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_open.3 8.3 (Berkeley) 4/19/94 33.\" $FreeBSD: src/lib/libkvm/kvm_open.3,v 1.5.2.6 2001/12/17 10:08:30 ru Exp $ 34.\" $DragonFly: src/lib/libkvm/kvm_open.3,v 1.4 2006/05/26 19:39:38 swildner Exp $ 35.\" 36.Dd May 5, 2009 37.Dt KVM_OPEN 3 38.Os 39.Sh NAME 40.Nm kvm_open , 41.Nm kvm_openfiles , 42.Nm kvm_close 43.Nd initialize kernel virtual memory access 44.Sh LIBRARY 45.Lb libkvm 46.Sh SYNOPSIS 47.In sys/types.h 48.In kvm.h 49.Ft kvm_t * 50.Fn kvm_open "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "const char *errstr" 51.Ft kvm_t * 52.Fn kvm_openfiles "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "char *errbuf" 53.Ft int 54.Fn kvm_close "kvm_t *kd" 55.Sh DESCRIPTION 56The functions 57.Fn kvm_open 58and 59.Fn kvm_openfiles 60return a descriptor used to access kernel virtual memory 61via the 62.Xr kvm 3 63library routines. Both active kernels (including vkernels) and crash 64dumps are accessible through this interface. 65.Pp 66.Fa execfile 67is the executable image of the kernel being examined. 68This file must contain a symbol table. 69If this argument is 70.Dv NULL , 71the currently running system is assumed, 72as determined from 73.Xr getbootfile 3 . 74.Pp 75.Fa corefile 76is the kernel memory device file. It can be /dev/mem, the path to 77the procfs mem file for a running vkernel (i.e. /proc/$pid/mem) 78or a crash dump core generated by 79.Xr savecore 8 . 80If 81.Fa corefile 82is 83.Dv NULL , 84the default indicated by 85.Dv _PATH_MEM 86from 87.In paths.h 88is used. 89.Pp 90.Fa swapfile 91should indicate the swap device. If 92.Dv NULL , 93.Dv _PATH_DRUM 94from 95.In paths.h 96is used. 97.Pp 98The 99.Fa flags 100argument indicates read/write access as in 101.Xr open 2 102and applies only to the core file. 103Only 104.Dv O_RDONLY , 105.Dv O_WRONLY , 106and 107.Dv O_RDWR 108are permitted. 109.Pp 110There are two open routines which differ only with respect to 111the error mechanism. 112One provides backward compatibility with the SunOS kvm library, while the 113other provides an improved error reporting framework. 114.Pp 115The 116.Fn kvm_open 117function is the Sun kvm compatible open call. Here, the 118.Fa errstr 119argument indicates how errors should be handled. If it is 120.Dv NULL , 121no errors are reported and the application cannot know the 122specific nature of the failed kvm call. 123If it is not 124.Dv NULL , 125errors are printed to stderr with 126.Fa errstr 127prepended to the message, as in 128.Xr perror 3 . 129Normally, the name of the program is used here. 130The string is assumed to persist at least until the corresponding 131.Fn kvm_close 132call. 133.Pp 134The 135.Fn kvm_openfiles 136function provides 137.Bx 138style error reporting. 139Here, error messages are not printed out by the library. 140Instead, the application obtains the error message 141corresponding to the most recent kvm library call using 142.Fn kvm_geterr 143(see 144.Xr kvm_geterr 3 ) . 145The results are undefined if the most recent kvm call did not produce 146an error. 147Since 148.Fn kvm_geterr 149requires a kvm descriptor, but the open routines return 150.Dv NULL 151on failure, 152.Fn kvm_geterr 153cannot be used to get the error message if open fails. 154Thus, 155.Fn kvm_openfiles 156will place any error message in the 157.Fa errbuf 158argument. This buffer should be _POSIX2_LINE_MAX characters large (from 159.In limits.h ) . 160.Sh RETURN VALUES 161The 162.Fn kvm_open 163and 164.Fn kvm_openfiles 165functions both return a descriptor to be used 166in all subsequent kvm library calls. 167The library is fully re-entrant. 168On failure, 169.Dv NULL 170is returned, in which case 171.Fn kvm_openfiles 172writes the error message into 173.Fa errbuf . 174.Pp 175The 176.Fn kvm_close 177function returns 0 on success and -1 on failure. 178.Sh SEE ALSO 179.Xr open 2 , 180.Xr kvm 3 , 181.Xr kvm_getargv 3 , 182.Xr kvm_getenvv 3 , 183.Xr kvm_geterr 3 , 184.Xr kvm_getprocs 3 , 185.Xr kvm_nlist 3 , 186.Xr kvm_read 3 , 187.Xr kvm_write 3 188.Sh BUGS 189There should not be two open calls. The ill-defined error semantics 190of the Sun library and the desire to have a backward-compatible library 191for 192.Bx 193left little choice. 194