1/* Advance to next CU header.
2   Copyright (C) 2002-2010 Red Hat, Inc.
3   This file is part of elfutils.
4   Written by Ulrich Drepper <drepper@redhat.com>, 2002.
5
6   This file is free software; you can redistribute it and/or modify
7   it under the terms of either
8
9     * the GNU Lesser General Public License as published by the Free
10       Software Foundation; either version 3 of the License, or (at
11       your option) any later version
12
13   or
14
15     * the GNU General Public License as published by the Free
16       Software Foundation; either version 2 of the License, or (at
17       your option) any later version
18
19   or both in parallel, as here.
20
21   elfutils is distributed in the hope that it will be useful, but
22   WITHOUT ANY WARRANTY; without even the implied warranty of
23   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
24   General Public License for more details.
25
26   You should have received copies of the GNU General Public License and
27   the GNU Lesser General Public License along with this program.  If
28   not, see <http://www.gnu.org/licenses/>.  */
29
30#ifdef HAVE_CONFIG_H
31# include <config.h>
32#endif
33
34#include <libdwP.h>
35#include <dwarf.h>
36
37
38int
39dwarf_next_unit (Dwarf *dwarf, Dwarf_Off off, Dwarf_Off *next_off,
40		 size_t *header_sizep, Dwarf_Half *versionp,
41		 Dwarf_Off *abbrev_offsetp, uint8_t *address_sizep,
42		 uint8_t *offset_sizep, uint64_t *type_signaturep,
43		 Dwarf_Off *type_offsetp)
44{
45  const bool debug_types = type_signaturep != NULL;
46  const size_t sec_idx = debug_types ? IDX_debug_types : IDX_debug_info;
47
48  /* Maybe there has been an error before.  */
49  if (dwarf == NULL)
50    return -1;
51
52  /* If we reached the end before don't do anything.  */
53  if (off == (Dwarf_Off) -1l
54      || unlikely (dwarf->sectiondata[sec_idx] == NULL)
55      /* Make sure there is enough space in the .debug_info section
56	 for at least the initial word.  We cannot test the rest since
57	 we don't know yet whether this is a 64-bit object or not.  */
58      || unlikely (off + 4 >= dwarf->sectiondata[sec_idx]->d_size))
59    {
60      *next_off = (Dwarf_Off) -1l;
61      return 1;
62    }
63
64  /* This points into the .debug_info section to the beginning of the
65     CU entry.  */
66  const unsigned char *data = dwarf->sectiondata[sec_idx]->d_buf;
67  const unsigned char *bytes = data + off;
68
69  /* The format of the CU header is described in dwarf2p1 7.5.1:
70
71     1.  A 4-byte or 12-byte unsigned integer representing the length
72	 of the .debug_info contribution for that compilation unit, not
73	 including the length field itself. In the 32-bit DWARF format,
74	 this is a 4-byte unsigned integer (which must be less than
75	 0xfffffff0); in the 64-bit DWARF format, this consists of the
76	 4-byte value 0xffffffff followed by an 8-byte unsigned integer
77	 that gives the actual length (see Section 7.2.2).
78
79      2. A 2-byte unsigned integer representing the version of the
80	 DWARF information for that compilation unit. For DWARF Version
81	 2.1, the value in this field is 2.
82
83      3. A 4-byte or 8-byte unsigned offset into the .debug_abbrev
84	 section. This offset associates the compilation unit with a
85	 particular set of debugging information entry abbreviations. In
86	 the 32-bit DWARF format, this is a 4-byte unsigned length; in
87	 the 64-bit DWARF format, this is an 8-byte unsigned length (see
88	 Section 7.4).
89
90      4. A 1-byte unsigned integer representing the size in bytes of
91	 an address on the target architecture. If the system uses
92	 segmented addressing, this value represents the size of the
93	 offset portion of an address.  */
94  uint64_t length = read_4ubyte_unaligned_inc (dwarf, bytes);
95  size_t offset_size = 4;
96  /* Lengths of 0xfffffff0 - 0xffffffff are escape codes.  Oxffffffff is
97     used to indicate that 64-bit dwarf information is being used, the
98     other values are currently reserved.  */
99  if (length == DWARF3_LENGTH_64_BIT)
100    offset_size = 8;
101  else if (unlikely (length >= DWARF3_LENGTH_MIN_ESCAPE_CODE
102		     && length <= DWARF3_LENGTH_MAX_ESCAPE_CODE))
103    {
104    invalid:
105      __libdw_seterrno (DWARF_E_INVALID_DWARF);
106      return -1;
107    }
108
109  /* Now we know how large the header is.  */
110  if (unlikely (DIE_OFFSET_FROM_CU_OFFSET (off, offset_size, debug_types)
111		>= dwarf->sectiondata[sec_idx]->d_size))
112    {
113      *next_off = -1;
114      return 1;
115    }
116
117  if (length == DWARF3_LENGTH_64_BIT)
118    /* This is a 64-bit DWARF format.  */
119    length = read_8ubyte_unaligned_inc (dwarf, bytes);
120
121  /* Read the version stamp.  Always a 16-bit value.  */
122  uint_fast16_t version = read_2ubyte_unaligned_inc (dwarf, bytes);
123
124  /* Get offset in .debug_abbrev.  Note that the size of the entry
125     depends on whether this is a 32-bit or 64-bit DWARF definition.  */
126  uint64_t abbrev_offset;
127  if (__libdw_read_offset_inc (dwarf, sec_idx, &bytes, offset_size,
128			       &abbrev_offset, IDX_debug_abbrev, 0))
129    return -1;
130
131  /* The address size.  Always an 8-bit value.  */
132  uint8_t address_size = *bytes++;
133
134  if (debug_types)
135    {
136      uint64_t type_sig8 = read_8ubyte_unaligned_inc (dwarf, bytes);
137
138      Dwarf_Off type_offset;
139      if (__libdw_read_offset_inc (dwarf, sec_idx, &bytes, offset_size,
140				   &type_offset, sec_idx, 0))
141	return -1;
142
143      /* Validate that the TYPE_OFFSET points past the header.  */
144      if (unlikely (type_offset < (size_t) (bytes - (data + off))))
145	goto invalid;
146
147      *type_signaturep = type_sig8;
148      if (type_offsetp != NULL)
149	*type_offsetp = type_offset;
150    }
151
152  /* Store the header length.  */
153  if (header_sizep != NULL)
154    *header_sizep = bytes - (data + off);
155
156  if (versionp != NULL)
157    *versionp = version;
158
159  if (abbrev_offsetp != NULL)
160    *abbrev_offsetp = abbrev_offset;
161
162  if (address_sizep != NULL)
163    *address_sizep = address_size;
164
165  /* Store the offset size.  */
166  if (offset_sizep != NULL)
167    *offset_sizep = offset_size;
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_next_unit)
176
177int
178dwarf_nextcu (Dwarf *dwarf, Dwarf_Off off, Dwarf_Off *next_off,
179	      size_t *header_sizep, Dwarf_Off *abbrev_offsetp,
180	      uint8_t *address_sizep, uint8_t *offset_sizep)
181{
182  return INTUSE(dwarf_next_unit) (dwarf, off, next_off, header_sizep, NULL,
183				  abbrev_offsetp, address_sizep, offset_sizep,
184				  NULL, NULL);
185}
186INTDEF(dwarf_nextcu)
187