| 1 | .\" Copyright (c) 1992, 1993 |
| 2 | .\" The Regents of the University of California. All rights reserved. |
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| 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. |
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| 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 sys/types.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 |
| 60 | The functions |
| 61 | .Fn kvm_open |
| 62 | and |
| 63 | .Fn kvm_openfiles |
| 64 | return a descriptor used to access kernel virtual memory |
| 65 | via the |
| 66 | .Xr kvm 3 |
| 67 | library routines. Both active kernels and crash dumps are accessible |
| 68 | through this interface. |
| 69 | .Pp |
| 70 | .Fa execfile |
| 71 | is the executable image of the kernel being examined. |
| 72 | This file must contain a symbol table. |
| 73 | If this argument is |
| 74 | .Dv NULL , |
| 75 | the currently running system is assumed, |
| 76 | as determined from |
| 77 | .Xr getbootfile 3 . |
| 78 | .Pp |
| 79 | .Fa corefile |
| 80 | is the kernel memory device file. It can be either /dev/mem |
| 81 | or a crash dump core generated by |
| 82 | .Xr savecore 8 . |
| 83 | If |
| 84 | .Fa corefile |
| 85 | is |
| 86 | .Dv NULL , |
| 87 | the default indicated by |
| 88 | .Dv _PATH_MEM |
| 89 | from |
| 90 | .In paths.h |
| 91 | is used. |
| 92 | .Pp |
| 93 | .Fa swapfile |
| 94 | should indicate the swap device. If |
| 95 | .Dv NULL , |
| 96 | .Dv _PATH_DRUM |
| 97 | from |
| 98 | .In paths.h |
| 99 | is used. |
| 100 | .Pp |
| 101 | The |
| 102 | .Fa flags |
| 103 | argument indicates read/write access as in |
| 104 | .Xr open 2 |
| 105 | and applies only to the core file. |
| 106 | Only |
| 107 | .Dv O_RDONLY , |
| 108 | .Dv O_WRONLY , |
| 109 | and |
| 110 | .Dv O_RDWR |
| 111 | are permitted. |
| 112 | .Pp |
| 113 | There are two open routines which differ only with respect to |
| 114 | the error mechanism. |
| 115 | One provides backward compatibility with the SunOS kvm library, while the |
| 116 | other provides an improved error reporting framework. |
| 117 | .Pp |
| 118 | The |
| 119 | .Fn kvm_open |
| 120 | function is the Sun kvm compatible open call. Here, the |
| 121 | .Fa errstr |
| 122 | argument indicates how errors should be handled. If it is |
| 123 | .Dv NULL , |
| 124 | no errors are reported and the application cannot know the |
| 125 | specific nature of the failed kvm call. |
| 126 | If it is not |
| 127 | .Dv NULL , |
| 128 | errors are printed to stderr with |
| 129 | .Fa errstr |
| 130 | prepended to the message, as in |
| 131 | .Xr perror 3 . |
| 132 | Normally, the name of the program is used here. |
| 133 | The string is assumed to persist at least until the corresponding |
| 134 | .Fn kvm_close |
| 135 | call. |
| 136 | .Pp |
| 137 | The |
| 138 | .Fn kvm_openfiles |
| 139 | function provides |
| 140 | .Bx |
| 141 | style error reporting. |
| 142 | Here, error messages are not printed out by the library. |
| 143 | Instead, the application obtains the error message |
| 144 | corresponding to the most recent kvm library call using |
| 145 | .Fn kvm_geterr |
| 146 | (see |
| 147 | .Xr kvm_geterr 3 ) . |
| 148 | The results are undefined if the most recent kvm call did not produce |
| 149 | an error. |
| 150 | Since |
| 151 | .Fn kvm_geterr |
| 152 | requires a kvm descriptor, but the open routines return |
| 153 | .Dv NULL |
| 154 | on failure, |
| 155 | .Fn kvm_geterr |
| 156 | cannot be used to get the error message if open fails. |
| 157 | Thus, |
| 158 | .Fn kvm_openfiles |
| 159 | will place any error message in the |
| 160 | .Fa errbuf |
| 161 | argument. This buffer should be _POSIX2_LINE_MAX characters large (from |
| 162 | .In limits.h ) . |
| 163 | .Sh RETURN VALUES |
| 164 | The |
| 165 | .Fn kvm_open |
| 166 | and |
| 167 | .Fn kvm_openfiles |
| 168 | functions both return a descriptor to be used |
| 169 | in all subsequent kvm library calls. |
| 170 | The library is fully re-entrant. |
| 171 | On failure, |
| 172 | .Dv NULL |
| 173 | is returned, in which case |
| 174 | .Fn kvm_openfiles |
| 175 | writes the error message into |
| 176 | .Fa errbuf . |
| 177 | .Pp |
| 178 | The |
| 179 | .Fn kvm_close |
| 180 | function 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 |
| 192 | There should not be two open calls. The ill-defined error semantics |
| 193 | of the Sun library and the desire to have a backward-compatible library |
| 194 | for |
| 195 | .Bx |
| 196 | left little choice. |