1.\" $NetBSD: minherit.2,v 1.11 2002/02/08 01:28:19 ross Exp $ 2.\" 3.\" Copyright (c) 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)minherit.2 8.1 (Berkeley) 6/9/93 35.\" 36.Dd June 9, 1993 37.Dt MINHERIT 2 38.Os 39.Sh NAME 40.Nm minherit 41.Nd control the inheritance of pages 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]sys/mman.h\*[Gt] 46.Ft int 47.Fn minherit "void *addr" "size_t len" "int inherit" 48.Sh DESCRIPTION 49The 50.Fn minherit 51system call 52changes the specified range of virtual addresses to have the specified 53fork-time inheritance characteristic 54.Fa inherit , 55which can be set to 56.Dv MAP_INHERIT_NONE , 57.Dv MAP_INHERIT_COPY , 58or 59.Dv MAP_INHERIT_SHARE . 60Also possible is 61.Dv MAP_INHERIT_DEFAULT , 62which defaults to 63.Dv MAP_INHERIT_COPY . 64Not all implementations will guarantee that the inheritance characteristic 65can be set on a page basis; 66the granularity of changes may be as large as an entire region. 67.Pp 68Normally, the entire address space is marked 69.Dv MAP_INHERIT_COPY ; 70when the process calls 71.Fn fork , 72the child receives a (virtual) copy of the entire address space. 73Pages or regions marked 74.Dv MAP_INHERIT_SHARE 75are shared between the address spaces, while pages or regions marked 76.Dv MAP_INHERIT_NONE 77will be unmapped in the child. 78.Sh SEE ALSO 79.Xr fork 2 , 80.Xr madvise 2 , 81.Xr mincore 2 , 82.Xr mprotect 2 , 83.Xr msync 2 , 84.Xr munmap 2 85.Sh HISTORY 86The 87.Fn minherit 88function first appeared in 89.Ox . 90.Sh BUGS 91If the a particular port does not support page-granularity 92inheritance, there's no way to figure out how large a region is 93actually affected by 94.Fn minherit . 95