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.Pa /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.Pa /dev/mem 51are allowed. 52.Pp 53Kernel virtual memory is accessed through the interface 54.Pa /dev/kmem 55in the same manner as 56.Pa /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. 76These attributes can be manipulated via 77.Fn ioctl 78calls performed on 79.Pa /dev/mem . 80Declarations and data types are to be found in 81.In sys/memrange.h . 82.Pp 83The specific attributes, and number of programmable ranges may vary between 84architectures. 85The full set of supported attributes is: 86.Bl -tag -width indent 87.It Dv MDF_UNCACHEABLE 88The region is not cached. 89.It Dv MDF_WRITECOMBINE 90Writes to the region may be combined or performed out of order. 91.It Dv MDF_WRITETHROUGH 92Writes to the region are committed synchronously. 93.It Dv MDF_WRITEBACK 94Writes to the region are committed asynchronously. 95.It Dv MDF_WRITEPROTECT 96The region cannot be written to. 97.El 98.Pp 99Memory ranges are described by 100.Vt struct mem_range_desc : 101.Bd -literal -offset indent 102u_int64_t mr_base; /\(** physical base address \(**/ 103u_int64_t mr_len; /\(** physical length of region \(**/ 104int mr_flags; /\(** attributes of region \(**/ 105char mr_owner[8]; 106.Ed 107.Pp 108In addition to the region attributes listed above, the following flags 109may also be set in the 110.Fa mr_flags 111field: 112.Bl -tag -width indent 113.It MDF_FIXBASE 114The region's base address cannot be changed. 115.It MDF_FIXLEN 116The region's length cannot be changed. 117.It MDF_FIRMWARE 118The region is believed to have been established by the system firmware. 119.It MDF_ACTIVE 120The region is currently active. 121.It MDF_BOGUS 122We believe the region to be invalid or otherwise erroneous. 123.It MDF_FIXACTIVE 124The region cannot be disabled. 125.It MDF_BUSY 126The region is currently owned by another process and may not be 127altered. 128.El 129.Pp 130Operations are performed using 131.Fa struct mem_range_op : 132.Bd -literal -offset indent 133struct mem_range_desc *mo_desc; 134int mo_arg[2]; 135.Ed 136.Pp 137The 138.Dv MEMRANGE_GET 139ioctl is used to retrieve current memory range attributes. 140If 141.Va mo_arg[0] 142is set to 0, it will be updated with the total number of memory range 143descriptors. 144If greater than 0, the array at 145.Va mo_desc 146will be filled with a corresponding number of descriptor structures, 147or the maximum, whichever is less. 148.Pp 149The 150.Dv MEMRANGE_SET 151ioctl is used to add, alter and remove memory range attributes. 152A range 153with the 154.Dv MDF_FIXACTIVE 155flag may not be removed; a range with the 156.Dv MDF_BUSY 157flag may not be removed or updated. 158.Pp 159.Va mo_arg[0] 160should be set to 161.Dv MEMRANGE_SET_UPDATE 162to update an existing or establish a new range, or to 163.Dv MEMRANGE_SET_REMOVE 164to remove a range. 165.Sh RETURN VALUES 166.Bl -tag -width Er 167.It Bq Er EOPNOTSUPP 168Memory range operations are not supported on this architecture. 169.It Bq Er ENXIO 170No memory range descriptors are available (e.g.\& firmware has not enabled 171any). 172.It Bq Er EINVAL 173The memory range supplied as an argument is invalid or overlaps another 174range in a fashion not supported by this architecture. 175.It Bq Er EBUSY 176An attempt to remove or update a range failed because the range is busy. 177.It Bq Er ENOSPC 178An attempt to create a new range failed due to a shortage of hardware 179resources (e.g.\& descriptor slots). 180.It Bq Er ENOENT 181An attempt to remove a range failed because no range matches the descriptor 182base/length supplied. 183.It Bq Er EPERM 184An attempt to remove a range failed because the range is permanently 185enabled. 186.El 187.Sh BUGS 188Busy range attributes are not yet managed correctly. 189.Sh FILES 190.Bl -tag -width /dev/kmem -compact 191.It Pa /dev/mem 192.It Pa /dev/kmem 193.El 194.Sh SEE ALSO 195.Xr memcontrol 8 196.Sh HISTORY 197The 198.Nm mem 199and 200.Nm kmem 201files appeared in 202.At v6 . 203The ioctl interface for memory range attributes was added in 204.Fx 3.2 . 205