1 /* Handle loading/unloading of shared object for transformation.
2 Copyright (C) 1997, 1998 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public License as
8 published by the Free Software Foundation; either version 2 of the
9 License, or (at your option) any later version.
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
14 Library General Public License for more details.
16 You should have received a copy of the GNU Library General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
26 #include <bits/libc-lock.h>
27 #include <elf/ldsodefs.h>
28 #include <sys/param.h>
30 #include <gconv_int.h>
33 /* This is a tuning parameter. If a transformation module is not used
34 anymore it gets not immediately unloaded. Instead we wait a certain
35 number of load attempts for further modules. If none of the
36 subsequent load attempts name the same object it finally gets unloaded.
37 Otherwise it is still available which hopefully is the frequent case.
38 The following number is the number of unloading attempts we wait
40 #define TRIES_BEFORE_UNLOAD 2
43 /* Array of loaded objects. This is shared by all threads so we have
44 to use semaphores to access it. */
49 /* Comparison function for searching `loaded_object' tree. */
51 known_compare (const void *p1, const void *p2)
53 const struct gconv_loaded_object *s1 =
54 (const struct gconv_loaded_object *) p1;
55 const struct gconv_loaded_object *s2 =
56 (const struct gconv_loaded_object *) p2;
58 return (intptr_t) s1->handle - (intptr_t) s2->handle;
65 struct gconv_loaded_object *args = (struct gconv_loaded_object *) a;
66 /* Open and relocate the shared object. */
67 args->handle = _dl_open (args->name, RTLD_LAZY);
73 dlerror_run (void (*operate) (void *), void *args)
75 char *last_errstring = NULL;
78 (void) _dl_catch_error (&last_errstring, operate, args);
80 result = last_errstring != NULL;
82 free (last_errstring);
90 /* Arguments to get_sym. */
94 /* Return values of get_sym. */
103 struct get_sym_args *args = (struct get_sym_args *) a;
104 struct link_map *scope[2] = { args->map, NULL };
106 args->loadbase = _dl_lookup_symbol (args->name, &args->ref,
107 scope, args->map->l_name, 0);
113 find_func (void *handle, const char *name)
115 struct get_sym_args args;
120 return (dlerror_run (get_sym, &args) ? NULL
121 : (void *) (args.loadbase + args.ref->st_value));
126 /* Open the gconv database if necessary. A non-negative return value
128 struct gconv_loaded_object *
130 __gconv_find_shlib (const char *name)
132 struct gconv_loaded_object *found;
134 /* Search the tree of shared objects previously requested. Data in
135 the tree are `loaded_object' structures, whose first member is a
136 `const char *', the lookup key. The search returns a pointer to
137 the tree node structure; the first member of the is a pointer to
138 our structure (i.e. what will be a `loaded_object'); since the
139 first member of that is the lookup key string, &FCT_NAME is close
140 enough to a pointer to our structure to use as a lookup key that
141 will be passed to `known_compare' (above). */
143 found = __tfind (&name, &loaded, known_compare);
146 /* This name was not known before. */
147 found = malloc (sizeof (struct gconv_loaded_object));
150 /* Point the tree node at this new structure. */
152 found->counter = -TRIES_BEFORE_UNLOAD - 1;
153 found->handle = NULL;
155 if (__tsearch (found, &loaded, known_compare) == NULL)
157 /* Something went wrong while inserting the entry. */
164 /* Try to load the shared object if the usage count is 0. This
165 implies that if the shared object is not loadable, the handle is
166 NULL and the usage count > 0. */
169 if (found->counter < -TRIES_BEFORE_UNLOAD)
171 if (dlerror_run (do_open, found) == 0)
173 found->fct = find_func (found->handle, "gconv");
174 if (found->fct == NULL)
176 /* Argh, no conversion function. There is something
178 __gconv_release_shlib (found);
183 found->init_fct = find_func (found->handle, "gconv_init");
184 found->end_fct = find_func (found->handle, "gconv_end");
186 /* We have succeeded in loading the shared object. */
191 /* Error while loading the shared object. */
194 else if (found->handle != NULL)
195 found->counter = MAX (found->counter + 1, 1);
202 /* This is very ugly but the tsearch functions provide no way to pass
203 information to the walker function. So we use a global variable.
204 It is MT safe since we use a lock. */
205 static struct gconv_loaded_object *release_handle;
208 do_release_shlib (const void *nodep, VISIT value, int level)
210 struct gconv_loaded_object *obj = *(struct gconv_loaded_object **) nodep;
212 if (value != preorder && value != leaf)
215 if (obj == release_handle)
216 /* This is the object we want to unload. Now set the release
219 else if (obj->counter <= 0)
221 if (--obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
223 /* Unload the shared object. We don't use the trick to
224 catch errors since in the case an error is signalled
225 something is really wrong. */
226 _dl_close (obj->handle);
234 /* Notify system that a shared object is not longer needed. */
237 __gconv_release_shlib (struct gconv_loaded_object *handle)
239 /* Urgh, this is ugly but we have no other possibility. */
240 release_handle = handle;
242 /* Process all entries. Please note that we also visit entries
243 with release counts <= 0. This way we can finally unload them
245 __twalk (loaded, do_release_shlib);