Line data Source code
1 : /* Advance to next CFI entry.
2 : Copyright (C) 2009-2010, 2014 Red Hat, Inc.
3 : This file is part of elfutils.
4 :
5 : This file is free software; you can redistribute it and/or modify
6 : it under the terms of either
7 :
8 : * the GNU Lesser General Public License as published by the Free
9 : Software Foundation; either version 3 of the License, or (at
10 : your option) any later version
11 :
12 : or
13 :
14 : * the GNU General Public License as published by the Free
15 : Software Foundation; either version 2 of the License, or (at
16 : your option) any later version
17 :
18 : or both in parallel, as here.
19 :
20 : elfutils is distributed in the hope that it will be useful, but
21 : WITHOUT ANY WARRANTY; without even the implied warranty of
22 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 : General Public License for more details.
24 :
25 : You should have received copies of the GNU General Public License and
26 : the GNU Lesser General Public License along with this program. If
27 : not, see <http://www.gnu.org/licenses/>. */
28 :
29 : #ifdef HAVE_CONFIG_H
30 : # include <config.h>
31 : #endif
32 :
33 : #include "cfi.h"
34 : #include "encoded-value.h"
35 :
36 : #include <string.h>
37 :
38 :
39 : int
40 24911 : dwarf_next_cfi (const unsigned char e_ident[],
41 : Elf_Data *data,
42 : bool eh_frame_p,
43 : Dwarf_Off off,
44 : Dwarf_Off *next_off,
45 : Dwarf_CFI_Entry *entry)
46 : {
47 : /* Dummy struct for memory-access.h macros. */
48 24911 : BYTE_ORDER_DUMMY (dw, e_ident);
49 :
50 : /* If we reached the end before don't do anything. */
51 24911 : if (off == (Dwarf_Off) -1l
52 : /* Make sure there is enough space in the .debug_frame section
53 : for at least the initial word. We cannot test the rest since
54 : we don't know yet whether this is a 64-bit object or not. */
55 24814 : || unlikely (off + 4 >= data->d_size))
56 : {
57 139 : done:
58 139 : *next_off = (Dwarf_Off) -1l;
59 139 : return 1;
60 : }
61 :
62 : /* This points into the .debug_frame section at the start of the entry. */
63 24773 : const uint8_t *bytes = data->d_buf + off;
64 24773 : const uint8_t *limit = data->d_buf + data->d_size;
65 :
66 : /* The format of a CFI entry is described in DWARF3 6.4.1:
67 : */
68 :
69 29256 : uint64_t length = read_4ubyte_unaligned_inc (&dw, bytes);
70 24773 : size_t offset_size = 4;
71 24773 : if (length == DWARF3_LENGTH_64_BIT)
72 : {
73 : /* This is the 64-bit DWARF format. */
74 0 : offset_size = 8;
75 0 : if (unlikely (limit - bytes < 8))
76 : {
77 0 : invalid:
78 0 : __libdw_seterrno (DWARF_E_INVALID_DWARF);
79 0 : return -1;
80 : }
81 0 : length = read_8ubyte_unaligned_inc (&dw, bytes);
82 : }
83 :
84 : /* Not explicitly in the DWARF spec, but mentioned in the LSB exception
85 : frames (.eh_frame) spec. If Length contains the value 0, then this
86 : CIE shall be considered a terminator and processing shall end. */
87 24773 : if (length == 0)
88 : goto done;
89 :
90 24772 : if (unlikely ((uint64_t) (limit - bytes) < length)
91 24772 : || unlikely (length < offset_size + 1))
92 : goto invalid;
93 :
94 : /* Now we know how large the entry is. Note the trick in the
95 : computation. If the offset_size is 4 the '- 4' term undoes the
96 : '2 *'. If offset_size is 8 this term computes the size of the
97 : escape value plus the 8 byte offset. */
98 24772 : *next_off = off + (2 * offset_size - 4) + length;
99 :
100 24772 : limit = bytes + length;
101 :
102 24772 : const uint8_t *const cie_pointer_start = bytes;
103 24772 : if (offset_size == 8)
104 0 : entry->cie.CIE_id = read_8ubyte_unaligned_inc (&dw, bytes);
105 : else
106 : {
107 29255 : entry->cie.CIE_id = read_4ubyte_unaligned_inc (&dw, bytes);
108 : /* Canonicalize the 32-bit CIE_ID value to 64 bits. */
109 24772 : if (!eh_frame_p && entry->cie.CIE_id == DW_CIE_ID_32)
110 68 : entry->cie.CIE_id = DW_CIE_ID_64;
111 : }
112 24772 : if (eh_frame_p)
113 : {
114 : /* Canonicalize the .eh_frame CIE pointer to .debug_frame format. */
115 24593 : if (entry->cie.CIE_id == 0)
116 3720 : entry->cie.CIE_id = DW_CIE_ID_64;
117 : else
118 : {
119 : /* In .eh_frame format, a CIE pointer is the distance from where
120 : it appears back to the beginning of the CIE. */
121 20873 : ptrdiff_t pos = cie_pointer_start - (const uint8_t *) data->d_buf;
122 20873 : if (unlikely (entry->cie.CIE_id > (Dwarf_Off) pos)
123 20873 : || unlikely (pos <= (ptrdiff_t) offset_size))
124 : goto invalid;
125 20873 : entry->cie.CIE_id = pos - entry->cie.CIE_id;
126 : }
127 : }
128 :
129 24772 : if (entry->cie.CIE_id == DW_CIE_ID_64)
130 : {
131 : /* Read the version stamp. Always an 8-bit value. */
132 3788 : uint8_t version = *bytes++;
133 :
134 3788 : if (version != 1 && (unlikely (version < 3) || unlikely (version > 4)))
135 : goto invalid;
136 :
137 3788 : entry->cie.augmentation = (const char *) bytes;
138 :
139 3788 : bytes = memchr (bytes, '\0', limit - bytes);
140 3788 : if (unlikely (bytes == NULL))
141 : goto invalid;
142 3788 : ++bytes;
143 :
144 : /* The address size for CFI is implicit in the ELF class. */
145 3788 : uint_fast8_t address_size = e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
146 3788 : uint_fast8_t segment_size = 0;
147 3788 : if (version >= 4)
148 : {
149 0 : if (unlikely (limit - bytes < 5))
150 : goto invalid;
151 : /* XXX We don't actually support address_size not matching the class.
152 : To do so, we'd have to return it here so that intern_new_cie
153 : could use it choose a specific fde_encoding. */
154 0 : if (unlikely (*bytes != address_size))
155 : {
156 0 : __libdw_seterrno (DWARF_E_VERSION);
157 0 : return -1;
158 : }
159 0 : address_size = *bytes++;
160 0 : segment_size = *bytes++;
161 : /* We don't actually support segment selectors. We'd have to
162 : roll this into the fde_encoding bits or something. */
163 0 : if (unlikely (segment_size != 0))
164 : {
165 0 : __libdw_seterrno (DWARF_E_VERSION);
166 0 : return -1;
167 : }
168 : }
169 :
170 3788 : const char *ap = entry->cie.augmentation;
171 :
172 : /* g++ v2 "eh" has pointer immediately following augmentation string,
173 : so it must be handled first. */
174 3788 : if (unlikely (ap[0] == 'e' && ap[1] == 'h'))
175 : {
176 0 : ap += 2;
177 0 : bytes += address_size;
178 : }
179 :
180 3788 : if (bytes >= limit)
181 : goto invalid;
182 3788 : get_uleb128 (entry->cie.code_alignment_factor, bytes, limit);
183 :
184 3788 : if (bytes >= limit)
185 : goto invalid;
186 3788 : get_sleb128 (entry->cie.data_alignment_factor, bytes, limit);
187 :
188 3788 : if (bytes >= limit)
189 : goto invalid;
190 :
191 3788 : if (version >= 3) /* DWARF 3+ */
192 0 : get_uleb128 (entry->cie.return_address_register, bytes, limit);
193 : else /* DWARF 2 */
194 3788 : entry->cie.return_address_register = *bytes++;
195 :
196 : /* If we have sized augmentation data,
197 : we don't need to grok it all. */
198 3788 : entry->cie.fde_augmentation_data_size = 0;
199 3788 : bool sized_augmentation = *ap == 'z';
200 3788 : if (sized_augmentation)
201 : {
202 3719 : if (bytes >= limit)
203 : goto invalid;
204 3719 : get_uleb128 (entry->cie.augmentation_data_size, bytes, limit);
205 3719 : if ((Dwarf_Word) (limit - bytes) < entry->cie.augmentation_data_size)
206 : goto invalid;
207 3719 : entry->cie.augmentation_data = bytes;
208 3719 : bytes += entry->cie.augmentation_data_size;
209 : }
210 : else
211 : {
212 69 : entry->cie.augmentation_data = bytes;
213 :
214 69 : for (; *ap != '\0'; ++ap)
215 : {
216 : uint8_t encoding;
217 0 : switch (*ap)
218 : {
219 0 : case 'L': /* Skip LSDA pointer encoding byte. */
220 : case 'R': /* Skip FDE address encoding byte. */
221 0 : encoding = *bytes++;
222 : entry->cie.fde_augmentation_data_size
223 0 : += encoded_value_size (data, e_ident, encoding, NULL);
224 0 : continue;
225 0 : case 'P': /* Skip encoded personality routine pointer. */
226 0 : encoding = *bytes++;
227 0 : bytes += encoded_value_size (data, e_ident, encoding, bytes);
228 0 : continue;
229 0 : case 'S': /* Skip signal-frame flag. */
230 0 : continue;
231 : default:
232 : /* Unknown augmentation string. initial_instructions might
233 : actually start with some augmentation data. */
234 : break;
235 : }
236 : break;
237 : }
238 : entry->cie.augmentation_data_size
239 69 : = bytes - entry->cie.augmentation_data;
240 : }
241 :
242 3788 : entry->cie.initial_instructions = bytes;
243 3788 : entry->cie.initial_instructions_end = limit;
244 : }
245 : else
246 : {
247 20984 : entry->fde.start = bytes;
248 20984 : entry->fde.end = limit;
249 : }
250 :
251 : return 0;
252 : }
253 : INTDEF (dwarf_next_cfi)
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