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.\" $OpenBSD: minherit.2,v 1.16 2019/01/11 18:46:30 deraadt 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 $Mdocdate: January 11 2019 $
.Dt MINHERIT 2
.Os
.Sh NAME
.Nm minherit
.Nd control the inheritance of pages
.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 pages to have the inheritance characteristic
.Fa inherit .
A page's inheritance characteristic controls how it will be mapped
in child processes as created by
.Xr fork 2 .
.Pp
The possible inheritance characteristics are:
.Pp
.Bl -tag -width MAP_INHERIT_SHARE -offset indent -compact
.It Dv MAP_INHERIT_NONE
Pages are not mapped in the child process.
.It Dv MAP_INHERIT_COPY
Private copy of pages are mapped in the child process.
.It Dv MAP_INHERIT_SHARE
Mapped pages are shared between the parent and child processes.
.It Dv MAP_INHERIT_ZERO
New anonymous pages (initialized to all zero bytes)
are mapped in the child process.
.El
.Pp
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.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn minherit
system call will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The virtual address range specified by the
.Fa addr
and
.Fa len
arguments is not valid.
.It Bq Er EINVAL
The
.Fa inherit
argument is invalid.
.El
.Sh SEE ALSO
.Xr madvise 2 ,
.Xr mprotect 2 ,
.Xr msync 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn minherit
function first appeared in
.Ox 2.0 .
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