NetBSD-5.0.2/lib/libc/sys/minherit.2

.\"	$NetBSD: minherit.2,v 1.18 2006/10/13 20:52:57 wiz Exp $
.\"
.\" Copyright (c) 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" 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.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
.\"
.\"	@(#)minherit.2	8.1 (Berkeley) 6/9/93
.\"
.Dd October 7, 2006
.Dt MINHERIT 2
.Os
.Sh NAME
.Nm minherit
.Nd control the inheritance of pages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn minherit "void *addr" "size_t len" "int inherit"
.Sh DESCRIPTION
The
.Fn minherit
system call
changes the specified range of virtual addresses to have the specified
fork-time inheritance characteristic
.Fa inherit ,
which can be set to
.Dv MAP_INHERIT_NONE ,
.Dv MAP_INHERIT_COPY ,
or
.Dv MAP_INHERIT_SHARE .
Also possible is
.Dv MAP_INHERIT_DEFAULT ,
which defaults to
.Dv MAP_INHERIT_COPY .
Not all implementations will guarantee that the inheritance characteristic
can be set on a page basis;
the granularity of changes may be as large as an entire region.
.Pp
Normally, the entire address space is marked
.Dv MAP_INHERIT_COPY ;
when the process calls
.Fn fork ,
the child receives a (virtual) copy of the entire address space.
Pages or regions marked
.Dv MAP_INHERIT_SHARE
are shared between the address spaces, while pages or regions marked
.Dv MAP_INHERIT_NONE
will be unmapped in the child.
.Sh RETURN VALUES
.Rv -std minherit
.Sh ERRORS
.Fn minherit
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
An invalid region or invalid parameters were specified.
.El
.Sh SEE ALSO
.Xr fork 2 ,
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn minherit
function first appeared in
.Ox .
.Sh BUGS
If a particular port does not support page-granularity
inheritance, there's no way to figure out how large a region is
actually affected by
.Fn minherit .