1 /* Handle loading and unloading shared objects for internal libc purposes.
2 Copyright (C) 1999-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <dlfcn.h>
20 #include <stdlib.h>
21 #include <ldsodefs.h>
22 #include <dl-hash.h>
23
24 extern int __libc_argc attribute_hidden;
25 extern char **__libc_argv attribute_hidden;
26
27 extern char **__environ;
28
29 /* The purpose of this file is to provide wrappers around the dynamic
30 linker error mechanism (similar to dlopen() et al in libdl) which
31 are usable from within libc. Generally we want to throw away the
32 string that dlerror() would return and just pass back a null pointer
33 for errors. This also lets the rest of libc not know about the error
34 handling mechanism.
35
36 Much of this code came from gconv_dl.c with slight modifications. */
37
38 static int
dlerror_run(void (* operate)(void *),void * args)39 dlerror_run (void (*operate) (void *), void *args)
40 {
41 const char *objname;
42 const char *last_errstring = NULL;
43 bool malloced;
44
45 int result = (GLRO (dl_catch_error) (&objname, &last_errstring, &malloced,
46 operate, args)
47 ?: last_errstring != NULL);
48
49 if (result && malloced)
50 GLRO (dl_error_free) ((char *) last_errstring);
51
52 return result;
53 }
54
55 /* These functions are called by dlerror_run... */
56
57 struct do_dlopen_args
58 {
59 /* Argument to do_dlopen. */
60 const char *name;
61 /* Opening mode. */
62 int mode;
63 /* This is the caller of the dlopen() function. */
64 const void *caller_dlopen;
65
66 /* Return from do_dlopen. */
67 struct link_map *map;
68 };
69
70 struct do_dlsym_args
71 {
72 /* Arguments to do_dlsym. */
73 struct link_map *map;
74 const char *name;
75
76 /* Return values of do_dlsym. */
77 lookup_t loadbase;
78 const ElfW(Sym) *ref;
79 };
80
81 struct do_dlvsym_args
82 {
83 /* dlvsym is like dlsym. */
84 struct do_dlsym_args dlsym;
85
86 /* But dlvsym needs a version as well. */
87 struct r_found_version version;
88 };
89
90 static void
do_dlopen(void * ptr)91 do_dlopen (void *ptr)
92 {
93 struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
94 /* Open and relocate the shared object. */
95 args->map = GLRO(dl_open) (args->name, args->mode, args->caller_dlopen,
96 __LM_ID_CALLER, __libc_argc, __libc_argv,
97 __environ);
98 }
99
100 static void
do_dlsym(void * ptr)101 do_dlsym (void *ptr)
102 {
103 struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
104 args->ref = NULL;
105 args->loadbase = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
106 args->map->l_local_scope, NULL, 0,
107 DL_LOOKUP_RETURN_NEWEST, NULL);
108 }
109
110 static void
do_dlvsym(void * ptr)111 do_dlvsym (void *ptr)
112 {
113 struct do_dlvsym_args *args = ptr;
114 args->dlsym.ref = NULL;
115 args->dlsym.loadbase
116 = GLRO(dl_lookup_symbol_x) (args->dlsym.name, args->dlsym.map,
117 &args->dlsym.ref,
118 args->dlsym.map->l_local_scope,
119 &args->version, 0, 0, NULL);
120 }
121
122 static void
do_dlclose(void * ptr)123 do_dlclose (void *ptr)
124 {
125 GLRO(dl_close) ((struct link_map *) ptr);
126 }
127
128 #ifndef SHARED
129 static void
do_dlsym_private(void * ptr)130 do_dlsym_private (void *ptr)
131 {
132 lookup_t l;
133 struct r_found_version vers;
134 vers.name = "GLIBC_PRIVATE";
135 vers.hidden = 1;
136 /* vers.hash = _dl_elf_hash (vers.name); */
137 vers.hash = 0x0963cf85;
138 vers.filename = NULL;
139
140 struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
141 args->ref = NULL;
142 l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
143 args->map->l_scope, &vers, 0, 0, NULL);
144 args->loadbase = l;
145 }
146 #endif
147
148 /* ... and these functions call dlerror_run. */
149
150 void *
__libc_dlopen_mode(const char * name,int mode)151 __libc_dlopen_mode (const char *name, int mode)
152 {
153 struct do_dlopen_args args;
154 args.name = name;
155 args.mode = mode;
156 args.caller_dlopen = RETURN_ADDRESS (0);
157
158 #ifdef SHARED
159 if (!rtld_active ())
160 return GLRO (dl_dlfcn_hook)->libc_dlopen_mode (name, mode);
161 #endif
162 return dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map;
163 }
164
165 #ifndef SHARED
166 void *
__libc_dlsym_private(struct link_map * map,const char * name)167 __libc_dlsym_private (struct link_map *map, const char *name)
168 {
169 struct do_dlsym_args sargs;
170 sargs.map = map;
171 sargs.name = name;
172
173 if (! dlerror_run (do_dlsym_private, &sargs))
174 return DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref);
175 return NULL;
176 }
177 #endif
178
179 void *
__libc_dlsym(void * map,const char * name)180 __libc_dlsym (void *map, const char *name)
181 {
182 struct do_dlsym_args args;
183 args.map = map;
184 args.name = name;
185
186 #ifdef SHARED
187 if (!rtld_active ())
188 return GLRO (dl_dlfcn_hook)->libc_dlsym (map, name);
189 #endif
190 return (dlerror_run (do_dlsym, &args) ? NULL
191 : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
192 }
193
194 /* Replacement for dlvsym. MAP must be a real map. This function
195 returns NULL without setting the dlerror value in case of static
196 dlopen from an old binary. */
197 void *
__libc_dlvsym(void * map,const char * name,const char * version)198 __libc_dlvsym (void *map, const char *name, const char *version)
199 {
200 #ifdef SHARED
201 if (!rtld_active ())
202 return GLRO (dl_dlfcn_hook)->libc_dlvsym (map, name, version);
203 #endif
204
205 struct do_dlvsym_args args;
206 args.dlsym.map = map;
207 args.dlsym.name = name;
208
209 /* See _dl_vsym in dl-sym.c. */
210 args.version.name = version;
211 args.version.hidden = 1;
212 args.version.hash = _dl_elf_hash (version);
213 args.version.filename = NULL;
214
215 return (dlerror_run (do_dlvsym, &args) ? NULL
216 : (void *) (DL_SYMBOL_ADDRESS (args.dlsym.loadbase,
217 args.dlsym.ref)));
218 }
219
220 int
__libc_dlclose(void * map)221 __libc_dlclose (void *map)
222 {
223 #ifdef SHARED
224 if (!rtld_active ())
225 return GLRO (dl_dlfcn_hook)->libc_dlclose (map);
226 #endif
227 return dlerror_run (do_dlclose, map);
228 }
229
230
231 static bool __libc_freeres_fn_section
free_slotinfo(struct dtv_slotinfo_list ** elemp)232 free_slotinfo (struct dtv_slotinfo_list **elemp)
233 {
234 size_t cnt;
235
236 if (*elemp == NULL)
237 /* Nothing here, all is removed (or there never was anything). */
238 return true;
239
240 if (!free_slotinfo (&(*elemp)->next))
241 /* We cannot free the entry. */
242 return false;
243
244 /* That cleared our next pointer for us. */
245
246 for (cnt = 0; cnt < (*elemp)->len; ++cnt)
247 if ((*elemp)->slotinfo[cnt].map != NULL)
248 /* Still used. */
249 return false;
250
251 /* We can remove the list element. */
252 free (*elemp);
253 *elemp = NULL;
254
255 return true;
256 }
257
258
libc_freeres_fn(free_mem)259 libc_freeres_fn (free_mem)
260 {
261 struct link_map *l;
262 struct r_search_path_elem *d;
263
264 /* Remove all search directories. */
265 d = GL(dl_all_dirs);
266 while (d != GLRO(dl_init_all_dirs))
267 {
268 struct r_search_path_elem *old = d;
269 d = d->next;
270 free (old);
271 }
272
273 for (Lmid_t ns = 0; ns < GL(dl_nns); ++ns)
274 {
275 for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)
276 {
277 struct libname_list *lnp = l->l_libname->next;
278
279 l->l_libname->next = NULL;
280
281 /* Remove all additional names added to the objects. */
282 while (lnp != NULL)
283 {
284 struct libname_list *old = lnp;
285 lnp = lnp->next;
286 if (! old->dont_free)
287 free (old);
288 }
289
290 /* Free the initfini dependency list. */
291 if (l->l_free_initfini)
292 free (l->l_initfini);
293 l->l_initfini = NULL;
294 }
295
296 if (__builtin_expect (GL(dl_ns)[ns]._ns_global_scope_alloc, 0) != 0
297 && (GL(dl_ns)[ns]._ns_main_searchlist->r_nlist
298 // XXX Check whether we need NS-specific initial_searchlist
299 == GLRO(dl_initial_searchlist).r_nlist))
300 {
301 /* All object dynamically loaded by the program are unloaded. Free
302 the memory allocated for the global scope variable. */
303 struct link_map **old = GL(dl_ns)[ns]._ns_main_searchlist->r_list;
304
305 /* Put the old map in. */
306 GL(dl_ns)[ns]._ns_main_searchlist->r_list
307 // XXX Check whether we need NS-specific initial_searchlist
308 = GLRO(dl_initial_searchlist).r_list;
309 /* Signal that the original map is used. */
310 GL(dl_ns)[ns]._ns_global_scope_alloc = 0;
311
312 /* Now free the old map. */
313 free (old);
314 }
315 }
316
317 /* Free the memory allocated for the dtv slotinfo array. We can do
318 this only if all modules which used this memory are unloaded. */
319 #ifdef SHARED
320 if (GL(dl_initial_dtv) == NULL)
321 /* There was no initial TLS setup, it was set up later when
322 it used the normal malloc. */
323 free_slotinfo (&GL(dl_tls_dtv_slotinfo_list));
324 else
325 #endif
326 /* The first element of the list does not have to be deallocated.
327 It was allocated in the dynamic linker (i.e., with a different
328 malloc), and in the static library it's in .bss space. */
329 free_slotinfo (&GL(dl_tls_dtv_slotinfo_list)->next);
330
331 void *scope_free_list = GL(dl_scope_free_list);
332 GL(dl_scope_free_list) = NULL;
333 free (scope_free_list);
334 }
335