.\" 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
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.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. 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.
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.\"     @(#)kvm_read.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libkvm/kvm_read.3,v 1.6.2.3 2001/12/17 10:08:30 ru Exp $
.\" $DragonFly: src/lib/libkvm/kvm_read.3,v 1.2 2003/06/17 04:26:49 dillon Exp $
.\"
.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 LIBRARY
.Lb libkvm
.Sh SYNOPSIS
.In kvm.h
.Ft ssize_t
.Fn kvm_read "kvm_t *kd" "unsigned long addr" "void *buf" "size_t nbytes"
.Ft ssize_t
.Fn kvm_write "kvm_t *kd" "unsigned 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 success, 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