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+.\" $FreeBSD$
+.\"
+.\" 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.
+.\" 4. 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 February 17, 1996
+.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 pages to have the inheritance characteristic
+.Fa inherit .
+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.
+.Fx
+is capable of adjusting inheritance characteristics on a page basis.
+Inheritance only effects children created by
+.Fn fork .
+It has no effect on
+.Fn exec .
+exec'd processes replace their address space entirely.
+This system call also
+has no effect on the parent's address space (other than to potentially
+share the address space with its children).
+.Pp
+Inheritance is a rather esoteric feature largely superseded by the
+.Dv MAP_SHARED
+feature of
+.Fn mmap .
+However, it is possible to use
+.Fn minherit
+to share a block of memory between parent and child that has been mapped
+.Dv MAP_PRIVATE .
+That is, modifications made by parent or child are shared but
+the original underlying file is left untouched.
+.Bl -tag -width ".Dv INHERIT_SHARE"
+.It Dv INHERIT_SHARE
+This option causes the address space in question to be shared between
+parent and child.
+It has no effect on how the original underlying backing
+store was mapped.
+.It Dv INHERIT_NONE
+This option prevents the address space in question from being inherited
+at all.
+The address space will be unmapped in the child.
+.It Dv INHERIT_COPY
+This option causes the child to inherit the address space as copy-on-write.
+This option also has an unfortunate side effect of causing the parent
+address space to become copy-on-write when the parent forks.
+If the original mapping was
+.Dv MAP_SHARED ,
+it will no longer be shared in the parent
+after the parent forks and there is no way to get the previous
+shared-backing-store mapping without unmapping and remapping the address
+space in the parent.
+.El
+.Sh RETURN VALUES
+.Rv -std minherit
+.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 EACCES
+The flags specified by the
+.Fa inherit
+argument were not valid for the pages specified
+by the
+.Fa addr
+and
+.Fa len
+arguments.
+.El
+.Sh SEE ALSO
+.Xr fork 2 ,
+.Xr madvise 2 ,
+.Xr mincore 2 ,
+.Xr mprotect 2 ,
+.Xr msync 2 ,
+.Xr munmap 2 ,
+.Xr rfork 2
+.Sh HISTORY
+The
+.Fn minherit
+system call first appeared in
+.Ox .
+.Sh BUGS
+Once you set inheritance to
+.Dv MAP_PRIVATE
+or
+.Dv MAP_SHARED ,
+there is no way to recover the original copy-on-write semantics
+short of unmapping and remapping the area.