debug/backtracesyms.c

   1 /* Return list with names for address in backtrace.
   2    Copyright (C) 1998-2017 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 (void *const *array, int size)
  38 {
  39   Dl_info info[size];
  40   int status[size];
  41   int cnt;
  42   size_t total = 0;
  43   char **result;
  44
  45   /* Fill in the information we can get from `dladdr'.  */
  46   for (cnt = 0; cnt < size; ++cnt)
  47     {
  48       struct link_map *map;
  49       status[cnt] = _dl_addr (array[cnt], &info[cnt], &map, NULL);
  50       if (status[cnt] && info[cnt].dli_fname && info[cnt].dli_fname[0] != '\0')
  51         {
  52           /* We have some info, compute the length of the string which will be
  53              "<file-name>(<sym-name>+offset) [address].  */
  54           total += (strlen (info[cnt].dli_fname ?: "")
  55                     + strlen (info[cnt].dli_sname ?: "")
  56                     + 3 + WORD_WIDTH + 3 + WORD_WIDTH + 5);
  57
  58           /* The load bias is more useful to the user than the load
  59              address.  The use of these addresses is to calculate an
  60              address in the ELF file, so its prelinked bias is not
  61              something we want to subtract out.  */
  62           info[cnt].dli_fbase = (void *) map->l_addr;
  63         }
  64       else
  65         total += 5 + WORD_WIDTH;
  66     }
  67
  68   /* Allocate memory for the result.  */
  69   result = (char **) malloc (size * sizeof (char *) + total);
  70   if (result != NULL)
  71     {
  72       char *last = (char *) (result + size);
  73
  74       for (cnt = 0; cnt < size; ++cnt)
  75         {
  76           result[cnt] = last;
  77
  78           if (status[cnt]
  79               && info[cnt].dli_fname != NULL && info[cnt].dli_fname[0] != '\0')
  80             {
  81               if (info[cnt].dli_sname == NULL)
  82                 /* We found no symbol name to use, so describe it as
  83                    relative to the file.  */
  84                 info[cnt].dli_saddr = info[cnt].dli_fbase;
  85
  86               if (info[cnt].dli_sname == NULL && info[cnt].dli_saddr == 0)
  87                 last += 1 + sprintf (last, "%s(%s) [%p]",
  88                                      info[cnt].dli_fname ?: "",
  89                                      info[cnt].dli_sname ?: "",
  90                                      array[cnt]);
  91               else
  92                 {
  93                   char sign;
  94                   ptrdiff_t offset;
  95                   if (array[cnt] >= (void *) info[cnt].dli_saddr)
  96                     {
  97                       sign = '+';
  98                       offset = array[cnt] - info[cnt].dli_saddr;
  99                     }
 100                   else
 101                     {
 102                       sign = '-';
 103                       offset = info[cnt].dli_saddr - array[cnt];
 104                     }
 105
 106                   last += 1 + sprintf (last, "%s(%s%c%#tx) [%p]",
 107                                        info[cnt].dli_fname ?: "",
 108                                        info[cnt].dli_sname ?: "",
 109                                        sign, offset, array[cnt]);
 110                 }
 111             }
 112           else
 113             last += 1 + sprintf (last, "[%p]", array[cnt]);
 114         }
 115       assert (last <= (char *) result + size * sizeof (char *) + total);
 116     }
 117
 118   return result;
 119 }
 120 weak_alias (__backtrace_symbols, backtrace_symbols)