.\"
.\" Copyright (c) 2009 Robert N. M. Watson
.\" All rights reserved.
.\"
.\" WARNING: THIS IS EXPERIMENTAL SECURITY SOFTWARE THAT MUST NOT BE RELIED
.\" ON IN PRODUCTION SYSTEMS.  IT WILL BREAK YOUR SOFTWARE IN NEW AND
.\" UNEXPECTED WAYS.
.\"
.\" This software was developed at the University of Cambridge Computer
.\" Laboratory with support from a grant from Google, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd January 18, 2009
.Dt PDFORK 2
.Os
.Sh NAME
.Nm pdfork ,
.Nm pdgetpid ,
.Nm pdkill ,
.Nm pdwait
.Nd System calls to manage process descriptors
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/procdesc.h
.Ft int
.Fn pdfork "int *fdp"
.Ft int
.Fn pdgetpid "int fd" "pid_t *pidp"
.Ft int
.Fn pdkill "int fd" "int signum"
.Ft int
.Fn pdwait "int fd" "int *status" "int options" "struct rusage *rusage"
.Sh DESCRIPTION
Process descriptors are special file descriptors that represent processes,
and are created using
.Fn pdfork ,
a variant of
.Xr fork 2 ,
which, if successful, returns a process descriptor in the integer pointed to
by
.Fa pidp .
.Pp
.Fn pdgetpid
queries the process ID (PID) if the process descriptor
.Fa fd .
.Pp
.Fn pdkill
is functionally identical to
.Xr kill 2 ,
except that it accepts a process descriptor,
.Fa fd ,
rather than a PID.
.Pp
.Fn pdwait
is currently unimplemented, but in the future will be functionally identical
to
.Xr wait4 2 ,
except that it accepts a process descriptor rather than a PID.
.Pp
The following system calls also have effects specific to process descriptors:
.Pp
.Xr fstat 2
queries status of a process descriptor; currently only the
.Fa sb_mode
field is defined; if the owner read, write, and execute bits are set then the
process represented by the process descriptor is still alive.
.Pp
.Xr poll 2
allows waiting for process state transitions; currently only
.Dv POLLHUP
is defined, and will be raised when the process dies.
.Pp
.Xr close 2
will close the process descriptor, and if the process is still alive,
terminate it with the signal
.Dv SIGKILL .
.Sh RETURN VALUES
.Sh ERRORS
.Sh SEE ALSO
.Xr close 2 ,
.Xr fork 2 ,
.Xr fstat 2 ,
.Xr kill 2 ,
.Xr poll 2 ,
.Xr wait4 2
.Sh HISTORY
Support for process descriptors mode was developed as part of the
.Tn TrustedBSD
Project.
.Sh BUGS
.Fn pdwait
is not yet implemented.
.Pp
WARNING: THIS IS EXPERIMENTAL SECURITY SOFTWARE THAT MUST NOT BE RELIED ON IN
PRODUCTION SYSTEMS.  IT WILL BREAK YOUR SOFTWARE IN NEW AND UNEXPECTED WAYS.
.Sh AUTHORS
These functions and the capability facility were created by
.An "Robert N. M. Watson" 
at the University of Cambridge Computer Laboratory with support from a grant
from Google, Inc.