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
44void
45try_split_file (Dwarf_CU *cu, const char *dwo_path)
46{
47  int split_fd = open (dwo_path, O_RDONLY);
48  if (split_fd != -1)
49    {
50      Dwarf *split_dwarf = dwarf_begin (split_fd, DWARF_C_READ);
51      if (split_dwarf != NULL)
52	{
53	  Dwarf_CU *split = NULL;
54	  while (dwarf_get_units (split_dwarf, split, &split,
55				  NULL, NULL, NULL, NULL) == 0)
56	    {
57	      if (split->unit_type == DW_UT_split_compile
58		  && cu->unit_id8 == split->unit_id8)
59		{
60		  if (tsearch (split->dbg, &cu->dbg->split_tree,
61			       __libdw_finddbg_cb) == NULL)
62		    {
63		      /* Something went wrong.  Don't link.  */
64		      __libdw_seterrno (DWARF_E_NOMEM);
65		      break;
66		    }
67
68		  /* Link skeleton and split compile units.  */
69		  __libdw_link_skel_split (cu, split);
70
71		  /* We have everything we need from this ELF
72		     file.  And we are going to close the fd to
73		     not run out of file descriptors.  */
74		  elf_cntl (split_dwarf->elf, ELF_C_FDDONE);
75		  break;
76		}
77	    }
78	  if (cu->split == (Dwarf_CU *) -1)
79	    dwarf_end (split_dwarf);
80	}
81      /* Always close, because we don't want to run out of file
82	 descriptors.  See also the elf_fcntl ELF_C_FDDONE call
83	 above.  */
84      close (split_fd);
85    }
86}
87
88Dwarf_CU *
89internal_function
90__libdw_find_split_unit (Dwarf_CU *cu)
91{
92  /* Only try once.  */
93  if (cu->split != (Dwarf_CU *) -1)
94    return cu->split;
95
96  /* We need a skeleton unit with a comp_dir and [GNU_]dwo_name attributes.
97     The split unit will be the first in the dwo file and should have the
98     same id as the skeleton.  */
99  if (cu->unit_type == DW_UT_skeleton)
100    {
101      Dwarf_Die cudie = CUDIE (cu);
102      Dwarf_Attribute dwo_name;
103      /* It is fine if dwo_dir doesn't exists, but then dwo_name needs
104	 to be an absolute path.  */
105      if (dwarf_attr (&cudie, DW_AT_dwo_name, &dwo_name) != NULL
106	  || dwarf_attr (&cudie, DW_AT_GNU_dwo_name, &dwo_name) != NULL)
107	{
108	  /* First try the dwo file name in the same directory
109	     as we found the skeleton file.  */
110	  const char *dwo_file = dwarf_formstring (&dwo_name);
111	  const char *debugdir = cu->dbg->debugdir;
112	  char *dwo_path = __libdw_filepath (debugdir, NULL, dwo_file);
113	  if (dwo_path != NULL)
114	    {
115	      try_split_file (cu, dwo_path);
116	      free (dwo_path);
117	    }
118
119	  if (cu->split == (Dwarf_CU *) -1)
120	    {
121	      /* Try compdir plus dwo_name.  */
122	      Dwarf_Attribute compdir;
123	      dwarf_attr (&cudie, DW_AT_comp_dir, &compdir);
124	      const char *dwo_dir = dwarf_formstring (&compdir);
125	      if (dwo_dir != NULL)
126		{
127		  dwo_path = __libdw_filepath (debugdir, dwo_dir, dwo_file);
128		  if (dwo_path != NULL)
129		    {
130		      try_split_file (cu, dwo_path);
131		      free (dwo_path);
132		    }
133		}
134	    }
135	  /* XXX If still not found we could try stripping dirs from the
136	     comp_dir and adding them from the comp_dir, assuming
137	     someone moved a whole build tree around.  */
138	}
139    }
140
141  /* If we found nothing, make sure we don't try again.  */
142  if (cu->split == (Dwarf_CU *) -1)
143    cu->split = NULL;
144
145  return cu->split;
146}
147