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)