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. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)kvm_read.3 8.1 (Berkeley) 6/4/93 37.\" $FreeBSD: src/lib/libkvm/kvm_read.3,v 1.6.2.3 2001/12/17 10:08:30 ru Exp $ 38.\" $DragonFly: src/lib/libkvm/kvm_read.3,v 1.4 2008/09/07 08:36:54 swildner Exp $ 39.\" 40.Dd January 8, 2006 41.Dt KVM_READ 3 42.Os 43.Sh NAME 44.Nm kvm_read , 45.Nm kvm_readstr , 46.Nm kvm_write 47.Nd read or write kernel virtual memory 48.Sh LIBRARY 49.Lb libkvm 50.Sh SYNOPSIS 51.In sys/types.h 52.In kvm.h 53.Ft ssize_t 54.Fn kvm_read "kvm_t *kd" "unsigned long addr" "void *buf" "size_t nbytes" 55.Ft "char *" 56.Fn kvm_readstr "kvm_t *kd" "unsigned long addr" "char *buf" "size_t *len" 57.Ft ssize_t 58.Fn kvm_write "kvm_t *kd" "unsigned long addr" "const void *buf" "size_t nbytes" 59.Sh DESCRIPTION 60The 61.Fn kvm_read , 62.Fn kvm_readstr 63and 64.Fn kvm_write 65functions are used to read and write kernel virtual memory (or a crash 66dump file). See 67.Fn kvm_open 3 68or 69.Fn kvm_openfiles 3 70for information regarding opening kernel virtual memory and crash dumps. 71.Pp 72The 73.Fn kvm_read 74function transfers 75.Fa nbytes 76bytes of data from 77the kernel space address 78.Fa addr 79to 80.Fa buf . 81Conversely, 82.Fn kvm_write 83transfers data from 84.Fa buf 85to 86.Fa addr . 87Unlike their SunOS counterparts, these functions cannot be used to 88read or write process address spaces. 89.Pp 90The 91.Fn kvm_readstr 92function exists for convenience to read NUL terminated strings 93from the kernel address space. 94If 95.Fa buf 96is 97.Dv NULL , 98.Fn kvm_readstr 99will allocate a sufficiently large buffer, which needs to be 100deallocated via 101.Xr free 3 102by the caller. 103If 104.Fa len 105is not 106.Dv NULL , 107.Fn kvm_readstr 108will interpret the value it is pointing to as the size of 109.Fa buf 110and will store the size of the complete string at 111.Fa addr . 112Note that if only 113.Fa buf 114is too small to hold the complete string, 115.Fn kvm_readstr 116will return 117.Dv NULL 118but set 119.Fa len 120to the size needed. 121.Sh RETURN VALUES 122For 123.Fn kvm_read 124and 125.Fn kvm_write 126the number of bytes actually transferred is returned, if the request 127was successful. 128Otherwise, -1 is returned. 129.Pp 130For 131.Fn kvm_readstr 132.Dv NULL 133is returned on failure. 134Upon success, the address of the string is returned, which will be 135.Fa buf 136if this was supplied. 137.Sh SEE ALSO 138.Xr kvm 3 , 139.Xr kvm_close 3 , 140.Xr kvm_getargv 3 , 141.Xr kvm_getenvv 3 , 142.Xr kvm_geterr 3 , 143.Xr kvm_getprocs 3 , 144.Xr kvm_nlist 3 , 145.Xr kvm_open 3 , 146.Xr kvm_openfiles 3 147