1 /* Advance to next CFI entry.
2 Copyright (C) 2009-2010 Red Hat, Inc.
3 This file is part of Red Hat elfutils.
4
5 Red Hat elfutils is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by the
7 Free Software Foundation; version 2 of the License.
8
9 Red Hat elfutils is distributed in the hope that it will be useful, but
10 WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 General Public License for more details.
13
14 You should have received a copy of the GNU General Public License along
15 with Red Hat elfutils; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
17
18 In addition, as a special exception, Red Hat, Inc. gives You the
19 additional right to link the code of Red Hat elfutils with code licensed
20 under any Open Source Initiative certified open source license
21 (http://www.opensource.org/licenses/index.php) which requires the
22 distribution of source code with any binary distribution and to
23 distribute linked combinations of the two. Non-GPL Code permitted under
24 this exception must only link to the code of Red Hat elfutils through
25 those well defined interfaces identified in the file named EXCEPTION
26 found in the source code files (the "Approved Interfaces"). The files
27 of Non-GPL Code may instantiate templates or use macros or inline
28 functions from the Approved Interfaces without causing the resulting
29 work to be covered by the GNU General Public License. Only Red Hat,
30 Inc. may make changes or additions to the list of Approved Interfaces.
31 Red Hat's grant of this exception is conditioned upon your not adding
32 any new exceptions. If you wish to add a new Approved Interface or
33 exception, please contact Red Hat. You must obey the GNU General Public
34 License in all respects for all of the Red Hat elfutils code and other
35 code used in conjunction with Red Hat elfutils except the Non-GPL Code
36 covered by this exception. If you modify this file, you may extend this
37 exception to your version of the file, but you are not obligated to do
38 so. If you do not wish to provide this exception without modification,
39 you must delete this exception statement from your version and license
40 this file solely under the GPL without exception.
41
42 Red Hat elfutils is an included package of the Open Invention Network.
43 An included package of the Open Invention Network is a package for which
44 Open Invention Network licensees cross-license their patents. No patent
45 license is granted, either expressly or impliedly, by designation as an
46 included package. Should you wish to participate in the Open Invention
47 Network licensing program, please visit www.openinventionnetwork.com
48 <http://www.openinventionnetwork.com>. */
49
50 #ifdef HAVE_CONFIG_H
51 # include <config.h>
52 #endif
53
54 #include "cfi.h"
55 #include "encoded-value.h"
56
57 #include <string.h>
58
59
60 int
dwarf_next_cfi(e_ident,data,eh_frame_p,off,next_off,entry)61 dwarf_next_cfi (e_ident, data, eh_frame_p, off, next_off, entry)
62 const unsigned char e_ident[];
63 Elf_Data *data;
64 bool eh_frame_p;
65 Dwarf_Off off;
66 Dwarf_Off *next_off;
67 Dwarf_CFI_Entry *entry;
68 {
69 /* Dummy struct for memory-access.h macros. */
70 BYTE_ORDER_DUMMY (dw, e_ident);
71
72 /* If we reached the end before don't do anything. */
73 if (off == (Dwarf_Off) -1l
74 /* Make sure there is enough space in the .debug_frame section
75 for at least the initial word. We cannot test the rest since
76 we don't know yet whether this is a 64-bit object or not. */
77 || unlikely (off + 4 >= data->d_size))
78 {
79 *next_off = (Dwarf_Off) -1l;
80 return 1;
81 }
82
83 /* This points into the .debug_frame section at the start of the entry. */
84 const uint8_t *bytes = data->d_buf + off;
85 const uint8_t *limit = data->d_buf + data->d_size;
86
87 /* The format of a CFI entry is described in DWARF3 6.4.1:
88 */
89
90 uint64_t length = read_4ubyte_unaligned_inc (&dw, bytes);
91 size_t offset_size = 4;
92 if (length == DWARF3_LENGTH_64_BIT)
93 {
94 /* This is the 64-bit DWARF format. */
95 offset_size = 8;
96 if (unlikely (limit - bytes < 8))
97 {
98 invalid:
99 __libdw_seterrno (DWARF_E_INVALID_DWARF);
100 return -1;
101 }
102 length = read_8ubyte_unaligned_inc (&dw, bytes);
103 }
104 if (unlikely ((uint64_t) (limit - bytes) < length)
105 || unlikely (length < offset_size + 1))
106 goto invalid;
107
108 /* Now we know how large the entry is. Note the trick in the
109 computation. If the offset_size is 4 the '- 4' term undoes the
110 '2 *'. If offset_size is 8 this term computes the size of the
111 escape value plus the 8 byte offset. */
112 *next_off = off + (2 * offset_size - 4) + length;
113
114 limit = bytes + length;
115
116 const uint8_t *const cie_pointer_start = bytes;
117 if (offset_size == 8)
118 entry->cie.CIE_id = read_8ubyte_unaligned_inc (&dw, bytes);
119 else
120 {
121 entry->cie.CIE_id = read_4ubyte_unaligned_inc (&dw, bytes);
122 /* Canonicalize the 32-bit CIE_ID value to 64 bits. */
123 if (!eh_frame_p && entry->cie.CIE_id == DW_CIE_ID_32)
124 entry->cie.CIE_id = DW_CIE_ID_64;
125 }
126 if (eh_frame_p)
127 {
128 /* Canonicalize the .eh_frame CIE pointer to .debug_frame format. */
129 if (entry->cie.CIE_id == 0)
130 entry->cie.CIE_id = DW_CIE_ID_64;
131 else
132 {
133 /* In .eh_frame format, a CIE pointer is the distance from where
134 it appears back to the beginning of the CIE. */
135 ptrdiff_t pos = cie_pointer_start - (const uint8_t *) data->d_buf;
136 if (unlikely (entry->cie.CIE_id > (Dwarf_Off) pos)
137 || unlikely (pos <= (ptrdiff_t) offset_size))
138 goto invalid;
139 entry->cie.CIE_id = pos - entry->cie.CIE_id;
140 }
141 }
142
143 if (entry->cie.CIE_id == DW_CIE_ID_64)
144 {
145 /* Read the version stamp. Always an 8-bit value. */
146 uint8_t version = *bytes++;
147
148 if (version != 1 && (unlikely (version < 3) || unlikely (version > 4)))
149 goto invalid;
150
151 entry->cie.augmentation = (const char *) bytes;
152
153 bytes = memchr (bytes, '\0', limit - bytes);
154 if (unlikely (bytes == NULL))
155 goto invalid;
156 ++bytes;
157
158 /* The address size for CFI is implicit in the ELF class. */
159 uint_fast8_t address_size = e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
160 uint_fast8_t segment_size = 0;
161 if (version >= 4)
162 {
163 if (unlikely (limit - bytes < 5))
164 goto invalid;
165 /* XXX We don't actually support address_size not matching the class.
166 To do so, we'd have to return it here so that intern_new_cie
167 could use it choose a specific fde_encoding. */
168 if (unlikely (*bytes != address_size))
169 {
170 __libdw_seterrno (DWARF_E_VERSION);
171 return -1;
172 }
173 address_size = *bytes++;
174 segment_size = *bytes++;
175 /* We don't actually support segment selectors. We'd have to
176 roll this into the fde_encoding bits or something. */
177 if (unlikely (segment_size != 0))
178 {
179 __libdw_seterrno (DWARF_E_VERSION);
180 return -1;
181 }
182 }
183
184 const char *ap = entry->cie.augmentation;
185
186 /* g++ v2 "eh" has pointer immediately following augmentation string,
187 so it must be handled first. */
188 if (unlikely (ap[0] == 'e' && ap[1] == 'h'))
189 {
190 ap += 2;
191 bytes += address_size;
192 }
193
194 get_uleb128 (entry->cie.code_alignment_factor, bytes);
195 get_sleb128 (entry->cie.data_alignment_factor, bytes);
196
197 if (version >= 3) /* DWARF 3+ */
198 get_uleb128 (entry->cie.return_address_register, bytes);
199 else /* DWARF 2 */
200 entry->cie.return_address_register = *bytes++;
201
202 /* If we have sized augmentation data,
203 we don't need to grok it all. */
204 entry->cie.fde_augmentation_data_size = 0;
205 bool sized_augmentation = *ap == 'z';
206 if (sized_augmentation)
207 {
208 get_uleb128 (entry->cie.augmentation_data_size, bytes);
209 if ((Dwarf_Word) (limit - bytes) < entry->cie.augmentation_data_size)
210 goto invalid;
211 entry->cie.augmentation_data = bytes;
212 bytes += entry->cie.augmentation_data_size;
213 }
214 else
215 {
216 entry->cie.augmentation_data = bytes;
217
218 for (; *ap != '\0'; ++ap)
219 {
220 uint8_t encoding;
221 switch (*ap)
222 {
223 case 'L': /* Skip LSDA pointer encoding byte. */
224 case 'R': /* Skip FDE address encoding byte. */
225 encoding = *bytes++;
226 entry->cie.fde_augmentation_data_size
227 += encoded_value_size (data, e_ident, encoding, NULL);
228 continue;
229 case 'P': /* Skip encoded personality routine pointer. */
230 encoding = *bytes++;
231 bytes += encoded_value_size (data, e_ident, encoding, bytes);
232 continue;
233 case 'S': /* Skip signal-frame flag. */
234 continue;
235 default:
236 /* Unknown augmentation string. initial_instructions might
237 actually start with some augmentation data. */
238 break;
239 }
240 break;
241 }
242 entry->cie.augmentation_data_size
243 = bytes - entry->cie.augmentation_data;
244 }
245
246 entry->cie.initial_instructions = bytes;
247 entry->cie.initial_instructions_end = limit;
248 }
249 else
250 {
251 entry->fde.start = bytes;
252 entry->fde.end = limit;
253 }
254
255 return 0;
256 }
257 INTDEF (dwarf_next_cfi)
258