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
38 int
dwarf_next_unit(Dwarf * dwarf,Dwarf_Off off,Dwarf_Off * next_off,size_t * header_sizep,Dwarf_Half * versionp,Dwarf_Off * abbrev_offsetp,uint8_t * address_sizep,uint8_t * offset_sizep,uint64_t * type_signaturep,Dwarf_Off * type_offsetp)39 dwarf_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 }
INTDEF(dwarf_next_unit)175 INTDEF(dwarf_next_unit)
176
177 int
178 dwarf_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 }
186 INTDEF(dwarf_nextcu)
187