1.\" $OpenBSD: kvm.3,v 1.3 2000/03/04 15:29:56 aaron Exp $ 2.\" $NetBSD: kvm.3,v 1.2 1996/03/18 22:33:11 thorpej Exp $ 3.\" 4.\" Copyright (c) 1992, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This code is derived from software developed by the Computer Systems 8.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 9.\" BG 91-66 and contributed to Berkeley. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. All advertising materials mentioning features or use of this software 20.\" must display the following acknowledgement: 21.\" This product includes software developed by the University of 22.\" California, Berkeley and its contributors. 23.\" 4. Neither the name of the University nor the names of its contributors 24.\" may be used to endorse or promote products derived from this software 25.\" without specific prior written permission. 26.\" 27.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37.\" SUCH DAMAGE. 38.\" 39.\" @(#)kvm.3 8.1 (Berkeley) 6/4/93 40.\" 41.Dd June 4, 1993 42.Dt KVM 3 43.Os 44.Sh NAME 45.Nm kvm 46.Nd kernel memory interface 47.Sh DESCRIPTION 48The 49.Xr kvm 3 50library provides a uniform interface for accessing kernel virtual memory 51images, including live systems and crashdumps. 52Access to live systems is via 53.Pa /dev/mem 54while crashdumps can be examined via the core file generated by 55.Xr savecore 8 . 56The interface behaves identically in both cases. 57Memory can be read and written, kernel symbol addresses can be 58looked up efficiently, and information about user processes can 59be gathered. 60.Pp 61.Fn kvm_open 62is first called to obtain a descriptor for all subsequent calls. 63.Sh COMPATIBILITY 64The kvm interface was first introduced in SunOS. 65A considerable 66number of programs have been developed that use this interface, 67making backward compatibility highly desirable. 68In most respects, the Sun kvm interface is consistent and clean. 69Accordingly, the generic portion of the interface (i.e., 70.Fn kvm_open , 71.Fn kvm_close , 72.Fn kvm_read , 73.Fn kvm_write , 74and 75.Fn kvm_nlist ) 76has been incorporated into the BSD interface. 77Indeed, many kvm 78applications (i.e., debuggers and statistical monitors) use only 79this subset of the interface. 80.Pp 81The process interface was not kept. 82This is not a portability 83issue since any code that manipulates processes is inherently 84machine dependent. 85.Pp 86Finally, the Sun kvm error reporting semantics are poorly defined. 87The library can be configured either to print errors to stderr automatically, 88or to print no error messages at all. 89In the latter case, the nature of the error cannot be determined. 90To overcome this, the BSD interface includes a 91routine, 92.Xr kvm_geterr 3 , 93to return (not print out) the error message 94corresponding to the most recent error condition on the 95given descriptor. 96.Sh FILES 97.Bl -tag -width /dev/mem -compact 98.It Pa /dev/mem 99interface to physical memory 100.El 101.Sh SEE ALSO 102.Xr kvm_close 3 , 103.Xr kvm_getargv 3 , 104.Xr kvm_getenvv 3 , 105.Xr kvm_geterr 3 , 106.Xr kvm_getloadavg 3 , 107.Xr kvm_getprocs 3 , 108.Xr kvm_nlist 3 , 109.Xr kvm_open 3 , 110.Xr kvm_openfiles 3 , 111.Xr kvm_read 3 , 112.Xr kvm_write 3 113