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.\" $FreeBSD$ 38.\" 39.Dd April 19, 1994 40.Dt KVM_OPEN 3 41.Os 42.Sh NAME 43.Nm kvm_open , 44.Nm kvm_openfiles , 45.Nm kvm_close 46.Nd initialize kernel virtual memory access 47.Sh SYNOPSIS 48.Fd #include <fcntl.h> 49.Fd #include <kvm.h> 50.br 51.Ft kvm_t * 52.Fn kvm_open "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "const char *errstr" 53.Ft kvm_t * 54.Fn kvm_openfiles "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "char *errbuf" 55.Ft int 56.Fn kvm_close "kvm_t *kd" 57.Sh DESCRIPTION 58The functions 59.Fn kvm_open 60and 61.Fn kvm_openfiles 62return a descriptor used to access kernel virtual memory 63via the 64.Xr kvm 3 65library routines. Both active kernels and crash dumps are accessible 66through this interface. 67.Pp 68.Fa execfile 69is the executable image of the kernel being examined. 70This file must contain a symbol table. 71If this argument is 72.Dv NULL , 73the currently running system is assumed, 74as determined from 75.Xr getbootfile 3 . 76.Pp 77.Fa corefile 78is the kernel memory device file. It can be either /dev/mem 79or a crash dump core generated by 80.Xr savecore 8 . 81If 82.Fa corefile 83is 84.Dv NULL , 85the default indicated by 86.Dv _PATH_MEM 87from <paths.h> is used. 88.Pp 89.Fa swapfile 90should indicate the swap device. If 91.Dv NULL , 92.Dv _PATH_DRUM 93from <paths.h> is used. 94.Pp 95The 96.Fa flags 97argument indicates read/write access as in 98.Xr open 2 99and applies only to the core file. 100Only 101.Dv O_RDONLY , 102.Dv O_WRONLY , 103and 104.Dv O_RDWR 105are permitted. 106.Pp 107There are two open routines which differ only with respect to 108the error mechanism. 109One provides backward compatibility with the SunOS kvm library, while the 110other provides an improved error reporting framework. 111.Pp 112The 113.Fn kvm_open 114function is the Sun kvm compatible open call. Here, the 115.Fa errstr 116argument indicates how errors should be handled. If it is 117.Dv NULL , 118no errors are reported and the application cannot know the 119specific nature of the failed kvm call. 120If it is not 121.Dv NULL , 122errors are printed to stderr with 123.Fa errstr 124prepended to the message, as in 125.Xr perror 3 . 126Normally, the name of the program is used here. 127The string is assumed to persist at least until the corresponding 128.Fn kvm_close 129call. 130.Pp 131The 132.Fn kvm_openfiles 133function provides BSD style error reporting. 134Here, error messages are not printed out by the library. 135Instead, the application obtains the error message 136corresponding to the most recent kvm library call using 137.Fn kvm_geterr 138(see 139.Xr kvm_geterr 3 ). 140The results are undefined if the most recent kvm call did not produce 141an error. 142Since 143.Fn kvm_geterr 144requires a kvm descriptor, but the open routines return 145.Dv NULL 146on failure, 147.Fn kvm_geterr 148cannot be used to get the error message if open fails. 149Thus, 150.Fn kvm_openfiles 151will place any error message in the 152.Fa errbuf 153argument. This buffer should be _POSIX2_LINE_MAX characters large (from 154<limits.h>). 155.Sh RETURN VALUES 156The 157.Fn kvm_open 158and 159.Fn kvm_openfiles 160functions both return a descriptor to be used 161in all subsequent kvm library calls. 162The library is fully re-entrant. 163On failure, 164.Dv NULL 165is returned, in which case 166.Fn kvm_openfiles 167writes the error message into 168.Fa errbuf . 169.Pp 170The 171.Fn kvm_close 172function returns 0 on success and -1 on failure. 173.Sh BUGS 174There should not be two open calls. The ill-defined error semantics 175of the Sun library and the desire to have a backward-compatible library 176for BSD left little choice. 177.Sh SEE ALSO 178.Xr open 2 , 179.Xr kvm 3 , 180.Xr kvm_getargv 3 , 181.Xr kvm_getenvv 3 , 182.Xr kvm_geterr 3 , 183.Xr kvm_getprocs 3 , 184.Xr kvm_nlist 3 , 185.Xr kvm_read 3 , 186.Xr kvm_write 3 187