1.\" Copyright (c) 1992, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software developed by the Computer Systems 5.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 6.\" BG 91-66 and contributed to Berkeley. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)kvm_read.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd November 27, 2015 36.Dt KVM_READ 3 37.Os 38.Sh NAME 39.Nm kvm_read , 40.Nm kvm_read2 , 41.Nm kvm_write 42.Nd read or write kernel virtual memory 43.Sh LIBRARY 44.Lb libkvm 45.Sh SYNOPSIS 46.In kvm.h 47.Ft ssize_t 48.Fn kvm_read "kvm_t *kd" "unsigned long addr" "void *buf" "size_t nbytes" 49.Ft ssize_t 50.Fn kvm_read2 "kvm_t *kd" "kvaddr_t addr" "void *buf" "size_t nbytes" 51.Ft ssize_t 52.Fn kvm_write "kvm_t *kd" "unsigned long addr" "const void *buf" "size_t nbytes" 53.Sh DESCRIPTION 54The 55.Fn kvm_read , 56.Fn kvm_read2 , 57and 58.Fn kvm_write 59functions are used to read and write kernel virtual memory (or a crash 60dump file). 61See 62.Fn kvm_open 3 63for information regarding opening kernel virtual memory and crash dumps. 64.Pp 65The 66.Fn kvm_read 67and 68.Fn kvm_read2 69functions transfer 70.Fa nbytes 71bytes of data from 72the kernel space address 73.Fa addr 74to 75.Fa buf . 76Conversely, 77.Fn kvm_write 78transfers data from 79.Fa buf 80to 81.Fa addr . 82Unlike their SunOS counterparts, these functions cannot be used to 83read or write process address spaces. 84.Pp 85The 86.Fn kvm_read2 87function uses a different type 88.Pq Vt kvaddr_t 89for the 90.Fa addr 91argument to allow use of addresses larger than 92.Dv ULONG_MAX 93when examining non-native kernel images. 94.Sh RETURN VALUES 95Upon success, the number of bytes actually transferred is returned. 96Otherwise, -1 is returned. 97.Sh SEE ALSO 98.Xr kvm 3 , 99.Xr kvm_close 3 , 100.Xr kvm_getargv 3 , 101.Xr kvm_getenvv 3 , 102.Xr kvm_geterr 3 , 103.Xr kvm_getprocs 3 , 104.Xr kvm_nlist 3 , 105.Xr kvm_open 3 , 106.Xr kvm_openfiles 3 107.Sh HISTORY 108The 109.Fn kvm_read2 110function first appeared in 111.Fx 11.0 . 112