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.\" %sccs.include.redist.man% 9.\" 10.\" @(#)kvm_open.3 8.3 (Berkeley) 04/19/94 11.\" 12.Dd 13.Dt KVM_OPEN 3 14.Os 15.Sh NAME 16.Nm kvm_open , 17.Nm kvm_openfiles , 18.Nm kvm_close 19.Nd initialize kernel virtual memory access 20.Sh SYNOPSIS 21.Fd #include <fcntl.h> 22.Fd #include <kvm.h> 23.br 24.Ft kvm_t * 25.Fn kvm_open "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "const char *errstr" 26.Ft kvm_t * 27.Fn kvm_openfiles "const char *execfile" "const char *corefile" "char *swapfile" "int flags" "char *errbuf" 28.Ft int 29.Fn kvm_close "kvm_t *kd" 30.Sh DESCRIPTION 31The functions 32.Fn kvm_open 33and 34.Fn kvm_openfiles 35return a descriptor used to access kernel virtual memory 36via the 37.Xr kvm 3 38library routines. Both active kernels and crash dumps are accessible 39through this interface. 40.Pp 41.Fa execfile 42is the executable image of the kernel being examined. 43This file must contain a symbol table. 44If this argument is 45.Dv NULL , 46the currently running system is assumed, 47which is indicated by 48.Dv _PATH_UNIX 49in <paths.h>. 50.Pp 51.Fa corefile 52is the kernel memory device file. It can be either /dev/mem 53or a crash dump core generated by 54.Xr savecore 8 . 55If 56.Fa corefile 57is 58.Dv NULL , 59the default indicated by 60.Dv _PATH_MEM 61from <paths.h> is used. 62.Pp 63.Fa swapfile 64should indicate the swap device. If 65.Dv NULL , 66.Dv _PATH_DRUM 67from <paths.h> is used. 68.Pp 69The 70.Fa flags 71argument indicates read/write access as in 72.Xr open 2 73and applies only to the core file. 74Only 75.Dv O_RDONLY , 76.Dv O_WRONLY , 77and 78.Dv O_RDWR 79are permitted. 80.Pp 81There are two open routines which differ only with respect to 82the error mechanism. 83One provides backward compatibility with the SunOS kvm library, while the 84other provides an improved error reporting framework. 85.Pp 86The 87.Fn kvm_open 88function is the Sun kvm compatible open call. Here, the 89.Fa errstr 90argument indicates how errors should be handled. If it is 91.Dv NULL , 92no errors are reported and the application cannot know the 93specific nature of the failed kvm call. 94If it is not 95.Dv NULL , 96errors are printed to stderr with 97.Fa errstr 98prepended to the message, as in 99.Xr perror 3 . 100Normally, the name of the program is used here. 101The string is assumed to persist at least until the corresponding 102.Fn kvm_close 103call. 104.Pp 105The 106.Fn kvm_openfiles 107function provides BSD style error reporting. 108Here, error messages are not printed out by the library. 109Instead, the application obtains the error message 110corresponding to the most recent kvm library call using 111.Fn kvm_geterr 112(see 113.Xr kvm_geterr 3 ). 114The results are undefined if the most recent kvm call did not produce 115an error. 116Since 117.Fn kvm_geterr 118requires a kvm descriptor, but the open routines return 119.Dv NULL 120on failure, 121.Fn kvm_geterr 122cannot be used to get the error message if open fails. 123Thus, 124.Fn kvm_openfiles 125will place any error message in the 126.Fa errbuf 127argument. This buffer should be _POSIX2_LINE_MAX characters large (from 128<limits.h>). 129.Sh RETURN VALUES 130The 131.Fn kvm_open 132and 133.Fn kvm_openfiles 134functions both return a descriptor to be used 135in all subsequent kvm library calls. 136The library is fully re-entrant. 137On failure, 138.Dv NULL 139is returned, in which case 140.Fn kvm_openfiles 141writes the error message into 142.Fa errbuf . 143.Pp 144The 145.Fn kvm_close 146function returns 0 on success and -1 on failure. 147.Sh BUGS 148There should not be two open calls. The ill-defined error semantics 149of the Sun library and the desire to have a backward-compatible library 150for BSD left little choice. 151.Sh SEE ALSO 152.Xr open 2 , 153.Xr kvm 3 , 154.Xr kvm_getargv 3 , 155.Xr kvm_getenvv 3 , 156.Xr kvm_geterr 3 , 157.Xr kvm_getprocs 3 , 158.Xr kvm_nlist 3 , 159.Xr kvm_read 3 , 160.Xr kvm_write 3 161