dlfcn/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995-2000,2002,2003,2004,2005 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <libintl.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <bits/libc-lock.h>
  26 #include <ldsodefs.h>
  27
  28 #if !defined SHARED && defined IS_IN_libdl
  29
  30 char *
  31 dlerror (void)
  32 {
  33   return __dlerror ();
  34 }
  35
  36 #else
  37
  38 /* Type for storing results of dynamic loading actions.  */
  39 struct dl_action_result
  40   {
  41     int errcode;
  42     int returned;
  43     const char *objname;
  44     const char *errstring;
  45   };
  46 static struct dl_action_result last_result;
  47 static struct dl_action_result *static_buf;
  48
  49 /* This is the key for the thread specific memory.  */
  50 static __libc_key_t key;
  51 __libc_once_define (static, once);
  52
  53 /* Destructor for the thread-specific data.  */
  54 static void init (void);
  55 static void free_key_mem (void *mem);
  56
  57
  58 char *
  59 __dlerror (void)
  60 {
  61   char *buf = NULL;
  62   struct dl_action_result *result;
  63
  64 # ifdef SHARED
  65   if (__builtin_expect (_dlfcn_hook != NULL, 0))
  66     return _dlfcn_hook->dlerror ();
  67 # endif
  68
  69   /* If we have not yet initialized the buffer do it now.  */
  70   __libc_once (once, init);
  71
  72   /* Get error string.  */
  73   result = (struct dl_action_result *) __libc_getspecific (key);
  74   if (result == NULL)
  75     result = &last_result;
  76
  77   /* Test whether we already returned the string.  */
  78   if (result->returned != 0)
  79     {
  80       /* We can now free the string.  */
  81       if (result->errstring != NULL)
  82         {
  83           if (strcmp (result->errstring, "out of memory") != 0)
  84             free ((char *) result->errstring);
  85           result->errstring = NULL;
  86         }
  87     }
  88   else if (result->errstring != NULL)
  89     {
  90       buf = (char *) result->errstring;
  91       int n;
  92       if (result->errcode == 0)
  93         n = __asprintf (&buf, "%s%s%s",
  94                         result->objname,
  95                         result->objname[0] == '\0' ? "" : ": ",
  96                         _(result->errstring));
  97       else
  98         n = __asprintf (&buf, "%s%s%s: %s",
  99                         result->objname,
 100                         result->objname[0] == '\0' ? "" : ": ",
 101                         _(result->errstring),
 102                         strerror (result->errcode));
 103       if (n != -1)
 104         {
 105           /* We don't need the error string anymore.  */
 106           if (strcmp (result->errstring, "out of memory") != 0)
 107             free ((char *) result->errstring);
 108           result->errstring = buf;
 109         }
 110
 111       /* Mark the error as returned.  */
 112       result->returned = 1;
 113     }
 114
 115   return buf;
 116 }
 117 # ifdef SHARED
 118 strong_alias (__dlerror, dlerror)
 119 # endif
 120
 121 int
 122 internal_function
 123 _dlerror_run (void (*operate) (void *), void *args)
 124 {
 125   struct dl_action_result *result;
 126
 127   /* If we have not yet initialized the buffer do it now.  */
 128   __libc_once (once, init);
 129
 130   /* Get error string and number.  */
 131   if (static_buf != NULL)
 132     result = static_buf;
 133   else
 134     {
 135       /* We don't use the static buffer and so we have a key.  Use it
 136          to get the thread-specific buffer.  */
 137       result = __libc_getspecific (key);
 138       if (result == NULL)
 139         {
 140           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 141           if (result == NULL)
 142             /* We are out of memory.  Since this is no really critical
 143                situation we carry on by using the global variable.
 144                This might lead to conflicts between the threads but
 145                they soon all will have memory problems.  */
 146             result = &last_result;
 147           else
 148             /* Set the tsd.  */
 149             __libc_setspecific (key, result);
 150         }
 151     }
 152
 153   if (result->errstring != NULL)
 154     {
 155       /* Free the error string from the last failed command.  This can
 156          happen if `dlerror' was not run after an error was found.  */
 157       if (strcmp (result->errstring, "out of memory") != 0)
 158         free ((char *) result->errstring);
 159       result->errstring = NULL;
 160     }
 161
 162   result->errcode = GLRO(dl_catch_error) (&result->objname, &result->errstring,
 163                                           operate, args);
 164
 165   /* If no error we mark that no error string is available.  */
 166   result->returned = result->errstring == NULL;
 167
 168   return result->errstring != NULL;
 169 }
 170
 171
 172 /* Initialize buffers for results.  */
 173 static void
 174 init (void)
 175 {
 176   if (__libc_key_create (&key, free_key_mem))
 177     /* Creating the key failed.  This means something really went
 178        wrong.  In any case use a static buffer which is better than
 179        nothing.  */
 180     static_buf = &last_result;
 181 }
 182
 183
 184 static void
 185 check_free (struct dl_action_result *rec)
 186 {
 187   if (rec->errstring != NULL
 188       && strcmp (rec->errstring, "out of memory") != 0)
 189     {
 190       /* We can free the string only if the allocation happened in the
 191          C library used by the dynamic linker.  This means, it is
 192          always the C library in the base namespave.  */
 193       struct link_map *map = NULL;
 194       Dl_info info;
 195       if (_dl_addr (check_free, &info, &map, NULL) != 0
 196           && map != NULL && map->l_ns == 0)
 197         free ((char *) rec->errstring);
 198     }
 199 }
 200
 201
 202 static void
 203 __attribute__ ((destructor))
 204 fini (void)
 205 {
 206   check_free (&last_result);
 207 }
 208
 209
 210 /* Free the thread specific data, this is done if a thread terminates.  */
 211 static void
 212 free_key_mem (void *mem)
 213 {
 214   check_free ((struct dl_action_result *) mem);
 215
 216   free (mem);
 217   __libc_setspecific (key, NULL);
 218 }
 219
 220 # ifdef SHARED
 221
 222 struct dlfcn_hook *_dlfcn_hook __attribute__((nocommon));
 223 libdl_hidden_data_def (_dlfcn_hook)
 224
 225 # else
 226
 227 static struct dlfcn_hook _dlfcn_hooks =
 228   {
 229     .dlopen = __dlopen,
 230     .dlclose = __dlclose,
 231     .dlsym = __dlsym,
 232     .dlvsym = __dlvsym,
 233     .dlerror = __dlerror,
 234     .dladdr = __dladdr,
 235     .dladdr1 = __dladdr1,
 236     .dlinfo = __dlinfo,
 237     .dlmopen = __dlmopen
 238   };
 239
 240 void
 241 __libc_register_dlfcn_hook (struct link_map *map)
 242 {
 243   struct dlfcn_hook **hook;
 244
 245   hook = (struct dlfcn_hook **) __libc_dlsym_private (map, "_dlfcn_hook");
 246   if (hook != NULL)
 247     *hook = &_dlfcn_hooks;
 248 }
 249 # endif
 250 #endif