160 lines
5.3 KiB
Groff
160 lines
5.3 KiB
Groff
.\"
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.\" Copyright (c) 2008 Apple Inc. All rights reserved.
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.\"
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.\" @APPLE_LICENSE_HEADER_START@
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.\"
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.\" This file contains Original Code and/or Modifications of Original Code
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.\" as defined in and that are subject to the Apple Public Source License
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.\" Version 2.0 (the 'License'). You may not use this file except in
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.\" compliance with the License. Please obtain a copy of the License at
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.\" http://www.opensource.apple.com/apsl/ and read it before using this
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.\" file.
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.\"
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.\" The Original Code and all software distributed under the License are
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.\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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.\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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.\" Please see the License for the specific language governing rights and
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.\" limitations under the License.
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.\"
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.\" @APPLE_LICENSE_HEADER_END@
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.\"
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.\"
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.\" $NetBSD: munmap.2,v 1.5 1995/02/27 12:35:03 cgd Exp $
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)munmap.2 8.2 (Berkeley) 4/15/94
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.\"
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.Dd October 16, 2008
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.Dt MUNMAP 2
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.Os
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.Sh NAME
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.Nm munmap
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.Nd remove a mapping
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.Sh SYNOPSIS
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.Fd #include <sys/mman.h>
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.Ft int
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.Fo munmap
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.Fa "void *addr"
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.Fa "size_t len"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn munmap
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system call
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deletes the mappings for the specified address range,
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causing further references to addresses within the range
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to generate invalid memory references.
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.Sh DIRTY PAGE HANDLING
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How
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.Fn munmap
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handles a dirty page, depends on what type of memory is being unmapped:
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.Pp
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.Bl -tag -width "[System V Shared]"
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.It Bq Anonymous
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If the memory is anonymous memory and if the last reference is going
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away, then the contents are discarded by definition of anonymous memory.
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.It Bq System V Shared
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If the memory mapping was created using System V shared memory, then
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the contents persist until the System V memory region is destroyed or
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the system is rebooted.
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.It Bq File mapping
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If the mapping maps data from a file (MAP_SHARED), then the memory will
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eventually be written back to disk if it's dirty. This will happen
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automatically at some point in the future (implementation dependent).
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Note: to force the memory to be written back to the disk, use
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.Xr msync 2 .
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.El
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.Pp
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If there are still other references to the memory when the munmap is
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done, then nothing is done to the memory itself and it may be swapped
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out if need be. The memory will continue to persist until the last
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reference goes away (except for System V shared memory in which case,
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see above).
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.Sh RETURN VALUES
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Upon successful completion,
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.Nm munmap
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returns zero.
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Otherwise, a value of -1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn munmap
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will fail if:
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.Bl -tag -width Er
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.\" ===========
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.It Bq Er EINVAL
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The
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.Fa addr
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parameter was not page aligned (i.e., a multiple of the page size).
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.\" ===========
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.It Bq Er EINVAL
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The
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.Fa len
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parameter was negative or zero.
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.\" ===========
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.It Bq Er EINVAL
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Some part of the region being unmapped is not part of the currently
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valid address space.
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.El
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.Sh LEGACY SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/mman.h>
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.Pp
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The include file
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.In sys/types.h
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is necessary.
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.Pp
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.Ft int
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.br
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.Fo munmap
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.Fa "caddr_t addr"
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.Fa "size_t len"
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.Fc ;
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.Pp
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The type of
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.Fa addr
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has changed.
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.Sh "SEE ALSO"
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.Xr getpagesize 3 ,
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.Xr msync 2 ,
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.Xr munmap 2 ,
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.Xr mprotect 2 ,
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.Xr madvise 2 ,
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.Xr mincore 2 ,
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.Xr compat 5
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.Sh HISTORY
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The
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.Fn munmap
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function first appeared in 4.4BSD.
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