1.\" 2.\" Copyright (c) 2008 Apple Inc. All rights reserved. 3.\" 4.\" @APPLE_LICENSE_HEADER_START@ 5.\" 6.\" This file contains Original Code and/or Modifications of Original Code 7.\" as defined in and that are subject to the Apple Public Source License 8.\" Version 2.0 (the 'License'). You may not use this file except in 9.\" compliance with the License. Please obtain a copy of the License at 10.\" http://www.opensource.apple.com/apsl/ and read it before using this 11.\" file. 12.\" 13.\" The Original Code and all software distributed under the License are 14.\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 15.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 16.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 17.\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 18.\" Please see the License for the specific language governing rights and 19.\" limitations under the License. 20.\" 21.\" @APPLE_LICENSE_HEADER_END@ 22.\" 23.\" 24.\" $NetBSD: munmap.2,v 1.5 1995/02/27 12:35:03 cgd Exp $ 25.\" 26.\" Copyright (c) 1991, 1993 27.\" The Regents of the University of California. All rights reserved. 28.\" 29.\" Redistribution and use in source and binary forms, with or without 30.\" modification, are permitted provided that the following conditions 31.\" are met: 32.\" 1. Redistributions of source code must retain the above copyright 33.\" notice, this list of conditions and the following disclaimer. 34.\" 2. Redistributions in binary form must reproduce the above copyright 35.\" notice, this list of conditions and the following disclaimer in the 36.\" documentation and/or other materials provided with the distribution. 37.\" 3. All advertising materials mentioning features or use of this software 38.\" must display the following acknowledgement: 39.\" This product includes software developed by the University of 40.\" California, Berkeley and its contributors. 41.\" 4. Neither the name of the University nor the names of its contributors 42.\" may be used to endorse or promote products derived from this software 43.\" without specific prior written permission. 44.\" 45.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 46.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 47.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 48.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 49.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 50.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 51.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 52.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 53.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 54.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 55.\" SUCH DAMAGE. 56.\" 57.\" @(#)munmap.2 8.2 (Berkeley) 4/15/94 58.\" 59.Dd October 16, 2008 60.Dt MUNMAP 2 61.Os 62.Sh NAME 63.Nm munmap 64.Nd remove a mapping 65.Sh SYNOPSIS 66.Fd #include <sys/mman.h> 67.Ft int 68.Fo munmap 69.Fa "void *addr" 70.Fa "size_t len" 71.Fc 72.Sh DESCRIPTION 73The 74.Fn munmap 75system call 76deletes the mappings for the specified address range, 77causing further references to addresses within the range 78to generate invalid memory references. 79.Sh DIRTY PAGE HANDLING 80How 81.Fn munmap 82handles a dirty page, depends on what type of memory is being unmapped: 83.Pp 84.Bl -tag -width "[System V Shared]" 85.It Bq Anonymous 86If the memory is anonymous memory and if the last reference is going 87away, then the contents are discarded by definition of anonymous memory. 88.It Bq System V Shared 89If the memory mapping was created using System V shared memory, then 90the contents persist until the System V memory region is destroyed or 91the system is rebooted. 92.It Bq File mapping 93If the mapping maps data from a file (MAP_SHARED), then the memory will 94eventually be written back to disk if it's dirty. This will happen 95automatically at some point in the future (implementation dependent). 96Note: to force the memory to be written back to the disk, use 97.Xr msync 2 . 98.El 99.Pp 100If there are still other references to the memory when the munmap is 101done, then nothing is done to the memory itself and it may be swapped 102out if need be. The memory will continue to persist until the last 103reference goes away (except for System V shared memory in which case, 104see above). 105.Sh RETURN VALUES 106Upon successful completion, 107.Nm munmap 108returns zero. 109Otherwise, a value of -1 is returned and 110.Va errno 111is set to indicate the error. 112.Sh ERRORS 113.Fn munmap 114will fail if: 115.Bl -tag -width Er 116.\" =========== 117.It Bq Er EINVAL 118The 119.Fa addr 120parameter was not page aligned (i.e., a multiple of the page size). 121.\" =========== 122.It Bq Er EINVAL 123The 124.Fa len 125parameter was negative or zero. 126.\" =========== 127.It Bq Er EINVAL 128Some part of the region being unmapped is not part of the currently 129valid address space. 130.El 131.Sh LEGACY SYNOPSIS 132.Fd #include <sys/types.h> 133.Fd #include <sys/mman.h> 134.Pp 135The include file 136.In sys/types.h 137is necessary. 138.Pp 139.Ft int 140.br 141.Fo munmap 142.Fa "caddr_t addr" 143.Fa "size_t len" 144.Fc ; 145.Pp 146The type of 147.Fa addr 148has changed. 149.Sh "SEE ALSO" 150.Xr getpagesize 3 , 151.Xr msync 2 , 152.Xr munmap 2 , 153.Xr mprotect 2 , 154.Xr madvise 2 , 155.Xr mincore 2 , 156.Xr compat 5 157.Sh HISTORY 158The 159.Fn munmap 160function first appeared in 4.4BSD. 161