1 /* Extract symbol list from binary.
2 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2005, 2007, 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 <fcntl.h>
35 #include <gelf.h>
36 #include <libelf.h>
37 #include <nlist.h>
38
39 #include "libelfP.h"
40
41
42 struct hashentry
43 {
44 const char *str;
45 GElf_Sym sym;
46 };
47 #define TYPE struct hashentry
48 /* XXX Use a better hash function some day. */
49 #define HASHFCT(str, len) INTUSE(elf_hash) (str)
50 #define COMPARE(p1, p2) strcmp ((p1)->str, (p2)->str)
51 #define CLASS static
52 #define PREFIX nlist_
53 #define xcalloc(n, m) calloc (n, m)
54 #define next_prime(s) __libelf_next_prime (s)
55 #include <fixedsizehash.h>
56
57
58 int
nlist(const char * filename,struct nlist * nl)59 nlist (const char *filename, struct nlist *nl)
60 {
61 int fd;
62 Elf *elf;
63 Elf_Scn *scn = NULL;
64 Elf_Scn *symscn = NULL;
65 GElf_Shdr shdr_mem;
66 GElf_Shdr *shdr = NULL;
67 Elf_Data *data;
68 struct nlist_fshash *table;
69 size_t nsyms;
70 size_t cnt;
71
72 /* Open the file. */
73 fd = open (filename, O_RDONLY);
74 if (fd == -1)
75 {
76 __libelf_seterrno (ELF_E_NOFILE);
77 goto fail;
78 }
79
80 /* For compatibility reasons (`nlist' existed before ELF and libelf)
81 we don't expect the caller to set the ELF version. Do this here
82 as if it hasn't happened yet. */
83 INTUSE(elf_version) (EV_CURRENT);
84
85 /* Now get an ELF descriptor. */
86 elf = INTUSE(elf_begin) (fd, ELF_C_READ_MMAP, NULL);
87 if (elf == NULL)
88 goto fail_fd;
89
90 /* Find a symbol table. We prefer the real symbol table but if it
91 does not exist use the dynamic symbol table. */
92 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
93 {
94 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
95 if (shdr == NULL)
96 goto fail_close;
97
98 /* That is what we are looking for. */
99 if (shdr->sh_type == SHT_SYMTAB)
100 {
101 symscn = scn;
102 break;
103 }
104
105 /* Better than nothing. Remember this section. */
106 if (shdr->sh_type == SHT_DYNSYM)
107 symscn = scn;
108 }
109
110 if (symscn == NULL)
111 /* We haven't found anything. Fail. */
112 goto fail_close;
113
114 /* Re-get the section header in case we found only the dynamic symbol
115 table. */
116 if (scn == NULL)
117 {
118 shdr = INTUSE(gelf_getshdr) (symscn, &shdr_mem);
119 if (unlikely (shdr == NULL))
120 goto fail_close;
121 }
122 /* SHDR->SH_LINK now contains the index of the string section. */
123
124 /* Get the data for the symbol section. */
125 data = INTUSE(elf_getdata) (symscn, NULL);
126 if (data == NULL)
127 goto fail_close;
128
129 /* How many symbols are there? */
130 nsyms = (shdr->sh_size
131 / INTUSE(gelf_fsize) (elf, ELF_T_SYM, 1, EV_CURRENT));
132
133 /* Create the hash table. */
134 table = nlist_fshash_init (nsyms);
135 if (table == NULL)
136 {
137 __libelf_seterrno (ELF_E_NOMEM);
138 goto fail_close;
139 }
140
141 /* Iterate over all the symbols in the section. */
142 for (cnt = 0; cnt < nsyms; ++cnt)
143 {
144 struct hashentry mem;
145 GElf_Sym *sym;
146
147 /* Get the symbol. */
148 sym = INTUSE(gelf_getsym) (data, cnt, &mem.sym);
149 if (sym == NULL)
150 goto fail_dealloc;
151
152 /* Get the name of the symbol. */
153 mem.str = INTUSE(elf_strptr) (elf, shdr->sh_link, sym->st_name);
154 if (mem.str == NULL)
155 goto fail_dealloc;
156
157 /* Don't allow zero-length strings. */
158 if (mem.str[0] == '\0')
159 continue;
160
161 /* And add it to the hash table. Note that we are using the
162 overwrite version. This will ensure that
163 a) global symbols are preferred over local symbols since
164 they are all located at the end
165 b) if there are multiple local symbols with the same name
166 the last one is used.
167 */
168 (void) nlist_fshash_overwrite (table, mem.str, 0, &mem);
169 }
170
171 /* Now it is time to look for the symbols the user asked for.
172 XXX What is a `null name/null string'? This is what the
173 standard says terminates the list. Is it a null pointer
174 or a zero-length string? We test for both... */
175 while (nl->n_name != NULL && nl->n_name[0] != '\0')
176 {
177 struct hashentry search;
178 const struct hashentry *found;
179
180 /* Search for a matching entry in the hash table. */
181 search.str = nl->n_name;
182 found = nlist_fshash_find (table, nl->n_name, 0, &search);
183
184 if (found != NULL)
185 {
186 /* Found it. */
187 nl->n_value = found->sym.st_value;
188 nl->n_scnum = found->sym.st_shndx;
189 nl->n_type = GELF_ST_TYPE (found->sym.st_info);
190 /* XXX What shall we fill in the next fields? */
191 nl->n_sclass = 0;
192 nl->n_numaux = 0;
193 }
194 else
195 {
196 /* Not there. */
197 nl->n_value = 0;
198 nl->n_scnum = 0;
199 nl->n_type = 0;
200 nl->n_sclass = 0;
201 nl->n_numaux = 0;
202 }
203
204 /* Next search request. */
205 ++nl;
206 }
207
208 /* Free the resources. */
209 nlist_fshash_fini (table);
210
211 /* We do not need the ELF descriptor anymore. */
212 (void) INTUSE(elf_end) (elf);
213
214 /* Neither the file descriptor. */
215 (void) close (fd);
216
217 return 0;
218
219 fail_dealloc:
220 nlist_fshash_fini (table);
221
222 fail_close:
223 /* We do not need the ELF descriptor anymore. */
224 (void) INTUSE(elf_end) (elf);
225
226 fail_fd:
227 /* Neither the file descriptor. */
228 (void) close (fd);
229
230 fail:
231 /* We have to set all entries to zero. */
232 while (nl->n_name != NULL && nl->n_name[0] != '\0')
233 {
234 nl->n_value = 0;
235 nl->n_scnum = 0;
236 nl->n_type = 0;
237 nl->n_sclass = 0;
238 nl->n_numaux = 0;
239
240 /* Next entry. */
241 ++nl;
242 }
243
244 return -1;
245 }
246