1.\" $NetBSD: kvm_open.3,v 1.6 1999/07/02 15:28:50 simonb 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 LIBRARY 49.Lb libkvm 50.Sh SYNOPSIS 51.Fd #include <fcntl.h> 52.Fd #include <kvm.h> 53.br 54.Ft kvm_t * 55.Fn kvm_open "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "const char *errstr" 56.Ft kvm_t * 57.Fn kvm_openfiles "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "char *errbuf" 58.Ft int 59.Fn kvm_close "kvm_t *kd" 60.Sh DESCRIPTION 61The functions 62.Fn kvm_open 63and 64.Fn kvm_openfiles 65return a descriptor used to access kernel virtual memory 66via the 67.Xr kvm 3 68library routines. Both active kernels and crash dumps are accessible 69through this interface. 70.Pp 71.Fa execfile 72is the executable image of the kernel being examined. 73This file must contain a symbol table. 74If this argument is 75.Dv NULL , 76the currently running system is assumed, 77which is indicated by 78.Dv _PATH_UNIX 79in 80.Pa Aq paths.h . 81.Pp 82.Fa corefile 83is the kernel memory device file. It can be either 84.Pa /dev/mem 85or a crash dump core generated by 86.Xr savecore 8 . 87If 88.Fa corefile 89is 90.Dv NULL , 91the default indicated by 92.Dv _PATH_MEM 93from 94.Pa Aq paths.h 95is used. 96.Pp 97.Fa swapfile 98should indicate the swap device. If 99.Dv NULL , 100.Dv _PATH_DRUM 101from 102.Pa Aq paths.h 103is used. 104.Pp 105The 106.Fa flags 107argument indicates read/write access as in 108.Xr open 2 109and applies only to the core file. 110Only 111.Dv O_RDONLY , 112.Dv O_WRONLY , 113and 114.Dv O_RDWR 115are permitted. 116.Pp 117There are two open routines which differ only with respect to 118the error mechanism. 119One provides backward compatibility with the SunOS kvm library, while the 120other provides an improved error reporting framework. 121.Pp 122The 123.Fn kvm_open 124function is the Sun kvm compatible open call. Here, the 125.Fa errstr 126argument indicates how errors should be handled. If it is 127.Dv NULL , 128no errors are reported and the application cannot know the 129specific nature of the failed kvm call. 130If it is not 131.Dv NULL , 132errors are printed to stderr with 133.Fa errstr 134prepended to the message, as in 135.Xr perror 3 . 136Normally, the name of the program is used here. 137The string is assumed to persist at least until the corresponding 138.Fn kvm_close 139call. 140.Pp 141The 142.Fn kvm_openfiles 143function provides 144.Bx 145style error reporting. 146Here, error messages are not printed out by the library. 147Instead, the application obtains the error message 148corresponding to the most recent kvm library call using 149.Fn kvm_geterr 150(see 151.Xr kvm_geterr 3 ). 152The results are undefined if the most recent kvm call did not produce 153an error. 154Since 155.Fn kvm_geterr 156requires a kvm descriptor, but the open routines return 157.Dv NULL 158on failure, 159.Fn kvm_geterr 160cannot be used to get the error message if open fails. 161Thus, 162.Fn kvm_openfiles 163will place any error message in the 164.Fa errbuf 165argument. This buffer should be _POSIX2_LINE_MAX characters large (from 166.Pa Aq limits.h ) . 167.Sh RETURN VALUES 168The 169.Fn kvm_open 170and 171.Fn kvm_openfiles 172functions both return a descriptor to be used 173in all subsequent kvm library calls. 174The library is fully re-entrant. 175On failure, 176.Dv NULL 177is returned, in which case 178.Fn kvm_openfiles 179writes the error message into 180.Fa errbuf . 181.Pp 182The 183.Fn kvm_close 184function returns 0 on success and -1 on failure. 185.Sh BUGS 186There should not be two open calls. The ill-defined error semantics 187of the Sun library and the desire to have a backward-compatible library 188for 189.Bx 190left little choice. 191.Sh SEE ALSO 192.Xr open 2 , 193.Xr kvm 3 , 194.Xr kvm_getargv 3 , 195.Xr kvm_getenvv 3 , 196.Xr kvm_geterr 3 , 197.Xr kvm_getprocs 3 , 198.Xr kvm_nlist 3 , 199.Xr kvm_read 3 , 200.Xr kvm_write 3 201