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-rw-r--r--iconv/gconv_dl.c254
1 files changed, 254 insertions, 0 deletions
diff --git a/iconv/gconv_dl.c b/iconv/gconv_dl.c
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--- /dev/null
+++ b/iconv/gconv_dl.c
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+/* Handle loading/unloading of shared object for transformation.
+ Copyright (C) 1997 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <dlfcn.h>
+#include <gconv.h>
+#include <inttypes.h>
+#include <link.h>
+#include <search.h>
+#include <stdlib.h>
+#include <string.h>
+#include <bits/libc-lock.h>
+#include <sys/param.h>
+
+
+/* This is a tuning parameter. If a transformation module is not used
+ anymore it gets not immediately unloaded. Instead we wait a certain
+ number of load attempts for further modules. If none of the
+ subsequent load attempts name the same object it finally gets unloaded.
+ Otherwise it is still available which hopefully is the frequent case.
+ The following number is the number of unloading attempts we wait
+ before unloading. */
+#define TRIES_BEFORE_UNLOAD 2
+
+
+/* Structure describing one loaded shared object. This normally are
+ objects to perform conversation but as a special case the db shared
+ object is also handled. */
+struct loaded_object
+{
+ /* Name of the object. */
+ const char *name;
+
+ /* Reference counter for the db functionality. If no conversion is
+ needed we unload the db library. */
+ int counter;
+
+ /* The handle for the shared object. */
+ void *handle;
+};
+
+
+/* Array of loaded objects. This is shared by all threads so we have
+ to use semaphores to access it. */
+static void *loaded;
+__libc_lock_define_initialized (static, lock)
+
+
+
+/* Comparison function for searching `loaded_object' tree. */
+static int
+known_compare (const void *p1, const void *p2)
+{
+ const struct loaded_object *s1 = (const struct loaded_object *) p1;
+ const struct loaded_object *s2 = (const struct loaded_object *) p2;
+
+ return (intptr_t) s1->handle - (intptr_t) s2->handle;
+}
+
+
+static void
+do_open (void *a)
+{
+ struct loaded_object *args = (struct loaded_object *) a;
+ /* Open and relocate the shared object. */
+ args->handle = _dl_open (args->name, RTLD_LAZY);
+}
+
+
+static int
+dlerror_run (void (*operate) (void *), void *args)
+{
+ char *last_errstring = NULL;
+ const char *last_object_name = NULL;
+ int result;
+
+ (void) _dl_catch_error (&last_errstring, &last_object_name, operate, args);
+
+ result = last_errstring != NULL;
+ if (result)
+ free (last_errstring);
+
+ return result;
+}
+
+
+struct get_sym_args
+{
+ /* Arguments to get_sym. */
+ struct link_map *map;
+ const char *name;
+
+ /* Return values of get_sym. */
+ ElfW(Addr) loadbase;
+ const ElfW(Sym) *ref;
+};
+
+static void
+get_sym (void *a)
+{
+ struct get_sym_args *args = (struct get_sym_args *) a;
+ struct link_map *scope[2] = { args->map, NULL };
+ args->ref = NULL;
+ args->loadbase = _dl_lookup_symbol (args->name, &args->ref,
+ scope, args->map->l_name, 0);
+}
+
+
+void *
+__gconv_find_func (void *handle, const char *name)
+{
+ struct get_sym_args args;
+
+ args.map = handle;
+ args.name = name;
+
+ return (dlerror_run (get_sym, &args) ? NULL
+ : (void *) (args.loadbase + args.ref->st_value));
+}
+
+
+
+/* Open the gconv database if necessary. A non-negative return value
+ means success. */
+void *
+__gconv_find_shlib (const char *name)
+{
+ void *result = NULL;
+ struct loaded_object *found;
+
+ /* Acquire the lock. */
+ __libc_lock_lock (lock);
+
+ /* Search the tree of shared objects previously requested. Data in
+ the tree are `loaded_object' structures, whose first member is a
+ `const char *', the lookup key. The search returns a pointer to
+ the tree node structure; the first member of the is a pointer to
+ our structure (i.e. what will be a `loaded_object'); since the
+ first member of that is the lookup key string, &FCT_NAME is close
+ enough to a pointer to our structure to use as a lookup key that
+ will be passed to `known_compare' (above). */
+
+ found = __tfind (&name, loaded, known_compare);
+ if (found == NULL)
+ {
+ /* This name was not known before. */
+ found = malloc (sizeof (struct loaded_object));
+ if (found != NULL)
+ {
+ /* Point the tree node at this new structure. */
+ found->name = name;
+ found->counter = -TRIES_BEFORE_UNLOAD - 1;
+ found->handle = NULL;
+
+ if (__tsearch (found, &loaded, known_compare) == NULL)
+ {
+ /* Something went wrong while inserting the entry. */
+ free (found);
+ found = NULL;
+ }
+ }
+ }
+
+ /* Try to load the shared object if the usage count is 0. This
+ implies that if the shared object is not loadable, the handle is
+ NULL and the usage count > 0. */
+ if (found != NULL)
+ {
+ if (found->counter < -TRIES_BEFORE_UNLOAD)
+ {
+ if (dlerror_run (do_open, found) == 0)
+ found->counter = 1;
+ }
+ else if (found->handle != NULL)
+ found->counter = MAX (found->counter + 1, 1);
+
+ result = found->handle;
+ }
+
+ /* Release the lock. */
+ __libc_lock_unlock (lock);
+
+ return result;
+}
+
+
+/* This is very ugly but the tsearch functions provide no way to pass
+ information to the walker function. So we use a global variable.
+ It is MT safe since we use a lock. */
+static void *release_handle;
+
+static void
+do_release_shlib (const void *nodep, VISIT value, int level)
+{
+ struct loaded_object *obj = (struct loaded_object *) nodep;
+
+ if (value != preorder && value != leaf)
+ return;
+
+ if (obj->handle == release_handle)
+ /* This is the object we want to unload. Now set the release
+ counter to zero. */
+ obj->counter = 0;
+ else if (obj->counter <= 0)
+ {
+ if (--obj->counter < -TRIES_BEFORE_UNLOAD && obj->handle != NULL)
+ {
+ /* Unload the shared object. We don't use the trick to
+ catch errors since in the case an error is signalled
+ something is really wrong. */
+ _dl_close ((struct link_map *) obj->handle);
+
+ obj->handle = NULL;
+ }
+ }
+}
+
+
+/* Notify system that a shared object is not longer needed. */
+int
+__gconv_release_shlib (void *handle)
+{
+ /* Acquire the lock. */
+ __libc_lock_lock (lock);
+
+ /* Urgh, this is ugly but we have no other possibility. */
+ release_handle = handle;
+
+ /* Process all entries. Please note that we also visit entries
+ with release counts <= 0. This way we can finally unload them
+ if necessary. */
+ __twalk (loaded, do_release_shlib);
+
+ /* Release the lock. */
+ __libc_lock_unlock (lock);
+
+ return GCONV_OK;
+}