1 /* Low-level DWARF 2 reading code
2
3 Copyright (C) 1994-2020 Free Software Foundation, Inc.
4
5 Adapted by Gary Funck (gary@intrepid.com), Intrepid Technology,
6 Inc. with support from Florida State University (under contract
7 with the Ada Joint Program Office), and Silicon Graphics, Inc.
8 Initial contribution by Brent Benson, Harris Computer Systems, Inc.,
9 based on Fred Fish's (Cygnus Support) implementation of DWARF 1
10 support.
11
12 This file is part of GDB.
13
14 This program is free software; you can redistribute it and/or modify
15 it under the terms of the GNU General Public License as published by
16 the Free Software Foundation; either version 3 of the License, or
17 (at your option) any later version.
18
19 This program is distributed in the hope that it will be useful,
20 but WITHOUT ANY WARRANTY; without even the implied warranty of
21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 GNU General Public License for more details.
23
24 You should have received a copy of the GNU General Public License
25 along with this program. If not, see <http://www.gnu.org/licenses/>. */
26
27 #ifndef GDB_DWARF2_LEB_H
28 #define GDB_DWARF2_LEB_H
29
30 /* Read dwarf information from a buffer. */
31
32 static inline unsigned int
read_1_byte(bfd * abfd,const gdb_byte * buf)33 read_1_byte (bfd *abfd, const gdb_byte *buf)
34 {
35 return bfd_get_8 (abfd, buf);
36 }
37
38 static inline int
read_1_signed_byte(bfd * abfd,const gdb_byte * buf)39 read_1_signed_byte (bfd *abfd, const gdb_byte *buf)
40 {
41 return bfd_get_signed_8 (abfd, buf);
42 }
43
44 static inline unsigned int
read_2_bytes(bfd * abfd,const gdb_byte * buf)45 read_2_bytes (bfd *abfd, const gdb_byte *buf)
46 {
47 return bfd_get_16 (abfd, buf);
48 }
49
50 static inline int
read_2_signed_bytes(bfd * abfd,const gdb_byte * buf)51 read_2_signed_bytes (bfd *abfd, const gdb_byte *buf)
52 {
53 return bfd_get_signed_16 (abfd, buf);
54 }
55
56 /* Read the next three bytes (little-endian order) as an unsigned integer. */
57 static inline unsigned int
read_3_bytes(bfd * abfd,const gdb_byte * buf)58 read_3_bytes (bfd *abfd, const gdb_byte *buf)
59 {
60 unsigned int result = 0;
61 for (int i = 0; i < 3; ++i)
62 {
63 unsigned char byte = bfd_get_8 (abfd, buf);
64 buf++;
65 result |= ((unsigned int) byte << (i * 8));
66 }
67 return result;
68 }
69
70 static inline unsigned int
read_4_bytes(bfd * abfd,const gdb_byte * buf)71 read_4_bytes (bfd *abfd, const gdb_byte *buf)
72 {
73 return bfd_get_32 (abfd, buf);
74 }
75
76 static inline int
read_4_signed_bytes(bfd * abfd,const gdb_byte * buf)77 read_4_signed_bytes (bfd *abfd, const gdb_byte *buf)
78 {
79 return bfd_get_signed_32 (abfd, buf);
80 }
81
82 static inline ULONGEST
read_8_bytes(bfd * abfd,const gdb_byte * buf)83 read_8_bytes (bfd *abfd, const gdb_byte *buf)
84 {
85 return bfd_get_64 (abfd, buf);
86 }
87
88 extern LONGEST read_signed_leb128 (bfd *, const gdb_byte *, unsigned int *);
89
90 extern ULONGEST read_unsigned_leb128 (bfd *, const gdb_byte *, unsigned int *);
91
92 /* Read the initial length from a section. The (draft) DWARF 3
93 specification allows the initial length to take up either 4 bytes
94 or 12 bytes. If the first 4 bytes are 0xffffffff, then the next 8
95 bytes describe the length and all offsets will be 8 bytes in length
96 instead of 4.
97
98 An older, non-standard 64-bit format is also handled by this
99 function. The older format in question stores the initial length
100 as an 8-byte quantity without an escape value. Lengths greater
101 than 2^32 aren't very common which means that the initial 4 bytes
102 is almost always zero. Since a length value of zero doesn't make
103 sense for the 32-bit format, this initial zero can be considered to
104 be an escape value which indicates the presence of the older 64-bit
105 format. As written, the code can't detect (old format) lengths
106 greater than 4GB. If it becomes necessary to handle lengths
107 somewhat larger than 4GB, we could allow other small values (such
108 as the non-sensical values of 1, 2, and 3) to also be used as
109 escape values indicating the presence of the old format.
110
111 The value returned via bytes_read should be used to increment the
112 relevant pointer after calling read_initial_length().
113
114 [ Note: read_initial_length() and read_offset() are based on the
115 document entitled "DWARF Debugging Information Format", revision
116 3, draft 8, dated November 19, 2001. This document was obtained
117 from:
118
119 http://reality.sgiweb.org/davea/dwarf3-draft8-011125.pdf
120
121 This document is only a draft and is subject to change. (So beware.)
122
123 Details regarding the older, non-standard 64-bit format were
124 determined empirically by examining 64-bit ELF files produced by
125 the SGI toolchain on an IRIX 6.5 machine.
126
127 - Kevin, July 16, 2002
128 ] */
129 extern LONGEST read_initial_length (bfd *abfd, const gdb_byte *buf,
130 unsigned int *bytes_read,
131 bool handle_nonstd = true);
132
133 /* Read an offset from the data stream. */
134 extern LONGEST read_offset (bfd *abfd, const gdb_byte *buf,
135 unsigned int offset_size);
136
137 static inline const gdb_byte *
read_n_bytes(bfd * abfd,const gdb_byte * buf,unsigned int size)138 read_n_bytes (bfd *abfd, const gdb_byte *buf, unsigned int size)
139 {
140 /* If the size of a host char is 8 bits, we can return a pointer
141 to the buffer, otherwise we have to copy the data to a buffer
142 allocated on the temporary obstack. */
143 gdb_assert (HOST_CHAR_BIT == 8);
144 return buf;
145 }
146
147 static inline const char *
read_direct_string(bfd * abfd,const gdb_byte * buf,unsigned int * bytes_read_ptr)148 read_direct_string (bfd *abfd, const gdb_byte *buf,
149 unsigned int *bytes_read_ptr)
150 {
151 /* If the size of a host char is 8 bits, we can return a pointer
152 to the string, otherwise we have to copy the string to a buffer
153 allocated on the temporary obstack. */
154 gdb_assert (HOST_CHAR_BIT == 8);
155 if (*buf == '\0')
156 {
157 *bytes_read_ptr = 1;
158 return NULL;
159 }
160 *bytes_read_ptr = strlen ((const char *) buf) + 1;
161 return (const char *) buf;
162 }
163
164 #endif /* GDB_DWARF2_LEB_H */
165