1/* Advance to next CU header.
2   Copyright (C) 2002, 2003, 2004, 2005, 2008 Red Hat, Inc.
3   This file is part of Red Hat elfutils.
4   Written by Ulrich Drepper <drepper@redhat.com>, 2002.
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
28   of Non-GPL Code may instantiate templates or use macros or inline
29   functions from the Approved Interfaces without causing the resulting
30   work to be covered by the GNU General Public License.  Only Red Hat,
31   Inc. may make changes or additions to the list of Approved Interfaces.
32   Red Hat's grant of this exception is conditioned upon your not adding
33   any new exceptions.  If you wish to add a new Approved Interface or
34   exception, please contact Red Hat.  You must obey the GNU General Public
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
48   Network licensing program, please visit www.openinventionnetwork.com
49   <http://www.openinventionnetwork.com>.  */
50
51#ifdef HAVE_CONFIG_H
52# include <config.h>
53#endif
54
55#include <libdwP.h>
56#include <dwarf.h>
57
58
59int
60dwarf_nextcu (dwarf, off, next_off, header_sizep, abbrev_offsetp,
61	      address_sizep, offset_sizep)
62     Dwarf *dwarf;
63     Dwarf_Off off;
64     Dwarf_Off *next_off;
65     size_t *header_sizep;
66     Dwarf_Off *abbrev_offsetp;
67     uint8_t *address_sizep;
68     uint8_t *offset_sizep;
69{
70  /* Maybe there has been an error before.  */
71  if (dwarf == NULL)
72    return -1;
73
74  /* If we reached the end before don't do anything.  */
75  if (off == (Dwarf_Off) -1l
76      /* Make sure there is enough space in the .debug_info section
77	 for at least the initial word.  We cannot test the rest since
78	 we don't know yet whether this is a 64-bit object or not.  */
79      || unlikely (off + 4 >= dwarf->sectiondata[IDX_debug_info]->d_size))
80    {
81      *next_off = (Dwarf_Off) -1l;
82      return 1;
83    }
84
85  /* This points into the .debug_info section to the beginning of the
86     CU entry.  */
87  char *bytes = (char *) dwarf->sectiondata[IDX_debug_info]->d_buf + off;
88
89  /* The format of the CU header is described in dwarf2p1 7.5.1:
90
91     1.  A 4-byte or 12-byte unsigned integer representing the length
92	 of the .debug_info contribution for that compilation unit, not
93	 including the length field itself. In the 32-bit DWARF format,
94	 this is a 4-byte unsigned integer (which must be less than
95	 0xfffffff0); in the 64-bit DWARF format, this consists of the
96	 4-byte value 0xffffffff followed by an 8-byte unsigned integer
97	 that gives the actual length (see Section 7.2.2).
98
99      2. A 2-byte unsigned integer representing the version of the
100	 DWARF information for that compilation unit. For DWARF Version
101	 2.1, the value in this field is 2.
102
103      3. A 4-byte or 8-byte unsigned offset into the .debug_abbrev
104	 section. This offset associates the compilation unit with a
105	 particular set of debugging information entry abbreviations. In
106	 the 32-bit DWARF format, this is a 4-byte unsigned length; in
107	 the 64-bit DWARF format, this is an 8-byte unsigned length (see
108	 Section 7.4).
109
110      4. A 1-byte unsigned integer representing the size in bytes of
111	 an address on the target architecture. If the system uses
112	 segmented addressing, this value represents the size of the
113	 offset portion of an address.  */
114  uint64_t length = read_4ubyte_unaligned_inc (dwarf, bytes);
115  size_t offset_size = 4;
116  /* Lengths of 0xfffffff0 - 0xffffffff are escape codes.  Oxffffffff is
117     used to indicate that 64-bit dwarf information is being used, the
118     other values are currently reserved.  */
119  if (length == DWARF3_LENGTH_64_BIT)
120    offset_size = 8;
121  else if (unlikely (length >= DWARF3_LENGTH_MIN_ESCAPE_CODE
122		     && length <= DWARF3_LENGTH_MAX_ESCAPE_CODE))
123    {
124      __libdw_seterrno (DWARF_E_INVALID_DWARF);
125      return -1;
126    }
127
128  /* Now we know how large the header is.  */
129  if (unlikely (DIE_OFFSET_FROM_CU_OFFSET (off, offset_size)
130		>= dwarf->sectiondata[IDX_debug_info]->d_size))
131    {
132      *next_off = -1;
133      return 1;
134    }
135
136  if (length == DWARF3_LENGTH_64_BIT)
137    /* This is a 64-bit DWARF format.  */
138    length = read_8ubyte_unaligned_inc (dwarf, bytes);
139
140  /* Read the version stamp.  Always a 16-bit value.
141     XXX Do we need the value?  */
142  read_2ubyte_unaligned_inc (dwarf, bytes);
143
144  /* Get offset in .debug_abbrev.  Note that the size of the entry
145     depends on whether this is a 32-bit or 64-bit DWARF definition.  */
146  uint64_t abbrev_offset;
147  if (offset_size == 4)
148    abbrev_offset = read_4ubyte_unaligned_inc (dwarf, bytes);
149  else
150    abbrev_offset = read_8ubyte_unaligned_inc (dwarf, bytes);
151  if (abbrev_offsetp != NULL)
152    *abbrev_offsetp = abbrev_offset;
153
154  /* The address size.  Always an 8-bit value.  */
155  uint8_t address_size = *bytes++;
156  if (address_sizep != NULL)
157    *address_sizep = address_size;
158
159  /* Store the offset size.  */
160  if (offset_sizep != NULL)
161    *offset_sizep = offset_size;
162
163  /* Store the header length.  */
164  if (header_sizep != NULL)
165    *header_sizep = (bytes
166		     - ((char *) dwarf->sectiondata[IDX_debug_info]->d_buf
167			+ off));
168
169  /* See definition of DIE_OFFSET_FROM_CU_OFFSET macro
170     for an explanation of the trick in this expression.  */
171  *next_off = off + 2 * offset_size - 4 + length;
172
173  return 0;
174}
175INTDEF(dwarf_nextcu)
176