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
dwarf_next_cfi(const unsigned char e_ident[],Elf_Data * data,bool eh_frame_p,Dwarf_Off off,Dwarf_Off * next_off,Dwarf_CFI_Entry * entry)40 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 BYTE_ORDER_DUMMY (dw, e_ident);
49
50 /* If we reached the end before don't do anything. */
51 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 || unlikely (off + 4 >= data->d_size))
56 {
57 *next_off = (Dwarf_Off) -1l;
58 return 1;
59 }
60
61 /* This points into the .debug_frame section at the start of the entry. */
62 const uint8_t *bytes = data->d_buf + off;
63 const uint8_t *limit = data->d_buf + data->d_size;
64
65 /* The format of a CFI entry is described in DWARF3 6.4.1:
66 */
67
68 uint64_t length = read_4ubyte_unaligned_inc (&dw, bytes);
69 size_t offset_size = 4;
70 if (length == DWARF3_LENGTH_64_BIT)
71 {
72 /* This is the 64-bit DWARF format. */
73 offset_size = 8;
74 if (unlikely (limit - bytes < 8))
75 {
76 invalid:
77 __libdw_seterrno (DWARF_E_INVALID_DWARF);
78 return -1;
79 }
80 length = read_8ubyte_unaligned_inc (&dw, bytes);
81 }
82 if (unlikely ((uint64_t) (limit - bytes) < length)
83 || unlikely (length < offset_size + 1))
84 goto invalid;
85
86 /* Now we know how large the entry is. Note the trick in the
87 computation. If the offset_size is 4 the '- 4' term undoes the
88 '2 *'. If offset_size is 8 this term computes the size of the
89 escape value plus the 8 byte offset. */
90 *next_off = off + (2 * offset_size - 4) + length;
91
92 limit = bytes + length;
93
94 const uint8_t *const cie_pointer_start = bytes;
95 if (offset_size == 8)
96 entry->cie.CIE_id = read_8ubyte_unaligned_inc (&dw, bytes);
97 else
98 {
99 entry->cie.CIE_id = read_4ubyte_unaligned_inc (&dw, bytes);
100 /* Canonicalize the 32-bit CIE_ID value to 64 bits. */
101 if (!eh_frame_p && entry->cie.CIE_id == DW_CIE_ID_32)
102 entry->cie.CIE_id = DW_CIE_ID_64;
103 }
104 if (eh_frame_p)
105 {
106 /* Canonicalize the .eh_frame CIE pointer to .debug_frame format. */
107 if (entry->cie.CIE_id == 0)
108 entry->cie.CIE_id = DW_CIE_ID_64;
109 else
110 {
111 /* In .eh_frame format, a CIE pointer is the distance from where
112 it appears back to the beginning of the CIE. */
113 ptrdiff_t pos = cie_pointer_start - (const uint8_t *) data->d_buf;
114 if (unlikely (entry->cie.CIE_id > (Dwarf_Off) pos)
115 || unlikely (pos <= (ptrdiff_t) offset_size))
116 goto invalid;
117 entry->cie.CIE_id = pos - entry->cie.CIE_id;
118 }
119 }
120
121 if (entry->cie.CIE_id == DW_CIE_ID_64)
122 {
123 /* Read the version stamp. Always an 8-bit value. */
124 uint8_t version = *bytes++;
125
126 if (version != 1 && (unlikely (version < 3) || unlikely (version > 4)))
127 goto invalid;
128
129 entry->cie.augmentation = (const char *) bytes;
130
131 bytes = memchr (bytes, '\0', limit - bytes);
132 if (unlikely (bytes == NULL))
133 goto invalid;
134 ++bytes;
135
136 /* The address size for CFI is implicit in the ELF class. */
137 uint_fast8_t address_size = e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
138 uint_fast8_t segment_size = 0;
139 if (version >= 4)
140 {
141 if (unlikely (limit - bytes < 5))
142 goto invalid;
143 /* XXX We don't actually support address_size not matching the class.
144 To do so, we'd have to return it here so that intern_new_cie
145 could use it choose a specific fde_encoding. */
146 if (unlikely (*bytes != address_size))
147 {
148 __libdw_seterrno (DWARF_E_VERSION);
149 return -1;
150 }
151 address_size = *bytes++;
152 segment_size = *bytes++;
153 /* We don't actually support segment selectors. We'd have to
154 roll this into the fde_encoding bits or something. */
155 if (unlikely (segment_size != 0))
156 {
157 __libdw_seterrno (DWARF_E_VERSION);
158 return -1;
159 }
160 }
161
162 const char *ap = entry->cie.augmentation;
163
164 /* g++ v2 "eh" has pointer immediately following augmentation string,
165 so it must be handled first. */
166 if (unlikely (ap[0] == 'e' && ap[1] == 'h'))
167 {
168 ap += 2;
169 bytes += address_size;
170 }
171
172 if (bytes >= limit)
173 goto invalid;
174 get_uleb128 (entry->cie.code_alignment_factor, bytes, limit);
175
176 if (bytes >= limit)
177 goto invalid;
178 get_sleb128 (entry->cie.data_alignment_factor, bytes, limit);
179
180 if (bytes >= limit)
181 goto invalid;
182
183 if (version >= 3) /* DWARF 3+ */
184 get_uleb128 (entry->cie.return_address_register, bytes, limit);
185 else /* DWARF 2 */
186 entry->cie.return_address_register = *bytes++;
187
188 /* If we have sized augmentation data,
189 we don't need to grok it all. */
190 entry->cie.fde_augmentation_data_size = 0;
191 bool sized_augmentation = *ap == 'z';
192 if (sized_augmentation)
193 {
194 if (bytes >= limit)
195 goto invalid;
196 get_uleb128 (entry->cie.augmentation_data_size, bytes, limit);
197 if ((Dwarf_Word) (limit - bytes) < entry->cie.augmentation_data_size)
198 goto invalid;
199 entry->cie.augmentation_data = bytes;
200 bytes += entry->cie.augmentation_data_size;
201 }
202 else
203 {
204 entry->cie.augmentation_data = bytes;
205
206 for (; *ap != '\0'; ++ap)
207 {
208 uint8_t encoding;
209 switch (*ap)
210 {
211 case 'L': /* Skip LSDA pointer encoding byte. */
212 case 'R': /* Skip FDE address encoding byte. */
213 encoding = *bytes++;
214 entry->cie.fde_augmentation_data_size
215 += encoded_value_size (data, e_ident, encoding, NULL);
216 continue;
217 case 'P': /* Skip encoded personality routine pointer. */
218 encoding = *bytes++;
219 bytes += encoded_value_size (data, e_ident, encoding, bytes);
220 continue;
221 case 'S': /* Skip signal-frame flag. */
222 continue;
223 default:
224 /* Unknown augmentation string. initial_instructions might
225 actually start with some augmentation data. */
226 break;
227 }
228 break;
229 }
230 entry->cie.augmentation_data_size
231 = bytes - entry->cie.augmentation_data;
232 }
233
234 entry->cie.initial_instructions = bytes;
235 entry->cie.initial_instructions_end = limit;
236 }
237 else
238 {
239 entry->fde.start = bytes;
240 entry->fde.end = limit;
241 }
242
243 return 0;
244 }
245 INTDEF (dwarf_next_cfi)
246