elf/dlerror.c

   1 /* Return error detail for failing <dlfcn.h> functions.
   2    Copyright (C) 1995, 1996, 1997, 1998 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <bits/libc-lock.h>
  25 #include <elf/ldsodefs.h>
  26
  27
  28 /* Type for storing results of dynamic loading actions.  */
  29 struct dl_action_result
  30   {
  31     int errcode;
  32     char *errstring;
  33   };
  34 static struct dl_action_result last_result;
  35 static struct dl_action_result *static_buf;
  36
  37
  38 /* This is the key for the thread specific memory.  */
  39 static __libc_key_t key;
  40
  41 /* Destructor for the thread-specific data.  */
  42 static void init (void);
  43 static void free_key_mem (void *mem);
  44
  45
  46 char *
  47 dlerror (void)
  48 {
  49   static char *buf;
  50   struct dl_action_result *result;
  51
  52   if (buf)
  53     {
  54       free (buf);
  55       buf = NULL;
  56     }
  57
  58   /* Get error string.  */
  59   result = (struct dl_action_result *) __libc_getspecific (key);
  60   if (result == NULL)
  61     result = &last_result;
  62
  63   if (! result->errstring)
  64     return NULL;
  65
  66   if (result->errcode == 0)
  67     buf = result->errstring;
  68   else
  69     {
  70       if (__asprintf (&buf, "%s: %s",
  71                       result->errstring, strerror (result->errcode)) == -1)
  72         buf = NULL;
  73
  74       /* We don't need the error string anymore.  */
  75       free (result->errstring);
  76     }
  77
  78   /* Reset the error indicator.  */
  79   result->errstring = NULL;
  80
  81   return buf;
  82 }
  83
  84 int
  85 internal_function
  86 _dlerror_run (void (*operate) (void *), void *args)
  87 {
  88   __libc_once_define (static, once);
  89   struct dl_action_result *result;
  90
  91   /* If we have not yet initialized the buffer do it now.  */
  92   __libc_once (once, init);
  93
  94   /* Get error string and number.  */
  95   if (static_buf != NULL)
  96     result = static_buf;
  97   else
  98     {
  99       /* We don't use the static buffer and so we have a key.  Use it
 100          to get the thread-specific buffer.  */
 101       result = __libc_getspecific (key);
 102       if (result == NULL)
 103         {
 104           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 105           if (result == NULL)
 106             /* We are out of memory.  Since this is no really critical
 107                situation we carry on by using the global variable.
 108                This might lead to conflicts between the threads but
 109                they soon all will have memory problems.  */
 110             result = &last_result;
 111           else
 112             /* Set the tsd.  */
 113             __libc_setspecific (key, result);
 114         }
 115     }
 116
 117   if (result->errstring != NULL)
 118     /* Free the error string from the last failed command.  This can
 119        happen if `dlerror' was not run after an error was found.  */
 120     free (result->errstring);
 121
 122   result->errcode = _dl_catch_error (&result->errstring, operate, args);
 123
 124   return result->errstring != NULL;
 125 }
 126
 127
 128 /* Initialize buffers for results.  */
 129 static void
 130 init (void)
 131 {
 132   if (__libc_key_create (&key, free_key_mem))
 133     /* Creating the key failed.  This means something really went
 134        wrong.  In any case use a static buffer which is better than
 135        nothing.  */
 136     static_buf = &last_result;
 137 }
 138
 139
 140 /* Free the thread specific data, this is done if a thread terminates.  */
 141 static void
 142 free_key_mem (void *mem)
 143 {
 144   free (mem);
 145   __libc_setspecific (key, NULL);
 146 }