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6973fc01 | 1 | /* Handle loading/unloading of shared object for transformation. |
bfff8b1b | 2 | Copyright (C) 1997-2017 Free Software Foundation, Inc. |
6973fc01 UD |
3 | This file is part of the GNU C Library. |
4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. | |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
41bdb6e2 AJ |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
6973fc01 UD |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
41bdb6e2 | 14 | Lesser General Public License for more details. |
6973fc01 | 15 | |
41bdb6e2 | 16 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 PE |
17 | License along with the GNU C Library; if not, see |
18 | <http://www.gnu.org/licenses/>. */ | |
6973fc01 | 19 | |
add40772 | 20 | #include <assert.h> |
6973fc01 | 21 | #include <dlfcn.h> |
6973fc01 | 22 | #include <inttypes.h> |
6973fc01 UD |
23 | #include <search.h> |
24 | #include <stdlib.h> | |
25 | #include <string.h> | |
ec999b8e | 26 | #include <libc-lock.h> |
6973fc01 UD |
27 | #include <sys/param.h> |
28 | ||
e62c19f1 | 29 | #include <gconv_int.h> |
915a6c51 | 30 | #include <sysdep.h> |
e62c19f1 | 31 | |
76a2102b UD |
32 | |
33 | #ifdef DEBUG | |
34 | /* For debugging purposes. */ | |
35 | static void print_all (void); | |
36 | #endif | |
37 | ||
38 | ||
6973fc01 UD |
39 | /* This is a tuning parameter. If a transformation module is not used |
40 | anymore it gets not immediately unloaded. Instead we wait a certain | |
41 | number of load attempts for further modules. If none of the | |
42 | subsequent load attempts name the same object it finally gets unloaded. | |
43 | Otherwise it is still available which hopefully is the frequent case. | |
44 | The following number is the number of unloading attempts we wait | |
45 | before unloading. */ | |
46 | #define TRIES_BEFORE_UNLOAD 2 | |
47 | ||
6973fc01 UD |
48 | /* Array of loaded objects. This is shared by all threads so we have |
49 | to use semaphores to access it. */ | |
50 | static void *loaded; | |
6973fc01 | 51 | |
6973fc01 UD |
52 | /* Comparison function for searching `loaded_object' tree. */ |
53 | static int | |
54 | known_compare (const void *p1, const void *p2) | |
55 | { | |
d64b6ad0 UD |
56 | const struct __gconv_loaded_object *s1 = |
57 | (const struct __gconv_loaded_object *) p1; | |
58 | const struct __gconv_loaded_object *s2 = | |
59 | (const struct __gconv_loaded_object *) p2; | |
6973fc01 | 60 | |
76a2102b | 61 | return strcmp (s1->name, s2->name); |
6973fc01 UD |
62 | } |
63 | ||
6973fc01 UD |
64 | /* Open the gconv database if necessary. A non-negative return value |
65 | means success. */ | |
d64b6ad0 | 66 | struct __gconv_loaded_object * |
e62c19f1 | 67 | internal_function |
6973fc01 UD |
68 | __gconv_find_shlib (const char *name) |
69 | { | |
d64b6ad0 | 70 | struct __gconv_loaded_object *found; |
7a68c94a | 71 | void *keyp; |
6973fc01 UD |
72 | |
73 | /* Search the tree of shared objects previously requested. Data in | |
74 | the tree are `loaded_object' structures, whose first member is a | |
75 | `const char *', the lookup key. The search returns a pointer to | |
76 | the tree node structure; the first member of the is a pointer to | |
77 | our structure (i.e. what will be a `loaded_object'); since the | |
78 | first member of that is the lookup key string, &FCT_NAME is close | |
79 | enough to a pointer to our structure to use as a lookup key that | |
80 | will be passed to `known_compare' (above). */ | |
81 | ||
7a68c94a UD |
82 | keyp = __tfind (&name, &loaded, known_compare); |
83 | if (keyp == NULL) | |
6973fc01 UD |
84 | { |
85 | /* This name was not known before. */ | |
0db59742 UD |
86 | size_t namelen = strlen (name) + 1; |
87 | ||
88 | found = malloc (sizeof (struct __gconv_loaded_object) + namelen); | |
6973fc01 UD |
89 | if (found != NULL) |
90 | { | |
91 | /* Point the tree node at this new structure. */ | |
0db59742 | 92 | found->name = (char *) memcpy (found + 1, name, namelen); |
6973fc01 UD |
93 | found->counter = -TRIES_BEFORE_UNLOAD - 1; |
94 | found->handle = NULL; | |
95 | ||
365afefc UD |
96 | if (__builtin_expect (__tsearch (found, &loaded, known_compare) |
97 | == NULL, 0)) | |
6973fc01 UD |
98 | { |
99 | /* Something went wrong while inserting the entry. */ | |
100 | free (found); | |
101 | found = NULL; | |
102 | } | |
103 | } | |
104 | } | |
7a68c94a | 105 | else |
d64b6ad0 | 106 | found = *(struct __gconv_loaded_object **) keyp; |
6973fc01 UD |
107 | |
108 | /* Try to load the shared object if the usage count is 0. This | |
109 | implies that if the shared object is not loadable, the handle is | |
110 | NULL and the usage count > 0. */ | |
111 | if (found != NULL) | |
112 | { | |
113 | if (found->counter < -TRIES_BEFORE_UNLOAD) | |
114 | { | |
fc5f4a97 | 115 | assert (found->handle == NULL); |
b3fc5f84 UD |
116 | found->handle = __libc_dlopen (found->name); |
117 | if (found->handle != NULL) | |
0d9f6793 | 118 | { |
b3fc5f84 | 119 | found->fct = __libc_dlsym (found->handle, "gconv"); |
0d9f6793 UD |
120 | if (found->fct == NULL) |
121 | { | |
122 | /* Argh, no conversion function. There is something | |
123 | wrong here. */ | |
124 | __gconv_release_shlib (found); | |
125 | found = NULL; | |
126 | } | |
127 | else | |
128 | { | |
b3fc5f84 UD |
129 | found->init_fct = __libc_dlsym (found->handle, "gconv_init"); |
130 | found->end_fct = __libc_dlsym (found->handle, "gconv_end"); | |
0d9f6793 | 131 | |
915a6c51 UD |
132 | #ifdef PTR_MANGLE |
133 | PTR_MANGLE (found->fct); | |
134 | if (found->init_fct != NULL) | |
135 | PTR_MANGLE (found->init_fct); | |
136 | if (found->end_fct != NULL) | |
137 | PTR_MANGLE (found->end_fct); | |
138 | #endif | |
139 | ||
0d9f6793 UD |
140 | /* We have succeeded in loading the shared object. */ |
141 | found->counter = 1; | |
142 | } | |
143 | } | |
144 | else | |
145 | /* Error while loading the shared object. */ | |
146 | found = NULL; | |
6973fc01 UD |
147 | } |
148 | else if (found->handle != NULL) | |
149 | found->counter = MAX (found->counter + 1, 1); | |
6973fc01 UD |
150 | } |
151 | ||
0d9f6793 | 152 | return found; |
6973fc01 UD |
153 | } |
154 | ||
155 | ||
156 | /* This is very ugly but the tsearch functions provide no way to pass | |
157 | information to the walker function. So we use a global variable. | |
158 | It is MT safe since we use a lock. */ | |
d64b6ad0 | 159 | static struct __gconv_loaded_object *release_handle; |
6973fc01 UD |
160 | |
161 | static void | |
17427edd | 162 | do_release_shlib (void *nodep, VISIT value, int level) |
6973fc01 | 163 | { |
d64b6ad0 | 164 | struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep; |
6973fc01 UD |
165 | |
166 | if (value != preorder && value != leaf) | |
167 | return; | |
168 | ||
0d9f6793 | 169 | if (obj == release_handle) |
add40772 UD |
170 | { |
171 | /* This is the object we want to unload. Now decrement the | |
172 | reference counter. */ | |
173 | assert (obj->counter > 0); | |
174 | --obj->counter; | |
175 | } | |
fc5f4a97 UD |
176 | else if (obj->counter <= 0 && obj->counter >= -TRIES_BEFORE_UNLOAD |
177 | && --obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL) | |
6973fc01 | 178 | { |
fc5f4a97 UD |
179 | /* Unload the shared object. */ |
180 | __libc_dlclose (obj->handle); | |
181 | obj->handle = NULL; | |
6973fc01 UD |
182 | } |
183 | } | |
184 | ||
185 | ||
186 | /* Notify system that a shared object is not longer needed. */ | |
b79f74cd | 187 | void |
e62c19f1 | 188 | internal_function |
d64b6ad0 | 189 | __gconv_release_shlib (struct __gconv_loaded_object *handle) |
6973fc01 | 190 | { |
6973fc01 UD |
191 | /* Urgh, this is ugly but we have no other possibility. */ |
192 | release_handle = handle; | |
193 | ||
194 | /* Process all entries. Please note that we also visit entries | |
195 | with release counts <= 0. This way we can finally unload them | |
196 | if necessary. */ | |
17427edd | 197 | __twalk (loaded, (__action_fn_t) do_release_shlib); |
6973fc01 | 198 | } |
e6df9a56 UD |
199 | |
200 | ||
201 | /* We run this if we debug the memory allocation. */ | |
7c11c4a1 | 202 | static void __libc_freeres_fn_section |
74454183 | 203 | do_release_all (void *nodep) |
e6df9a56 | 204 | { |
d64b6ad0 | 205 | struct __gconv_loaded_object *obj = (struct __gconv_loaded_object *) nodep; |
e6df9a56 | 206 | |
b3fc5f84 | 207 | /* Unload the shared object. */ |
74454183 | 208 | if (obj->handle != NULL) |
9a0a9895 | 209 | __libc_dlclose (obj->handle); |
e6df9a56 UD |
210 | |
211 | free (obj); | |
212 | } | |
213 | ||
c877418f | 214 | libc_freeres_fn (free_mem) |
e6df9a56 | 215 | { |
74454183 | 216 | __tdestroy (loaded, do_release_all); |
f6e50e66 | 217 | loaded = NULL; |
e6df9a56 | 218 | } |
76a2102b UD |
219 | |
220 | ||
221 | #ifdef DEBUG | |
f2b3078e MS |
222 | |
223 | #include <stdio.h> | |
224 | ||
76a2102b UD |
225 | static void |
226 | do_print (const void *nodep, VISIT value, int level) | |
227 | { | |
228 | struct __gconv_loaded_object *obj = *(struct __gconv_loaded_object **) nodep; | |
229 | ||
230 | printf ("%10s: \"%s\", %d\n", | |
231 | value == leaf ? "leaf" : | |
232 | value == preorder ? "preorder" : | |
233 | value == postorder ? "postorder" : "endorder", | |
234 | obj->name, obj->counter); | |
235 | } | |
236 | ||
f2b3078e | 237 | static void __attribute__ ((used)) |
76a2102b UD |
238 | print_all (void) |
239 | { | |
240 | __twalk (loaded, do_print); | |
241 | } | |
242 | #endif |