1 /* Copyright (C) 1999-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18 #include <assert.h>
19 #include <stdlib.h>
20 #include <stdint.h>
21
22 #include <libc-lock.h>
23 #include "exit.h"
24 #include <sysdep.h>
25
26 #undef __cxa_atexit
27
28 /* See concurrency notes in stdlib/exit.h where this lock is declared. */
29 __libc_lock_define_initialized (, __exit_funcs_lock)
30
31
32 int
33 attribute_hidden
__internal_atexit(void (* func)(void *),void * arg,void * d,struct exit_function_list ** listp)34 __internal_atexit (void (*func) (void *), void *arg, void *d,
35 struct exit_function_list **listp)
36 {
37 struct exit_function *new;
38
39 /* As a QoI issue we detect NULL early with an assertion instead
40 of a SIGSEGV at program exit when the handler is run (bug 20544). */
41 assert (func != NULL);
42
43 __libc_lock_lock (__exit_funcs_lock);
44 new = __new_exitfn (listp);
45
46 if (new == NULL)
47 {
48 __libc_lock_unlock (__exit_funcs_lock);
49 return -1;
50 }
51
52 #ifdef PTR_MANGLE
53 PTR_MANGLE (func);
54 #endif
55 new->func.cxa.fn = (void (*) (void *, int)) func;
56 new->func.cxa.arg = arg;
57 new->func.cxa.dso_handle = d;
58 new->flavor = ef_cxa;
59 __libc_lock_unlock (__exit_funcs_lock);
60 return 0;
61 }
62
63
64 /* Register a function to be called by exit or when a shared library
65 is unloaded. This function is only called from code generated by
66 the C++ compiler. */
67 int
__cxa_atexit(void (* func)(void *),void * arg,void * d)68 __cxa_atexit (void (*func) (void *), void *arg, void *d)
69 {
70 return __internal_atexit (func, arg, d, &__exit_funcs);
71 }
72 libc_hidden_def (__cxa_atexit)
73
74
75 static struct exit_function_list initial;
76 struct exit_function_list *__exit_funcs = &initial;
77 uint64_t __new_exitfn_called;
78
79 /* Must be called with __exit_funcs_lock held. */
80 struct exit_function *
__new_exitfn(struct exit_function_list ** listp)81 __new_exitfn (struct exit_function_list **listp)
82 {
83 struct exit_function_list *p = NULL;
84 struct exit_function_list *l;
85 struct exit_function *r = NULL;
86 size_t i = 0;
87
88 if (__exit_funcs_done)
89 /* Exit code is finished processing all registered exit functions,
90 therefore we fail this registration. */
91 return NULL;
92
93 for (l = *listp; l != NULL; p = l, l = l->next)
94 {
95 for (i = l->idx; i > 0; --i)
96 if (l->fns[i - 1].flavor != ef_free)
97 break;
98
99 if (i > 0)
100 break;
101
102 /* This block is completely unused. */
103 l->idx = 0;
104 }
105
106 if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
107 {
108 /* The last entry in a block is used. Use the first entry in
109 the previous block if it exists. Otherwise create a new one. */
110 if (p == NULL)
111 {
112 assert (l != NULL);
113 p = (struct exit_function_list *)
114 calloc (1, sizeof (struct exit_function_list));
115 if (p != NULL)
116 {
117 p->next = *listp;
118 *listp = p;
119 }
120 }
121
122 if (p != NULL)
123 {
124 r = &p->fns[0];
125 p->idx = 1;
126 }
127 }
128 else
129 {
130 /* There is more room in the block. */
131 r = &l->fns[i];
132 l->idx = i + 1;
133 }
134
135 /* Mark entry as used, but we don't know the flavor now. */
136 if (r != NULL)
137 {
138 r->flavor = ef_us;
139 ++__new_exitfn_called;
140 }
141
142 return r;
143 }
144