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 #include <unistd.h>
39
40 #include "libelfP.h"
41
42
43 struct hashentry
44 {
45 const char *str;
46 GElf_Sym sym;
47 };
48 #define TYPE struct hashentry
49 /* XXX Use a better hash function some day. */
50 #define HASHFCT(str, len) INTUSE(elf_hash) (str)
51 #define COMPARE(p1, p2) strcmp ((p1)->str, (p2)->str)
52 #define CLASS static
53 #define PREFIX nlist_
54 #define xcalloc(n, m) calloc (n, m)
55 #define next_prime(s) __libelf_next_prime (s)
56 #include <fixedsizehash.h>
57
58
59 int
nlist(const char * filename,struct nlist * nl)60 nlist (const char *filename, struct nlist *nl)
61 {
62 int fd;
63 Elf *elf;
64 Elf_Scn *scn = NULL;
65 Elf_Scn *symscn = NULL;
66 GElf_Shdr shdr_mem;
67 GElf_Shdr *shdr = NULL;
68 Elf_Data *data;
69 struct nlist_fshash *table;
70 size_t nsyms;
71 size_t cnt;
72
73 /* Open the file. */
74 fd = open (filename, O_RDONLY);
75 if (fd == -1)
76 {
77 __libelf_seterrno (ELF_E_NOFILE);
78 goto fail;
79 }
80
81 /* For compatibility reasons (`nlist' existed before ELF and libelf)
82 we don't expect the caller to set the ELF version. Do this here
83 as if it hasn't happened yet. */
84 INTUSE(elf_version) (EV_CURRENT);
85
86 /* Now get an ELF descriptor. */
87 elf = INTUSE(elf_begin) (fd, ELF_C_READ_MMAP, NULL);
88 if (elf == NULL)
89 goto fail_fd;
90
91 /* Find a symbol table. We prefer the real symbol table but if it
92 does not exist use the dynamic symbol table. */
93 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL)
94 {
95 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem);
96 if (shdr == NULL)
97 goto fail_close;
98
99 /* That is what we are looking for. */
100 if (shdr->sh_type == SHT_SYMTAB)
101 {
102 symscn = scn;
103 break;
104 }
105
106 /* Better than nothing. Remember this section. */
107 if (shdr->sh_type == SHT_DYNSYM)
108 symscn = scn;
109 }
110
111 if (symscn == NULL)
112 /* We haven't found anything. Fail. */
113 goto fail_close;
114
115 /* Re-get the section header in case we found only the dynamic symbol
116 table. */
117 if (scn == NULL)
118 {
119 shdr = INTUSE(gelf_getshdr) (symscn, &shdr_mem);
120 if (unlikely (shdr == NULL))
121 goto fail_close;
122 }
123 /* SHDR->SH_LINK now contains the index of the string section. */
124
125 /* Get the data for the symbol section. */
126 data = INTUSE(elf_getdata) (symscn, NULL);
127 if (data == NULL)
128 goto fail_close;
129
130 /* How many symbols are there? */
131 nsyms = (shdr->sh_size
132 / INTUSE(gelf_fsize) (elf, ELF_T_SYM, 1, EV_CURRENT));
133
134 /* Create the hash table. */
135 table = nlist_fshash_init (nsyms);
136 if (table == NULL)
137 {
138 __libelf_seterrno (ELF_E_NOMEM);
139 goto fail_close;
140 }
141
142 /* Iterate over all the symbols in the section. */
143 for (cnt = 0; cnt < nsyms; ++cnt)
144 {
145 struct hashentry mem;
146 GElf_Sym *sym;
147
148 /* Get the symbol. */
149 sym = INTUSE(gelf_getsym) (data, cnt, &mem.sym);
150 if (sym == NULL)
151 goto fail_dealloc;
152
153 /* Get the name of the symbol. */
154 mem.str = INTUSE(elf_strptr) (elf, shdr->sh_link, sym->st_name);
155 if (mem.str == NULL)
156 goto fail_dealloc;
157
158 /* Don't allow zero-length strings. */
159 if (mem.str[0] == '\0')
160 continue;
161
162 /* And add it to the hash table. Note that we are using the
163 overwrite version. This will ensure that
164 a) global symbols are preferred over local symbols since
165 they are all located at the end
166 b) if there are multiple local symbols with the same name
167 the last one is used.
168 */
169 (void) nlist_fshash_overwrite (table, mem.str, 0, &mem);
170 }
171
172 /* Now it is time to look for the symbols the user asked for.
173 XXX What is a `null name/null string'? This is what the
174 standard says terminates the list. Is it a null pointer
175 or a zero-length string? We test for both... */
176 while (nl->n_name != NULL && nl->n_name[0] != '\0')
177 {
178 struct hashentry search;
179 const struct hashentry *found;
180
181 /* Search for a matching entry in the hash table. */
182 search.str = nl->n_name;
183 found = nlist_fshash_find (table, nl->n_name, 0, &search);
184
185 if (found != NULL)
186 {
187 /* Found it. */
188 nl->n_value = found->sym.st_value;
189 nl->n_scnum = found->sym.st_shndx;
190 nl->n_type = GELF_ST_TYPE (found->sym.st_info);
191 /* XXX What shall we fill in the next fields? */
192 nl->n_sclass = 0;
193 nl->n_numaux = 0;
194 }
195 else
196 {
197 /* Not there. */
198 nl->n_value = 0;
199 nl->n_scnum = 0;
200 nl->n_type = 0;
201 nl->n_sclass = 0;
202 nl->n_numaux = 0;
203 }
204
205 /* Next search request. */
206 ++nl;
207 }
208
209 /* Free the resources. */
210 nlist_fshash_fini (table);
211
212 /* We do not need the ELF descriptor anymore. */
213 (void) INTUSE(elf_end) (elf);
214
215 /* Neither the file descriptor. */
216 (void) close (fd);
217
218 return 0;
219
220 fail_dealloc:
221 nlist_fshash_fini (table);
222
223 fail_close:
224 /* We do not need the ELF descriptor anymore. */
225 (void) INTUSE(elf_end) (elf);
226
227 fail_fd:
228 /* Neither the file descriptor. */
229 (void) close (fd);
230
231 fail:
232 /* We have to set all entries to zero. */
233 while (nl->n_name != NULL && nl->n_name[0] != '\0')
234 {
235 nl->n_value = 0;
236 nl->n_scnum = 0;
237 nl->n_type = 0;
238 nl->n_sclass = 0;
239 nl->n_numaux = 0;
240
241 /* Next entry. */
242 ++nl;
243 }
244
245 return -1;
246 }
247