| 1 | .\" |
| 2 | .\" Copyright (c) 2003 Alexey Zelkin <phantom@FreeBSD.org> |
| 3 | .\" All rights reserved. |
| 4 | .\" |
| 5 | .\" Redistribution and use in source and binary forms, with or without |
| 6 | .\" modification, are permitted provided that the following conditions |
| 7 | .\" are met: |
| 8 | .\" 1. Redistributions of source code must retain the above copyright |
| 9 | .\" notice, this list of conditions and the following disclaimer. |
| 10 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| 11 | .\" notice, this list of conditions and the following disclaimer in the |
| 12 | .\" documentation and/or other materials provided with the distribution. |
| 13 | .\" |
| 14 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| 15 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 16 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 17 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| 18 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 19 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 20 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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| 26 | .\" $FreeBSD: head/lib/libc/gen/dlinfo.3 206622 2010-04-14 19:08:06Z uqs $ |
| 27 | .\" |
| 28 | .Dd February 22, 2018 |
| 29 | .Dt DLINFO 3 |
| 30 | .Os |
| 31 | .Sh NAME |
| 32 | .Nm dlinfo |
| 33 | .Nd information about dynamically loaded object |
| 34 | .Sh LIBRARY |
| 35 | This function is not in a library. |
| 36 | It is included in every dynamically linked program automatically. |
| 37 | .Sh SYNOPSIS |
| 38 | .In link.h |
| 39 | .In dlfcn.h |
| 40 | .Ft int |
| 41 | .Fn dlinfo "void * restrict handle" "int request" "void * restrict p" |
| 42 | .Sh DESCRIPTION |
| 43 | The |
| 44 | .Fn dlinfo |
| 45 | function provides information about dynamically loaded object. |
| 46 | The action taken by |
| 47 | .Fn dlinfo |
| 48 | and exact meaning and type of |
| 49 | .Fa p |
| 50 | argument depend on value of the |
| 51 | .Fa request |
| 52 | argument provided by caller. |
| 53 | .Pp |
| 54 | The |
| 55 | .Fa handle |
| 56 | argument is either the value returned from the |
| 57 | .Xr dlopen 3 |
| 58 | function call or special handle |
| 59 | .Dv RTLD_SELF . |
| 60 | If |
| 61 | .Fa handle |
| 62 | is the value returned from |
| 63 | .Xr dlopen 3 , |
| 64 | the information returned by the |
| 65 | .Fn dlinfo |
| 66 | function pertains to the specified object. |
| 67 | If handle is the special handle |
| 68 | .Dv RTLD_SELF , |
| 69 | the information returned pertains to the caller itself. |
| 70 | .Pp |
| 71 | Possible values for the |
| 72 | .Fa request |
| 73 | argument are: |
| 74 | .Bl -tag -width indent |
| 75 | .It Dv RTLD_DI_LINKMAP |
| 76 | Retrieve the |
| 77 | .Vt Link_map |
| 78 | .Pq Vt "struct link_map" |
| 79 | structure pointer for the specified |
| 80 | .Fa handle . |
| 81 | On successful return, the |
| 82 | .Fa p |
| 83 | argument is filled with the pointer to the |
| 84 | .Vt Link_map |
| 85 | structure |
| 86 | .Pq Fa "Link_map **p" |
| 87 | describing a shared object specified by the |
| 88 | .Fa handle |
| 89 | argument. |
| 90 | The |
| 91 | .Vt Link_map |
| 92 | structures are maintained as a doubly linked list by |
| 93 | .Xr ld-elf.so.2 1 , |
| 94 | in the same order as |
| 95 | .Xr dlopen 3 |
| 96 | and |
| 97 | .Xr dlclose 3 |
| 98 | are called. |
| 99 | See |
| 100 | .Sx EXAMPLES , |
| 101 | example 1. |
| 102 | .Pp |
| 103 | The |
| 104 | .Vt Link_map |
| 105 | structure is defined in |
| 106 | .In link.h |
| 107 | and has the following members: |
| 108 | .Bd -literal -offset indent |
| 109 | caddr_t l_addr; /* Base Address of library */ |
| 110 | const char *l_name; /* Absolute Path to Library */ |
| 111 | const void *l_ld; /* Pointer to .dynamic in memory */ |
| 112 | struct link_map *l_next, /* linked list of mapped libs */ |
| 113 | *l_prev; |
| 114 | .Ed |
| 115 | .Bl -tag -width ".Va l_addr" |
| 116 | .It Va l_addr |
| 117 | The base address of the object loaded into memory. |
| 118 | .It Va l_name |
| 119 | The full name of the loaded shared object. |
| 120 | .It Va l_ld |
| 121 | The address of the dynamic linking information segment |
| 122 | .Pq Dv PT_DYNAMIC |
| 123 | loaded into memory. |
| 124 | .It Va l_next |
| 125 | The next |
| 126 | .Vt Link_map |
| 127 | structure on the link-map list. |
| 128 | .It Va l_prev |
| 129 | The previous |
| 130 | .Vt Link_map |
| 131 | structure on the link-map list. |
| 132 | .El |
| 133 | .It Dv RTLD_DI_SERINFO |
| 134 | Retrieve the library search paths associated with the given |
| 135 | .Fa handle |
| 136 | argument. |
| 137 | The |
| 138 | .Fa p |
| 139 | argument should point to |
| 140 | .Vt Dl_serinfo |
| 141 | structure buffer |
| 142 | .Pq Fa "Dl_serinfo *p" . |
| 143 | The |
| 144 | .Vt Dl_serinfo |
| 145 | structure must be initialized first with the |
| 146 | .Dv RTLD_DI_SERINFOSIZE |
| 147 | request. |
| 148 | .Pp |
| 149 | The returned |
| 150 | .Vt Dl_serinfo |
| 151 | structure contains |
| 152 | .Va dls_cnt |
| 153 | .Vt Dl_serpath |
| 154 | entries. |
| 155 | Each entry's |
| 156 | .Va dlp_name |
| 157 | field points to the search path. |
| 158 | The corresponding |
| 159 | .Va dlp_info |
| 160 | field contains one of more flags indicating the origin of the path (see the |
| 161 | .Dv LA_SER_* |
| 162 | flags defined in the |
| 163 | .In link.h |
| 164 | header file). |
| 165 | See |
| 166 | .Sx EXAMPLES , |
| 167 | example 2, for a usage example. |
| 168 | .It Dv RTLD_DI_SERINFOSIZE |
| 169 | Initialize a |
| 170 | .Vt Dl_serinfo |
| 171 | structure for use in a |
| 172 | .Dv RTLD_DI_SERINFO |
| 173 | request. |
| 174 | Both the |
| 175 | .Va dls_cnt |
| 176 | and |
| 177 | .Va dls_size |
| 178 | fields are returned to indicate the number of search paths applicable |
| 179 | to the handle, and the total size of a |
| 180 | .Vt Dl_serinfo |
| 181 | buffer required to hold |
| 182 | .Va dls_cnt |
| 183 | .Vt Dl_serpath |
| 184 | entries and the associated search path strings. |
| 185 | See |
| 186 | .Sx EXAMPLES , |
| 187 | example 2, for a usage example. |
| 188 | .It Va RTLD_DI_ORIGIN |
| 189 | Retrieve the origin of the dynamic object associated with the handle. |
| 190 | On successful return, |
| 191 | .Fa p |
| 192 | argument is filled with the |
| 193 | .Vt char |
| 194 | pointer |
| 195 | .Pq Fa "char *p" . |
| 196 | .El |
| 197 | .Sh RETURN VALUES |
| 198 | The |
| 199 | .Fn dlinfo |
| 200 | function returns 0 on success, or \-1 if an error occurred. |
| 201 | Whenever an error has been detected, a message detailing it can |
| 202 | be retrieved via a call to |
| 203 | .Xr dlerror 3 . |
| 204 | .Sh EXAMPLES |
| 205 | Example 1: Using |
| 206 | .Fn dlinfo |
| 207 | to retrieve |
| 208 | .Vt Link_map |
| 209 | structure. |
| 210 | .Pp |
| 211 | The following example shows how dynamic library can detect the list |
| 212 | of shared libraries loaded after caller's one. |
| 213 | For simplicity, error checking has been omitted. |
| 214 | .Bd -literal -offset indent |
| 215 | Link_map *map; |
| 216 | |
| 217 | dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map); |
| 218 | |
| 219 | while (map != NULL) { |
| 220 | printf("%p: %s\\n", map->l_addr, map->l_name); |
| 221 | map = map->l_next; |
| 222 | } |
| 223 | .Ed |
| 224 | .Pp |
| 225 | Example 2: Using |
| 226 | .Fn dlinfo |
| 227 | to retrieve the library search paths. |
| 228 | .Pp |
| 229 | The following example shows how a dynamic object can inspect the library |
| 230 | search paths that would be used to locate a simple filename with |
| 231 | .Xr dlopen 3 . |
| 232 | For simplicity, error checking has been omitted. |
| 233 | .Bd -literal -offset indent |
| 234 | Dl_serinfo _info, *info = &_info; |
| 235 | Dl_serpath *path; |
| 236 | unsigned int cnt; |
| 237 | |
| 238 | /* determine search path count and required buffer size */ |
| 239 | dlinfo(RTLD_SELF, RTLD_DI_SERINFOSIZE, (void *)info); |
| 240 | |
| 241 | /* allocate new buffer and initialize */ |
| 242 | info = malloc(_info.dls_size); |
| 243 | info->dls_size = _info.dls_size; |
| 244 | info->dls_cnt = _info.dls_cnt; |
| 245 | |
| 246 | /* obtain sarch path information */ |
| 247 | dlinfo(RTLD_SELF, RTLD_DI_SERINFO, (void *)info); |
| 248 | |
| 249 | path = &info->dls_serpath[0]; |
| 250 | |
| 251 | for (cnt = 1; cnt <= info->dls_cnt; cnt++, path++) { |
| 252 | (void) printf("%2d: %s\\n", cnt, path->dls_name); |
| 253 | } |
| 254 | .Ed |
| 255 | .Sh SEE ALSO |
| 256 | .Xr rtld 1 , |
| 257 | .Xr dlfcn 3 |
| 258 | .Sh HISTORY |
| 259 | The |
| 260 | .Fn dlinfo |
| 261 | function first appeared in the Solaris operating system. |
| 262 | In |
| 263 | .Fx , |
| 264 | it first appeared in |
| 265 | .Fx 4.8 . |
| 266 | .Sh AUTHORS |
| 267 | .An -nosplit |
| 268 | The |
| 269 | .Fx |
| 270 | implementation of the |
| 271 | .Fn dlinfo |
| 272 | function was originally written by |
| 273 | .An Alexey Zelkin Aq Mt phantom@FreeBSD.org |
| 274 | and later extended and improved by |
| 275 | .An Alexander Kabaev Aq Mt kan@FreeBSD.org . |
| 276 | .Pp |
| 277 | The manual page for this function was written by |
| 278 | .An Alexey Zelkin Aq Mt phantom@FreeBSD.org . |