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      1 /* Find the split (or skeleton) unit for a given unit.
      2    Copyright (C) 2018 Red Hat, Inc.
      3    This file is part of elfutils.
      4 
      5    This file is free software; you can redistribute it and/or modify
      6    it under the terms of either
      7 
      8      * the GNU Lesser General Public License as published by the Free
      9        Software Foundation; either version 3 of the License, or (at
     10        your option) any later version
     11 
     12    or
     13 
     14      * the GNU General Public License as published by the Free
     15        Software Foundation; either version 2 of the License, or (at
     16        your option) any later version
     17 
     18    or both in parallel, as here.
     19 
     20    elfutils is distributed in the hope that it will be useful, but
     21    WITHOUT ANY WARRANTY; without even the implied warranty of
     22    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     23    General Public License for more details.
     24 
     25    You should have received copies of the GNU General Public License and
     26    the GNU Lesser General Public License along with this program.  If
     27    not, see <http://www.gnu.org/licenses/>.  */
     28 
     29 #ifdef HAVE_CONFIG_H
     30 # include <config.h>
     31 #endif
     32 
     33 #include "libdwP.h"
     34 #include "libelfP.h"
     35 
     36 #include <limits.h>
     37 #include <search.h>
     38 #include <stdlib.h>
     39 #include <string.h>
     40 #include <sys/types.h>
     41 #include <sys/stat.h>
     42 #include <fcntl.h>
     43 #include <unistd.h>
     44 
     45 void
     46 try_split_file (Dwarf_CU *cu, const char *dwo_path)
     47 {
     48   int split_fd = open (dwo_path, O_RDONLY);
     49   if (split_fd != -1)
     50     {
     51       Dwarf *split_dwarf = dwarf_begin (split_fd, DWARF_C_READ);
     52       if (split_dwarf != NULL)
     53 	{
     54 	  Dwarf_CU *split = NULL;
     55 	  while (dwarf_get_units (split_dwarf, split, &split,
     56 				  NULL, NULL, NULL, NULL) == 0)
     57 	    {
     58 	      if (split->unit_type == DW_UT_split_compile
     59 		  && cu->unit_id8 == split->unit_id8)
     60 		{
     61 		  if (tsearch (split->dbg, &cu->dbg->split_tree,
     62 			       __libdw_finddbg_cb) == NULL)
     63 		    {
     64 		      /* Something went wrong.  Don't link.  */
     65 		      __libdw_seterrno (DWARF_E_NOMEM);
     66 		      break;
     67 		    }
     68 
     69 		  /* Link skeleton and split compile units.  */
     70 		  __libdw_link_skel_split (cu, split);
     71 
     72 		  /* We have everything we need from this ELF
     73 		     file.  And we are going to close the fd to
     74 		     not run out of file descriptors.  */
     75 		  elf_cntl (split_dwarf->elf, ELF_C_FDDONE);
     76 		  break;
     77 		}
     78 	    }
     79 	  if (cu->split == (Dwarf_CU *) -1)
     80 	    dwarf_end (split_dwarf);
     81 	}
     82       /* Always close, because we don't want to run out of file
     83 	 descriptors.  See also the elf_fcntl ELF_C_FDDONE call
     84 	 above.  */
     85       close (split_fd);
     86     }
     87 }
     88 
     89 Dwarf_CU *
     90 internal_function
     91 __libdw_find_split_unit (Dwarf_CU *cu)
     92 {
     93   /* Only try once.  */
     94   if (cu->split != (Dwarf_CU *) -1)
     95     return cu->split;
     96 
     97   /* We need a skeleton unit with a comp_dir and [GNU_]dwo_name attributes.
     98      The split unit will be the first in the dwo file and should have the
     99      same id as the skeleton.  */
    100   if (cu->unit_type == DW_UT_skeleton)
    101     {
    102       Dwarf_Die cudie = CUDIE (cu);
    103       Dwarf_Attribute dwo_name;
    104       /* It is fine if dwo_dir doesn't exists, but then dwo_name needs
    105 	 to be an absolute path.  */
    106       if (dwarf_attr (&cudie, DW_AT_dwo_name, &dwo_name) != NULL
    107 	  || dwarf_attr (&cudie, DW_AT_GNU_dwo_name, &dwo_name) != NULL)
    108 	{
    109 	  /* First try the dwo file name in the same directory
    110 	     as we found the skeleton file.  */
    111 	  const char *dwo_file = dwarf_formstring (&dwo_name);
    112 	  const char *debugdir = cu->dbg->debugdir;
    113 	  char *dwo_path = __libdw_filepath (debugdir, NULL, dwo_file);
    114 	  if (dwo_path != NULL)
    115 	    {
    116 	      try_split_file (cu, dwo_path);
    117 	      free (dwo_path);
    118 	    }
    119 
    120 	  if (cu->split == (Dwarf_CU *) -1)
    121 	    {
    122 	      /* Try compdir plus dwo_name.  */
    123 	      Dwarf_Attribute compdir;
    124 	      dwarf_attr (&cudie, DW_AT_comp_dir, &compdir);
    125 	      const char *dwo_dir = dwarf_formstring (&compdir);
    126 	      if (dwo_dir != NULL)
    127 		{
    128 		  dwo_path = __libdw_filepath (debugdir, dwo_dir, dwo_file);
    129 		  if (dwo_path != NULL)
    130 		    {
    131 		      try_split_file (cu, dwo_path);
    132 		      free (dwo_path);
    133 		    }
    134 		}
    135 	    }
    136 	  /* XXX If still not found we could try stripping dirs from the
    137 	     comp_dir and adding them from the comp_dir, assuming
    138 	     someone moved a whole build tree around.  */
    139 	}
    140     }
    141 
    142   /* If we found nothing, make sure we don't try again.  */
    143   if (cu->split == (Dwarf_CU *) -1)
    144     cu->split = NULL;
    145 
    146   return cu->split;
    147 }
    148