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 April 19, 1994 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 fcntl.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 and crash dumps are accessible 68through 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 either /dev/mem 81or a crash dump core generated by 82.Xr savecore 8 . 83If 84.Fa corefile 85is 86.Dv NULL , 87the default indicated by 88.Dv _PATH_MEM 89from 90.In paths.h 91is used. 92.Pp 93.Fa swapfile 94should indicate the swap device. If 95.Dv NULL , 96.Dv _PATH_DRUM 97from 98.In paths.h 99is used. 100.Pp 101The 102.Fa flags 103argument indicates read/write access as in 104.Xr open 2 105and applies only to the core file. 106Only 107.Dv O_RDONLY , 108.Dv O_WRONLY , 109and 110.Dv O_RDWR 111are permitted. 112.Pp 113There are two open routines which differ only with respect to 114the error mechanism. 115One provides backward compatibility with the SunOS kvm library, while the 116other provides an improved error reporting framework. 117.Pp 118The 119.Fn kvm_open 120function is the Sun kvm compatible open call. Here, the 121.Fa errstr 122argument indicates how errors should be handled. If it is 123.Dv NULL , 124no errors are reported and the application cannot know the 125specific nature of the failed kvm call. 126If it is not 127.Dv NULL , 128errors are printed to stderr with 129.Fa errstr 130prepended to the message, as in 131.Xr perror 3 . 132Normally, the name of the program is used here. 133The string is assumed to persist at least until the corresponding 134.Fn kvm_close 135call. 136.Pp 137The 138.Fn kvm_openfiles 139function provides 140.Bx 141style error reporting. 142Here, error messages are not printed out by the library. 143Instead, the application obtains the error message 144corresponding to the most recent kvm library call using 145.Fn kvm_geterr 146(see 147.Xr kvm_geterr 3 ) . 148The results are undefined if the most recent kvm call did not produce 149an error. 150Since 151.Fn kvm_geterr 152requires a kvm descriptor, but the open routines return 153.Dv NULL 154on failure, 155.Fn kvm_geterr 156cannot be used to get the error message if open fails. 157Thus, 158.Fn kvm_openfiles 159will place any error message in the 160.Fa errbuf 161argument. This buffer should be _POSIX2_LINE_MAX characters large (from 162.In limits.h ) . 163.Sh RETURN VALUES 164The 165.Fn kvm_open 166and 167.Fn kvm_openfiles 168functions both return a descriptor to be used 169in all subsequent kvm library calls. 170The library is fully re-entrant. 171On failure, 172.Dv NULL 173is returned, in which case 174.Fn kvm_openfiles 175writes the error message into 176.Fa errbuf . 177.Pp 178The 179.Fn kvm_close 180function returns 0 on success and -1 on failure. 181.Sh SEE ALSO 182.Xr open 2 , 183.Xr kvm 3 , 184.Xr kvm_getargv 3 , 185.Xr kvm_getenvv 3 , 186.Xr kvm_geterr 3 , 187.Xr kvm_getprocs 3 , 188.Xr kvm_nlist 3 , 189.Xr kvm_read 3 , 190.Xr kvm_write 3 191.Sh BUGS 192There should not be two open calls. The ill-defined error semantics 193of the Sun library and the desire to have a backward-compatible library 194for 195.Bx 196left little choice. 197