1 /* $OpenBSD: resolve.c,v 1.56 2011/06/27 16:47:50 sthen Exp $ */ 2 3 /* 4 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 */ 28 29 #define _DYN_LOADER 30 31 #include <sys/types.h> 32 33 #include <nlist.h> 34 #include <link.h> 35 #include "syscall.h" 36 #include "archdep.h" 37 #include "resolve.h" 38 #include "dl_prebind.h" 39 40 elf_object_t *_dl_objects; 41 elf_object_t *_dl_last_object; 42 elf_object_t *_dl_loading_object; 43 44 /* 45 * Add a new dynamic object to the object list. 46 */ 47 void 48 _dl_add_object(elf_object_t *object) 49 { 50 51 /* 52 * if this is a new object, prev will be NULL 53 * != NULL if an object already in the list 54 * prev == NULL for the first item in the list, but that will 55 * be the executable. 56 */ 57 if (object->prev != NULL) 58 return; 59 60 if (_dl_objects == NULL) { /* First object ? */ 61 _dl_last_object = _dl_objects = object; 62 } else { 63 _dl_last_object->next = object; 64 object->prev = _dl_last_object; 65 _dl_last_object = object; 66 } 67 } 68 69 /* 70 * Initialize a new dynamic object. 71 */ 72 elf_object_t * 73 _dl_finalize_object(const char *objname, Elf_Dyn *dynp, Elf_Phdr *phdrp, 74 int phdrc, const int objtype, const long lbase, const long obase) 75 { 76 elf_object_t *object; 77 #if 0 78 _dl_printf("objname [%s], dynp %p, objtype %x lbase %lx, obase %lx\n", 79 objname, dynp, objtype, lbase, obase); 80 #endif 81 object = _dl_malloc(sizeof(elf_object_t)); 82 object->prev = object->next = NULL; 83 84 object->load_dyn = dynp; 85 while (dynp->d_tag != DT_NULL) { 86 if (dynp->d_tag < DT_NUM) 87 object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val; 88 else if (dynp->d_tag >= DT_LOPROC && 89 dynp->d_tag < DT_LOPROC + DT_PROCNUM) 90 object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] = 91 dynp->d_un.d_val; 92 if (dynp->d_tag == DT_TEXTREL) 93 object->dyn.textrel = 1; 94 if (dynp->d_tag == DT_SYMBOLIC) 95 object->dyn.symbolic = 1; 96 if (dynp->d_tag == DT_BIND_NOW) 97 object->obj_flags = RTLD_NOW; 98 dynp++; 99 } 100 101 /* 102 * Now relocate all pointer to dynamic info, but only 103 * the ones which have pointer values. 104 */ 105 if (object->Dyn.info[DT_PLTGOT]) 106 object->Dyn.info[DT_PLTGOT] += obase; 107 if (object->Dyn.info[DT_HASH]) 108 object->Dyn.info[DT_HASH] += obase; 109 if (object->Dyn.info[DT_STRTAB]) 110 object->Dyn.info[DT_STRTAB] += obase; 111 if (object->Dyn.info[DT_SYMTAB]) 112 object->Dyn.info[DT_SYMTAB] += obase; 113 if (object->Dyn.info[DT_RELA]) 114 object->Dyn.info[DT_RELA] += obase; 115 if (object->Dyn.info[DT_SONAME]) 116 object->Dyn.info[DT_SONAME] += object->Dyn.info[DT_STRTAB]; 117 if (object->Dyn.info[DT_RPATH]) 118 object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB]; 119 if (object->Dyn.info[DT_REL]) 120 object->Dyn.info[DT_REL] += obase; 121 if (object->Dyn.info[DT_INIT]) 122 object->Dyn.info[DT_INIT] += obase; 123 if (object->Dyn.info[DT_FINI]) 124 object->Dyn.info[DT_FINI] += obase; 125 if (object->Dyn.info[DT_JMPREL]) 126 object->Dyn.info[DT_JMPREL] += obase; 127 128 if (object->Dyn.info[DT_HASH] != 0) { 129 Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH]; 130 131 object->nbuckets = hashtab[0]; 132 object->nchains = hashtab[1]; 133 object->buckets = hashtab + 2; 134 object->chains = object->buckets + object->nbuckets; 135 } 136 137 object->phdrp = phdrp; 138 object->phdrc = phdrc; 139 object->obj_type = objtype; 140 object->load_base = lbase; 141 object->obj_base = obase; 142 object->load_name = _dl_strdup(objname); 143 if (_dl_loading_object == NULL) { 144 /* 145 * no loading object, object is the loading object, 146 * as it is either executable, or dlopened() 147 */ 148 _dl_loading_object = object->load_object = object; 149 DL_DEB(("head %s\n", object->load_name )); 150 } else { 151 object->load_object = _dl_loading_object; 152 } 153 DL_DEB(("obj %s has %s as head\n", object->load_name, 154 _dl_loading_object->load_name )); 155 object->refcount = 0; 156 TAILQ_INIT(&object->child_list); 157 object->opencount = 0; /* # dlopen() & exe */ 158 object->grprefcount = 0; 159 /* default dev, inode for dlopen-able objects. */ 160 object->dev = 0; 161 object->inode = 0; 162 object->lastlookup = 0; 163 TAILQ_INIT(&object->grpsym_list); 164 TAILQ_INIT(&object->grpref_list); 165 166 return(object); 167 } 168 169 void 170 _dl_tailq_free(struct dep_node *n) 171 { 172 struct dep_node *next; 173 174 while (n != NULL) { 175 next = TAILQ_NEXT(n, next_sib); 176 _dl_free(n); 177 n = next; 178 } 179 } 180 181 elf_object_t *free_objects; 182 183 void _dl_cleanup_objects(void); 184 void 185 _dl_cleanup_objects() 186 { 187 elf_object_t *nobj, *head; 188 struct dep_node *n, *next; 189 190 n = TAILQ_FIRST(&_dlopened_child_list); 191 while (n != NULL) { 192 next = TAILQ_NEXT(n, next_sib); 193 if (OBJECT_DLREF_CNT(n->data) == 0) { 194 TAILQ_REMOVE(&_dlopened_child_list, n, next_sib); 195 _dl_free(n); 196 } 197 n = next; 198 } 199 200 head = free_objects; 201 free_objects = NULL; 202 while (head != NULL) { 203 if (head->load_name) 204 _dl_free(head->load_name); 205 if (head->sod.sod_name) 206 _dl_free((char *)head->sod.sod_name); 207 _dl_tailq_free(TAILQ_FIRST(&head->grpsym_list)); 208 _dl_tailq_free(TAILQ_FIRST(&head->child_list)); 209 _dl_tailq_free(TAILQ_FIRST(&head->grpref_list)); 210 nobj = head->next; 211 _dl_free(head); 212 head = nobj; 213 } 214 } 215 216 void 217 _dl_remove_object(elf_object_t *object) 218 { 219 object->prev->next = object->next; 220 if (object->next) 221 object->next->prev = object->prev; 222 223 if (_dl_last_object == object) 224 _dl_last_object = object->prev; 225 226 object->next = free_objects; 227 free_objects = object; 228 } 229 230 231 int _dl_find_symbol_obj(elf_object_t *object, const char *name, 232 unsigned long hash, int flags, const Elf_Sym **ref, 233 const Elf_Sym **weak_sym, 234 elf_object_t **weak_object); 235 236 sym_cache *_dl_symcache; 237 int _dl_symcachestat_hits; 238 int _dl_symcachestat_lookups; 239 240 241 Elf_Addr 242 _dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx, 243 const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj) 244 { 245 Elf_Addr ret; 246 const Elf_Sym *sym; 247 const char *symn; 248 const elf_object_t *sobj; 249 250 _dl_symcachestat_lookups ++; 251 if (_dl_symcache != NULL && 252 symidx < req_obj->nchains && 253 _dl_symcache[symidx].obj != NULL && 254 _dl_symcache[symidx].sym != NULL && 255 _dl_symcache[symidx].flags == flags) { 256 257 _dl_symcachestat_hits++; 258 sobj = _dl_symcache[symidx].obj; 259 *this = _dl_symcache[symidx].sym; 260 if (pobj) 261 *pobj = sobj; 262 if (_dl_prebind_validate) /* XXX */ 263 prebind_validate(req_obj, symidx, flags, ref_sym); 264 return sobj->obj_base; 265 } 266 267 sym = req_obj->dyn.symtab; 268 sym += symidx; 269 symn = req_obj->dyn.strtab + sym->st_name; 270 271 ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj); 272 273 if (pobj) 274 *pobj = sobj; 275 276 if (_dl_symcache != NULL && symidx < req_obj->nchains) { 277 #if 0 278 DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n", 279 symidx, 280 _dl_symcache[symidx].sym, *this, 281 _dl_symcache[symidx].obj, sobj, sobj->load_name, 282 sobj->dyn.strtab + (*this)->st_name, 283 _dl_symcache[symidx].flags, flags, req_obj->load_name)); 284 #endif 285 286 _dl_symcache[symidx].sym = *this; 287 _dl_symcache[symidx].obj = sobj; 288 _dl_symcache[symidx].flags = flags; 289 } 290 291 return ret; 292 } 293 294 int _dl_searchnum = 0; 295 void 296 _dl_newsymsearch(void) 297 { 298 _dl_searchnum += 1; 299 300 if (_dl_searchnum < 0) { 301 /* 302 * If the signed number rolls over, reset all counters so 303 * we dont get accidental collision. 304 */ 305 elf_object_t *walkobj; 306 for (walkobj = _dl_objects; 307 walkobj != NULL; 308 walkobj = walkobj->next) { 309 walkobj->lastlookup = 0; 310 } 311 _dl_searchnum = 1; 312 } 313 } 314 315 Elf_Addr 316 _dl_find_symbol(const char *name, const Elf_Sym **this, 317 int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj, 318 const elf_object_t **pobj) 319 { 320 const Elf_Sym *weak_sym = NULL; 321 unsigned long h = 0; 322 const char *p = name; 323 elf_object_t *object = NULL, *weak_object = NULL; 324 int found = 0; 325 struct dep_node *n, *m; 326 327 328 while (*p) { 329 unsigned long g; 330 h = (h << 4) + *p++; 331 if ((g = h & 0xf0000000)) 332 h ^= g >> 24; 333 h &= ~g; 334 } 335 336 if (req_obj->dyn.symbolic) 337 if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym, 338 &weak_object)) { 339 object = req_obj; 340 found = 1; 341 goto found; 342 } 343 344 if (flags & SYM_SEARCH_OBJ) { 345 if (_dl_find_symbol_obj(req_obj, name, h, flags, this, 346 &weak_sym, &weak_object)) { 347 object = req_obj; 348 found = 1; 349 } 350 } else if (flags & SYM_DLSYM) { 351 if (_dl_find_symbol_obj(req_obj, name, h, flags, this, 352 &weak_sym, &weak_object)) { 353 object = req_obj; 354 found = 1; 355 } 356 if (weak_object != NULL && found == 0) { 357 object=weak_object; 358 *this = weak_sym; 359 found = 1; 360 } 361 /* search dlopened obj and all children */ 362 363 if (found == 0) { 364 TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list, 365 next_sib) { 366 if (_dl_find_symbol_obj(n->data, name, h, 367 flags, this, 368 &weak_sym, &weak_object)) { 369 object = n->data; 370 found = 1; 371 break; 372 } 373 } 374 } 375 } else { 376 int skip = 0; 377 378 if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT)) 379 skip = 1; 380 381 _dl_newsymsearch(); 382 383 /* 384 * search dlopened objects: global or req_obj == dlopened_obj 385 * and and it's children 386 */ 387 TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) { 388 if (((n->data->obj_flags & RTLD_GLOBAL) == 0) && 389 (n->data != req_obj->load_object)) 390 continue; 391 392 n->data->lastlookup_head = _dl_searchnum; 393 TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) { 394 if (skip == 1) { 395 if (m->data == req_obj) { 396 skip = 0; 397 if (flags & SYM_SEARCH_NEXT) 398 continue; 399 } else 400 continue; 401 } 402 if ((flags & SYM_SEARCH_OTHER) && 403 (m->data == req_obj)) 404 continue; 405 m->data->lastlookup = _dl_searchnum; 406 if (_dl_find_symbol_obj(m->data, name, h, flags, 407 this, &weak_sym, &weak_object)) { 408 object = m->data; 409 found = 1; 410 goto found; 411 } 412 } 413 } 414 } 415 416 found: 417 if (weak_object != NULL && found == 0) { 418 object=weak_object; 419 *this = weak_sym; 420 found = 1; 421 } 422 423 424 if (found == 0) { 425 if ((ref_sym == NULL || 426 (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) && 427 (flags & SYM_WARNNOTFOUND)) 428 _dl_printf("%s:%s: undefined symbol '%s'\n", 429 _dl_progname, req_obj->load_name, name); 430 return (0); 431 } 432 433 if (ref_sym != NULL && ref_sym->st_size != 0 && 434 (ref_sym->st_size != (*this)->st_size) && 435 (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) { 436 _dl_printf("%s:%s: %s : WARNING: " 437 "symbol(%s) size mismatch, relink your program\n", 438 _dl_progname, req_obj->load_name, 439 object->load_name, name); 440 } 441 442 if (pobj) 443 *pobj = object; 444 445 return (object->obj_base); 446 } 447 448 int 449 _dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash, 450 int flags, const Elf_Sym **this, const Elf_Sym **weak_sym, 451 elf_object_t **weak_object) 452 { 453 const Elf_Sym *symt = object->dyn.symtab; 454 const char *strt = object->dyn.strtab; 455 long si; 456 const char *symn; 457 458 for (si = object->buckets[hash % object->nbuckets]; 459 si != STN_UNDEF; si = object->chains[si]) { 460 const Elf_Sym *sym = symt + si; 461 462 if (sym->st_value == 0) 463 continue; 464 465 if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE && 466 ELF_ST_TYPE(sym->st_info) != STT_OBJECT && 467 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 468 continue; 469 470 symn = strt + sym->st_name; 471 if (sym != *this && _dl_strcmp(symn, name)) 472 continue; 473 474 /* allow this symbol if we are referring to a function 475 * which has a value, even if section is UNDEF. 476 * this allows &func to refer to PLT as per the 477 * ELF spec. st_value is checked above. 478 * if flags has SYM_PLT set, we must have actual 479 * symbol, so this symbol is skipped. 480 */ 481 if (sym->st_shndx == SHN_UNDEF) { 482 if ((flags & SYM_PLT) || sym->st_value == 0 || 483 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 484 continue; 485 } 486 487 if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) { 488 *this = sym; 489 return 1; 490 } else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) { 491 if (!*weak_sym) { 492 *weak_sym = sym; 493 *weak_object = object; 494 } 495 } 496 } 497 return 0; 498 } 499 500 void 501 _dl_debug_state(void) 502 { 503 /* Debugger stub */ 504 } 505