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.\" 34.Dd November 27, 2015 35.Dt KVM_READ 3 36.Os 37.Sh NAME 38.Nm kvm_read , 39.Nm kvm_read2 , 40.Nm kvm_write 41.Nd read or write kernel virtual memory 42.Sh LIBRARY 43.Lb libkvm 44.Sh SYNOPSIS 45.In kvm.h 46.Ft ssize_t 47.Fn kvm_read "kvm_t *kd" "unsigned long addr" "void *buf" "size_t nbytes" 48.Ft ssize_t 49.Fn kvm_read2 "kvm_t *kd" "kvaddr_t addr" "void *buf" "size_t nbytes" 50.Ft ssize_t 51.Fn kvm_write "kvm_t *kd" "unsigned long addr" "const void *buf" "size_t nbytes" 52.Sh DESCRIPTION 53The 54.Fn kvm_read , 55.Fn kvm_read2 , 56and 57.Fn kvm_write 58functions are used to read and write kernel virtual memory (or a crash 59dump file). 60See 61.Fn kvm_open 3 62for information regarding opening kernel virtual memory and crash dumps. 63.Pp 64The 65.Fn kvm_read 66and 67.Fn kvm_read2 68functions transfer 69.Fa nbytes 70bytes of data from 71the kernel space address 72.Fa addr 73to 74.Fa buf . 75Conversely, 76.Fn kvm_write 77transfers data from 78.Fa buf 79to 80.Fa addr . 81Unlike their SunOS counterparts, these functions cannot be used to 82read or write process address spaces. 83.Pp 84The 85.Fn kvm_read2 86function uses a different type 87.Pq Vt kvaddr_t 88for the 89.Fa addr 90argument to allow use of addresses larger than 91.Dv ULONG_MAX 92when examining non-native kernel images. 93.Sh RETURN VALUES 94Upon success, the number of bytes actually transferred is returned. 95Otherwise, -1 is returned. 96.Sh SEE ALSO 97.Xr kvm 3 , 98.Xr kvm_close 3 , 99.Xr kvm_getargv 3 , 100.Xr kvm_getenvv 3 , 101.Xr kvm_geterr 3 , 102.Xr kvm_getprocs 3 , 103.Xr kvm_nlist 3 , 104.Xr kvm_open 3 , 105.Xr kvm_openfiles 3 106.Sh HISTORY 107The 108.Fn kvm_read2 109function first appeared in 110.Fx 11.0 . 111