debug/backtracesyms.c

   1 /* Return list with names for address in backtrace.
   2    Copyright (C) 1998-2023 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <execinfo.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24
  25 #include <ldsodefs.h>
  26
  27 #if __ELF_NATIVE_CLASS == 32
  28 # define WORD_WIDTH 8
  29 #else
  30 /* We assume 64bits.  */
  31 # define WORD_WIDTH 16
  32 #endif
  33
  34
  35 char **
  36 __backtrace_symbols (void *const *array, int size)
  37 {
  38   Dl_info info[size];
  39   int status[size];
  40   int cnt;
  41   size_t total = 0;
  42   char **result;
  43
  44   /* Fill in the information we can get from `dladdr'.  */
  45   for (cnt = 0; cnt < size; ++cnt)
  46     {
  47       struct link_map *map;
  48       status[cnt] = _dl_addr (array[cnt], &info[cnt], &map, NULL);
  49       if (status[cnt] && info[cnt].dli_fname && info[cnt].dli_fname[0] != '\0')
  50         {
  51           /* We have some info, compute the length of the string which will be
  52              "<file-name>(<sym-name>+offset) [address].  */
  53           total += (strlen (info[cnt].dli_fname ?: "")
  54                     + strlen (info[cnt].dli_sname ?: "")
  55                     + 3 + WORD_WIDTH + 3 + WORD_WIDTH + 5);
  56
  57           /* The load bias is more useful to the user than the load
  58              address.  The use of these addresses is to calculate an
  59              address in the ELF file, so its prelinked bias is not
  60              something we want to subtract out.  */
  61           info[cnt].dli_fbase = (void *) map->l_addr;
  62         }
  63       else
  64         total += 5 + WORD_WIDTH;
  65     }
  66
  67   /* Allocate memory for the result.  */
  68   result = (char **) malloc (size * sizeof (char *) + total);
  69   if (result != NULL)
  70     {
  71       char *last = (char *) (result + size);
  72
  73       for (cnt = 0; cnt < size; ++cnt)
  74         {
  75           result[cnt] = last;
  76
  77           if (status[cnt]
  78               && info[cnt].dli_fname != NULL && info[cnt].dli_fname[0] != '\0')
  79             {
  80               if (info[cnt].dli_sname == NULL)
  81                 /* We found no symbol name to use, so describe it as
  82                    relative to the file.  */
  83                 info[cnt].dli_saddr = info[cnt].dli_fbase;
  84
  85               if (info[cnt].dli_sname == NULL && info[cnt].dli_saddr == 0)
  86                 last += 1 + sprintf (last, "%s(%s) [%p]",
  87                                      info[cnt].dli_fname ?: "",
  88                                      info[cnt].dli_sname ?: "",
  89                                      array[cnt]);
  90               else
  91                 {
  92                   char sign;
  93                   ptrdiff_t offset;
  94                   if (array[cnt] >= (void *) info[cnt].dli_saddr)
  95                     {
  96                       sign = '+';
  97                       offset = array[cnt] - info[cnt].dli_saddr;
  98                     }
  99                   else
 100                     {
 101                       sign = '-';
 102                       offset = info[cnt].dli_saddr - array[cnt];
 103                     }
 104
 105                   last += 1 + sprintf (last, "%s(%s%c%#tx) [%p]",
 106                                        info[cnt].dli_fname ?: "",
 107                                        info[cnt].dli_sname ?: "",
 108                                        sign, offset, array[cnt]);
 109                 }
 110             }
 111           else
 112             last += 1 + sprintf (last, "[%p]", array[cnt]);
 113         }
 114       assert (last <= (char *) result + size * sizeof (char *) + total);
 115     }
 116
 117   return result;
 118 }
 119 weak_alias (__backtrace_symbols, backtrace_symbols)