1/* Call the termination functions of loaded shared objects.
2 Copyright (C) 1995-2022 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. */
26typedef void (*fini_t) (void);
27
28
29void
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#ifdef SHARED
68 _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
69#endif
70
71 /* Now we can allocate an array to hold all the pointers and
72 copy the pointers in. */
73 struct link_map *maps[nloaded];
74
75 unsigned int i;
76 struct link_map *l;
77 assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
78 for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
79 /* Do not handle ld.so in secondary namespaces. */
80 if (l == l->l_real)
81 {
82 assert (i < nloaded);
83
84 maps[i] = l;
85 l->l_idx = i;
86 ++i;
87
88 /* Bump l_direct_opencount of all objects so that they
89 are not dlclose()ed from underneath us. */
90 ++l->l_direct_opencount;
91 }
92 assert (ns != LM_ID_BASE || i == nloaded);
93 assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
94 unsigned int nmaps = i;
95
96 /* Now we have to do the sorting. We can skip looking for the
97 binary itself which is at the front of the search list for
98 the main namespace. */
99 _dl_sort_maps (maps, nmaps, (ns == LM_ID_BASE), true);
100
101 /* We do not rely on the linked list of loaded object anymore
102 from this point on. We have our own list here (maps). The
103 various members of this list cannot vanish since the open
104 count is too high and will be decremented in this loop. So
105 we release the lock so that some code which might be called
106 from a destructor can directly or indirectly access the
107 lock. */
108 __rtld_lock_unlock_recursive (GL(dl_load_lock));
109
110 /* 'maps' now contains the objects in the right order. Now
111 call the destructors. We have to process this array from
112 the front. */
113 for (i = 0; i < nmaps; ++i)
114 {
115 struct link_map *l = maps[i];
116
117 if (l->l_init_called)
118 {
119 /* Make sure nothing happens if we are called twice. */
120 l->l_init_called = 0;
121
122 /* Is there a destructor function? */
123 if (l->l_info[DT_FINI_ARRAY] != NULL
124 || (ELF_INITFINI && l->l_info[DT_FINI] != NULL))
125 {
126 /* When debugging print a message first. */
127 if (__builtin_expect (GLRO(dl_debug_mask)
128 & DL_DEBUG_IMPCALLS, 0))
129 _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
130 DSO_FILENAME (l->l_name),
131 ns);
132
133 /* First see whether an array is given. */
134 if (l->l_info[DT_FINI_ARRAY] != NULL)
135 {
136 ElfW(Addr) *array =
137 (ElfW(Addr) *) (l->l_addr
138 + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
139 unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
140 / sizeof (ElfW(Addr)));
141 while (i-- > 0)
142 ((fini_t) array[i]) ();
143 }
144
145 /* Next try the old-style destructor. */
146 if (ELF_INITFINI && l->l_info[DT_FINI] != NULL)
147 DL_CALL_DT_FINI
148 (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
149 }
150
151#ifdef SHARED
152 /* Auditing checkpoint: another object closed. */
153 _dl_audit_objclose (l);
154#endif
155 }
156
157 /* Correct the previous increment. */
158 --l->l_direct_opencount;
159 }
160
161#ifdef SHARED
162 _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
163#endif
164 }
165 }
166
167#ifdef SHARED
168 if (! do_audit && GLRO(dl_naudit) > 0)
169 {
170 do_audit = 1;
171 goto again;
172 }
173
174 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS))
175 _dl_debug_printf ("\nruntime linker statistics:\n"
176 " final number of relocations: %lu\n"
177 "final number of relocations from cache: %lu\n",
178 GL(dl_num_relocations),
179 GL(dl_num_cache_relocations));
180#endif
181}
182

source code of glibc/elf/dl-fini.c