1/* Return child of current DIE.
2   Copyright (C) 2003-2011 Red Hat, Inc.
3   This file is part of Red Hat elfutils.
4   Written by Ulrich Drepper <drepper@redhat.com>, 2003.
5
6   Red Hat elfutils is free software; you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by the
8   Free Software Foundation; version 2 of the License.
9
10   Red Hat elfutils is distributed in the hope that it will be useful, but
11   WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   General Public License for more details.
14
15   You should have received a copy of the GNU General Public License along
16   with Red Hat elfutils; if not, write to the Free Software Foundation,
17   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
18
19   In addition, as a special exception, Red Hat, Inc. gives You the
20   additional right to link the code of Red Hat elfutils with code licensed
21   under any Open Source Initiative certified open source license
22   (http://www.opensource.org/licenses/index.php) which requires the
23   distribution of source code with any binary distribution and to
24   distribute linked combinations of the two.  Non-GPL Code permitted under
25   this exception must only link to the code of Red Hat elfutils through
26   those well defined interfaces identified in the file named EXCEPTION
27   found in the source code files (the "Approved Interfaces").  The files
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31   Inc. may make changes or additions to the list of Approved Interfaces.
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35   License in all respects for all of the Red Hat elfutils code and other
36   code used in conjunction with Red Hat elfutils except the Non-GPL Code
37   covered by this exception.  If you modify this file, you may extend this
38   exception to your version of the file, but you are not obligated to do
39   so.  If you do not wish to provide this exception without modification,
40   you must delete this exception statement from your version and license
41   this file solely under the GPL without exception.
42
43   Red Hat elfutils is an included package of the Open Invention Network.
44   An included package of the Open Invention Network is a package for which
45   Open Invention Network licensees cross-license their patents.  No patent
46   license is granted, either expressly or impliedly, by designation as an
47   included package.  Should you wish to participate in the Open Invention
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49   <http://www.openinventionnetwork.com>.  */
50
51#ifdef HAVE_CONFIG_H
52# include <config.h>
53#endif
54
55#include "libdwP.h"
56#include <string.h>
57
58/* Some arbitrary value not conflicting with any existing code.  */
59#define INVALID 0xffffe444
60
61
62unsigned char *
63internal_function
64__libdw_find_attr (Dwarf_Die *die, unsigned int search_name,
65		   unsigned int *codep, unsigned int *formp)
66{
67  Dwarf *dbg = die->cu->dbg;
68  const unsigned char *readp = (unsigned char *) die->addr;
69
70  /* First we have to get the abbreviation code so that we can decode
71     the data in the DIE.  */
72  unsigned int abbrev_code;
73  get_uleb128 (abbrev_code, readp);
74
75  /* Find the abbreviation entry.  */
76  Dwarf_Abbrev *abbrevp = die->abbrev;
77  if (abbrevp == NULL)
78    {
79      abbrevp = __libdw_findabbrev (die->cu, abbrev_code);
80      die->abbrev = abbrevp ?: DWARF_END_ABBREV;
81    }
82  if (unlikely (die->abbrev == DWARF_END_ABBREV))
83    {
84    invalid_dwarf:
85      __libdw_seterrno (DWARF_E_INVALID_DWARF);
86      return NULL;
87    }
88
89  /* Search the name attribute.  */
90  unsigned char *const endp
91    = ((unsigned char *) dbg->sectiondata[IDX_debug_abbrev]->d_buf
92       + dbg->sectiondata[IDX_debug_abbrev]->d_size);
93
94  const unsigned char *attrp = die->abbrev->attrp;
95  while (1)
96    {
97      /* Are we still in bounds?  This test needs to be refined.  */
98      if (unlikely (attrp + 1 >= endp))
99	goto invalid_dwarf;
100
101      /* Get attribute name and form.
102
103	 XXX We don't check whether this reads beyond the end of the
104	 section.  */
105      unsigned int attr_name;
106      get_uleb128 (attr_name, attrp);
107      unsigned int attr_form;
108      get_uleb128 (attr_form, attrp);
109
110      /* We can stop if we found the attribute with value zero.  */
111      if (attr_name == 0 && attr_form == 0)
112	break;
113
114      /* Is this the name attribute?  */
115      if (attr_name == search_name && search_name != INVALID)
116	{
117	  if (codep != NULL)
118	    *codep = attr_name;
119	  if (formp != NULL)
120	    *formp = attr_form;
121
122	  return (unsigned char *) readp;
123	}
124
125      /* Skip over the rest of this attribute (if there is any).  */
126      if (attr_form != 0)
127	{
128	  size_t len = __libdw_form_val_len (dbg, die->cu, attr_form, readp);
129
130	  if (unlikely (len == (size_t) -1l))
131	    {
132	      readp = NULL;
133	      break;
134	    }
135
136	  // XXX We need better boundary checks.
137	  readp += len;
138	}
139    }
140
141  // XXX Do we need other values?
142  if (codep != NULL)
143    *codep = INVALID;
144  if (formp != NULL)
145    *formp = INVALID;
146
147  return (unsigned char *) readp;
148}
149
150
151int
152dwarf_child (die, result)
153     Dwarf_Die *die;
154     Dwarf_Die *result;
155{
156  /* Ignore previous errors.  */
157  if (die == NULL)
158    return -1;
159
160  /* Skip past the last attribute.  */
161  void *addr = NULL;
162
163  /* If we already know there are no children do not search.  */
164  if (die->abbrev != DWARF_END_ABBREV
165      && (die->abbrev == NULL || die->abbrev->has_children))
166    addr = __libdw_find_attr (die, INVALID, NULL, NULL);
167  if (unlikely (die->abbrev == (Dwarf_Abbrev *) -1l))
168    return -1;
169
170  /* Make sure the DIE really has children.  */
171  if (! die->abbrev->has_children)
172    /* There cannot be any children.  */
173    return 1;
174
175  if (addr == NULL)
176    return -1;
177
178  /* RESULT can be the same as DIE.  So preserve what we need.  */
179  struct Dwarf_CU *cu = die->cu;
180  Elf_Data *cu_sec = cu_data (cu);
181
182  /* It's kosher (just suboptimal) to have a null entry first thing (7.5.3).
183     So if this starts with ULEB128 of 0 (even with silly encoding of 0),
184     it is a kosher null entry and we do not really have any children.  */
185  const unsigned char *code = addr;
186  const unsigned char *endp = (cu_sec->d_buf + cu_sec->d_size);
187  while (1)
188    {
189      if (unlikely (code >= endp)) /* Truncated section.  */
190	return 1;
191      if (unlikely (*code == 0x80))
192	++code;
193      else
194	break;
195    }
196  if (unlikely (*code == '\0'))
197    return 1;
198
199  /* Clear the entire DIE structure.  This signals we have not yet
200     determined any of the information.  */
201  memset (result, '\0', sizeof (Dwarf_Die));
202
203  /* We have the address.  */
204  result->addr = addr;
205
206  /* Same CU as the parent.  */
207  result->cu = cu;
208
209  return 0;
210}
211INTDEF(dwarf_child)
212