.\"	$OpenBSD: kvm_read.3,v 1.6 2003/06/02 20:18:41 millert Exp $
.\"	$NetBSD: kvm_read.3,v 1.2 1996/03/18 22:34:01 thorpej Exp $
.\"
.\" Copyright (c) 1992, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software developed by the Computer Systems
.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract
.\" BG 91-66 and contributed to Berkeley.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    notice, this list of conditions and the following disclaimer in the
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.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\"     @(#)kvm_read.3	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt KVM_READ 3
.Os
.Sh NAME
.Nm kvm_read ,
.Nm kvm_write
.Nd read or write kernel virtual memory
.Sh SYNOPSIS
.Fd #include <kvm.h>
.Ft ssize_t
.Fn kvm_read "kvm_t *kd" "u_long addr" "void *buf" "size_t nbytes"
.Ft ssize_t
.Fn kvm_write "kvm_t *kd" "u_long addr" "const void *buf" "size_t nbytes"
.Sh DESCRIPTION
The
.Fn kvm_read
and
.Fn kvm_write
functions are used to read and write kernel virtual memory (or a crash
dump file).
See
.Fn kvm_open 3
or
.Fn kvm_openfiles 3
for information regarding opening kernel virtual memory and crash dumps.
.Pp
The
.Fn kvm_read
function transfers
.Fa nbytes
bytes of data from
the kernel space address
.Fa addr
to
.Fa buf .
Conversely,
.Fn kvm_write
transfers data from
.Fa buf
to
.Fa addr .
Unlike their SunOS counterparts, these functions cannot be used to
read or write process address spaces.
.Sh RETURN VALUES
Upon successful completion, the number of bytes actually transferred is
returned.
Otherwise, \-1 is returned.
.Sh SEE ALSO
.Xr kvm 3 ,
.Xr kvm_close 3 ,
.Xr kvm_getargv 3 ,
.Xr kvm_getenvv 3 ,
.Xr kvm_geterr 3 ,
.Xr kvm_getprocs 3 ,
.Xr kvm_nlist 3 ,
.Xr kvm_open 3 ,
.Xr kvm_openfiles 3