1 /* Return section header.
2 Copyright (C) 1998-2002, 2005, 2007, 2009, 2012, 2014, 2015 Red Hat, Inc.
3 This file is part of elfutils.
4 Written by Ulrich Drepper <drepper@redhat.com>, 1998.
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 <stdbool.h>
37
38 #include "libelfP.h"
39 #include "common.h"
40
41 #ifndef LIBELFBITS
42 # define LIBELFBITS 32
43 #endif
44
45
ElfW2(LIBELFBITS,Shdr)46 static ElfW2(LIBELFBITS,Shdr) *
47 load_shdr_wrlock (Elf_Scn *scn)
48 {
49 ElfW2(LIBELFBITS,Shdr) *result;
50
51 /* Read the section header table. */
52 Elf *elf = scn->elf;
53 ElfW2(LIBELFBITS,Ehdr) *ehdr = elf->state.ELFW(elf,LIBELFBITS).ehdr;
54
55 /* Try again, maybe the data is there now. */
56 result = scn->shdr.ELFW(e,LIBELFBITS);
57 if (result != NULL)
58 goto out;
59
60 size_t shnum;
61 if (__elf_getshdrnum_rdlock (elf, &shnum) != 0
62 || shnum > SIZE_MAX / sizeof (ElfW2(LIBELFBITS,Shdr)))
63 goto out;
64 size_t size = shnum * sizeof (ElfW2(LIBELFBITS,Shdr));
65
66 /* Allocate memory for the section headers. We know the number
67 of entries from the ELF header. */
68 ElfW2(LIBELFBITS,Shdr) *shdr = elf->state.ELFW(elf,LIBELFBITS).shdr =
69 (ElfW2(LIBELFBITS,Shdr) *) malloc (size);
70 if (elf->state.ELFW(elf,LIBELFBITS).shdr == NULL)
71 {
72 __libelf_seterrno (ELF_E_NOMEM);
73 goto out;
74 }
75 elf->state.ELFW(elf,LIBELFBITS).shdr_malloced = 1;
76
77 if (elf->map_address != NULL)
78 {
79 /* First see whether the information in the ELF header is
80 valid and it does not ask for too much. */
81 if (unlikely (ehdr->e_shoff >= elf->maximum_size)
82 || unlikely (elf->maximum_size - ehdr->e_shoff < size))
83 {
84 /* Something is wrong. */
85 __libelf_seterrno (ELF_E_INVALID_SECTION_HEADER);
86 goto free_and_out;
87 }
88
89 ElfW2(LIBELFBITS,Shdr) *notcvt;
90
91 /* All the data is already mapped. If we could use it
92 directly this would already have happened. Unless
93 we allocated the memory ourselves and the ELF_F_MALLOCED
94 flag is set. */
95 void *file_shdr = ((char *) elf->map_address
96 + elf->start_offset + ehdr->e_shoff);
97
98 assert ((elf->flags & ELF_F_MALLOCED)
99 || ehdr->e_ident[EI_DATA] != MY_ELFDATA
100 || elf->cmd == ELF_C_READ_MMAP
101 || (! ALLOW_UNALIGNED
102 && ((uintptr_t) file_shdr
103 & (__alignof__ (ElfW2(LIBELFBITS,Shdr)) - 1)) != 0));
104
105 /* Now copy the data and at the same time convert the byte order. */
106 if (ehdr->e_ident[EI_DATA] == MY_ELFDATA)
107 {
108 assert ((elf->flags & ELF_F_MALLOCED)
109 || elf->cmd == ELF_C_READ_MMAP
110 || ! ALLOW_UNALIGNED);
111 memcpy (shdr, file_shdr, size);
112 }
113 else
114 {
115 bool copy = ! (ALLOW_UNALIGNED
116 || ((uintptr_t) file_shdr
117 & (__alignof__ (ElfW2(LIBELFBITS,Shdr)) - 1))
118 == 0);
119 if (! copy)
120 notcvt = (ElfW2(LIBELFBITS,Shdr) *)
121 ((char *) elf->map_address
122 + elf->start_offset + ehdr->e_shoff);
123 else
124 {
125 notcvt = (ElfW2(LIBELFBITS,Shdr) *) malloc (size);
126 if (unlikely (notcvt == NULL))
127 {
128 __libelf_seterrno (ELF_E_NOMEM);
129 goto out;
130 }
131 memcpy (notcvt, ((char *) elf->map_address
132 + elf->start_offset + ehdr->e_shoff),
133 size);
134 }
135
136 for (size_t cnt = 0; cnt < shnum; ++cnt)
137 {
138 CONVERT_TO (shdr[cnt].sh_name, notcvt[cnt].sh_name);
139 CONVERT_TO (shdr[cnt].sh_type, notcvt[cnt].sh_type);
140 CONVERT_TO (shdr[cnt].sh_flags, notcvt[cnt].sh_flags);
141 CONVERT_TO (shdr[cnt].sh_addr, notcvt[cnt].sh_addr);
142 CONVERT_TO (shdr[cnt].sh_offset, notcvt[cnt].sh_offset);
143 CONVERT_TO (shdr[cnt].sh_size, notcvt[cnt].sh_size);
144 CONVERT_TO (shdr[cnt].sh_link, notcvt[cnt].sh_link);
145 CONVERT_TO (shdr[cnt].sh_info, notcvt[cnt].sh_info);
146 CONVERT_TO (shdr[cnt].sh_addralign,
147 notcvt[cnt].sh_addralign);
148 CONVERT_TO (shdr[cnt].sh_entsize, notcvt[cnt].sh_entsize);
149
150 /* If this is a section with an extended index add a
151 reference in the section which uses the extended
152 index. */
153 if (shdr[cnt].sh_type == SHT_SYMTAB_SHNDX
154 && shdr[cnt].sh_link < shnum)
155 elf->state.ELFW(elf,LIBELFBITS).scns.data[shdr[cnt].sh_link].shndx_index
156 = cnt;
157
158 /* Set the own shndx_index field in case it has not yet
159 been set. */
160 if (elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shndx_index == 0)
161 elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shndx_index
162 = -1;
163 }
164
165 if (copy)
166 free (notcvt);
167 }
168 }
169 else if (likely (elf->fildes != -1))
170 {
171 /* Read the header. */
172 ssize_t n = pread_retry (elf->fildes,
173 elf->state.ELFW(elf,LIBELFBITS).shdr, size,
174 elf->start_offset + ehdr->e_shoff);
175 if (unlikely ((size_t) n != size))
176 {
177 /* Severe problems. We cannot read the data. */
178 __libelf_seterrno (ELF_E_READ_ERROR);
179 goto free_and_out;
180 }
181
182 /* If the byte order of the file is not the same as the one
183 of the host convert the data now. */
184 if (ehdr->e_ident[EI_DATA] != MY_ELFDATA)
185 for (size_t cnt = 0; cnt < shnum; ++cnt)
186 {
187 CONVERT (shdr[cnt].sh_name);
188 CONVERT (shdr[cnt].sh_type);
189 CONVERT (shdr[cnt].sh_flags);
190 CONVERT (shdr[cnt].sh_addr);
191 CONVERT (shdr[cnt].sh_offset);
192 CONVERT (shdr[cnt].sh_size);
193 CONVERT (shdr[cnt].sh_link);
194 CONVERT (shdr[cnt].sh_info);
195 CONVERT (shdr[cnt].sh_addralign);
196 CONVERT (shdr[cnt].sh_entsize);
197 }
198 }
199 else
200 {
201 /* The file descriptor was already enabled and not all data was
202 read. Undo the allocation. */
203 __libelf_seterrno (ELF_E_FD_DISABLED);
204
205 free_and_out:
206 free (shdr);
207 elf->state.ELFW(elf,LIBELFBITS).shdr = NULL;
208 elf->state.ELFW(elf,LIBELFBITS).shdr_malloced = 0;
209
210 goto out;
211 }
212
213 /* Set the pointers in the `scn's. */
214 for (size_t cnt = 0; cnt < shnum; ++cnt)
215 elf->state.ELFW(elf,LIBELFBITS).scns.data[cnt].shdr.ELFW(e,LIBELFBITS)
216 = &elf->state.ELFW(elf,LIBELFBITS).shdr[cnt];
217
218 result = scn->shdr.ELFW(e,LIBELFBITS);
219 assert (result != NULL);
220
221 out:
222 return result;
223 }
224
225 static bool
scn_valid(Elf_Scn * scn)226 scn_valid (Elf_Scn *scn)
227 {
228 if (scn == NULL)
229 return false;
230
231 if (unlikely (scn->elf->state.elf.ehdr == NULL))
232 {
233 __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
234 return false;
235 }
236
237 if (unlikely (scn->elf->class != ELFW(ELFCLASS,LIBELFBITS)))
238 {
239 __libelf_seterrno (ELF_E_INVALID_CLASS);
240 return false;
241 }
242
243 return true;
244 }
245
ElfW2(LIBELFBITS,Shdr)246 ElfW2(LIBELFBITS,Shdr) *
247 internal_function
248 __elfw2(LIBELFBITS,getshdr_rdlock) (Elf_Scn *scn)
249 {
250 ElfW2(LIBELFBITS,Shdr) *result;
251
252 if (!scn_valid (scn))
253 return NULL;
254
255 result = scn->shdr.ELFW(e,LIBELFBITS);
256 if (result == NULL)
257 {
258 rwlock_unlock (scn->elf->lock);
259 rwlock_wrlock (scn->elf->lock);
260 result = scn->shdr.ELFW(e,LIBELFBITS);
261 if (result == NULL)
262 result = load_shdr_wrlock (scn);
263 }
264
265 return result;
266 }
267
ElfW2(LIBELFBITS,Shdr)268 ElfW2(LIBELFBITS,Shdr) *
269 internal_function
270 __elfw2(LIBELFBITS,getshdr_wrlock) (Elf_Scn *scn)
271 {
272 ElfW2(LIBELFBITS,Shdr) *result;
273
274 if (!scn_valid (scn))
275 return NULL;
276
277 result = scn->shdr.ELFW(e,LIBELFBITS);
278 if (result == NULL)
279 result = load_shdr_wrlock (scn);
280
281 return result;
282 }
283
ElfW2(LIBELFBITS,Shdr)284 ElfW2(LIBELFBITS,Shdr) *
285 elfw2(LIBELFBITS,getshdr) (Elf_Scn *scn)
286 {
287 ElfW2(LIBELFBITS,Shdr) *result;
288
289 if (!scn_valid (scn))
290 return NULL;
291
292 rwlock_rdlock (scn->elf->lock);
293 result = __elfw2(LIBELFBITS,getshdr_rdlock) (scn);
294 rwlock_unlock (scn->elf->lock);
295
296 return result;
297 }
298