2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
289 lines
7.5 KiB
Groff
289 lines
7.5 KiB
Groff
.\" $NetBSD: mmap.2,v 1.41 2009/02/27 16:48:02 wiz 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. 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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.\" @(#)mmap.2 8.4 (Berkeley) 5/11/95
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.\"
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.Dd February 27, 2009
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.Dt MMAP 2
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.Os
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.Sh NAME
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.Nm mmap
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.Nd map files or devices into memory
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft void *
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.Fn mmap "void *addr" "size_t len" "int prot" "int flags" "int fd" "off_t offset"
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.Sh DESCRIPTION
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The
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.Nm mmap
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function causes the pages starting at
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.Fa addr
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and continuing for at most
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.Fa len
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bytes to be mapped from the object described by
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.Fa fd ,
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starting at byte offset
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.Fa offset .
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If
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.Fa len
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is not a multiple of the pagesize, the mapped region may extend past the
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specified range.
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Any such extension beyond the end of the mapped object will be zero-filled.
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.Pp
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If
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.Fa addr
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is non-zero, it is used as a hint to the system.
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(As a convenience to the system, the actual address of the region may differ
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from the address supplied.)
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If
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.Fa addr
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is zero, an address will be selected by the system.
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The actual starting address of the region is returned.
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A successful
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.Fa mmap
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deletes any previous mapping in the allocated address range.
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.Pp
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The protections (region accessibility) are specified in the
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.Fa prot
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argument by
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.Em OR Ns 'ing
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the following values:
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.Pp
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.Bl -tag -width PROT_WRITEXX
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.It Dv PROT_EXEC
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Pages may be executed.
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.It Dv PROT_READ
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Pages may be read.
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.It Dv PROT_WRITE
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Pages may be written.
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.It Dv PROT_NONE
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Pages may not be accessed.
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.El
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.Pp
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.Bf -symbolic
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Note that, due to hardware limitations, on some platforms
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.Dv PROT_WRITE
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may imply
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.Dv PROT_READ ,
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and
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.Dv PROT_READ
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may imply
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.Dv PROT_EXEC .
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Portable programs should not rely on these flags being separately
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enforceable.
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.Ef
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.Pp
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The
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.Fa flags
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parameter specifies the type of the mapped object, mapping options and
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whether modifications made to the mapped copy of the page are private
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to the process or are to be shared with other references.
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Note that either
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.Dv MAP_SHARED
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or
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.Dv MAP_PRIVATE
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must be specified.
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Sharing, mapping type and options are specified in the
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.Fa flags
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argument by
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.Em OR Ns 'ing
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the following values:
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.Pp
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.Bl -tag -width MAP_HASSEMAPHOREXX
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.It Dv MAP_ALIGNED(n)
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Request that the allocation be aligned to the given boundary.
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The parameter
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.Ar n
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should be the base 2 logarithm of the desired alignment (e.g., to
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request alignment to 16K, use 14 as the value for n).
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The alignment must be equal to or greater than the platform's page
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size as returned by
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.Xr sysconf 3
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with the
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.Dv _SC_PAGESIZE
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request.
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.It Dv MAP_ANON
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Map anonymous memory not associated with any specific file.
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The file descriptor is not used for creating
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.Dv MAP_ANON
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regions, and must be specified as \-1.
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The mapped memory will be zero filled.
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.It Dv MAP_FILE
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Mapped from a regular file or character-special device memory.
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.It Dv MAP_FIXED
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Do not permit the system to select a different address than the one
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specified.
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If the specified address cannot be used,
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.Nm mmap
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will fail.
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If MAP_FIXED is specified,
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.Fa addr
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must be a multiple of the pagesize.
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Use of this option is discouraged.
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.It Dv MAP_HASSEMAPHORE
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Notify the kernel that the region may contain semaphores and that special
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handling may be necessary.
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.It Dv MAP_INHERIT
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Permit regions to be inherited across
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.Xr execve 2
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system calls.
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.It Dv MAP_TRYFIXED
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Attempt to use the address
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.Fa addr
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even if it falls within the normally protected process data or
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text segment memory regions.
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If the requested region of memory
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is actually present in the memory map, a different address will
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be selected as if
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.Dv MAP_TRYFIXED
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had not been specified.
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If
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.Fa addr
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is
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.Fa NULL ,
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this flag is ignored and the system will select a mapping address.
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.It Dv MAP_WIRED
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Lock the mapped region into memory as with
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.Xr mlock 2 .
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.It Dv MAP_PRIVATE
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Modifications made by this process are private, however modifications made by
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other processes using
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.Dv MAP_SHARED
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will be seen.
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.It Dv MAP_SHARED
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Modifications are shared.
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.El
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.Pp
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The
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.Xr close 2
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function does not unmap pages, see
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.Xr munmap 2
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for further information.
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.Pp
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The current design does not allow a process to specify the location of
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swap space.
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In the future we may define an additional mapping type,
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.Dv MAP_SWAP ,
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in which
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the file descriptor argument specifies a file or device to which swapping
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should be done.
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.Pp
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If
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.Dv MAP_FIXED
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is not specified, the system will attempt to place the mapping in an
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unused portion of the address space chosen to minimize possible
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collision between mapped regions and the heap.
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.Sh RETURN VALUES
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Upon successful completion,
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.Nm mmap
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returns a pointer to the mapped region.
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Otherwise, a value of
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.Dv MAP_FAILED
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is returned and
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.Va errno
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is set to indicate the error.
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The symbol
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.Dv MAP_FAILED
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is defined in the header
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.Ao Pa sys/mman.h Ac .
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No successful return from
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.Fn mmap
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will return the value
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.Dv MAP_FAILED .
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.Sh ERRORS
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.Fn mmap
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EACCES
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The flag
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.Dv PROT_READ
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was specified as part of the
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.Fa prot
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parameter and
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.Fa fd
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was not open for reading.
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The flags
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.Dv MAP_SHARED
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and
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.Dv PROT_WRITE
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were specified as part of the
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.Fa flags
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and
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.Fa prot
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parameters and
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.Fa fd
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was not open for writing.
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.It Bq Er EBADF
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.Fa fd
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is not a valid open file descriptor.
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.It Bq Er EINVAL
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.\"One of
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.\".Dv MAP_ANON
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.\"or
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.\".Dv MAP_FILE
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.\"was not specified as part of the
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.\".Fa flags
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.\"parameter.
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.Dv MAP_FIXED
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was specified and the
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.Fa addr
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parameter was not page aligned or was outside of the
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valid address range for a process.
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.Dv MAP_ANON was specified and
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.Fa fd
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was not \-1.
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.It Bq Er ENODEV
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.Fa fd
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did not reference a regular or character special file.
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.It Bq Er ENOMEM
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.Dv MAP_FIXED
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was specified and the
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.Fa addr
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parameter wasn't available.
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.Dv MAP_ANON
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was specified and insufficient memory was available.
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.It Bq Er EOVERFLOW
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.Fa fd
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references a regular file and the value of
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.Fa offset
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plus
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.Fa len
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would exceed the offset maximum established in its open file description.
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.El
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.Sh SEE ALSO
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.Xr madvise 2 ,
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.Xr mincore 2 ,
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.Xr mlock 2 ,
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.Xr mprotect 2 ,
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.Xr msync 2 ,
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.Xr munmap 2 ,
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.Xr getpagesize 3 ,
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.Xr sysconf 3
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