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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)mem.4 5.3 (Berkeley) 5/2/91 33.\" $FreeBSD$ 34.\" 35.Dd May 2, 1991 36.Dt MEM 4 37.Os 38.Sh NAME 39.Nm mem , 40.Nm kmem 41.Nd memory files 42.Sh DESCRIPTION 43The special file 44.Nm /dev/mem 45is an interface to the physical memory of the computer. 46Byte offsets in this file are interpreted as physical memory addresses. 47Reading and writing this file is equivalent to reading and writing 48memory itself. 49Only offsets within the bounds of 50.Nm /dev/mem 51are allowed. 52.Pp 53Kernel virtual memory is accessed through the interface 54.Nm /dev/kmem 55in the same manner as 56.Nm /dev/mem . 57Only kernel virtual addresses that are currently mapped to memory are allowed. 58.Pp 59On 60.Tn ISA 61the 62.Tn I/O 63memory space begins at physical address 0x000a0000 64and runs to 0x00100000. 65The 66per-process data 67size 68for the current process 69is 70.Dv UPAGES 71long, and ends at virtual 72address 0xf0000000. 73.Sh IOCTL INTERFACE 74Several architectures allow attributes to be associated with ranges of physical 75memory. These attributes can be manipulated via 76.Fn ioctl 77calls performed on 78.Nm /dev/mem . 79Declarations and data types are to be found in 80.Pa <memrange.h> 81.Pp 82The specific attributes, and number of programmable ranges may vary between 83architectures. The full set of supported attributes is: 84.Bl -tag -width 10 85.It MDF_UNCACHEABLE 86The region is not cached. 87.It MDF_WRITECOMBINE 88Writes to the region may be combined or performed out of order. 89.It MDF_WRITETHROUGH 90Writes to the region are committed synchronously. 91.It MDF_WRITEBACK 92Writes to the region are committed asynchronously. 93.It MDF_WRITEPROTECT 94The region cannot be written to. 95.El 96.Pp 97Memory ranges are described by 98.Fa struct mem_range_desc : 99.Bd -literal -offset indent 100u_int64_t mr_base; /\(** physical base address \(**/ 101u_int64_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 10 111.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 firmare. 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.Fa MEMRANGE_GET 137ioctl is used to retrieve current memory range attributes. 138If 139.Fa mo_arg[0] 140is set to 0, it will be updated with the total number of memory range 141descriptors. If greater than 0, the array at 142.Fa mo_desc 143will be filled with a corresponding number of descriptor structures, 144or the maximum, whichever is less. 145.Pp 146The 147.Fa MEMRANGE_SET 148ioctl is used to add, alter and remove memory range attributes. A range 149with the MDF_FIXACTIVE flag may not be removed; a range with the MDF_BUSY 150flag may not be removed or updated. 151.Pp 152.Fa mo_arg[0] 153should be set to MEMRANGE_SET_UPDATE to update an existing 154or establish a new range, or to MEMRANGE_SET_REMOVE to remove a range. 155.Pp 156.Sh RETURN VALUES 157.Bl -tag -width 10 158.It EOPNOTSUPP 159Memory range operations are not supported on this architecture. 160.It ENXIO 161No memory range descriptors are available (eg. firmware has not enabled 162any). 163.It EINVAL 164The memory range supplied as an argument is invalid or overlaps another 165range in a fashion not supported by this architecture. 166.It EBUSY 167An attempt to remove or update a range failed because the range is busy. 168.It ENOSPC 169An attempt to create a new range failed due to a shortage of hardware 170resources (eg. descriptor slots). 171.It ENOENT 172An attempt to remove a range failed because no range matches the descriptor 173base/length supplued. 174.It EPERM 175An attempt to remove a range failed because the range is permanently 176enabled. 177.El 178.Sh BUGS 179Busy range attributes are not yet managed correctly. 180.Sh FILES 181.Bl -tag -width Pa -compact 182.It Pa /dev/mem 183.It Pa /dev/kmem 184.El 185.Sh SEE ALSO 186.Xr memcontrol 8 187.Sh HISTORY 188The 189.Nm mem , 190.Nm kmem 191files appeared in 192.At v6 . 193The ioctl interface for memory range attributes was added in 194.Fx 3.2 . 195