1 /* Extract symbol list from binary.
2 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2005, 2007 Red Hat, Inc.
3 This file is part of Red Hat elfutils.
4 Written by Ulrich Drepper <drepper@redhat.com>, 1998.
5
6 Red Hat elfutils is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by the
8 Free Software Foundation; version 2 of the License.
9
10 Red Hat elfutils is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
14
15 You should have received a copy of the GNU General Public License along
16 with Red Hat elfutils; if not, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
18
19 In addition, as a special exception, Red Hat, Inc. gives You the
20 additional right to link the code of Red Hat elfutils with code licensed
21 under any Open Source Initiative certified open source license
22 (http://www.opensource.org/licenses/index.php) which requires the
23 distribution of source code with any binary distribution and to
24 distribute linked combinations of the two. Non-GPL Code permitted under
25 this exception must only link to the code of Red Hat elfutils through
26 those well defined interfaces identified in the file named EXCEPTION
27 found in the source code files (the "Approved Interfaces"). The files
28 of Non-GPL Code may instantiate templates or use macros or inline
29 functions from the Approved Interfaces without causing the resulting
30 work to be covered by the GNU General Public License. Only Red Hat,
31 Inc. may make changes or additions to the list of Approved Interfaces.
32 Red Hat's grant of this exception is conditioned upon your not adding
33 any new exceptions. If you wish to add a new Approved Interface or
34 exception, please contact Red Hat. You must obey the GNU General Public
35 License in all respects for all of the Red Hat elfutils code and other
36 code used in conjunction with Red Hat elfutils except the Non-GPL Code
37 covered by this exception. If you modify this file, you may extend this
38 exception to your version of the file, but you are not obligated to do
39 so. If you do not wish to provide this exception without modification,
40 you must delete this exception statement from your version and license
41 this file solely under the GPL without exception.
42
43 Red Hat elfutils is an included package of the Open Invention Network.
44 An included package of the Open Invention Network is a package for which
45 Open Invention Network licensees cross-license their patents. No patent
46 license is granted, either expressly or impliedly, by designation as an
47 included package. Should you wish to participate in the Open Invention
48 Network licensing program, please visit www.openinventionnetwork.com
49 <http://www.openinventionnetwork.com>. */
50
51 #ifdef HAVE_CONFIG_H
52 # include <config.h>
53 #endif
54
55 #include <fcntl.h>
56 #include <gelf.h>
57 #include <libelf.h>
58 #include <nlist.h>
59 #include <unistd.h>
60
61 #include "libelfP.h"
62
63
64 struct hashentry
65 {
66 const char *str;
67 GElf_Sym sym;
68 };
69 #define TYPE struct hashentry
70 /* XXX Use a better hash function some day. */
71 #define HASHFCT(str, len) INTUSE(elf_hash) (str)
72 #define COMPARE(p1, p2) strcmp ((p1)->str, (p2)->str)
73 #define CLASS static
74 #define PREFIX nlist_
75 #define xcalloc(n, m) calloc (n, m)
76 #define next_prime(s) __libelf_next_prime (s)
77 #include <fixedsizehash.h>
78
79
80 int
nlist(const char * filename,struct nlist * nl)81 nlist (const char *filename, struct nlist *nl)
82 {
83 int fd;
84 Elf *elf;
85 Elf_Scn *scn = NULL;
86 Elf_Scn *symscn = NULL;
87 GElf_Shdr shdr_mem;
88 GElf_Shdr *shdr = NULL;
89 Elf_Data *data;
90 struct nlist_fshash *table;
91 size_t nsyms;
92 size_t cnt;
93
94 /* Open the file. */
95 fd = open (filename, O_RDONLY);
96 if (fd == -1)
97 {
98 __libelf_seterrno (ELF_E_NOFILE);
99 goto fail;
100 }
101
102 /* For compatibility reasons (`nlist' existed before ELF and libelf)
103 we don't expect the caller to set the ELF version. Do this here
104 if it hasn't happened yet. */
105 if (__libelf_version_initialized == 0)
106 INTUSE(elf_version) (EV_CURRENT);
107
108 /* Now get an ELF descriptor. */
109 elf = INTUSE(elf_begin) (fd, ELF_C_READ_MMAP, NULL);
110 if (elf == NULL)
111 goto fail_fd;
112
113 /* Find a symbol table. We prefer the real symbol table but if it
114 does not exist use the dynamic symbol table. */
115 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
116 {
117 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
118 if (shdr == NULL)
119 goto fail_close;
120
121 /* That is what we are looking for. */
122 if (shdr->sh_type == SHT_SYMTAB)
123 {
124 symscn = scn;
125 break;
126 }
127
128 /* Better than nothing. Remember this section. */
129 if (shdr->sh_type == SHT_DYNSYM)
130 symscn = scn;
131 }
132
133 if (symscn == NULL)
134 /* We haven't found anything. Fail. */
135 goto fail_close;
136
137 /* Re-get the section header in case we found only the dynamic symbol
138 table. */
139 if (scn == NULL)
140 shdr = INTUSE(gelf_getshdr) (symscn, &shdr_mem);
141 /* SHDR->SH_LINK now contains the index of the string section. */
142
143 /* Get the data for the symbol section. */
144 data = INTUSE(elf_getdata) (symscn, NULL);
145 if (data == NULL)
146 goto fail_close;
147
148 /* How many symbols are there? */
149 nsyms = (shdr->sh_size
150 / INTUSE(gelf_fsize) (elf, ELF_T_SYM, 1, data->d_version));
151
152 /* Create the hash table. */
153 table = nlist_fshash_init (nsyms);
154 if (table == NULL)
155 {
156 __libelf_seterrno (ELF_E_NOMEM);
157 goto fail_close;
158 }
159
160 /* Iterate over all the symbols in the section. */
161 for (cnt = 0; cnt < nsyms; ++cnt)
162 {
163 struct hashentry mem;
164 GElf_Sym *sym;
165
166 /* Get the symbol. */
167 sym = INTUSE(gelf_getsym) (data, cnt, &mem.sym);
168 if (sym == NULL)
169 goto fail_dealloc;
170
171 /* Get the name of the symbol. */
172 mem.str = INTUSE(elf_strptr) (elf, shdr->sh_link, sym->st_name);
173 if (mem.str == NULL)
174 goto fail_dealloc;
175
176 /* Don't allow zero-length strings. */
177 if (mem.str[0] == '\0')
178 continue;
179
180 /* And add it to the hash table. Note that we are using the
181 overwrite version. This will ensure that
182 a) global symbols are preferred over local symbols since
183 they are all located at the end
184 b) if there are multiple local symbols with the same name
185 the last one is used.
186 */
187 (void) nlist_fshash_overwrite (table, mem.str, 0, &mem);
188 }
189
190 /* Now it is time to look for the symbols the user asked for.
191 XXX What is a `null name/null string'? This is what the
192 standard says terminates the list. Is it a null pointer
193 or a zero-length string? We test for both... */
194 while (nl->n_name != NULL && nl->n_name[0] != '\0')
195 {
196 struct hashentry search;
197 const struct hashentry *found;
198
199 /* Search for a matching entry in the hash table. */
200 search.str = nl->n_name;
201 found = nlist_fshash_find (table, nl->n_name, 0, &search);
202
203 if (found != NULL)
204 {
205 /* Found it. */
206 nl->n_value = found->sym.st_value;
207 nl->n_scnum = found->sym.st_shndx;
208 nl->n_type = GELF_ST_TYPE (found->sym.st_info);
209 /* XXX What shall we fill in the next fields? */
210 nl->n_sclass = 0;
211 nl->n_numaux = 0;
212 }
213 else
214 {
215 /* Not there. */
216 nl->n_value = 0;
217 nl->n_scnum = 0;
218 nl->n_type = 0;
219 nl->n_sclass = 0;
220 nl->n_numaux = 0;
221 }
222
223 /* Next search request. */
224 ++nl;
225 }
226
227 /* Free the resources. */
228 nlist_fshash_fini (table);
229
230 /* We do not need the ELF descriptor anymore. */
231 (void) INTUSE(elf_end) (elf);
232
233 /* Neither the file descriptor. */
234 (void) close (fd);
235
236 return 0;
237
238 fail_dealloc:
239 nlist_fshash_fini (table);
240
241 fail_close:
242 /* We do not need the ELF descriptor anymore. */
243 (void) INTUSE(elf_end) (elf);
244
245 fail_fd:
246 /* Neither the file descriptor. */
247 (void) close (fd);
248
249 fail:
250 /* We have to set all entries to zero. */
251 while (nl->n_name != NULL && nl->n_name[0] != '\0')
252 {
253 nl->n_value = 0;
254 nl->n_scnum = 0;
255 nl->n_type = 0;
256 nl->n_sclass = 0;
257 nl->n_numaux = 0;
258
259 /* Next entry. */
260 ++nl;
261 }
262
263 return -1;
264 }
265