1 /* loader-dlopen.c -- dynamic linking with dlopen/dlsym
2
3 Copyright (C) 1998-2000, 2004, 2006-2008, 2011-2015 Free Software
4 Foundation, Inc.
5 Written by Thomas Tanner, 1998
6
7 NOTE: The canonical source of this file is maintained with the
8 GNU Libtool package. Report bugs to bug-libtool@gnu.org.
9
10 GNU Libltdl is free software; you can redistribute it and/or
11 modify it under the terms of the GNU Lesser General Public
12 License as published by the Free Software Foundation; either
13 version 2 of the License, or (at your option) any later version.
14
15 As a special exception to the GNU Lesser General Public License,
16 if you distribute this file as part of a program or library that
17 is built using GNU Libtool, you may include this file under the
18 same distribution terms that you use for the rest of that program.
19
20 GNU Libltdl is distributed in the hope that it will be useful,
21 but WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 GNU Lesser General Public License for more details.
24
25 You should have received a copy of the GNU Lesser General Public
26 License along with GNU Libltdl; see the file COPYING.LIB. If not, a
27 copy can be downloaded from http://www.gnu.org/licenses/lgpl.html,
28 or obtained by writing to the Free Software Foundation, Inc.,
29 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
30 */
31
32 #include "lt__private.h"
33 #include "lt_dlloader.h"
34
35 /* Use the preprocessor to rename non-static symbols to avoid namespace
36 collisions when the loader code is statically linked into libltdl.
37 Use the "<module_name>_LTX_" prefix so that the symbol addresses can
38 be fetched from the preloaded symbol list by lt_dlsym(): */
39 #define get_vtable dlopen_LTX_get_vtable
40
41 LT_BEGIN_C_DECLS
42 LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
43 LT_END_C_DECLS
44
45
46 /* Boilerplate code to set up the vtable for hooking this loader into
47 libltdl's loader list: */
48 static int vl_exit (lt_user_data loader_data);
49 static lt_module vm_open (lt_user_data loader_data, const char *filename,
50 lt_dladvise advise);
51 static int vm_close (lt_user_data loader_data, lt_module module);
52 static void * vm_sym (lt_user_data loader_data, lt_module module,
53 const char *symbolname);
54
55 static lt_dlvtable *vtable = 0;
56
57 /* Return the vtable for this loader, only the name and sym_prefix
58 attributes (plus the virtual function implementations, obviously)
59 change between loaders. */
60 lt_dlvtable *
get_vtable(lt_user_data loader_data)61 get_vtable (lt_user_data loader_data)
62 {
63 if (!vtable)
64 {
65 vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
66 }
67
68 if (vtable && !vtable->name)
69 {
70 vtable->name = "lt_dlopen";
71 #if defined DLSYM_USCORE
72 vtable->sym_prefix = "_";
73 #endif
74 vtable->module_open = vm_open;
75 vtable->module_close = vm_close;
76 vtable->find_sym = vm_sym;
77 vtable->dlloader_exit = vl_exit;
78 vtable->dlloader_data = loader_data;
79 vtable->priority = LT_DLLOADER_PREPEND;
80 }
81
82 if (vtable && (vtable->dlloader_data != loader_data))
83 {
84 LT__SETERROR (INIT_LOADER);
85 return 0;
86 }
87
88 return vtable;
89 }
90
91
92
93 /* --- IMPLEMENTATION --- */
94
95
96 #if defined HAVE_DLFCN_H
97 # include <dlfcn.h>
98 #endif
99
100 #if defined HAVE_SYS_DL_H
101 # include <sys/dl.h>
102 #endif
103
104
105 /* We may have to define LT_LAZY_OR_NOW in the command line if we
106 find out it does not work in some platform. */
107 #if !defined LT_LAZY_OR_NOW
108 # if defined RTLD_LAZY
109 # define LT_LAZY_OR_NOW RTLD_LAZY
110 # else
111 # if defined DL_LAZY
112 # define LT_LAZY_OR_NOW DL_LAZY
113 # endif
114 # endif /* !RTLD_LAZY */
115 #endif
116 #if !defined LT_LAZY_OR_NOW
117 # if defined RTLD_NOW
118 # define LT_LAZY_OR_NOW RTLD_NOW
119 # else
120 # if defined DL_NOW
121 # define LT_LAZY_OR_NOW DL_NOW
122 # endif
123 # endif /* !RTLD_NOW */
124 #endif
125 #if !defined LT_LAZY_OR_NOW
126 # define LT_LAZY_OR_NOW 0
127 #endif /* !LT_LAZY_OR_NOW */
128
129 /* We only support local and global symbols from modules for loaders
130 that provide such a thing, otherwise the system default is used. */
131 #if !defined RTLD_GLOBAL
132 # if defined DL_GLOBAL
133 # define RTLD_GLOBAL DL_GLOBAL
134 # endif
135 #endif /* !RTLD_GLOBAL */
136 #if !defined RTLD_LOCAL
137 # if defined DL_LOCAL
138 # define RTLD_LOCAL DL_LOCAL
139 # endif
140 #endif /* !RTLD_LOCAL */
141
142 #if defined HAVE_DLERROR
143 # define DLERROR(arg) dlerror ()
144 #else
145 # define DLERROR(arg) LT__STRERROR (arg)
146 #endif
147
148 #define DL__SETERROR(errorcode) \
149 LT__SETERRORSTR (DLERROR (errorcode))
150
151
152 /* A function called through the vtable when this loader is no
153 longer needed by the application. */
154 static int
vl_exit(lt_user_data loader_data LT__UNUSED)155 vl_exit (lt_user_data loader_data LT__UNUSED)
156 {
157 vtable = NULL;
158 return 0;
159 }
160
161
162 /* A function called through the vtable to open a module with this
163 loader. Returns an opaque representation of the newly opened
164 module for processing with this loader's other vtable functions. */
165 static lt_module
vm_open(lt_user_data loader_data LT__UNUSED,const char * filename,lt_dladvise advise)166 vm_open (lt_user_data loader_data LT__UNUSED, const char *filename,
167 lt_dladvise advise)
168 {
169 int module_flags = LT_LAZY_OR_NOW;
170 lt_module module;
171 #ifdef RTLD_MEMBER
172 int len = LT_STRLEN (filename);
173 #endif
174
175 if (advise)
176 {
177 #ifdef RTLD_GLOBAL
178 /* If there is some means of asking for global symbol resolution,
179 do so. */
180 if (advise->is_symglobal)
181 module_flags |= RTLD_GLOBAL;
182 #else
183 /* Otherwise, reset that bit so the caller can tell it wasn't
184 acted on. */
185 advise->is_symglobal = 0;
186 #endif
187
188 /* And similarly for local only symbol resolution. */
189 #ifdef RTLD_LOCAL
190 if (advise->is_symlocal)
191 module_flags |= RTLD_LOCAL;
192 #else
193 advise->is_symlocal = 0;
194 #endif
195 }
196
197 #ifdef RTLD_MEMBER /* AIX */
198 if (len >= 4) /* at least "l(m)" */
199 {
200 /* Advise loading an archive member only if the filename really
201 contains both the opening and closing parent, and a member. */
202 if (filename[len-1] == ')')
203 {
204 const char *opening = strrchr(filename, '(');
205 if (opening && opening < (filename+len-2) && strchr(opening+1, '/') == NULL)
206 module_flags |= RTLD_MEMBER;
207 }
208 }
209 #endif
210
211 module = dlopen (filename, module_flags);
212
213 #if defined RTLD_MEMBER && defined LT_SHARED_LIB_MEMBER
214 if (!module && len && !(module_flags & RTLD_MEMBER) && errno == ENOEXEC)
215 {
216 /* Loading without a member specified failed with "Exec format error".
217 So the file is there, but either has wrong bitwidth, or is an
218 archive eventually containing the default shared archive member.
219 Retry with default member, getting same error in worst case. */
220 const char *member = LT_SHARED_LIB_MEMBER;
221
222 char *attempt = MALLOC (char, len + strlen (member) + 1);
223 if (!attempt)
224 {
225 LT__SETERROR (NO_MEMORY);
226 return module;
227 }
228
229 sprintf (attempt, "%s%s", filename, member);
230 module = vm_open (loader_data, attempt, advise);
231 FREE (attempt);
232 return module;
233 }
234 #endif
235
236 if (!module)
237 {
238 DL__SETERROR (CANNOT_OPEN);
239 }
240
241 return module;
242 }
243
244
245 /* A function called through the vtable when a particular module
246 should be unloaded. */
247 static int
vm_close(lt_user_data loader_data LT__UNUSED,lt_module module)248 vm_close (lt_user_data loader_data LT__UNUSED, lt_module module)
249 {
250 int errors = 0;
251
252 if (dlclose (module) != 0)
253 {
254 DL__SETERROR (CANNOT_CLOSE);
255 ++errors;
256 }
257
258 return errors;
259 }
260
261
262 /* A function called through the vtable to get the address of
263 a symbol loaded from a particular module. */
264 static void *
vm_sym(lt_user_data loader_data LT__UNUSED,lt_module module,const char * name)265 vm_sym (lt_user_data loader_data LT__UNUSED, lt_module module, const char *name)
266 {
267 void *address = dlsym (module, name);
268
269 if (!address)
270 {
271 DL__SETERROR (SYMBOL_NOT_FOUND);
272 }
273
274 return address;
275 }
276