FreeBSD-5.3/share/man/man9/pmap_extract.9

.\"
.\" 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.
.\"
.\" $FreeBSD: src/share/man/man9/pmap_extract.9,v 1.3 2004/07/06 07:02:31 ru Exp $
.\"
.Dd July 21, 2003
.Dt PMAP_EXTRACT 9
.Os
.Sh NAME
.Nm pmap_extract ,
.Nm pmap_extract_and_hold
.Nd map a virtual address to a physical page
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/pmap.h
.Ft vm_paddr_t
.Fn pmap_extract "pmap_t pmap" "vm_offset_t va"
.Ft vm_paddr_t
.Fn pmap_extract_and_hold "pmap_t pmap" "vm_offset_t va" "vm_prot_t prot"
.Sh DESCRIPTION
The
.Fn pmap_extract
function maps a virtual address to a physical page.
In certain situations, callers may use
.Fn pmap_extract_and_hold
instead, to ensure that the returned page is held.
.Pp
The
.Fn pmap_extract_and_hold
function maps a virtual address to a physical page, and atomically holds
the returned page for use by the caller, only if the mapping permits
the given page protection.
.Sh IMPLEMENTATION NOTES
Currently, the page protection requested by the caller is not verified.
.Pp
In the
.Fn pmap_extract_and_hold
function, the
.Va Giant
lock is held for the duration of the call to ensure that only a single
caller is present.
.Sh RETURN VALUES
The
.Fn pmap_extract
function will return the physical page address associated with the
virtual address
.Fa va
inside the physical map
.Fa pmap .
If the mapping does not exist, or if the
.Fa pmap
parameter is
.Dv NULL ,
then
.Dv NULL
will be returned.
.Pp
The
.Fn pmap_extract_and_hold
function will return the physical page address associated with the
virtual address
.Fa va
inside the physical map
.Fa pmap .
If the mapping does not exist, the result is a no-op, and
.Dv NULL
will
be returned.
.Sh SEE ALSO
.Xr mutex 9 ,
.Xr pmap 9
.Sh AUTHORS
.An -nosplit
The
.Fn pmap_extract_and_hold
function was implemented by
.An Alan L. Cox Aq alc@imimic.com .
This manual page was written by
.An Bruce M Simpson Aq bms@spc.org .