1.\" Copyright (c) 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)mem.4 5.3 (Berkeley) 5/2/91 29.\" $FreeBSD$ 30.\" 31.Dd October 3, 2004 32.Dt MEM 4 33.Os 34.Sh NAME 35.Nm mem , 36.Nm kmem 37.Nd memory files 38.Sh SYNOPSIS 39.Cd "device mem" 40.Sh DESCRIPTION 41The special file 42.Pa /dev/mem 43is an interface to the physical memory of the computer. 44Byte offsets in this file are interpreted as physical memory addresses. 45Reading and writing this file is equivalent to reading and writing 46memory itself. 47Only offsets within the bounds of 48.Pa /dev/mem 49are allowed. 50.Pp 51Kernel virtual memory is accessed through the interface 52.Pa /dev/kmem 53in the same manner as 54.Pa /dev/mem . 55Only kernel virtual addresses that are currently mapped to memory are allowed. 56.Pp 57On 58.Tn ISA 59the 60.Tn I/O 61memory space begins at physical address 0x000a0000 62and runs to 0x00100000. 63The 64per-process data 65size 66for the current process 67is 68.Dv UPAGES 69long, and ends at virtual 70address 0xf0000000. 71.Sh IOCTL INTERFACE 72Several architectures allow attributes to be associated with ranges of physical 73memory. 74These attributes can be manipulated via 75.Fn ioctl 76calls performed on 77.Pa /dev/mem . 78Declarations and data types are to be found in 79.In sys/memrange.h . 80.Pp 81The specific attributes, and number of programmable ranges may vary between 82architectures. 83The full set of supported attributes is: 84.Bl -tag -width indent 85.It Dv MDF_UNCACHEABLE 86The region is not cached. 87.It Dv MDF_WRITECOMBINE 88Writes to the region may be combined or performed out of order. 89.It Dv MDF_WRITETHROUGH 90Writes to the region are committed synchronously. 91.It Dv MDF_WRITEBACK 92Writes to the region are committed asynchronously. 93.It Dv MDF_WRITEPROTECT 94The region cannot be written to. 95.El 96.Pp 97Memory ranges are described by 98.Vt struct mem_range_desc : 99.Bd -literal -offset indent 100uint64_t mr_base; /\(** physical base address \(**/ 101uint64_t mr_len; /\(** physical length of region \(**/ 102int mr_flags; /\(** attributes of region \(**/ 103char mr_owner[8]; 104.Ed 105.Pp 106In addition to the region attributes listed above, the following flags 107may also be set in the 108.Fa mr_flags 109field: 110.Bl -tag -width indent 111.It MDF_FIXBASE 112The region's base address cannot be changed. 113.It MDF_FIXLEN 114The region's length cannot be changed. 115.It MDF_FIRMWARE 116The region is believed to have been established by the system firmware. 117.It MDF_ACTIVE 118The region is currently active. 119.It MDF_BOGUS 120We believe the region to be invalid or otherwise erroneous. 121.It MDF_FIXACTIVE 122The region cannot be disabled. 123.It MDF_BUSY 124The region is currently owned by another process and may not be 125altered. 126.El 127.Pp 128Operations are performed using 129.Fa struct mem_range_op : 130.Bd -literal -offset indent 131struct mem_range_desc *mo_desc; 132int mo_arg[2]; 133.Ed 134.Pp 135The 136.Dv MEMRANGE_GET 137ioctl is used to retrieve current memory range attributes. 138If 139.Va mo_arg[0] 140is set to 0, it will be updated with the total number of memory range 141descriptors. 142If greater than 0, the array at 143.Va mo_desc 144will be filled with a corresponding number of descriptor structures, 145or the maximum, whichever is less. 146.Pp 147The 148.Dv MEMRANGE_SET 149ioctl is used to add, alter and remove memory range attributes. 150A range 151with the 152.Dv MDF_FIXACTIVE 153flag may not be removed; a range with the 154.Dv MDF_BUSY 155flag may not be removed or updated. 156.Pp 157.Va mo_arg[0] 158should be set to 159.Dv MEMRANGE_SET_UPDATE 160to update an existing or establish a new range, or to 161.Dv MEMRANGE_SET_REMOVE 162to remove a range. 163.Sh RETURN VALUES 164.Bl -tag -width Er 165.It Bq Er EOPNOTSUPP 166Memory range operations are not supported on this architecture. 167.It Bq Er ENXIO 168No memory range descriptors are available (e.g.\& firmware has not enabled 169any). 170.It Bq Er EINVAL 171The memory range supplied as an argument is invalid or overlaps another 172range in a fashion not supported by this architecture. 173.It Bq Er EBUSY 174An attempt to remove or update a range failed because the range is busy. 175.It Bq Er ENOSPC 176An attempt to create a new range failed due to a shortage of hardware 177resources (e.g.\& descriptor slots). 178.It Bq Er ENOENT 179An attempt to remove a range failed because no range matches the descriptor 180base/length supplied. 181.It Bq Er EPERM 182An attempt to remove a range failed because the range is permanently 183enabled. 184.El 185.Sh FILES 186.Bl -tag -width /dev/kmem -compact 187.It Pa /dev/mem 188.It Pa /dev/kmem 189.El 190.Sh SEE ALSO 191.Xr kvm 3 , 192.Xr memcontrol 8 193.Sh HISTORY 194The 195.Nm mem 196and 197.Nm kmem 198files appeared in 199.At v6 . 200The ioctl interface for memory range attributes was added in 201.Fx 3.2 . 202.Sh BUGS 203Busy range attributes are not yet managed correctly. 204.Pp 205This device is required for all users of 206.Xr kvm 3 207to operate. 208