1.\" $FreeBSD: src/lib/libc/sys/minherit.2,v 1.7.2.6 2001/12/14 18:34:01 ru Exp $ 2.\" $DragonFly: src/lib/libc/sys/minherit.2,v 1.4 2007/09/14 23:47:53 swildner Exp $ 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)minherit.2 8.1 (Berkeley) 6/9/93 32.\" 33.Dd February 17, 1996 34.Dt MINHERIT 2 35.Os 36.Sh NAME 37.Nm minherit 38.Nd control the inheritance of pages 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/types.h 43.In sys/mman.h 44.Ft int 45.Fn minherit "void *addr" "size_t len" "int inherit" 46.Sh DESCRIPTION 47The 48.Fn minherit 49system call 50changes the specified pages to have the inheritance characteristic 51.Fa inherit . 52Not all implementations will guarantee that the inheritance characteristic 53can be set on a page basis; 54the granularity of changes may be as large as an entire region. 55.Dx 56is capable of adjusting inheritance characteristics on a page basis. 57Inheritance only affects children created by 58.Fn fork . 59It has no effect on 60.Fn exec . 61exec'd processes replace their address space entirely. 62This function also 63has no effect on the parent's address space (other than to potentially 64share the address space with its children). 65.Pp 66Inheritance is a rather esoteric feature largely superseded by the 67.Dv MAP_SHARED 68feature of 69.Fn mmap . 70However, it is possible to use 71.Fn minherit 72to share a block of memory between parent and child that has been mapped 73.Dv MAP_PRIVATE . 74That is, modifications made by parent or child are shared but 75the original underlying file is left untouched. 76.Bl -tag -width ".Dv INHERIT_SHARE" 77.It Dv INHERIT_SHARE 78This option causes the address space in question to be shared between 79parent and child. 80It has no effect on how the original underlying backing 81store was mapped. 82.It Dv INHERIT_NONE 83This option prevents the address space in question from being inherited 84at all. 85The address space will be unmapped in the child. 86.It Dv INHERIT_COPY 87This option causes the child to inherit the address space as copy-on-write. 88This option also has an unfortunate side effect of causing the parent 89address space to become copy-on-write when the parent forks. 90If the original mapping was 91.Dv MAP_SHARED , 92it will no longer be shared in the parent 93after the parent forks and there is no way to get the previous 94shared-backing-store mapping without unmapping and remapping the address 95space in the parent. 96.El 97.Sh RETURN VALUES 98.Rv -std minherit 99.Sh ERRORS 100The 101.Fn minherit 102function will fail if: 103.Bl -tag -width Er 104.It Bq Er EINVAL 105The virtual address range specified by the 106.Fa addr 107and 108.Fa len 109arguments is not valid. 110.It Bq Er EACCES 111The flags specified by the 112.Fa inherit 113argument were not valid for the pages specified 114by the 115.Fa addr 116and 117.Fa len 118arguments. 119.El 120.Sh SEE ALSO 121.Xr fork 2 , 122.Xr madvise 2 , 123.Xr mincore 2 , 124.Xr mprotect 2 , 125.Xr msync 2 , 126.Xr munmap 2 , 127.Xr rfork 2 128.Sh HISTORY 129The 130.Fn minherit 131function first appeared in 132.Ox . 133