1.\" $NetBSD: kvm_open.3,v 1.2 1996/03/18 22:33:52 thorpej Exp $ 2.\" 3.\" Copyright (c) 1992, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software developed by the Computer Systems 7.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 8.\" BG 91-66 and contributed to Berkeley. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the University of 21.\" California, Berkeley and its contributors. 22.\" 4. Neither the name of the University nor the names of its contributors 23.\" may be used to endorse or promote products derived from this software 24.\" without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36.\" SUCH DAMAGE. 37.\" 38.\" @(#)kvm_open.3 8.3 (Berkeley) 4/19/94 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 SYNOPSIS 49.Fd #include <fcntl.h> 50.Fd #include <kvm.h> 51.br 52.Ft kvm_t * 53.Fn kvm_open "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "const char *errstr" 54.Ft kvm_t * 55.Fn kvm_openfiles "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "char *errbuf" 56.Ft int 57.Fn kvm_close "kvm_t *kd" 58.Sh DESCRIPTION 59The functions 60.Fn kvm_open 61and 62.Fn kvm_openfiles 63return a descriptor used to access kernel virtual memory 64via the 65.Xr kvm 3 66library routines. Both active kernels and crash dumps are accessible 67through this interface. 68.Pp 69.Fa execfile 70is the executable image of the kernel being examined. 71This file must contain a symbol table. 72If this argument is 73.Dv NULL , 74the currently running system is assumed, 75which is indicated by 76.Dv _PATH_UNIX 77in <paths.h>. 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 <paths.h> is used. 90.Pp 91.Fa swapfile 92should indicate the swap device. If 93.Dv NULL , 94.Dv _PATH_DRUM 95from <paths.h> is used. 96.Pp 97The 98.Fa flags 99argument indicates read/write access as in 100.Xr open 2 101and applies only to the core file. 102Only 103.Dv O_RDONLY , 104.Dv O_WRONLY , 105and 106.Dv O_RDWR 107are permitted. 108.Pp 109There are two open routines which differ only with respect to 110the error mechanism. 111One provides backward compatibility with the SunOS kvm library, while the 112other provides an improved error reporting framework. 113.Pp 114The 115.Fn kvm_open 116function is the Sun kvm compatible open call. Here, the 117.Fa errstr 118argument indicates how errors should be handled. If it is 119.Dv NULL , 120no errors are reported and the application cannot know the 121specific nature of the failed kvm call. 122If it is not 123.Dv NULL , 124errors are printed to stderr with 125.Fa errstr 126prepended to the message, as in 127.Xr perror 3 . 128Normally, the name of the program is used here. 129The string is assumed to persist at least until the corresponding 130.Fn kvm_close 131call. 132.Pp 133The 134.Fn kvm_openfiles 135function provides BSD style error reporting. 136Here, error messages are not printed out by the library. 137Instead, the application obtains the error message 138corresponding to the most recent kvm library call using 139.Fn kvm_geterr 140(see 141.Xr kvm_geterr 3 ). 142The results are undefined if the most recent kvm call did not produce 143an error. 144Since 145.Fn kvm_geterr 146requires a kvm descriptor, but the open routines return 147.Dv NULL 148on failure, 149.Fn kvm_geterr 150cannot be used to get the error message if open fails. 151Thus, 152.Fn kvm_openfiles 153will place any error message in the 154.Fa errbuf 155argument. This buffer should be _POSIX2_LINE_MAX characters large (from 156<limits.h>). 157.Sh RETURN VALUES 158The 159.Fn kvm_open 160and 161.Fn kvm_openfiles 162functions both return a descriptor to be used 163in all subsequent kvm library calls. 164The library is fully re-entrant. 165On failure, 166.Dv NULL 167is returned, in which case 168.Fn kvm_openfiles 169writes the error message into 170.Fa errbuf . 171.Pp 172The 173.Fn kvm_close 174function returns 0 on success and -1 on failure. 175.Sh BUGS 176There should not be two open calls. The ill-defined error semantics 177of the Sun library and the desire to have a backward-compatible library 178for BSD left little choice. 179.Sh SEE ALSO 180.Xr open 2 , 181.Xr kvm 3 , 182.Xr kvm_getargv 3 , 183.Xr kvm_getenvv 3 , 184.Xr kvm_geterr 3 , 185.Xr kvm_getprocs 3 , 186.Xr kvm_nlist 3 , 187.Xr kvm_read 3 , 188.Xr kvm_write 3 189