1 | /* Call the termination functions of loaded shared objects. |
2 | Copyright (C) 1995-2016 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 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <assert.h> |
20 | #include <string.h> |
21 | #include <ldsodefs.h> |
22 | |
23 | |
24 | /* Type of the constructor functions. */ |
25 | typedef void (*fini_t) (void); |
26 | |
27 | |
28 | void |
29 | internal_function |
30 | _dl_sort_fini (struct link_map **maps, size_t nmaps, char *used, Lmid_t ns) |
31 | { |
32 | /* A list of one element need not be sorted. */ |
33 | if (nmaps == 1) |
34 | return; |
35 | |
36 | /* We can skip looking for the binary itself which is at the front |
37 | of the search list for the main namespace. */ |
38 | unsigned int i = ns == LM_ID_BASE; |
39 | uint16_t seen[nmaps]; |
40 | memset (seen, 0, nmaps * sizeof (seen[0])); |
41 | while (1) |
42 | { |
43 | /* Keep track of which object we looked at this round. */ |
44 | ++seen[i]; |
45 | struct link_map *thisp = maps[i]; |
46 | |
47 | /* Do not handle ld.so in secondary namespaces and object which |
48 | are not removed. */ |
49 | if (thisp != thisp->l_real || thisp->l_idx == -1) |
50 | goto skip; |
51 | |
52 | /* Find the last object in the list for which the current one is |
53 | a dependency and move the current object behind the object |
54 | with the dependency. */ |
55 | unsigned int k = nmaps - 1; |
56 | while (k > i) |
57 | { |
58 | struct link_map **runp = maps[k]->l_initfini; |
59 | if (runp != NULL) |
60 | /* Look through the dependencies of the object. */ |
61 | while (*runp != NULL) |
62 | if (__glibc_unlikely (*runp++ == thisp)) |
63 | { |
64 | move: |
65 | /* Move the current object to the back past the last |
66 | object with it as the dependency. */ |
67 | memmove (&maps[i], &maps[i + 1], |
68 | (k - i) * sizeof (maps[0])); |
69 | maps[k] = thisp; |
70 | |
71 | if (used != NULL) |
72 | { |
73 | char here_used = used[i]; |
74 | memmove (&used[i], &used[i + 1], |
75 | (k - i) * sizeof (used[0])); |
76 | used[k] = here_used; |
77 | } |
78 | |
79 | if (seen[i + 1] > nmaps - i) |
80 | { |
81 | ++i; |
82 | goto next_clear; |
83 | } |
84 | |
85 | uint16_t this_seen = seen[i]; |
86 | memmove (&seen[i], &seen[i + 1], (k - i) * sizeof (seen[0])); |
87 | seen[k] = this_seen; |
88 | |
89 | goto next; |
90 | } |
91 | |
92 | if (__glibc_unlikely (maps[k]->l_reldeps != NULL)) |
93 | { |
94 | unsigned int m = maps[k]->l_reldeps->act; |
95 | struct link_map **relmaps = &maps[k]->l_reldeps->list[0]; |
96 | |
97 | /* Look through the relocation dependencies of the object. */ |
98 | while (m-- > 0) |
99 | if (__glibc_unlikely (relmaps[m] == thisp)) |
100 | { |
101 | /* If a cycle exists with a link time dependency, |
102 | preserve the latter. */ |
103 | struct link_map **runp = thisp->l_initfini; |
104 | if (runp != NULL) |
105 | while (*runp != NULL) |
106 | if (__glibc_unlikely (*runp++ == maps[k])) |
107 | goto ignore; |
108 | goto move; |
109 | } |
110 | ignore:; |
111 | } |
112 | |
113 | --k; |
114 | } |
115 | |
116 | skip: |
117 | if (++i == nmaps) |
118 | break; |
119 | next_clear: |
120 | memset (&seen[i], 0, (nmaps - i) * sizeof (seen[0])); |
121 | |
122 | next:; |
123 | } |
124 | } |
125 | |
126 | |
127 | void |
128 | internal_function |
129 | _dl_fini (void) |
130 | { |
131 | /* Lots of fun ahead. We have to call the destructors for all still |
132 | loaded objects, in all namespaces. The problem is that the ELF |
133 | specification now demands that dependencies between the modules |
134 | are taken into account. I.e., the destructor for a module is |
135 | called before the ones for any of its dependencies. |
136 | |
137 | To make things more complicated, we cannot simply use the reverse |
138 | order of the constructors. Since the user might have loaded objects |
139 | using `dlopen' there are possibly several other modules with its |
140 | dependencies to be taken into account. Therefore we have to start |
141 | determining the order of the modules once again from the beginning. */ |
142 | |
143 | /* We run the destructors of the main namespaces last. As for the |
144 | other namespaces, we pick run the destructors in them in reverse |
145 | order of the namespace ID. */ |
146 | #ifdef SHARED |
147 | int do_audit = 0; |
148 | again: |
149 | #endif |
150 | for (Lmid_t ns = GL(dl_nns) - 1; ns >= 0; --ns) |
151 | { |
152 | /* Protect against concurrent loads and unloads. */ |
153 | __rtld_lock_lock_recursive (GL(dl_load_lock)); |
154 | |
155 | unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded; |
156 | /* No need to do anything for empty namespaces or those used for |
157 | auditing DSOs. */ |
158 | if (nloaded == 0 |
159 | #ifdef SHARED |
160 | || GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit |
161 | #endif |
162 | ) |
163 | __rtld_lock_unlock_recursive (GL(dl_load_lock)); |
164 | else |
165 | { |
166 | /* Now we can allocate an array to hold all the pointers and |
167 | copy the pointers in. */ |
168 | struct link_map *maps[nloaded]; |
169 | |
170 | unsigned int i; |
171 | struct link_map *l; |
172 | assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL); |
173 | for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next) |
174 | /* Do not handle ld.so in secondary namespaces. */ |
175 | if (l == l->l_real) |
176 | { |
177 | assert (i < nloaded); |
178 | |
179 | maps[i] = l; |
180 | l->l_idx = i; |
181 | ++i; |
182 | |
183 | /* Bump l_direct_opencount of all objects so that they |
184 | are not dlclose()ed from underneath us. */ |
185 | ++l->l_direct_opencount; |
186 | } |
187 | assert (ns != LM_ID_BASE || i == nloaded); |
188 | assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1); |
189 | unsigned int nmaps = i; |
190 | |
191 | /* Now we have to do the sorting. */ |
192 | _dl_sort_fini (maps, nmaps, NULL, ns); |
193 | |
194 | /* We do not rely on the linked list of loaded object anymore |
195 | from this point on. We have our own list here (maps). The |
196 | various members of this list cannot vanish since the open |
197 | count is too high and will be decremented in this loop. So |
198 | we release the lock so that some code which might be called |
199 | from a destructor can directly or indirectly access the |
200 | lock. */ |
201 | __rtld_lock_unlock_recursive (GL(dl_load_lock)); |
202 | |
203 | /* 'maps' now contains the objects in the right order. Now |
204 | call the destructors. We have to process this array from |
205 | the front. */ |
206 | for (i = 0; i < nmaps; ++i) |
207 | { |
208 | struct link_map *l = maps[i]; |
209 | |
210 | if (l->l_init_called) |
211 | { |
212 | /* Make sure nothing happens if we are called twice. */ |
213 | l->l_init_called = 0; |
214 | |
215 | /* Is there a destructor function? */ |
216 | if (l->l_info[DT_FINI_ARRAY] != NULL |
217 | || l->l_info[DT_FINI] != NULL) |
218 | { |
219 | /* When debugging print a message first. */ |
220 | if (__builtin_expect (GLRO(dl_debug_mask) |
221 | & DL_DEBUG_IMPCALLS, 0)) |
222 | _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n" , |
223 | DSO_FILENAME (l->l_name), |
224 | ns); |
225 | |
226 | /* First see whether an array is given. */ |
227 | if (l->l_info[DT_FINI_ARRAY] != NULL) |
228 | { |
229 | ElfW(Addr) *array = |
230 | (ElfW(Addr) *) (l->l_addr |
231 | + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr); |
232 | unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val |
233 | / sizeof (ElfW(Addr))); |
234 | while (i-- > 0) |
235 | ((fini_t) array[i]) (); |
236 | } |
237 | |
238 | /* Next try the old-style destructor. */ |
239 | if (l->l_info[DT_FINI] != NULL) |
240 | DL_CALL_DT_FINI |
241 | (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr); |
242 | } |
243 | |
244 | #ifdef SHARED |
245 | /* Auditing checkpoint: another object closed. */ |
246 | if (!do_audit && __builtin_expect (GLRO(dl_naudit) > 0, 0)) |
247 | { |
248 | struct audit_ifaces *afct = GLRO(dl_audit); |
249 | for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt) |
250 | { |
251 | if (afct->objclose != NULL) |
252 | /* Return value is ignored. */ |
253 | (void) afct->objclose (&l->l_audit[cnt].cookie); |
254 | |
255 | afct = afct->next; |
256 | } |
257 | } |
258 | #endif |
259 | } |
260 | |
261 | /* Correct the previous increment. */ |
262 | --l->l_direct_opencount; |
263 | } |
264 | } |
265 | } |
266 | |
267 | #ifdef SHARED |
268 | if (! do_audit && GLRO(dl_naudit) > 0) |
269 | { |
270 | do_audit = 1; |
271 | goto again; |
272 | } |
273 | |
274 | if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS)) |
275 | _dl_debug_printf ("\nruntime linker statistics:\n" |
276 | " final number of relocations: %lu\n" |
277 | "final number of relocations from cache: %lu\n" , |
278 | GL(dl_num_relocations), |
279 | GL(dl_num_cache_relocations)); |
280 | #endif |
281 | } |
282 | |