diff options
Diffstat (limited to 'iconv/gconv_dl.c')
| -rw-r--r-- | iconv/gconv_dl.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/iconv/gconv_dl.c b/iconv/gconv_dl.c new file mode 100644 index 0000000000..a0003a82db --- /dev/null +++ b/iconv/gconv_dl.c @@ -0,0 +1,254 @@ +/* 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; +} |