debug/backtracesyms.c

   1 /* Return list with names for address in backtrace.
   2    Copyright (C) 1998-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <execinfo.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25
  26 #include <ldsodefs.h>
  27
  28 #if __ELF_NATIVE_CLASS == 32
  29 # define WORD_WIDTH 8
  30 #else
  31 /* We assume 64bits.  */
  32 # define WORD_WIDTH 16
  33 #endif
  34
  35
  36 char **
  37 __backtrace_symbols (array, size)
  38      void *const *array;
  39      int size;
  40 {
  41   Dl_info info[size];
  42   int status[size];
  43   int cnt;
  44   size_t total = 0;
  45   char **result;
  46
  47   /* Fill in the information we can get from `dladdr'.  */
  48   for (cnt = 0; cnt < size; ++cnt)
  49     {
  50       struct link_map *map;
  51       status[cnt] = _dl_addr (array[cnt], &info[cnt], &map, NULL);
  52       if (status[cnt] && info[cnt].dli_fname && info[cnt].dli_fname[0] != '\0')
  53         {
  54           /* We have some info, compute the length of the string which will be
  55              "<file-name>(<sym-name>+offset) [address].  */
  56           total += (strlen (info[cnt].dli_fname ?: "")
  57                     + strlen (info[cnt].dli_sname ?: "")
  58                     + 3 + WORD_WIDTH + 3 + WORD_WIDTH + 5);
  59
  60           /* The load bias is more useful to the user than the load
  61              address.  The use of these addresses is to calculate an
  62              address in the ELF file, so its prelinked bias is not
  63              something we want to subtract out.  */
  64           info[cnt].dli_fbase = (void *) map->l_addr;
  65         }
  66       else
  67         total += 5 + WORD_WIDTH;
  68     }
  69
  70   /* Allocate memory for the result.  */
  71   result = (char **) malloc (size * sizeof (char *) + total);
  72   if (result != NULL)
  73     {
  74       char *last = (char *) (result + size);
  75
  76       for (cnt = 0; cnt < size; ++cnt)
  77         {
  78           result[cnt] = last;
  79
  80           if (status[cnt]
  81               && info[cnt].dli_fname != NULL && info[cnt].dli_fname[0] != '\0')
  82             {
  83               if (info[cnt].dli_sname == NULL)
  84                 /* We found no symbol name to use, so describe it as
  85                    relative to the file.  */
  86                 info[cnt].dli_saddr = info[cnt].dli_fbase;
  87
  88               if (info[cnt].dli_sname == NULL && info[cnt].dli_saddr == 0)
  89                 last += 1 + sprintf (last, "%s(%s) [%p]",
  90                                      info[cnt].dli_fname ?: "",
  91                                      info[cnt].dli_sname ?: "",
  92                                      array[cnt]);
  93               else
  94                 {
  95                   char sign;
  96                   ptrdiff_t offset;
  97                   if (array[cnt] >= (void *) info[cnt].dli_saddr)
  98                     {
  99                       sign = '+';
 100                       offset = array[cnt] - info[cnt].dli_saddr;
 101                     }
 102                   else
 103                     {
 104                       sign = '-';
 105                       offset = info[cnt].dli_saddr - array[cnt];
 106                     }
 107
 108                   last += 1 + sprintf (last, "%s(%s%c%#tx) [%p]",
 109                                        info[cnt].dli_fname ?: "",
 110                                        info[cnt].dli_sname ?: "",
 111                                        sign, offset, array[cnt]);
 112                 }
 113             }
 114           else
 115             last += 1 + sprintf (last, "[%p]", array[cnt]);
 116         }
 117       assert (last <= (char *) result + size * sizeof (char *) + total);
 118     }
 119
 120   return result;
 121 }
 122 weak_alias (__backtrace_symbols, backtrace_symbols)