sigproc_printf ("WriteFile arg %d failed, %E", a - argv);
		break;
	      }
	if (!WriteFile (tothem, "", 1, &nr, NULL))
	  {
	    sigproc_printf ("WriteFile null failed, %E");
	    break;
	  }
	break;
      }
    case PICOM_CWD:
      {
	sigproc_printf ("processing PICOM_CWD");
	unsigned int n = strlen (cygheap->cwd.get (path, 1, 1,
						   CYG_MAX_PATH)) + 1;
	if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  sigproc_printf ("WriteFile sizeof cwd failed, %E");
	else if (!WriteFile (tothem, path, n, &nr, NULL))
	  sigproc_printf ("WriteFile cwd failed, %E");
	break;
      }
    case PICOM_ROOT:
      {
	sigproc_printf ("processing PICOM_ROOT");
	unsigned n;
	if (cygheap->root.exists ())
	  n = strlen (strcpy (path, cygheap->root.posix_path ())) + 1;
	else
	  n = strlen (strcpy (path, "/")) + 1;
	if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  sigproc_printf ("WriteFile sizeof root failed, %E");
	else if (!WriteFile (tothem, path, n, &nr, NULL))
	  sigproc_printf ("WriteFile root failed, %E");
	break;
      }
    case PICOM_FDS:
      {
	sigproc_printf ("processing PICOM_FDS");
	unsigned int n = 0;
	int fd;
	cygheap_fdenum cfd;
	while ((fd = cfd.next ()) >= 0)
	  n += sizeof (int);
	cfd.rewind ();
	if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  sigproc_printf ("WriteFile sizeof fds failed, %E");
	else
	  while ((fd = cfd.next ()) >= 0)
	    if (!WriteFile (tothem, &fd, sizeof fd, &nr, NULL))
	      {
		sigproc_printf ("WriteFile fd %d failed, %E", fd);
		break;
	      }
	break;
      }
    case PICOM_PIPE_FHANDLER:
      {
	sigproc_printf ("processing PICOM_FDS");
	HANDLE hdl = si._si_commune._si_pipe_fhandler;
	unsigned int n = 0;
	cygheap_fdenum cfd;
	while (cfd.next () >= 0)
	  if (cfd->get_handle () == hdl)
	    {
	      fhandler_pipe *fh = cfd;
	      n = sizeof *fh;
	      if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
		sigproc_printf ("WriteFile sizeof hdl failed, %E");
	      else if (!WriteFile (tothem, fh, n, &nr, NULL))
		sigproc_printf ("WriteFile hdl failed, %E");
	      break;
	    }
	if (!n && !WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  sigproc_printf ("WriteFile sizeof hdl failed, %E");
	break;
      }
    case PICOM_FD:
      {
	sigproc_printf ("processing PICOM_FD");
	int fd = si._si_commune._si_fd;
	unsigned int n = 0;
	cygheap_fdget cfd (fd);
	if (cfd < 0)
	  n = strlen (strcpy (path, "")) + 1;
	else
	  n = strlen (cfd->get_proc_fd_name (path)) + 1;
	if (!WriteFile (tothem, &n, sizeof n, &nr, NULL))
	  sigproc_printf ("WriteFile sizeof fd failed, %E");
	else if (!WriteFile (tothem, path, n, &nr, NULL))
	  sigproc_printf ("WriteFile fd failed, %E");
	break;
      }
    case PICOM_FIFO:
      {
	sigproc_printf ("processing PICOM_FIFO for %s", si._si_commune._si_str);
	fhandler_fifo *fh = cygheap->fdtab.find_fifo (si._si_commune._si_str);
	HANDLE it[2];
	if (fh == NULL)
	  it[0] = it[1] = NULL;
	else
	  {
	    it[0] = fh->get_handle ();
	    it[1] = fh->get_output_handle ();
	  }

	debug_printf ("fifo %sfound %p, %p", fh ? "" : "not ", it[0], it[1]);
	if (!WriteFile (tothem, it, sizeof (it), &nr, NULL))
	  {
	    /*__seterrno ();*/	// this is run from the signal thread, so don't set errno
	    sigproc_printf ("WriteFile read handle failed, %E");
	  }
	WaitForSingleObject (process_sync, INFINITE);
	process_sync = NULL;
	if (fh)
	  fh->close_one_end ();
	break;
      }
    }
  if (process_sync)
    {
      DWORD res = WaitForSingleObject (process_sync, 5000);
      if (res != WAIT_OBJECT_0)
	sigproc_printf ("WFSO failed - %d, %E", res);
      else
	sigproc_printf ("synchronized with pid %d", si.si_pid);
      ForceCloseHandle (process_sync);
    }
  CloseHandle (tothem);
  _my_tls._ctinfo->auto_release ();
  return 0;
}

commune_result
_pinfo::commune_request (__uint32_t code, ...)
{
  DWORD nr;
  commune_result res;
  va_list args;
  siginfo_t si = {0};
  HANDLE& hp = si._si_commune._si_process_handle;
  HANDLE& fromthem = si._si_commune._si_read_handle;
  HANDLE request_sync = NULL;
  bool locked = false;

  va_start (args, code);

  res.s = NULL;
  res.n = 0;

  if (!this || !pid)
    {
      set_errno (ESRCH);
      goto err;
    }

  si._si_commune._si_code = code;
  switch (code)
    {
    case PICOM_PIPE_FHANDLER:
      si._si_commune._si_pipe_fhandler = va_arg (args, HANDLE);
      break;

    case PICOM_FD:
      si._si_commune._si_fd = va_arg (args, int);
      break;

    case PICOM_FIFO:
      si._si_commune._si_str = va_arg (args, char *);
    break;
    }

  locked = true;
  char name_buf[CYG_MAX_PATH];
  request_sync = CreateSemaphore (&sec_none_nih, 0, LONG_MAX,
				  shared_name (name_buf, "commune", myself->pid));
  if (!request_sync)
    goto err;
  ProtectHandle (request_sync);

  si.si_signo = __SIGCOMMUNE;
  if (sig_send (this, si))
    {
      ForceCloseHandle (request_sync);	/* don't signal semaphore since there was apparently no receiving process */
      request_sync = NULL;
      goto err;
    }

  size_t n;
  switch (code)
    {
    case PICOM_CMDLINE:
    case PICOM_CWD:
    case PICOM_ROOT:
    case PICOM_FDS:
    case PICOM_FD:
    case PICOM_PIPE_FHANDLER:
      if (!ReadFile (fromthem, &n, sizeof n, &nr, NULL) || nr != sizeof n)
	{
	  __seterrno ();
	  goto err;
	}
      if (!n)
	res.s = NULL;
      else
	{
	  res.s = (char *) cmalloc (HEAP_COMMUNE, n);
	  char *p;
	  for (p = res.s; n && ReadFile (fromthem, p, n, &nr, NULL); p += nr, n -= nr)
	    continue;
	  if (n)
	    {
	      __seterrno ();
	      goto err;
	    }
	  res.n = p - res.s;
	}
      break;
    case PICOM_FIFO:
      {
	lock_process now ();
	DWORD x = ReadFile (fromthem, res.handles, sizeof (res.handles), &nr, NULL);
	if (!x || nr != sizeof (res.handles))
	  {
	    __seterrno ();
	    goto err;
	  }
	for (int i = 0; i < 2; i++)
	  if (!DuplicateHandle (hp, res.handles[i], hMainProc, &res.handles[i],
				0, false, DUPLICATE_SAME_ACCESS))
	    {
	      if (i)
		CloseHandle (res.handles[0]);
	      res.handles[0] = res.handles[1] = NULL;	/* FIXME: possibly left a handle open in child? */
	      goto err;
	    }
	break;
      }
    }
  goto out;

err:
  memset (&res, 0, sizeof (res));

out:
  if (request_sync)
    {
      LONG res;
      ReleaseSemaphore (request_sync, 1, &res);
      ForceCloseHandle (request_sync);
    }
  if (hp)
    CloseHandle (hp);
  if (fromthem)
    CloseHandle (fromthem);
  return res;
}

fhandler_pipe *
_pinfo::pipe_fhandler (HANDLE hdl, size_t &n)
{
  if (!this || !pid)
    return NULL;
  if (pid == myself->pid)
    return NULL;
  commune_result cr = commune_request (PICOM_PIPE_FHANDLER, hdl);
  n = cr.n;
  return (fhandler_pipe *) cr.s;
}

char *
_pinfo::fd (int fd, size_t &n)
{
  char *s;
  if (!this || !pid)
    return NULL;
  if (pid != myself->pid)
    {
      commune_result cr = commune_request (PICOM_FD, fd);
      s = cr.s;
      n = cr.n;
    }
  else
    {
      cygheap_fdget cfd (fd);
      if (cfd < 0)
	s = cstrdup ("");
      else
	s = cfd->get_proc_fd_name ((char *) cmalloc (HEAP_COMMUNE, CYG_MAX_PATH));
      n = strlen (s) + 1;
    }
  return s;
}

char *
_pinfo::fds (size_t &n)
{
  char *s;
  if (!this || !pid)
    return NULL;
  if (pid != myself->pid)
    {
      commune_result cr = commune_request (PICOM_FDS);
      s = cr.s;
      n = cr.n;
    }
  else
    {
      n = 0;
      int fd;
      cygheap_fdenum cfd (true);
      while ((fd = cfd.next ()) >= 0)
	n += sizeof (int);
      cfd.rewind ();
      s = (char *) cmalloc (HEAP_COMMUNE, n);
      int *p = (int *) s;
      while ((fd = cfd.next ()) >= 0 && (char *) p - s < (int) n)
	*p++ = fd;
    }
  return s;
}

char *
_pinfo::root (size_t& n)
{
  char *s;
  if (!this || !pid)
    return NULL;
  if (pid != myself->pid)
    {
      commune_result cr = commune_request (PICOM_ROOT);
      s = cr.s;
      n = cr.n;
    }
  else
    {
      if (cygheap->root.exists ())
	s = cstrdup (cygheap->root.posix_path ());
      else
	s = cstrdup ("/");
      n = strlen (s) + 1;
    }
  return s;
}

char *
_pinfo::cwd (size_t& n)
{
  char *s;
  if (!this || !pid)
    return NULL;
  if (pid != myself->pid)
    {
      commune_result cr = commune_request (PICOM_CWD);
      s = cr.s;
      n = cr.n;
    }
  else
    {
      s = (char *) cmalloc (HEAP_COMMUNE, CYG_MAX_PATH);
      cygheap->cwd.get (s, 1, 1, CYG_MAX_PATH);
      n = strlen (s) + 1;
    }
  return s;
}

char *
_pinfo::cmdline (size_t& n)
{
  char *s;
  if (!this || !pid)
    return NULL;
  if (pid != myself->pid)
    {
      commune_result cr = commune_request (PICOM_CMDLINE);
      s = cr.s;
      n = cr.n;
    }
  else
    {
      n = 1;
      for (char **a = __argv; *a; a++)
	n += strlen (*a) + 1;
      char *p;
      p = s = (char *) cmalloc (HEAP_COMMUNE, n);
      for (char **a = __argv; *a; a++)
	{
	  strcpy (p, *a);
	  p = strchr (p, '\0') + 1;
	}
      *p = '\0';
    }
  return s;
}

/* This is the workhorse which waits for the write end of the pipe
   created during new process creation.  If the pipe is closed or a zero
   is received on the pipe, it is assumed that the cygwin pid has exited.
   Otherwise, various "signals" can be sent to the parent to inform the
   parent to perform a certain action. */
static DWORD WINAPI
proc_waiter (void *arg)
{
  pinfo vchild = *(pinfo *) arg;
  ((pinfo *) arg)->waiter_ready = true;

  siginfo_t si = {0};
  si.si_signo = SIGCHLD;
  si.si_code = CLD_EXITED;
  si.si_pid = vchild->pid;
#if 0	// FIXME: This is tricky to get right
  si.si_utime = pchildren[rc]->rusage_self.ru_utime;
  si.si_stime = pchildren[rc].rusage_self.ru_stime;
#endif
  pid_t pid = vchild->pid;

  for (;;)
    {
      DWORD nb;
      char buf = '\0';

      if (!ReadFile (vchild.rd_proc_pipe, &buf, 1, &nb, NULL)
	  && GetLastError () != ERROR_BROKEN_PIPE)
	{
	  system_printf ("error on read of child wait pipe %p, %E", vchild.rd_proc_pipe);
	  break;
	}

      si.si_uid = vchild->uid;

      switch (buf)
	{
	case __ALERT_ALIVE:
	  continue;
	case 0:
	  /* Child exited.  Do some cleanup and signal myself.  */
	  CloseHandle (vchild.rd_proc_pipe);
	  vchild.rd_proc_pipe = NULL;
	  vchild.maybe_set_exit_code_from_windows ();
	  if (WIFEXITED (vchild->exitcode))
	    si.si_code = CLD_EXITED;
	  else if (WCOREDUMP (vchild->exitcode))
	    si.si_code = CLD_DUMPED;
	  else
	    si.si_code = CLD_KILLED;
	  si.si_status = vchild->exitcode;
	  vchild->process_state = PID_EXITED;
	  /* This should always be last.  Do not use vchild-> beyond this point */
	  break;
	case SIGTTIN:
	case SIGTTOU:
	case SIGTSTP:
	case SIGSTOP:
	  if (ISSTATE (myself, PID_NOCLDSTOP))	// FIXME: No need for this flag to be in _pinfo any longer
	    continue;
	  /* Child stopped.  Signal myself.  */
	  si.si_code = CLD_STOPPED;
	  break;
	case SIGCONT:
	  continue;
	default:
	  system_printf ("unknown value %d on proc pipe", buf);
	  continue;
	}

      /* Special case:  If the "child process" that died is us, then we're
	 execing.  Just call proc_subproc directly and then exit this loop.
	 We're done here.  */
      if (hExeced)
	{
	  /* execing.  no signals available now. */
	  proc_subproc (PROC_CLEARWAIT, 0);
	  break;
	}

      /* Send a SIGCHLD to myself.   We do this here, rather than in proc_subproc
	 to avoid the proc_subproc lock since the signal thread will eventually
	 be calling proc_subproc and could unnecessarily block. */
      sig_send (myself_nowait, si);

      /* If we're just stopped or got a continue signal, keep looping.
	 Otherwise, return this thread to the pool. */
      if (buf != '\0')
	sigproc_printf ("looping");
      else
	break;
    }

  sigproc_printf ("exiting wait thread for pid %d", pid);
  vchild.wait_thread = NULL;
  _my_tls._ctinfo->auto_release ();	/* automatically return the cygthread to the cygthread pool */
  return 0;
}

HANDLE
_pinfo::dup_proc_pipe (HANDLE hProcess)
{
  DWORD flags = DUPLICATE_SAME_ACCESS;
  HANDLE orig_wr_proc_pipe = wr_proc_pipe;
  /* Can't set DUPLICATE_CLOSE_SOURCE for exec case because we could be
     execing a non-cygwin process and we need to set the exit value before the
     parent sees it.  */
  if (this != myself || is_toplevel_proc)
    flags |= DUPLICATE_CLOSE_SOURCE;
  bool res = DuplicateHandle (hMainProc, wr_proc_pipe, hProcess, &wr_proc_pipe,
			      0, FALSE, flags);
  if (!res && WaitForSingleObject (hProcess, 0) != WAIT_OBJECT_0)
    {
      wr_proc_pipe = orig_wr_proc_pipe;
      system_printf ("DuplicateHandle failed, pid %d, hProcess %p, wr_proc_pipe %p, %E",
		     pid, hProcess, wr_proc_pipe);
    }
  else
    {
      wr_proc_pipe_owner = dwProcessId;
      sigproc_printf ("duped wr_proc_pipe %p for pid %d(%u)", wr_proc_pipe,
		      pid, dwProcessId);
      res = true;
    }
  return orig_wr_proc_pipe;
}

/* function to set up the process pipe and kick off proc_waiter */
int
pinfo::wait ()
{
  /* FIXME: execed processes should be able to wait for pids that were started
     by the process which execed them. */
  if (!CreatePipe (&rd_proc_pipe, &((*this)->wr_proc_pipe), &sec_none_nih, 16))
    {
      system_printf ("Couldn't create pipe tracker for pid %d, %E",
		     (*this)->pid);
      return 0;
    }

  if (!(*this)->dup_proc_pipe (hProcess))
    {
      system_printf ("Couldn't duplicate pipe topid %d(%p), %E", (*this)->pid, hProcess);
      return 0;
    }

  preserve ();		/* Preserve the shared memory associated with the pinfo */

  waiter_ready = false;
  /* Fire up a new thread to track the subprocess */
  cygthread *h = new cygthread (proc_waiter, 0, this, "proc_waiter");
  if (!h)
    sigproc_printf ("tracking thread creation failed for pid %d", (*this)->pid);
  else
    {
      wait_thread = h;
      sigproc_printf ("created tracking thread for pid %d, winpid %p, rd_pipe %p",
		      (*this)->pid, (*this)->dwProcessId, rd_proc_pipe);
    }

  return 1;
}

void
_pinfo::sync_proc_pipe ()
{
  if (wr_proc_pipe && wr_proc_pipe != INVALID_HANDLE_VALUE)
    while (wr_proc_pipe_owner != GetCurrentProcessId ())
      low_priority_sleep (0);
}

/* function to send a "signal" to the parent when something interesting happens
   in the child. */
bool
_pinfo::alert_parent (char sig)
{
  DWORD nb = 0;

  /* Send something to our parent.  If the parent has gone away, close the pipe.
     Don't send if this is an exec stub.

     FIXME: Is there a race here if we run this while another thread is attempting
     to exec()? */
  if (wr_proc_pipe == INVALID_HANDLE_VALUE || !myself->wr_proc_pipe || hExeced)
    /* no parent */;
  else
    {
      sync_proc_pipe ();
      if (WriteFile (wr_proc_pipe, &sig, 1, &nb, NULL))
	/* all is well */;
      else if (GetLastError () != ERROR_BROKEN_PIPE)
	debug_printf ("sending %d notification to parent failed, %E", sig);
      else
	{
	  ppid = 1;
	  HANDLE closeit = wr_proc_pipe;
	  wr_proc_pipe = INVALID_HANDLE_VALUE;
	  CloseHandle (closeit);
	}
    }
  return (bool) nb;
}

void
pinfo::release ()
{
  if (procinfo)
    {
      void *unmap_procinfo = procinfo;
      procinfo = NULL;
      UnmapViewOfFile (unmap_procinfo);
    }
  if (h)
    {
      HANDLE close_h = h;
      h = NULL;
      ForceCloseHandle1 (close_h, pinfo_shared_handle);
    }
}

/* DOCTOOL-START

<sect1 id="func-cygwin-winpid-to-pid">
  <title>cygwin_winpid_to_pid</title>

  <funcsynopsis><funcprototype>
    <funcdef>extern "C" pid_t
      <function>cygwin_winpid_to_pid</function>
      </funcdef>
      <paramdef>int <parameter>winpid</parameter></paramdef>
  </funcprototype></funcsynopsis>

  <para>Given a windows pid, converts to the corresponding Cygwin
pid, if any.  Returns -1 if windows pid does not correspond to
a cygwin pid.</para>
  <example>
    <title>Example use of cygwin_winpid_to_pid</title>
    <programlisting>
      extern "C" cygwin_winpid_to_pid (int winpid);
      pid_t mypid;
      mypid = cygwin_winpid_to_pid (windows_pid);
    </programlisting>
  </example>
</sect1>

   DOCTOOL-END */

extern "C" pid_t
cygwin_winpid_to_pid (int winpid)
{
  pinfo p (cygwin_pid (winpid));
  if (p)
    return p->pid;

  set_errno (ESRCH);
  return (pid_t) -1;
}

#include <tlhelp32.h>

#define slop_pidlist 200
#define size_pidlist(i) (sizeof (pidlist[0]) * ((i) + 1))
#define size_pinfolist(i) (sizeof (pinfolist[0]) * ((i) + 1))
class _onreturn
{
  HANDLE *h;
public:
  ~_onreturn ()
  {
    if (h)
      {
	CloseHandle (*h);
	*h = NULL;
      }
  }
  void no_close_p_handle () {h = NULL;}
  _onreturn (HANDLE& _h): h (&_h) {}
};

inline void
winpids::add (DWORD& nelem, bool winpid, DWORD pid)
{
  pid_t cygpid = cygwin_pid (pid);

  if (nelem >= npidlist)
    {
      npidlist += slop_pidlist;
      pidlist = (DWORD *) realloc (pidlist, size_pidlist (npidlist + 1));
      pinfolist = (pinfo *) realloc (pinfolist, size_pinfolist (npidlist + 1));
    }

  pinfo& p = pinfolist[nelem];

  /* Open a the process to prevent a subsequent exit from invalidating the
     shared memory region. */
  p.hProcess = OpenProcess (PROCESS_QUERY_INFORMATION, false, pid);
  _onreturn onreturn (p.hProcess);

  /* If we couldn't open the process then we don't have rights to it and should
     make a copy of the shared memory area if it exists (it may not).
  */
  bool perform_copy;
  if (!p.hProcess)
    perform_copy = true;
  else
    perform_copy = make_copy;

  p.init (cygpid, PID_NOREDIR | pinfo_access, NULL);

  /* If we're just looking for winpids then don't do any special cygwin "stuff* */
  if (winpid)
    goto out;

  /* !p means that we couldn't find shared memory for this pid.  Probably means
     that it isn't a cygwin process. */
  if (!p)
    {
      if (!pinfo_access)
	return;
      p.init (cygpid, PID_NOREDIR, NULL);
      if (!p)
	return;
      }

  /* Scan list of previously recorded pids to make sure that this pid hasn't
     shown up before.  This can happen when a process execs. */
  for (unsigned i = 0; i < nelem; i++)
    if (pinfolist[i]->pid == p->pid)
      {
	if ((_pinfo *) p != (_pinfo *) myself)
	  p.release ();
	return;
      }

out:
  /* Exit here.

     If p is "false" then, eventually any opened process handle will be closed and
     the function will exit without adding anything to the pid list.

     If p is "true" then we've discovered a cygwin process.

     Handle "myself" differently.  Don't copy it and close/zero the handle we
     just opened to it.
     If not performing a copy, then keep the process handle open for the duration
     of the life of the procinfo region to potential races when a new process uses
     this pid.
     Otherwise, malloc some memory for a copy of the shared memory.

     If the malloc failed, then "oh well".  Just keep the shared memory around
     and eventually close the handle when the winpids goes out of scope.

     If malloc succeeds, copy the procinfo we just grabbed into the new region,
     release the shared memory and allow the handle to be closed when this
     function returns.

     Oh, and add the pid to the list and bump the number of elements.  */

  if (p)
    {
      if (p == (_pinfo *) myself)
	/* handle specially.  Close the handle but (eventually) don't
	   deallocate procinfo in release call */;
      else if (!perform_copy)
	onreturn.no_close_p_handle ();	/* Don't close the handle until release */
      else
	{
	  _pinfo *pnew = (_pinfo *) malloc (sizeof (*p.procinfo));
	  if (!pnew)
	    onreturn.no_close_p_handle ();
	  else
	    {
	      *pnew = *p.procinfo;
	      if ((_pinfo *) p != (_pinfo *) myself)
		p.release ();
	      p.procinfo = pnew;
	      p.destroy = false;
	    }
	}
    }
  if (p || winpid)
    pidlist[nelem++] = pid;
}

DWORD
winpids::enumNT (bool winpid)
{
  static DWORD szprocs;
  static SYSTEM_PROCESSES *procs;

  DWORD nelem = 0;
  if (!szprocs)
    procs = (SYSTEM_PROCESSES *) malloc (sizeof (*procs) + (szprocs = 200 * sizeof (*procs)));

  NTSTATUS res;
  for (;;)
    {
      res = NtQuerySystemInformation (SystemProcessesAndThreadsInformation,
				      procs, szprocs, NULL);
      if (res == 0)
	break;

      if (res == STATUS_INFO_LENGTH_MISMATCH)
	procs =  (SYSTEM_PROCESSES *) realloc (procs, szprocs += 200 * sizeof (*procs));
      else
	{
	  system_printf ("error %p reading system process information", res);
	  return 0;
	}
    }

  SYSTEM_PROCESSES *px = procs;
  for (;;)
    {
      if (px->ProcessId)
	add (nelem, winpid, px->ProcessId);
      if (!px->NextEntryDelta)
	break;
      px = (SYSTEM_PROCESSES *) ((char *) px + px->NextEntryDelta);
    }

  return nelem;
}

DWORD
winpids::enum9x (bool winpid)
{
  DWORD nelem = 0;

  HANDLE h = CreateToolhelp32Snapshot (TH32CS_SNAPPROCESS, 0);
  if (!h)
    {
      system_printf ("Couldn't create process snapshot, %E");
      return 0;
    }

  PROCESSENTRY32 proc;
  proc.dwSize = sizeof (proc);

  if (Process32First (h, &proc))
    do
      {
	if (proc.th32ProcessID)
	  add (nelem, winpid, proc.th32ProcessID);
      }
    while (Process32Next (h, &proc));

  CloseHandle (h);
  return nelem;
}

void
winpids::set (bool winpid)
{
  __malloc_lock ();
  npids = (this->*enum_processes) (winpid);
  if (pidlist)
    pidlist[npids] = 0;
  __malloc_unlock ();
}

DWORD
winpids::enum_init (bool winpid)
{
  if (wincap.is_winnt ())
    enum_processes = &winpids::enumNT;
  else
    enum_processes = &winpids::enum9x;

  return (this->*enum_processes) (winpid);
}

void
winpids::release ()
{
  _pinfo *p;
  for (unsigned i = 0; i < npids; i++)
    if (pinfolist[i] == (_pinfo *) myself)
      continue;
    else if (pinfolist[i].hProcess)
      {
	if (pinfolist[i])
	  pinfolist[i].release ();
	CloseHandle (pinfolist[i].hProcess);
      }
    else if ((p = pinfolist[i]))
      {
	pinfolist[i].procinfo = NULL;
	free (p);
      }
}

winpids::~winpids ()
{
  if (npidlist)
    {
      release ();
      free (pidlist);
      free (pinfolist);
    }
}