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.\"
.\" Copyright (c) 2003 Bruce M Simpson <bms@spc.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd September 12, 2013
.Dt VM_MAP_FIND 9
.Os
.Sh NAME
.Nm vm_map_find
.Nd find a free region within a map, and optionally map a vm_object
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_map.h
.Ft int
.Fo vm_map_find
.Fa "vm_map_t map" "vm_object_t object" "vm_ooffset_t offset"
.Fa "vm_offset_t *addr" "vm_size_t length" "vm_offset_t max_addr"
.Fa "int find_space" "vm_prot_t prot" "vm_prot_t max" "int cow"
.Fc
.Sh DESCRIPTION
The
.Fn vm_map_find
function attempts to find a free region in the target
.Fa map ,
with the given
.Fa length.
If a free region is found,
.Fn vm_map_find
creates a mapping of
.Fa object
via a call to
.Xr vm_map_insert 9 .
.Pp
The arguments
.Fa offset ,
.Fa prot ,
.Fa max ,
and
.Fa cow
are passed unchanged to
.Xr vm_map_insert 9
when creating the mapping, if and only if a free region is found.
.Pp
If
.Fa object
is
.Pf non- Dv NULL ,
the reference count on the object must be incremented
by the caller before calling this function to account for the new entry.
.Pp
If
.Fa max_addr
is non-zero,
it specifies an upper bound on the mapping.
The mapping will only succeed if a free region can be found that resides
entirely below
.Fa max_addr .
.Pp
The
.Fa find_space
argument specifies the strategy to use when searching for a free region of
the requested length.
For all values other than
.Dv VMFS_NO_SPACE ,
.Xr vm_map_findspace 9
is called to locate a free region of the requested length with a starting
address at or above
.Fa *addr .
The following strategies are supported:
.Bl -tag -width "Dv VMFS_ALIGNED_SPACE Ns"
.It Dv VMFS_NO_SPACE
The mapping will only succeed if there is a free region of the requested
length at the given address
.Fa *addr .
.It Dv VMFS_ANY_SPACE
The mapping will succeed as long as there is a free region.
.It Dv VMFS_SUPER_SPACE
The mapping will succeed as long as there is a free region that begins on
a superpage boundary.
If
.Fa object
is
.Pf non- Dv NULL
and is already backed by superpages,
then the mapping will require a free region that aligns relative to the
existing superpages rather than one beginning on a superpage boundary.
.It Dv VMFS_OPTIMAL_SPACE
The mapping will succeed as long as there is a free region.
However, if
.Fa object
is
.Pf non- Dv NULL
and is already backed by superpages,
this strategy will attempt to find a free region aligned relative to
the existing superpages.
.It Dv VMFS_ALIGNED_SPACE Ns Pq Fa n
The mapping will succeed as long as there is a free region that aligns on
a
.Pf 2^ Fa n
boundary.
.El
.Sh IMPLEMENTATION NOTES
This function acquires a lock on
.Fa map
by calling
.Xr vm_map_lock 9 ,
and holds it until the function returns.
.Pp
The search for a free region is defined to be first-fit, from the address
.Fa addr
onwards.
.Sh RETURN VALUES
The
.Fn vm_map_find
function returns
.Dv KERN_SUCCESS
if the mapping was successfully created.
If space could not be found or
.Fa find_space
was
.Dv VMFS_NO_SPACE
and the given address,
.Fa addr ,
was already mapped,
.Dv KERN_NO_SPACE
will be returned.
If the discovered range turned out to be bogus,
.Dv KERN_INVALID_ADDRESS
will be returned.
.Sh SEE ALSO
.Xr vm_map 9 ,
.Xr vm_map_findspace 9 ,
.Xr vm_map_insert 9 ,
.Xr vm_map_lock 9
.Sh AUTHORS
This manual page was written by
.An Bruce M Simpson Aq Mt bms@spc.org .
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