1 | /* Look up a symbol in a shared object loaded by `dlopen'. |
2 | Copyright (C) 1999-2017 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <assert.h> |
20 | #include <stddef.h> |
21 | #include <setjmp.h> |
22 | #include <stdlib.h> |
23 | #include <libintl.h> |
24 | |
25 | #include <dlfcn.h> |
26 | #include <ldsodefs.h> |
27 | #include <dl-hash.h> |
28 | #include <sysdep-cancel.h> |
29 | #include <dl-tls.h> |
30 | #include <dl-irel.h> |
31 | |
32 | |
33 | #ifdef SHARED |
34 | /* Systems which do not have tls_index also probably have to define |
35 | DONT_USE_TLS_INDEX. */ |
36 | |
37 | # ifndef __TLS_GET_ADDR |
38 | # define __TLS_GET_ADDR __tls_get_addr |
39 | # endif |
40 | |
41 | /* Return the symbol address given the map of the module it is in and |
42 | the symbol record. This is used in dl-sym.c. */ |
43 | static void * |
44 | internal_function |
45 | _dl_tls_symaddr (struct link_map *map, const ElfW(Sym) *ref) |
46 | { |
47 | # ifndef DONT_USE_TLS_INDEX |
48 | tls_index tmp = |
49 | { |
50 | .ti_module = map->l_tls_modid, |
51 | .ti_offset = ref->st_value |
52 | }; |
53 | |
54 | return __TLS_GET_ADDR (&tmp); |
55 | # else |
56 | return __TLS_GET_ADDR (map->l_tls_modid, ref->st_value); |
57 | # endif |
58 | } |
59 | #endif |
60 | |
61 | |
62 | struct call_dl_lookup_args |
63 | { |
64 | /* Arguments to do_dlsym. */ |
65 | struct link_map *map; |
66 | const char *name; |
67 | struct r_found_version *vers; |
68 | int flags; |
69 | |
70 | /* Return values of do_dlsym. */ |
71 | lookup_t loadbase; |
72 | const ElfW(Sym) **refp; |
73 | }; |
74 | |
75 | static void |
76 | call_dl_lookup (void *ptr) |
77 | { |
78 | struct call_dl_lookup_args *args = (struct call_dl_lookup_args *) ptr; |
79 | args->map = GLRO(dl_lookup_symbol_x) (args->name, args->map, args->refp, |
80 | args->map->l_scope, args->vers, 0, |
81 | args->flags, NULL); |
82 | } |
83 | |
84 | |
85 | static void * |
86 | internal_function |
87 | do_sym (void *handle, const char *name, void *who, |
88 | struct r_found_version *vers, int flags) |
89 | { |
90 | const ElfW(Sym) *ref = NULL; |
91 | lookup_t result; |
92 | ElfW(Addr) caller = (ElfW(Addr)) who; |
93 | |
94 | struct link_map *l = _dl_find_dso_for_object (caller); |
95 | /* If the address is not recognized the call comes from the main |
96 | program (we hope). */ |
97 | struct link_map *match = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded; |
98 | |
99 | if (handle == RTLD_DEFAULT) |
100 | { |
101 | /* Search the global scope. We have the simple case where |
102 | we look up in the scope of an object which was part of |
103 | the initial binary. And then the more complex part |
104 | where the object is dynamically loaded and the scope |
105 | array can change. */ |
106 | if (RTLD_SINGLE_THREAD_P) |
107 | result = GLRO(dl_lookup_symbol_x) (name, match, &ref, |
108 | match->l_scope, vers, 0, |
109 | flags | DL_LOOKUP_ADD_DEPENDENCY, |
110 | NULL); |
111 | else |
112 | { |
113 | struct call_dl_lookup_args args; |
114 | args.name = name; |
115 | args.map = match; |
116 | args.vers = vers; |
117 | args.flags |
118 | = flags | DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK; |
119 | args.refp = &ref; |
120 | |
121 | THREAD_GSCOPE_SET_FLAG (); |
122 | |
123 | const char *objname; |
124 | const char *errstring = NULL; |
125 | bool malloced; |
126 | int err = _dl_catch_error (&objname, &errstring, &malloced, |
127 | call_dl_lookup, &args); |
128 | |
129 | THREAD_GSCOPE_RESET_FLAG (); |
130 | |
131 | if (__glibc_unlikely (errstring != NULL)) |
132 | { |
133 | /* The lookup was unsuccessful. Rethrow the error. */ |
134 | char *errstring_dup = strdupa (errstring); |
135 | char *objname_dup = strdupa (objname); |
136 | if (malloced) |
137 | free ((char *) errstring); |
138 | |
139 | _dl_signal_error (err, objname_dup, NULL, errstring_dup); |
140 | /* NOTREACHED */ |
141 | } |
142 | |
143 | result = args.map; |
144 | } |
145 | } |
146 | else if (handle == RTLD_NEXT) |
147 | { |
148 | if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded)) |
149 | { |
150 | if (match == NULL |
151 | || caller < match->l_map_start |
152 | || caller >= match->l_map_end) |
153 | _dl_signal_error (0, NULL, NULL, N_("\ |
154 | RTLD_NEXT used in code not dynamically loaded" )); |
155 | } |
156 | |
157 | struct link_map *l = match; |
158 | while (l->l_loader != NULL) |
159 | l = l->l_loader; |
160 | |
161 | result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope, |
162 | vers, 0, 0, match); |
163 | } |
164 | else |
165 | { |
166 | /* Search the scope of the given object. */ |
167 | struct link_map *map = handle; |
168 | result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope, |
169 | vers, 0, flags, NULL); |
170 | } |
171 | |
172 | if (ref != NULL) |
173 | { |
174 | void *value; |
175 | |
176 | #ifdef SHARED |
177 | if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS) |
178 | /* The found symbol is a thread-local storage variable. |
179 | Return the address for to the current thread. */ |
180 | value = _dl_tls_symaddr (result, ref); |
181 | else |
182 | #endif |
183 | value = DL_SYMBOL_ADDRESS (result, ref); |
184 | |
185 | /* Resolve indirect function address. */ |
186 | if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC)) |
187 | { |
188 | DL_FIXUP_VALUE_TYPE fixup |
189 | = DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value); |
190 | fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup)); |
191 | value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup); |
192 | } |
193 | |
194 | #ifdef SHARED |
195 | /* Auditing checkpoint: we have a new binding. Provide the |
196 | auditing libraries the possibility to change the value and |
197 | tell us whether further auditing is wanted. */ |
198 | if (__glibc_unlikely (GLRO(dl_naudit) > 0)) |
199 | { |
200 | const char *strtab = (const char *) D_PTR (result, |
201 | l_info[DT_STRTAB]); |
202 | /* Compute index of the symbol entry in the symbol table of |
203 | the DSO with the definition. */ |
204 | unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, |
205 | l_info[DT_SYMTAB])); |
206 | |
207 | if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0) |
208 | { |
209 | unsigned int altvalue = 0; |
210 | struct audit_ifaces *afct = GLRO(dl_audit); |
211 | /* Synthesize a symbol record where the st_value field is |
212 | the result. */ |
213 | ElfW(Sym) sym = *ref; |
214 | sym.st_value = (ElfW(Addr)) value; |
215 | |
216 | for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt) |
217 | { |
218 | if (afct->symbind != NULL |
219 | && ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM) |
220 | != 0 |
221 | || ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO) |
222 | != 0))) |
223 | { |
224 | unsigned int flags = altvalue | LA_SYMB_DLSYM; |
225 | uintptr_t new_value |
226 | = afct->symbind (&sym, ndx, |
227 | &match->l_audit[cnt].cookie, |
228 | &result->l_audit[cnt].cookie, |
229 | &flags, strtab + ref->st_name); |
230 | if (new_value != (uintptr_t) sym.st_value) |
231 | { |
232 | altvalue = LA_SYMB_ALTVALUE; |
233 | sym.st_value = new_value; |
234 | } |
235 | } |
236 | |
237 | afct = afct->next; |
238 | } |
239 | |
240 | value = (void *) sym.st_value; |
241 | } |
242 | } |
243 | #endif |
244 | |
245 | return value; |
246 | } |
247 | |
248 | return NULL; |
249 | } |
250 | |
251 | |
252 | void * |
253 | internal_function |
254 | _dl_vsym (void *handle, const char *name, const char *version, void *who) |
255 | { |
256 | struct r_found_version vers; |
257 | |
258 | /* Compute hash value to the version string. */ |
259 | vers.name = version; |
260 | vers.hidden = 1; |
261 | vers.hash = _dl_elf_hash (version); |
262 | /* We don't have a specific file where the symbol can be found. */ |
263 | vers.filename = NULL; |
264 | |
265 | return do_sym (handle, name, who, &vers, 0); |
266 | } |
267 | |
268 | |
269 | void * |
270 | internal_function |
271 | _dl_sym (void *handle, const char *name, void *who) |
272 | { |
273 | return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST); |
274 | } |
275 | |