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 <link.h>
  21 #include <dlfcn.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <stdlib.h>
  25 #include <bits/libc-lock.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   if (__libc_internal_tsd_get != NULL)
  60     {
  61       result = (struct dl_action_result *) __libc_getspecific (key);
  62       if (result == NULL)
  63         result = &last_result;
  64     }
  65   else
  66     result = &last_result;
  67
  68   if (! result->errstring)
  69     return NULL;
  70
  71   if (result->errcode == 0)
  72     buf = result->errstring;
  73   else
  74     {
  75       if (asprintf (&buf, "%s: %s",
  76                     result->errstring, strerror (result->errcode)) == -1)
  77         buf = NULL;
  78
  79       /* We don't need the error string anymore.  */
  80       free (result->errstring);
  81     }
  82
  83   /* Reset the error indicator.  */
  84   result->errstring = NULL;
  85
  86   return buf;
  87 }
  88
  89 int
  90 _dlerror_run (void (*operate) (void *), void *args)
  91 {
  92   __libc_once_define (static, once);
  93   struct dl_action_result *result;
  94
  95   /* If we have not yet initialized the buffer do it now.  */
  96   __libc_once (once, init);
  97
  98   /* Get error string and number.  */
  99   if (static_buf != NULL)
 100     result = static_buf;
 101   else
 102     {
 103       /* We don't use the static buffer and so we have a key.  Use it
 104          to get the thread-specific buffer.  */
 105       result = __libc_getspecific (key);
 106       if (result == NULL)
 107         {
 108           result = (struct dl_action_result *) calloc (1, sizeof (*result));
 109           if (result == NULL)
 110             /* We are out of memory.  Since this is no really critical
 111                situation we carry on by using the global variable.
 112                This might lead to conflicts between the threads but
 113                they soon all will have memory problems.  */
 114             result = &last_result;
 115           else
 116             /* Set the tsd.  */
 117             __libc_setspecific (key, result);
 118         }
 119     }
 120
 121   if (result->errstring != NULL)
 122     /* Free the error string from the last failed command.  This can
 123        happen if `dlerror' was not run after an error was found.  */
 124     free (result->errstring);
 125
 126   result->errcode = _dl_catch_error (&result->errstring, operate, args);
 127
 128   return result->errstring != NULL;
 129 }
 130
 131
 132 /* Initialize buffers for results.  */
 133 static void
 134 init (void)
 135 {
 136   if (__libc_key_create (&key, free_key_mem))
 137     /* Creating the key failed.  This means something really went
 138        wrong.  In any case use a static buffer which is better than
 139        nothing.  */
 140     static_buf = &last_result;
 141 }
 142
 143
 144 /* Free the thread specific data, this is done if a thread terminates.  */
 145 static void
 146 free_key_mem (void *mem)
 147 {
 148   free (mem);
 149   __libc_setspecific (key, NULL);
 150 }