85 lines
2.6 KiB
Groff
85 lines
2.6 KiB
Groff
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.\" $NetBSD: mem.4,v 1.1 2004/09/22 16:38:26 jkunz Exp $
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.\"
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.\" $OpenBSD: mem.4,v 1.1 2004/03/17 00:42:43 miod Exp $
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.\"
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.\" Copyright (c) 2004, Miodrag Vallat.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" 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,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 16, 2004
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.Dt MEM 4 hp700
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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 and memory controller
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.Sh SYNOPSIS
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.Cd "mem* at mainbus0"
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.Sh DESCRIPTION
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The
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.Nm
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driver controls and restricts access to the systems memory
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by the hardware buses and the processor.
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.Pp
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It also provides an interface to userland through the special files
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.Pa /dev/mem
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and
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.Pa /dev/kmem .
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Physical memory is accessed through
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.Pa /dev/mem ,
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while kernel virtual memory is accessed through
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.Pa /dev/kmem .
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Access to kernel virtual addresses not currently mapped to memory will fail.
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On hp700, the physical memory range is always contiguous and starts at
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address 0; kernel virtual memory begins at address 0 as well.
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.Pp
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The writeability of the
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.Pa /dev/mem
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and
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.Pa /dev/kmem
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special files are controlled by the system securelevel in addition to the
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filesystem permissions.
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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 HISTORY
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The
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.Nm
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driver originates from
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.Ox .
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It was ported to
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.Nx 1.6
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by Matthew Fredette.
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.Sh BUGS
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On some systems featuring a
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.Dq Viper
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memory controller,
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.Nx
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may not configure bus arbitration correctly, causing the boot process
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to freeze during either
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.Nm
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or
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.Xr cpu 4
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device probe.
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