.\"	$OpenBSD: kvm_read.3,v 1.8 2011/08/18 13:01:26 jmc 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.
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.\"     @(#)kvm_read.3	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: August 18 2011 $
.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
.Xr kvm_open 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_geterr 3 ,
.Xr kvm_getprocs 3 ,
.Xr kvm_nlist 3 ,
.Xr kvm_open 3