1 /* Return section index of section header string table.
2 Copyright (C) 2002, 2005, 2009, 2014, 2015 Red Hat, Inc.
3 This file is part of elfutils.
4 Written by Ulrich Drepper <drepper@redhat.com>, 2002.
5
6 This file is free software; you can redistribute it and/or modify
7 it under the terms of either
8
9 * the GNU Lesser General Public License as published by the Free
10 Software Foundation; either version 3 of the License, or (at
11 your option) any later version
12
13 or
14
15 * the GNU General Public License as published by the Free
16 Software Foundation; either version 2 of the License, or (at
17 your option) any later version
18
19 or both in parallel, as here.
20
21 elfutils is distributed in the hope that it will be useful, but
22 WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 General Public License for more details.
25
26 You should have received copies of the GNU General Public License and
27 the GNU Lesser General Public License along with this program. If
28 not, see <http://www.gnu.org/licenses/>. */
29
30 #ifdef HAVE_CONFIG_H
31 # include <config.h>
32 #endif
33
34 #include <assert.h>
35 #include <errno.h>
36 #include <gelf.h>
37 #include <stddef.h>
38
39 #include "libelfP.h"
40 #include "common.h"
41
42
43 int
elf_getshdrstrndx(Elf * elf,size_t * dst)44 elf_getshdrstrndx (Elf *elf, size_t *dst)
45 {
46 int result = 0;
47
48 if (elf == NULL)
49 return -1;
50
51 if (unlikely (elf->kind != ELF_K_ELF))
52 {
53 __libelf_seterrno (ELF_E_INVALID_HANDLE);
54 return -1;
55 }
56
57 rwlock_rdlock (elf->lock);
58
59 /* We rely here on the fact that the `elf' element is a common prefix
60 of `elf32' and `elf64'. */
61 assert (offsetof (struct Elf, state.elf.ehdr)
62 == offsetof (struct Elf, state.elf32.ehdr));
63 assert (sizeof (elf->state.elf.ehdr)
64 == sizeof (elf->state.elf32.ehdr));
65 assert (offsetof (struct Elf, state.elf.ehdr)
66 == offsetof (struct Elf, state.elf64.ehdr));
67 assert (sizeof (elf->state.elf.ehdr)
68 == sizeof (elf->state.elf64.ehdr));
69
70 if (unlikely (elf->state.elf.ehdr == NULL))
71 {
72 __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
73 result = -1;
74 }
75 else
76 {
77 Elf32_Word num;
78
79 num = (elf->class == ELFCLASS32
80 ? elf->state.elf32.ehdr->e_shstrndx
81 : elf->state.elf64.ehdr->e_shstrndx);
82
83 /* Determine whether the index is too big to fit in the ELF
84 header. */
85 if (unlikely (num == SHN_XINDEX))
86 {
87 /* Yes. Search the zeroth section header. */
88 if (elf->class == ELFCLASS32)
89 {
90 size_t offset;
91 if (unlikely (elf->state.elf32.scns.cnt == 0))
92 {
93 /* Cannot use SHN_XINDEX without section headers. */
94 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
95 result = -1;
96 goto out;
97 }
98
99 if (elf->state.elf32.scns.data[0].shdr.e32 != NULL)
100 {
101 num = elf->state.elf32.scns.data[0].shdr.e32->sh_link;
102 goto success;
103 }
104
105 offset = elf->state.elf32.ehdr->e_shoff;
106
107 if (elf->map_address != NULL
108 && elf->state.elf32.ehdr->e_ident[EI_DATA] == MY_ELFDATA
109 && (ALLOW_UNALIGNED
110 || (((size_t) ((char *) elf->map_address
111 + elf->start_offset + offset))
112 & (__alignof__ (Elf32_Shdr) - 1)) == 0))
113 {
114 /* First see whether the information in the ELF header is
115 valid and it does not ask for too much. */
116 if (unlikely (elf->maximum_size - offset
117 < sizeof (Elf32_Shdr)))
118 {
119 /* Something is wrong. */
120 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
121 result = -1;
122 goto out;
123 }
124
125 /* We can directly access the memory. */
126 num = ((Elf32_Shdr *) (elf->map_address + elf->start_offset
127 + offset))->sh_link;
128 }
129 else
130 {
131 /* We avoid reading in all the section headers. Just read
132 the first one. */
133 Elf32_Shdr shdr_mem;
134 ssize_t r;
135
136 if (unlikely ((r = pread_retry (elf->fildes, &shdr_mem,
137 sizeof (Elf32_Shdr), offset))
138 != sizeof (Elf32_Shdr)))
139 {
140 /* We must be able to read this ELF section header. */
141 if (r < 0)
142 __libelf_seterrno (ELF_E_INVALID_FILE);
143 else
144 __libelf_seterrno (ELF_E_INVALID_ELF);
145 result = -1;
146 goto out;
147 }
148
149 if (elf->state.elf32.ehdr->e_ident[EI_DATA] != MY_ELFDATA)
150 CONVERT (shdr_mem.sh_link);
151 num = shdr_mem.sh_link;
152 }
153 }
154 else
155 {
156 if (unlikely (elf->state.elf64.scns.cnt == 0))
157 {
158 /* Cannot use SHN_XINDEX without section headers. */
159 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
160 result = -1;
161 goto out;
162 }
163
164 if (elf->state.elf64.scns.data[0].shdr.e64 != NULL)
165 {
166 num = elf->state.elf64.scns.data[0].shdr.e64->sh_link;
167 goto success;
168 }
169
170 size_t offset = elf->state.elf64.ehdr->e_shoff;
171
172 if (elf->map_address != NULL
173 && elf->state.elf64.ehdr->e_ident[EI_DATA] == MY_ELFDATA
174 && (ALLOW_UNALIGNED
175 || (((size_t) ((char *) elf->map_address
176 + elf->start_offset + offset))
177 & (__alignof__ (Elf64_Shdr) - 1)) == 0))
178 {
179 /* First see whether the information in the ELF header is
180 valid and it does not ask for too much. */
181 if (unlikely (elf->maximum_size - offset
182 < sizeof (Elf64_Shdr)))
183 {
184 /* Something is wrong. */
185 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
186 result = -1;
187 goto out;
188 }
189
190 /* We can directly access the memory. */
191 num = ((Elf64_Shdr *) (elf->map_address + elf->start_offset
192 + offset))->sh_link;
193 }
194 else
195 {
196 /* We avoid reading in all the section headers. Just read
197 the first one. */
198 Elf64_Shdr shdr_mem;
199 ssize_t r;
200
201 if (unlikely ((r = pread_retry (elf->fildes, &shdr_mem,
202 sizeof (Elf64_Shdr), offset))
203 != sizeof (Elf64_Shdr)))
204 {
205 /* We must be able to read this ELF section header. */
206 if (r < 0)
207 __libelf_seterrno (ELF_E_INVALID_FILE);
208 else
209 __libelf_seterrno (ELF_E_INVALID_ELF);
210 result = -1;
211 goto out;
212 }
213
214 if (elf->state.elf64.ehdr->e_ident[EI_DATA] != MY_ELFDATA)
215 CONVERT (shdr_mem.sh_link);
216 num = shdr_mem.sh_link;
217 }
218 }
219 }
220
221 /* Store the result. */
222 success:
223 *dst = num;
224 }
225
226 out:
227 rwlock_unlock (elf->lock);
228
229 return result;
230 }
231 INTDEF(elf_getshdrstrndx)
232 /* Alias for the deprecated name. */
233 strong_alias (elf_getshdrstrndx, elf_getshstrndx)
234