1 /* Advance to next CU header.
2 Copyright (C) 2002, 2003, 2004 Red Hat, Inc.
3 Written by Ulrich Drepper <drepper@redhat.com>, 2002.
4
5 This program is Open Source software; you can redistribute it and/or
6 modify it under the terms of the Open Software License version 1.0 as
7 published by the Open Source Initiative.
8
9 You should have received a copy of the Open Software License along
10 with this program; if not, you may obtain a copy of the Open Software
11 License version 1.0 from http://www.opensource.org/licenses/osl.php or
12 by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
13 3001 King Ranch Road, Ukiah, CA 95482. */
14
15 #ifdef HAVE_CONFIG_H
16 # include <config.h>
17 #endif
18
19 #include <libdwP.h>
20
21
22 int
dwarf_nextcu(dwarf,off,next_off,header_sizep,abbrev_offsetp,address_sizep,offset_sizep)23 dwarf_nextcu (dwarf, off, next_off, header_sizep, abbrev_offsetp,
24 address_sizep, offset_sizep)
25 Dwarf *dwarf;
26 Dwarf_Off off;
27 Dwarf_Off *next_off;
28 size_t *header_sizep;
29 Dwarf_Off *abbrev_offsetp;
30 uint8_t *address_sizep;
31 uint8_t *offset_sizep;
32 {
33 /* Maybe there has been an error before. */
34 if (dwarf == NULL)
35 return -1;
36
37 /* If we reached the end before don't do anything. */
38 if (off == (Dwarf_Off) -1l
39 /* Make sure there is enough space in the .debug_info section
40 for at least the initial word. We cannot test the rest since
41 we don't know yet whether this is a 64-bit object or not. */
42 || unlikely (off + 4 >= dwarf->sectiondata[IDX_debug_info]->d_size))
43 {
44 *next_off = (Dwarf_Off) -1l;
45 return 1;
46 }
47
48 /* This points into the .debug_info section to the beginning of the
49 CU entry. */
50 char *bytes = (char *) dwarf->sectiondata[IDX_debug_info]->d_buf + off;
51
52 /* The format of the CU header is described in dwarf2p1 7.5.1:
53
54 1. A 4-byte or 12-byte unsigned integer representing the length
55 of the .debug_info contribution for that compilation unit, not
56 including the length field itself. In the 32-bit DWARF format,
57 this is a 4-byte unsigned integer (which must be less than
58 0xffffff00); in the 64-bit DWARF format, this consists of the
59 4-byte value 0xffffffff followed by an 8-byte unsigned integer
60 that gives the actual length (see Section 7.4).
61
62 2. A 2-byte unsigned integer representing the version of the
63 DWARF information for that compilation unit. For DWARF Version
64 2.1, the value in this field is 2.
65
66 3. A 4-byte or 8-byte unsigned offset into the .debug_abbrev
67 section. This offset associates the compilation unit with a
68 particular set of debugging information entry abbreviations. In
69 the 32-bit DWARF format, this is a 4-byte unsigned length; in
70 the 64-bit DWARF format, this is an 8-byte unsigned length (see
71 Section 7.4).
72
73 4. A 1-byte unsigned integer representing the size in bytes of
74 an address on the target architecture. If the system uses
75 segmented addressing, this value represents the size of the
76 offset portion of an address. */
77 uint64_t length = read_4ubyte_unaligned_inc (dwarf, bytes);
78 size_t offset_size = 4;
79 if (length == 0xffffffffu)
80 offset_size = 8;
81
82 /* Now we know how large the header is. Note the trick in the
83 computation. If the offset_size is 4 the '- 4' term undoes the
84 '2 *'. If offset_size is 8 this term computes the size of the
85 escape value plus the 8 byte offset. */
86 if (unlikely (off + 2 * offset_size - 4 + sizeof (uint16_t)
87 + offset_size + sizeof (uint8_t)
88 >= dwarf->sectiondata[IDX_debug_info]->d_size))
89 {
90 *next_off = -1;
91 return 1;
92 }
93
94 if (length == 0xffffffffu)
95 /* This is a 64-bit DWARF format. */
96 length = read_8ubyte_unaligned_inc (dwarf, bytes);
97
98 /* Read the version stamp. Always a 16-bit value.
99 XXX Do we need the value? */
100 read_2ubyte_unaligned_inc (dwarf, bytes);
101
102 /* Get offset in .debug_abbrev. Note that the size of the entry
103 depends on whether this is a 32-bit or 64-bit DWARF definition. */
104 uint64_t abbrev_offset;
105 if (offset_size == 4)
106 abbrev_offset = read_4ubyte_unaligned_inc (dwarf, bytes);
107 else
108 abbrev_offset = read_8ubyte_unaligned_inc (dwarf, bytes);
109 if (abbrev_offsetp != NULL)
110 *abbrev_offsetp = abbrev_offset;
111
112 /* The address size. Always an 8-bit value. */
113 uint8_t address_size = *bytes++;
114 if (address_sizep != NULL)
115 *address_sizep = address_size;
116
117 /* Store the offset size. */
118 if (offset_sizep != NULL)
119 *offset_sizep = offset_size;
120
121 /* Store the header length. */
122 if (header_sizep != NULL)
123 *header_sizep = (bytes
124 - ((char *) dwarf->sectiondata[IDX_debug_info]->d_buf
125 + off));
126
127 /* See above for an explanation of the trick in this formula. */
128 *next_off = off + 2 * offset_size - 4 + length;
129
130 return 0;
131 }
132