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: src/share/man/man4/mem.4,v 1.7.2.5 2002/02/27 03:39:23 dd Exp $ 30.\" 31.Dd May 2, 1991 32.Dt MEM 4 33.Os 34.Sh NAME 35.Nm mem , 36.Nm kmem 37.Nd memory files 38.Sh DESCRIPTION 39The special file 40.Pa /dev/mem 41is an interface to the physical memory of the computer. 42Byte offsets in this file are interpreted as physical memory addresses. 43Reading and writing this file is equivalent to reading and writing 44memory itself. 45Only offsets within the bounds of 46.Pa /dev/mem 47are allowed. 48.Pp 49Kernel virtual memory is accessed through the interface 50.Pa /dev/kmem 51in the same manner as 52.Pa /dev/mem . 53Only kernel virtual addresses that are currently mapped to memory are allowed. 54.Pp 55On 56.Tn ISA 57the 58.Tn I/O 59memory space begins at physical address 0x000a0000 60and runs to 0x00100000. 61The 62per-process data 63size 64for the current process 65is 66.Dv UPAGES 67long, and ends at virtual 68address 0xf0000000. 69.Sh IOCTL INTERFACE 70Several architectures allow attributes to be associated with ranges of physical 71memory. 72These attributes can be manipulated via 73.Fn ioctl 74calls performed on 75.Pa /dev/mem . 76Declarations and data types are to be found in 77.In sys/memrange.h . 78.Pp 79The specific attributes, and number of programmable ranges may vary between 80architectures. 81The full set of supported attributes is: 82.Bl -tag -width indent 83.It Dv MDF_UNCACHEABLE 84The region is not cached. 85.It Dv MDF_WRITECOMBINE 86Writes to the region may be combined or performed out of order. 87.It Dv MDF_WRITETHROUGH 88Writes to the region are committed synchronously. 89.It Dv MDF_WRITEBACK 90Writes to the region are committed asynchronously. 91.It Dv MDF_WRITEPROTECT 92The region cannot be written to. 93.El 94.Pp 95Memory ranges are described by 96.Vt struct mem_range_desc : 97.Bd -literal -offset indent 98u_int64_t mr_base; /\(** physical base address \(**/ 99u_int64_t mr_len; /\(** physical length of region \(**/ 100int mr_flags; /\(** attributes of region \(**/ 101char mr_owner[8]; 102.Ed 103.Pp 104In addition to the region attributes listed above, the following flags 105may also be set in the 106.Fa mr_flags 107field: 108.Bl -tag -width indent 109.It Dv MDF_FIXBASE 110The region's base address cannot be changed. 111.It Dv MDF_FIXLEN 112The region's length cannot be changed. 113.It Dv MDF_FIRMWARE 114The region is believed to have been established by the system firmware. 115.It Dv MDF_ACTIVE 116The region is currently active. 117.It Dv MDF_BOGUS 118We believe the region to be invalid or otherwise erroneous. 119.It Dv MDF_FIXACTIVE 120The region cannot be disabled. 121.It Dv MDF_BUSY 122The region is currently owned by another process and may not be 123altered. 124.El 125.Pp 126Operations are performed using 127.Fa struct mem_range_op : 128.Bd -literal -offset indent 129struct mem_range_desc *mo_desc; 130int mo_arg[2]; 131.Ed 132.Pp 133The 134.Dv MEMRANGE_GET 135ioctl is used to retrieve current memory range attributes. 136If 137.Va mo_arg[0] 138is set to 0, it will be updated with the total number of memory range 139descriptors. 140If greater than 0, the array at 141.Va mo_desc 142will be filled with a corresponding number of descriptor structures, 143or the maximum, whichever is less. 144.Pp 145The 146.Dv MEMRANGE_SET 147ioctl is used to add, alter and remove memory range attributes. A range 148with the 149.Dv MDF_FIXACTIVE 150flag may not be removed; a range with the 151.Dv MDF_BUSY 152flag may not be removed or updated. 153.Pp 154.Va mo_arg[0] 155should be set to 156.Dv MEMRANGE_SET_UPDATE 157to update an existing or establish a new range, or to 158.Dv MEMRANGE_SET_REMOVE 159to remove a range. 160.Sh FILES 161.Bl -tag -width /dev/kmem -compact 162.It Pa /dev/mem 163.It Pa /dev/kmem 164.El 165.Sh ERRORS 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 (eg. 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 (eg. 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 SEE ALSO 188.Xr memcontrol 8 189.Sh HISTORY 190The 191.Nm mem 192and 193.Nm kmem 194files appeared in 195.At v6 . 196The ioctl interface for memory range attributes was added in 197.Fx 3.2 . 198.Sh BUGS 199Busy range attributes are not yet managed correctly. 200