1 | /* Look up a symbol in a shared object loaded by `dlopen'. |
2 | Copyright (C) 1999-2018 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 | _dl_tls_symaddr (struct link_map *map, const ElfW(Sym) *ref) |
45 | { |
46 | # ifndef DONT_USE_TLS_INDEX |
47 | tls_index tmp = |
48 | { |
49 | .ti_module = map->l_tls_modid, |
50 | .ti_offset = ref->st_value |
51 | }; |
52 | |
53 | return __TLS_GET_ADDR (&tmp); |
54 | # else |
55 | return __TLS_GET_ADDR (map->l_tls_modid, ref->st_value); |
56 | # endif |
57 | } |
58 | #endif |
59 | |
60 | |
61 | struct call_dl_lookup_args |
62 | { |
63 | /* Arguments to do_dlsym. */ |
64 | struct link_map *map; |
65 | const char *name; |
66 | struct r_found_version *vers; |
67 | int flags; |
68 | |
69 | /* Return values of do_dlsym. */ |
70 | lookup_t loadbase; |
71 | const ElfW(Sym) **refp; |
72 | }; |
73 | |
74 | static void |
75 | call_dl_lookup (void *ptr) |
76 | { |
77 | struct call_dl_lookup_args *args = (struct call_dl_lookup_args *) ptr; |
78 | args->map = GLRO(dl_lookup_symbol_x) (args->name, args->map, args->refp, |
79 | args->map->l_scope, args->vers, 0, |
80 | args->flags, NULL); |
81 | } |
82 | |
83 | |
84 | static void * |
85 | do_sym (void *handle, const char *name, void *who, |
86 | struct r_found_version *vers, int flags) |
87 | { |
88 | const ElfW(Sym) *ref = NULL; |
89 | lookup_t result; |
90 | ElfW(Addr) caller = (ElfW(Addr)) who; |
91 | |
92 | struct link_map *l = _dl_find_dso_for_object (caller); |
93 | /* If the address is not recognized the call comes from the main |
94 | program (we hope). */ |
95 | struct link_map *match = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded; |
96 | |
97 | if (handle == RTLD_DEFAULT) |
98 | { |
99 | /* Search the global scope. We have the simple case where |
100 | we look up in the scope of an object which was part of |
101 | the initial binary. And then the more complex part |
102 | where the object is dynamically loaded and the scope |
103 | array can change. */ |
104 | if (RTLD_SINGLE_THREAD_P) |
105 | result = GLRO(dl_lookup_symbol_x) (name, match, &ref, |
106 | match->l_scope, vers, 0, |
107 | flags | DL_LOOKUP_ADD_DEPENDENCY, |
108 | NULL); |
109 | else |
110 | { |
111 | struct call_dl_lookup_args args; |
112 | args.name = name; |
113 | args.map = match; |
114 | args.vers = vers; |
115 | args.flags |
116 | = flags | DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK; |
117 | args.refp = &ref; |
118 | |
119 | THREAD_GSCOPE_SET_FLAG (); |
120 | struct dl_exception exception; |
121 | int err = _dl_catch_exception (&exception, call_dl_lookup, &args); |
122 | THREAD_GSCOPE_RESET_FLAG (); |
123 | if (__glibc_unlikely (exception.errstring != NULL)) |
124 | _dl_signal_exception (err, &exception, NULL); |
125 | |
126 | result = args.map; |
127 | } |
128 | } |
129 | else if (handle == RTLD_NEXT) |
130 | { |
131 | if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded)) |
132 | { |
133 | if (match == NULL |
134 | || caller < match->l_map_start |
135 | || caller >= match->l_map_end) |
136 | _dl_signal_error (0, NULL, NULL, N_("\ |
137 | RTLD_NEXT used in code not dynamically loaded" )); |
138 | } |
139 | |
140 | struct link_map *l = match; |
141 | while (l->l_loader != NULL) |
142 | l = l->l_loader; |
143 | |
144 | result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope, |
145 | vers, 0, 0, match); |
146 | } |
147 | else |
148 | { |
149 | /* Search the scope of the given object. */ |
150 | struct link_map *map = handle; |
151 | result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope, |
152 | vers, 0, flags, NULL); |
153 | } |
154 | |
155 | if (ref != NULL) |
156 | { |
157 | void *value; |
158 | |
159 | #ifdef SHARED |
160 | if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS) |
161 | /* The found symbol is a thread-local storage variable. |
162 | Return the address for to the current thread. */ |
163 | value = _dl_tls_symaddr (result, ref); |
164 | else |
165 | #endif |
166 | value = DL_SYMBOL_ADDRESS (result, ref); |
167 | |
168 | /* Resolve indirect function address. */ |
169 | if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC)) |
170 | { |
171 | DL_FIXUP_VALUE_TYPE fixup |
172 | = DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value); |
173 | fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup)); |
174 | value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup); |
175 | } |
176 | |
177 | #ifdef SHARED |
178 | /* Auditing checkpoint: we have a new binding. Provide the |
179 | auditing libraries the possibility to change the value and |
180 | tell us whether further auditing is wanted. */ |
181 | if (__glibc_unlikely (GLRO(dl_naudit) > 0)) |
182 | { |
183 | const char *strtab = (const char *) D_PTR (result, |
184 | l_info[DT_STRTAB]); |
185 | /* Compute index of the symbol entry in the symbol table of |
186 | the DSO with the definition. */ |
187 | unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, |
188 | l_info[DT_SYMTAB])); |
189 | |
190 | if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0) |
191 | { |
192 | unsigned int altvalue = 0; |
193 | struct audit_ifaces *afct = GLRO(dl_audit); |
194 | /* Synthesize a symbol record where the st_value field is |
195 | the result. */ |
196 | ElfW(Sym) sym = *ref; |
197 | sym.st_value = (ElfW(Addr)) value; |
198 | |
199 | for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt) |
200 | { |
201 | if (afct->symbind != NULL |
202 | && ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM) |
203 | != 0 |
204 | || ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO) |
205 | != 0))) |
206 | { |
207 | unsigned int flags = altvalue | LA_SYMB_DLSYM; |
208 | uintptr_t new_value |
209 | = afct->symbind (&sym, ndx, |
210 | &match->l_audit[cnt].cookie, |
211 | &result->l_audit[cnt].cookie, |
212 | &flags, strtab + ref->st_name); |
213 | if (new_value != (uintptr_t) sym.st_value) |
214 | { |
215 | altvalue = LA_SYMB_ALTVALUE; |
216 | sym.st_value = new_value; |
217 | } |
218 | } |
219 | |
220 | afct = afct->next; |
221 | } |
222 | |
223 | value = (void *) sym.st_value; |
224 | } |
225 | } |
226 | #endif |
227 | |
228 | return value; |
229 | } |
230 | |
231 | return NULL; |
232 | } |
233 | |
234 | |
235 | void * |
236 | _dl_vsym (void *handle, const char *name, const char *version, void *who) |
237 | { |
238 | struct r_found_version vers; |
239 | |
240 | /* Compute hash value to the version string. */ |
241 | vers.name = version; |
242 | vers.hidden = 1; |
243 | vers.hash = _dl_elf_hash (version); |
244 | /* We don't have a specific file where the symbol can be found. */ |
245 | vers.filename = NULL; |
246 | |
247 | return do_sym (handle, name, who, &vers, 0); |
248 | } |
249 | |
250 | |
251 | void * |
252 | _dl_sym (void *handle, const char *name, void *who) |
253 | { |
254 | return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST); |
255 | } |
256 | |