212 lines
6.2 KiB
Groff
212 lines
6.2 KiB
Groff
.\" Copyright (c) 1991 The Regents of the University of California.
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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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.\" 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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.\" @(#)mem.4 5.3 (Berkeley) 5/2/91
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.\" $FreeBSD$
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.\"
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.Dd October 3, 2004
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.Dt MEM 4
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.Os
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.Sh NAME
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.Nm mem ,
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.Nm kmem
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.Nd memory files
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.Sh SYNOPSIS
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.Cd "device mem"
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.Sh DESCRIPTION
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The special file
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.Pa /dev/mem
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is an interface to the physical memory of the computer.
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Byte offsets in this file are interpreted as physical memory addresses.
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Reading and writing this file is equivalent to reading and writing
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memory itself.
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Only offsets within the bounds of
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.Pa /dev/mem
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are allowed.
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.Pp
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Kernel virtual memory is accessed through the interface
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.Pa /dev/kmem
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in the same manner as
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.Pa /dev/mem .
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Only kernel virtual addresses that are currently mapped to memory are allowed.
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.Pp
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On
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.Tn ISA
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the
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.Tn I/O
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memory space begins at physical address 0x000a0000
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and runs to 0x00100000.
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The
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per-process data
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size
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for the current process
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is
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.Dv UPAGES
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long, and ends at virtual
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address 0xf0000000.
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.Sh IOCTL INTERFACE
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Several architectures allow attributes to be associated with ranges of physical
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memory.
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These attributes can be manipulated via
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.Fn ioctl
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calls performed on
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.Pa /dev/mem .
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Declarations and data types are to be found in
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.In sys/memrange.h .
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.Pp
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The specific attributes, and number of programmable ranges may vary between
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architectures.
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The full set of supported attributes is:
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.Bl -tag -width indent
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.It Dv MDF_UNCACHEABLE
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The region is not cached.
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.It Dv MDF_WRITECOMBINE
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Writes to the region may be combined or performed out of order.
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.It Dv MDF_WRITETHROUGH
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Writes to the region are committed synchronously.
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.It Dv MDF_WRITEBACK
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Writes to the region are committed asynchronously.
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.It Dv MDF_WRITEPROTECT
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The region cannot be written to.
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.El
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.Pp
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Memory ranges are described by
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.Vt struct mem_range_desc :
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.Bd -literal -offset indent
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u_int64_t mr_base; /\(** physical base address \(**/
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u_int64_t mr_len; /\(** physical length of region \(**/
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int mr_flags; /\(** attributes of region \(**/
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char mr_owner[8];
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.Ed
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.Pp
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In addition to the region attributes listed above, the following flags
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may also be set in the
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.Fa mr_flags
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field:
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.Bl -tag -width indent
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.It MDF_FIXBASE
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The region's base address cannot be changed.
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.It MDF_FIXLEN
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The region's length cannot be changed.
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.It MDF_FIRMWARE
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The region is believed to have been established by the system firmware.
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.It MDF_ACTIVE
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The region is currently active.
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.It MDF_BOGUS
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We believe the region to be invalid or otherwise erroneous.
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.It MDF_FIXACTIVE
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The region cannot be disabled.
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.It MDF_BUSY
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The region is currently owned by another process and may not be
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altered.
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.El
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.Pp
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Operations are performed using
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.Fa struct mem_range_op :
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.Bd -literal -offset indent
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struct mem_range_desc *mo_desc;
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int mo_arg[2];
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.Ed
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.Pp
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The
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.Dv MEMRANGE_GET
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ioctl is used to retrieve current memory range attributes.
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If
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.Va mo_arg[0]
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is set to 0, it will be updated with the total number of memory range
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descriptors.
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If greater than 0, the array at
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.Va mo_desc
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will be filled with a corresponding number of descriptor structures,
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or the maximum, whichever is less.
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.Pp
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The
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.Dv MEMRANGE_SET
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ioctl is used to add, alter and remove memory range attributes.
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A range
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with the
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.Dv MDF_FIXACTIVE
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flag may not be removed; a range with the
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.Dv MDF_BUSY
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flag may not be removed or updated.
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.Pp
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.Va mo_arg[0]
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should be set to
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.Dv MEMRANGE_SET_UPDATE
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to update an existing or establish a new range, or to
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.Dv MEMRANGE_SET_REMOVE
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to remove a range.
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.Sh RETURN VALUES
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.Bl -tag -width Er
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.It Bq Er EOPNOTSUPP
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Memory range operations are not supported on this architecture.
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.It Bq Er ENXIO
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No memory range descriptors are available (e.g.\& firmware has not enabled
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any).
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.It Bq Er EINVAL
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The memory range supplied as an argument is invalid or overlaps another
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range in a fashion not supported by this architecture.
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.It Bq Er EBUSY
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An attempt to remove or update a range failed because the range is busy.
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.It Bq Er ENOSPC
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An attempt to create a new range failed due to a shortage of hardware
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resources (e.g.\& descriptor slots).
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.It Bq Er ENOENT
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An attempt to remove a range failed because no range matches the descriptor
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base/length supplied.
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.It Bq Er EPERM
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An attempt to remove a range failed because the range is permanently
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enabled.
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.El
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.Sh FILES
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.Bl -tag -width /dev/kmem -compact
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.It Pa /dev/mem
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.It Pa /dev/kmem
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.El
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.Sh SEE ALSO
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.Xr kvm 3 ,
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.Xr memcontrol 8
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.Sh HISTORY
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The
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.Nm mem
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and
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.Nm kmem
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files appeared in
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.At v6 .
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The ioctl interface for memory range attributes was added in
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.Fx 3.2 .
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.Sh BUGS
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Busy range attributes are not yet managed correctly.
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.Pp
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This device is required for all users of
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.Xr kvm 3
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to operate.
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