162 lines
4.6 KiB
Groff
162 lines
4.6 KiB
Groff
.\"
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.\" Copyright (c) 2003 Bruce M Simpson <bms@spc.org>
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.\" 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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.\" $FreeBSD$
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.\"
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.Dd September 12, 2013
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.Dt VM_MAP_FIND 9
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.Os
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.Sh NAME
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.Nm vm_map_find
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.Nd find a free region within a map, and optionally map a vm_object
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.Sh SYNOPSIS
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.In sys/param.h
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.In vm/vm.h
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.In vm/vm_map.h
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.Ft int
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.Fo vm_map_find
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.Fa "vm_map_t map" "vm_object_t object" "vm_ooffset_t offset"
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.Fa "vm_offset_t *addr" "vm_size_t length" "vm_offset_t max_addr"
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.Fa "int find_space" "vm_prot_t prot" "vm_prot_t max" "int cow"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn vm_map_find
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function attempts to find a free region in the target
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.Fa map ,
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with the given
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.Fa length.
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If a free region is found,
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.Fn vm_map_find
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creates a mapping of
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.Fa object
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via a call to
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.Xr vm_map_insert 9 .
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.Pp
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The arguments
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.Fa offset ,
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.Fa prot ,
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.Fa max ,
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and
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.Fa cow
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are passed unchanged to
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.Xr vm_map_insert 9
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when creating the mapping, if and only if a free region is found.
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.Pp
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If
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.Fa object
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is
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.Pf non- Dv NULL ,
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the reference count on the object must be incremented
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by the caller before calling this function to account for the new entry.
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.Pp
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If
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.Fa max_addr
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is non-zero,
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it specifies an upper bound on the mapping.
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The mapping will only succeed if a free region can be found that resides
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entirely below
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.Fa max_addr .
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.Pp
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The
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.Fa find_space
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argument specifies the strategy to use when searching for a free region of
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the requested length.
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For all values other than
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.Dv VMFS_NO_SPACE ,
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.Xr vm_map_findspace 9
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is called to locate a free region of the requested length with a starting
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address at or above
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.Fa *addr .
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The following strategies are supported:
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.Bl -tag -width "Dv VMFS_ALIGNED_SPACE Ns"
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.It Dv VMFS_NO_SPACE
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The mapping will only succeed if there is a free region of the requested
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length at the given address
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.Fa *addr .
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.It Dv VMFS_ANY_SPACE
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The mapping will succeed as long as there is a free region.
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.It Dv VMFS_SUPER_SPACE
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The mapping will succeed as long as there is a free region that begins on
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a superpage boundary.
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If
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.Fa object
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is
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.Pf non- Dv NULL
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and is already backed by superpages,
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then the mapping will require a free region that aligns relative to the
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existing superpages rather than one beginning on a superpage boundary.
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.It Dv VMFS_OPTIMAL_SPACE
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The mapping will succeed as long as there is a free region.
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However, if
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.Fa object
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is
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.Pf non- Dv NULL
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and is already backed by superpages,
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this strategy will attempt to find a free region aligned relative to
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the existing superpages.
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.It Dv VMFS_ALIGNED_SPACE Ns Pq Fa n
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The mapping will succeed as long as there is a free region that aligns on
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a
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.Pf 2^ Fa n
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boundary.
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.El
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.Sh IMPLEMENTATION NOTES
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This function acquires a lock on
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.Fa map
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by calling
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.Xr vm_map_lock 9 ,
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and holds it until the function returns.
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.Pp
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The search for a free region is defined to be first-fit, from the address
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.Fa addr
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onwards.
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.Sh RETURN VALUES
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The
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.Fn vm_map_find
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function returns
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.Dv KERN_SUCCESS
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if the mapping was successfully created.
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If space could not be found or
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.Fa find_space
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was
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.Dv VMFS_NO_SPACE
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and the given address,
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.Fa addr ,
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was already mapped,
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.Dv KERN_NO_SPACE
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will be returned.
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If the discovered range turned out to be bogus,
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.Dv KERN_INVALID_ADDRESS
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will be returned.
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.Sh SEE ALSO
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.Xr vm_map 9 ,
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.Xr vm_map_findspace 9 ,
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.Xr vm_map_insert 9 ,
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.Xr vm_map_lock 9
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.Sh AUTHORS
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This manual page was written by
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.An Bruce M Simpson Aq bms@spc.org .
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