resolve.c revision 1.26
1/* $OpenBSD: resolve.c,v 1.26 2005/04/06 00:16:53 deraadt 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 39elf_object_t *_dl_objects; 40elf_object_t *_dl_last_object; 41 42/* 43 * Add a new dynamic object to the object list. 44 */ 45void 46_dl_add_object(elf_object_t *object) 47{ 48 49 /* 50 * if this is a new object, prev will be NULL 51 * != NULL if an object already in the list 52 * prev == NULL for the first item in the list, but that will 53 * be the executable. 54 */ 55 if (object->prev != NULL) 56 return; 57 58 if (_dl_objects == NULL) { /* First object ? */ 59 _dl_last_object = _dl_objects = object; 60 } else { 61 _dl_last_object->next = object; 62 object->prev = _dl_last_object; 63 _dl_last_object = object; 64 } 65} 66 67/* 68 * Initialize a new dynamic object. 69 */ 70elf_object_t * 71_dl_finalize_object(const char *objname, Elf_Dyn *dynp, const u_long *dl_data, 72 const int objtype, const long laddr, const long loff) 73{ 74 elf_object_t *object; 75#if 0 76 _dl_printf("objname [%s], dynp %p, dl_data %p, objtype %x laddr %lx, loff %lx\n", 77 objname, dynp, dl_data, objtype, laddr, loff); 78#endif 79 object = _dl_malloc(sizeof(elf_object_t)); 80 object->prev = object->next = NULL; 81 82 object->load_dyn = dynp; 83 while (dynp->d_tag != DT_NULL) { 84 if (dynp->d_tag < DT_NUM) 85 object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val; 86 else if (dynp->d_tag >= DT_LOPROC && 87 dynp->d_tag < DT_LOPROC + DT_NUM) 88 object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] = 89 dynp->d_un.d_val; 90 if (dynp->d_tag == DT_TEXTREL) 91 object->dyn.textrel = 1; 92 if (dynp->d_tag == DT_SYMBOLIC) 93 object->dyn.symbolic = 1; 94 if (dynp->d_tag == DT_BIND_NOW) 95 object->dyn.bind_now = 1; 96 dynp++; 97 } 98 99 /* 100 * Now relocate all pointer to dynamic info, but only 101 * the ones which have pointer values. 102 */ 103 if (object->Dyn.info[DT_PLTGOT]) 104 object->Dyn.info[DT_PLTGOT] += loff; 105 if (object->Dyn.info[DT_HASH]) 106 object->Dyn.info[DT_HASH] += loff; 107 if (object->Dyn.info[DT_STRTAB]) 108 object->Dyn.info[DT_STRTAB] += loff; 109 if (object->Dyn.info[DT_SYMTAB]) 110 object->Dyn.info[DT_SYMTAB] += loff; 111 if (object->Dyn.info[DT_RELA]) 112 object->Dyn.info[DT_RELA] += loff; 113 if (object->Dyn.info[DT_SONAME]) 114 object->Dyn.info[DT_SONAME] += loff; 115 if (object->Dyn.info[DT_RPATH]) 116 object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB]; 117 if (object->Dyn.info[DT_REL]) 118 object->Dyn.info[DT_REL] += loff; 119 if (object->Dyn.info[DT_INIT]) 120 object->Dyn.info[DT_INIT] += loff; 121 if (object->Dyn.info[DT_FINI]) 122 object->Dyn.info[DT_FINI] += loff; 123 if (object->Dyn.info[DT_JMPREL]) 124 object->Dyn.info[DT_JMPREL] += loff; 125 126 if (object->Dyn.info[DT_HASH] != 0) { 127 Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH]; 128 129 object->nbuckets = hashtab[0]; 130 object->nchains = hashtab[1]; 131 object->buckets = hashtab + 2; 132 object->chains = object->buckets + object->nbuckets; 133 } 134 135 if (dl_data) { 136 object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr]; 137 object->phdrc = dl_data[AUX_phnum]; 138 } 139 object->obj_type = objtype; 140 object->load_addr = laddr; 141 object->load_offs = loff; 142 object->load_name = _dl_strdup(objname); 143 object->refcount = 1; 144 object->first_child = NULL; 145 object->last_child = NULL; 146 /* default dev, inode for dlopen-able objects. */ 147 object->dev = 0; 148 object->inode = 0; 149 150 return(object); 151} 152 153void 154_dl_remove_object(elf_object_t *object) 155{ 156 elf_object_t *depobj; 157 158 object->prev->next = object->next; 159 if (object->next) 160 object->next->prev = object->prev; 161 162 if (_dl_last_object == object) 163 _dl_last_object = object->prev; 164 165 if (object->load_name) 166 _dl_free(object->load_name); 167 168 while ((depobj = object->dep_next)) { 169 object->dep_next = object->dep_next->dep_next; 170 _dl_free(depobj); 171 } 172 _dl_free(object); 173} 174 175 176elf_object_t * 177_dl_lookup_object(const char *name) 178{ 179 elf_object_t *object; 180 181 object = _dl_objects; 182 while (object) { 183 if (_dl_strcmp(name, object->load_name) == 0) 184 return(object); 185 object = object->next; 186 } 187 return(0); 188} 189 190int find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash, 191 int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym, 192 elf_object_t **weak_object); 193 194sym_cache *_dl_symcache; 195int _dl_symcachestat_hits; 196int _dl_symcachestat_lookups; 197 198Elf_Addr 199_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx, 200 elf_object_t *startlook, const Elf_Sym **ref, const elf_object_t **pobj, 201 int flags, int req_size) 202{ 203 Elf_Addr ret; 204 const Elf_Sym *sym; 205 const char *symn; 206 const elf_object_t *sobj; 207 208 _dl_symcachestat_lookups ++; 209 if ((_dl_symcache != NULL) && 210 (symidx < req_obj->nchains) && 211 (_dl_symcache[symidx].obj != NULL) && 212 (_dl_symcache[symidx].sym != NULL) && 213 (_dl_symcache[symidx].flags == flags)) { 214 215 _dl_symcachestat_hits++; 216 sobj = _dl_symcache[symidx].obj; 217 *ref = _dl_symcache[symidx].sym; 218 if (pobj) 219 *pobj = sobj; 220 return sobj->load_offs; 221 } 222 223 sym = req_obj->dyn.symtab; 224 sym += symidx; 225 symn = req_obj->dyn.strtab + sym->st_name; 226 227 ret = _dl_find_symbol(symn, startlook, ref, &sobj, 228 flags, req_size, req_obj); 229 230 if (pobj) 231 *pobj = sobj; 232 233 if ((_dl_symcache != NULL) && 234 (symidx < req_obj->nchains)) { 235 _dl_symcache[symidx].sym = *ref; 236 _dl_symcache[symidx].obj = sobj; 237 _dl_symcache[symidx].flags = flags; 238 } 239 240 return ret; 241} 242 243Elf_Addr 244_dl_find_symbol(const char *name, elf_object_t *startlook, 245 const Elf_Sym **ref, const elf_object_t **pobj, 246 int flags, int req_size, elf_object_t *req_obj) 247{ 248 const Elf_Sym *weak_sym = NULL; 249 unsigned long h = 0; 250 const char *p = name; 251 elf_object_t *object, *weak_object = NULL; 252 int found = 0; 253 int lastchance = 0; 254 255 while (*p) { 256 unsigned long g; 257 h = (h << 4) + *p++; 258 if ((g = h & 0xf0000000)) 259 h ^= g >> 24; 260 h &= ~g; 261 } 262 263 if (req_obj->dyn.symbolic) 264 if (find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym, 265 &weak_object)) { 266 object = req_obj; 267 found = 1; 268 goto found; 269 } 270 271retry_nonglobal_dlo: 272 for (object = startlook; object; 273 object = ((flags & SYM_SEARCH_SELF) ? 0 : object->next)) { 274 275 if ((lastchance == 0) && 276 ((object->obj_flags & RTLD_GLOBAL) == 0) && 277 (object->obj_type == OBJTYPE_DLO) && 278 (object != req_obj)) 279 continue; 280 281 if (find_symbol_obj(object, name, h, flags, ref, &weak_sym, 282 &weak_object)) { 283 found = 1; 284 break; 285 } 286 } 287 288found: 289 if (weak_object != NULL && found == 0) { 290 object=weak_object; 291 *ref = weak_sym; 292 found = 1; 293 } 294 295 if (found == 0) { 296 if (lastchance == 0) { 297 lastchance = 1; 298 goto retry_nonglobal_dlo; 299 } 300 if (flags & SYM_WARNNOTFOUND) 301 _dl_printf("%s:%s: undefined symbol '%s'\n", 302 _dl_progname, req_obj->load_name, name); 303 return (0); 304 } 305 306 if (req_size != (*ref)->st_size && req_size != 0 && 307 (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) { 308 _dl_printf("%s:%s: %s : WARNING: " 309 "symbol(%s) size mismatch, relink your program\n", 310 _dl_progname, req_obj->load_name, 311 object->load_name, name); 312 } 313 314 if (pobj) 315 *pobj = object; 316 317 return (object->load_offs); 318} 319 320int 321find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash, 322 int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym, 323 elf_object_t **weak_object) 324{ 325 const Elf_Sym *symt = object->dyn.symtab; 326 const char *strt = object->dyn.strtab; 327 long si; 328 const char *symn; 329 330 for (si = object->buckets[hash % object->nbuckets]; 331 si != STN_UNDEF; si = object->chains[si]) { 332 const Elf_Sym *sym = symt + si; 333 334 if (sym->st_value == 0) 335 continue; 336 337 if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE && 338 ELF_ST_TYPE(sym->st_info) != STT_OBJECT && 339 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 340 continue; 341 342 symn = strt + sym->st_name; 343 if (sym != *ref && _dl_strcmp(symn, name)) 344 continue; 345 346 /* allow this symbol if we are referring to a function 347 * which has a value, even if section is UNDEF. 348 * this allows &func to refer to PLT as per the 349 * ELF spec. st_value is checked above. 350 * if flags has SYM_PLT set, we must have actual 351 * symbol, so this symbol is skipped. 352 */ 353 if (sym->st_shndx == SHN_UNDEF) { 354 if ((flags & SYM_PLT) || sym->st_value == 0 || 355 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 356 continue; 357 } 358 359 if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) { 360 *ref = sym; 361 return 1; 362 } else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) { 363 if (!*weak_sym) { 364 *weak_sym = sym; 365 *weak_object = object; 366 } 367 } 368 } 369 return 0; 370} 371