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_open.3 8.3 (Berkeley) 4/19/94 37.\" $FreeBSD: src/lib/libkvm/kvm_open.3,v 1.5.2.6 2001/12/17 10:08:30 ru Exp $ 38.\" $DragonFly: src/lib/libkvm/kvm_open.3,v 1.4 2006/05/26 19:39:38 swildner Exp $ 39.\" 40.Dd May 5, 2009 41.Dt KVM_OPEN 3 42.Os 43.Sh NAME 44.Nm kvm_open , 45.Nm kvm_openfiles , 46.Nm kvm_close 47.Nd initialize kernel virtual memory access 48.Sh LIBRARY 49.Lb libkvm 50.Sh SYNOPSIS 51.In sys/types.h 52.In kvm.h 53.Ft kvm_t * 54.Fn kvm_open "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "const char *errstr" 55.Ft kvm_t * 56.Fn kvm_openfiles "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "char *errbuf" 57.Ft int 58.Fn kvm_close "kvm_t *kd" 59.Sh DESCRIPTION 60The functions 61.Fn kvm_open 62and 63.Fn kvm_openfiles 64return a descriptor used to access kernel virtual memory 65via the 66.Xr kvm 3 67library routines. Both active kernels (including vkernels) and crash 68dumps are accessible through this interface. 69.Pp 70.Fa execfile 71is the executable image of the kernel being examined. 72This file must contain a symbol table. 73If this argument is 74.Dv NULL , 75the currently running system is assumed, 76as determined from 77.Xr getbootfile 3 . 78.Pp 79.Fa corefile 80is the kernel memory device file. It can be /dev/mem, the path to 81the procfs mem file for a running vkernel (i.e. /proc/$pid/mem) 82or a crash dump core generated by 83.Xr savecore 8 . 84If 85.Fa corefile 86is 87.Dv NULL , 88the default indicated by 89.Dv _PATH_MEM 90from 91.In paths.h 92is used. 93.Pp 94.Fa swapfile 95should indicate the swap device. If 96.Dv NULL , 97.Dv _PATH_DRUM 98from 99.In paths.h 100is used. 101.Pp 102The 103.Fa flags 104argument indicates read/write access as in 105.Xr open 2 106and applies only to the core file. 107Only 108.Dv O_RDONLY , 109.Dv O_WRONLY , 110and 111.Dv O_RDWR 112are permitted. 113.Pp 114There are two open routines which differ only with respect to 115the error mechanism. 116One provides backward compatibility with the SunOS kvm library, while the 117other provides an improved error reporting framework. 118.Pp 119The 120.Fn kvm_open 121function is the Sun kvm compatible open call. Here, the 122.Fa errstr 123argument indicates how errors should be handled. If it is 124.Dv NULL , 125no errors are reported and the application cannot know the 126specific nature of the failed kvm call. 127If it is not 128.Dv NULL , 129errors are printed to stderr with 130.Fa errstr 131prepended to the message, as in 132.Xr perror 3 . 133Normally, the name of the program is used here. 134The string is assumed to persist at least until the corresponding 135.Fn kvm_close 136call. 137.Pp 138The 139.Fn kvm_openfiles 140function provides 141.Bx 142style error reporting. 143Here, error messages are not printed out by the library. 144Instead, the application obtains the error message 145corresponding to the most recent kvm library call using 146.Fn kvm_geterr 147(see 148.Xr kvm_geterr 3 ) . 149The results are undefined if the most recent kvm call did not produce 150an error. 151Since 152.Fn kvm_geterr 153requires a kvm descriptor, but the open routines return 154.Dv NULL 155on failure, 156.Fn kvm_geterr 157cannot be used to get the error message if open fails. 158Thus, 159.Fn kvm_openfiles 160will place any error message in the 161.Fa errbuf 162argument. This buffer should be _POSIX2_LINE_MAX characters large (from 163.In limits.h ) . 164.Sh RETURN VALUES 165The 166.Fn kvm_open 167and 168.Fn kvm_openfiles 169functions both return a descriptor to be used 170in all subsequent kvm library calls. 171The library is fully re-entrant. 172On failure, 173.Dv NULL 174is returned, in which case 175.Fn kvm_openfiles 176writes the error message into 177.Fa errbuf . 178.Pp 179The 180.Fn kvm_close 181function returns 0 on success and -1 on failure. 182.Sh SEE ALSO 183.Xr open 2 , 184.Xr kvm 3 , 185.Xr kvm_getargv 3 , 186.Xr kvm_getenvv 3 , 187.Xr kvm_geterr 3 , 188.Xr kvm_getprocs 3 , 189.Xr kvm_nlist 3 , 190.Xr kvm_read 3 , 191.Xr kvm_write 3 192.Sh BUGS 193There should not be two open calls. The ill-defined error semantics 194of the Sun library and the desire to have a backward-compatible library 195for 196.Bx 197left little choice. 198