elf/dl-libc.c

   1 /* Handle loading and unloading shared objects for internal libc purposes.
   2    Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Zack Weinberg <zack@rabi.columbia.edu>, 1999.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   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.
  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
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <ldsodefs.h>
  24
  25 /* The purpose of this file is to provide wrappers around the dynamic
  26    linker error mechanism (similar to dlopen() et al in libdl) which
  27    are usable from within libc.  Generally we want to throw away the
  28    string that dlerror() would return and just pass back a null pointer
  29    for errors.  This also lets the rest of libc not know about the error
  30    handling mechanism.
  31
  32    Much of this code came from gconv_dl.c with slight modifications. */
  33
  34 static int
  35 internal_function
  36 dlerror_run (void (*operate) (void *), void *args)
  37 {
  38   const char *objname;
  39   const char *last_errstring = NULL;
  40   int result;
  41
  42   (void) _dl_catch_error (&objname, &last_errstring, operate, args);
  43
  44   result = last_errstring != NULL;
  45   if (result && last_errstring != _dl_out_of_memory)
  46     free ((char *) last_errstring);
  47
  48   return result;
  49 }
  50
  51 /* These functions are called by dlerror_run... */
  52
  53 struct do_dlopen_args
  54 {
  55   /* Argument to do_dlopen.  */
  56   const char *name;
  57
  58   /* Return from do_dlopen.  */
  59   struct link_map *map;
  60 };
  61
  62 struct do_dlsym_args
  63 {
  64   /* Arguments to do_dlsym.  */
  65   struct link_map *map;
  66   const char *name;
  67
  68   /* Return values of do_dlsym.  */
  69   lookup_t loadbase;
  70   const ElfW(Sym) *ref;
  71 };
  72
  73 static void
  74 do_dlopen (void *ptr)
  75 {
  76   struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
  77   /* Open and relocate the shared object.  */
  78   args->map = _dl_open (args->name, RTLD_LAZY, NULL);
  79 }
  80
  81 static void
  82 do_dlsym (void *ptr)
  83 {
  84   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
  85   args->ref = NULL;
  86   args->loadbase = _dl_lookup_symbol (args->name, args->map, &args->ref,
  87                                       args->map->l_local_scope, 0,
  88                                       DL_LOOKUP_RETURN_NEWEST);
  89 }
  90
  91 static void
  92 do_dlclose (void *ptr)
  93 {
  94   _dl_close ((struct link_map *) ptr);
  95 }
  96
  97 /* ... and these functions call dlerror_run. */
  98
  99 void *
 100 __libc_dlopen (const char *__name)
 101 {
 102   struct do_dlopen_args args;
 103   args.name = __name;
 104
 105   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 106 }
 107
 108 void *
 109 __libc_dlsym (void *__map, const char *__name)
 110 {
 111   struct do_dlsym_args args;
 112   args.map = __map;
 113   args.name = __name;
 114
 115   return (dlerror_run (do_dlsym, &args) ? NULL
 116           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 117 }
 118
 119 int
 120 __libc_dlclose (void *__map)
 121 {
 122   return dlerror_run (do_dlclose, __map);
 123 }
 124
 125
 126 static void
 127 free_mem (void)
 128 {
 129   struct link_map *l;
 130   struct r_search_path_elem *d;
 131
 132   /* Remove all search directories.  */
 133   d = GL(dl_all_dirs);
 134   while (d != GL(dl_init_all_dirs))
 135     {
 136       struct r_search_path_elem *old = d;
 137       d = d->next;
 138       free (old);
 139     }
 140
 141   /* Remove all additional names added to the objects.  */
 142   for (l = GL(dl_loaded); l != NULL; l = l->l_next)
 143     {
 144       struct libname_list *lnp = l->l_libname->next;
 145
 146       l->l_libname->next = NULL;
 147
 148       while (lnp != NULL)
 149         {
 150           struct libname_list *old = lnp;
 151           lnp = lnp->next;
 152           if (! old->dont_free)
 153             free (old);
 154         }
 155     }
 156 }
 157 text_set_element (__libc_subfreeres, free_mem);