1 /* Call the termination functions of loaded shared objects.
2 Copyright (C) 1995-2021 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 <assert.h>
20 #include <string.h>
21 #include <ldsodefs.h>
22 #include <elf-initfini.h>
23
24
25 /* Type of the constructor functions. */
26 typedef void (*fini_t) (void);
27
28
29 void
_dl_fini(void)30 _dl_fini (void)
31 {
32 /* Lots of fun ahead. We have to call the destructors for all still
33 loaded objects, in all namespaces. The problem is that the ELF
34 specification now demands that dependencies between the modules
35 are taken into account. I.e., the destructor for a module is
36 called before the ones for any of its dependencies.
37
38 To make things more complicated, we cannot simply use the reverse
39 order of the constructors. Since the user might have loaded objects
40 using `dlopen' there are possibly several other modules with its
41 dependencies to be taken into account. Therefore we have to start
42 determining the order of the modules once again from the beginning. */
43
44 /* We run the destructors of the main namespaces last. As for the
45 other namespaces, we pick run the destructors in them in reverse
46 order of the namespace ID. */
47 #ifdef SHARED
48 int do_audit = 0;
49 again:
50 #endif
51 for (Lmid_t ns = GL(dl_nns) - 1; ns >= 0; --ns)
52 {
53 /* Protect against concurrent loads and unloads. */
54 __rtld_lock_lock_recursive (GL(dl_load_lock));
55
56 unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded;
57 /* No need to do anything for empty namespaces or those used for
58 auditing DSOs. */
59 if (nloaded == 0
60 #ifdef SHARED
61 || GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit
62 #endif
63 )
64 __rtld_lock_unlock_recursive (GL(dl_load_lock));
65 else
66 {
67 /* Now we can allocate an array to hold all the pointers and
68 copy the pointers in. */
69 struct link_map *maps[nloaded];
70
71 unsigned int i;
72 struct link_map *l;
73 assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
74 for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
75 /* Do not handle ld.so in secondary namespaces. */
76 if (l == l->l_real)
77 {
78 assert (i < nloaded);
79
80 maps[i] = l;
81 l->l_idx = i;
82 ++i;
83
84 /* Bump l_direct_opencount of all objects so that they
85 are not dlclose()ed from underneath us. */
86 ++l->l_direct_opencount;
87 }
88 assert (ns != LM_ID_BASE || i == nloaded);
89 assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
90 unsigned int nmaps = i;
91
92 /* Now we have to do the sorting. We can skip looking for the
93 binary itself which is at the front of the search list for
94 the main namespace. */
95 _dl_sort_maps (maps, nmaps, (ns == LM_ID_BASE), true);
96
97 /* We do not rely on the linked list of loaded object anymore
98 from this point on. We have our own list here (maps). The
99 various members of this list cannot vanish since the open
100 count is too high and will be decremented in this loop. So
101 we release the lock so that some code which might be called
102 from a destructor can directly or indirectly access the
103 lock. */
104 __rtld_lock_unlock_recursive (GL(dl_load_lock));
105
106 /* 'maps' now contains the objects in the right order. Now
107 call the destructors. We have to process this array from
108 the front. */
109 for (i = 0; i < nmaps; ++i)
110 {
111 struct link_map *l = maps[i];
112
113 if (l->l_init_called)
114 {
115 /* Make sure nothing happens if we are called twice. */
116 l->l_init_called = 0;
117
118 /* Is there a destructor function? */
119 if (l->l_info[DT_FINI_ARRAY] != NULL
120 || (ELF_INITFINI && l->l_info[DT_FINI] != NULL))
121 {
122 /* When debugging print a message first. */
123 if (__builtin_expect (GLRO(dl_debug_mask)
124 & DL_DEBUG_IMPCALLS, 0))
125 _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
126 DSO_FILENAME (l->l_name),
127 ns);
128
129 /* First see whether an array is given. */
130 if (l->l_info[DT_FINI_ARRAY] != NULL)
131 {
132 ElfW(Addr) *array =
133 (ElfW(Addr) *) (l->l_addr
134 + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
135 unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
136 / sizeof (ElfW(Addr)));
137 while (i-- > 0)
138 ((fini_t) array[i]) ();
139 }
140
141 /* Next try the old-style destructor. */
142 if (ELF_INITFINI && l->l_info[DT_FINI] != NULL)
143 DL_CALL_DT_FINI
144 (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
145 }
146
147 #ifdef SHARED
148 /* Auditing checkpoint: another object closed. */
149 _dl_audit_objclose (l);
150 #endif
151 }
152
153 /* Correct the previous increment. */
154 --l->l_direct_opencount;
155 }
156 }
157 }
158
159 #ifdef SHARED
160 if (! do_audit && GLRO(dl_naudit) > 0)
161 {
162 do_audit = 1;
163 goto again;
164 }
165
166 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS))
167 _dl_debug_printf ("\nruntime linker statistics:\n"
168 " final number of relocations: %lu\n"
169 "final number of relocations from cache: %lu\n",
170 GL(dl_num_relocations),
171 GL(dl_num_cache_relocations));
172 #endif
173 }
174