1 /* $OpenBSD: resolve.c,v 1.22 2004/05/25 15:56:18 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 39 elf_object_t *_dl_objects; 40 elf_object_t *_dl_last_object; 41 42 /* 43 * Add a new dynamic object to the object list. 44 */ 45 void 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 */ 70 elf_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 80 object = _dl_malloc(sizeof(elf_object_t)); 81 object->prev = object->next = NULL; 82 83 object->load_dyn = dynp; 84 while (dynp->d_tag != DT_NULL) { 85 if (dynp->d_tag < DT_NUM) 86 object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val; 87 else if (dynp->d_tag >= DT_LOPROC && 88 dynp->d_tag < DT_LOPROC + DT_NUM) 89 object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] = 90 dynp->d_un.d_val; 91 if (dynp->d_tag == DT_TEXTREL) 92 object->dyn.textrel = 1; 93 if (dynp->d_tag == DT_SYMBOLIC) 94 object->dyn.symbolic = 1; 95 if (dynp->d_tag == DT_BIND_NOW) 96 object->dyn.bind_now = 1; 97 dynp++; 98 } 99 100 /* 101 * Now relocate all pointer to dynamic info, but only 102 * the ones which have pointer values. 103 */ 104 if (object->Dyn.info[DT_PLTGOT]) 105 object->Dyn.info[DT_PLTGOT] += loff; 106 if (object->Dyn.info[DT_HASH]) 107 object->Dyn.info[DT_HASH] += loff; 108 if (object->Dyn.info[DT_STRTAB]) 109 object->Dyn.info[DT_STRTAB] += loff; 110 if (object->Dyn.info[DT_SYMTAB]) 111 object->Dyn.info[DT_SYMTAB] += loff; 112 if (object->Dyn.info[DT_RELA]) 113 object->Dyn.info[DT_RELA] += loff; 114 if (object->Dyn.info[DT_SONAME]) 115 object->Dyn.info[DT_SONAME] += loff; 116 if (object->Dyn.info[DT_RPATH]) 117 object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB]; 118 if (object->Dyn.info[DT_REL]) 119 object->Dyn.info[DT_REL] += loff; 120 if (object->Dyn.info[DT_INIT]) 121 object->Dyn.info[DT_INIT] += loff; 122 if (object->Dyn.info[DT_FINI]) 123 object->Dyn.info[DT_FINI] += loff; 124 if (object->Dyn.info[DT_JMPREL]) 125 object->Dyn.info[DT_JMPREL] += loff; 126 127 if (object->Dyn.info[DT_HASH] != 0) { 128 Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH]; 129 130 object->nbuckets = hashtab[0]; 131 object->nchains = hashtab[1]; 132 object->buckets = hashtab + 2; 133 object->chains = object->buckets + object->nbuckets; 134 } 135 136 if (dl_data) { 137 object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr]; 138 object->phdrc = dl_data[AUX_phnum]; 139 } 140 object->obj_type = objtype; 141 object->load_addr = laddr; 142 object->load_offs = loff; 143 object->load_name = _dl_strdup(objname); 144 object->refcount = 1; 145 object->first_child = NULL; 146 object->last_child = NULL; 147 return(object); 148 } 149 150 void 151 _dl_remove_object(elf_object_t *object) 152 { 153 elf_object_t *depobj; 154 155 object->prev->next = object->next; 156 if (object->next) 157 object->next->prev = object->prev; 158 159 if (_dl_last_object == object) 160 _dl_last_object = object->prev; 161 162 if (object->load_name) 163 _dl_free(object->load_name); 164 165 while ((depobj = object->dep_next)) { 166 object->dep_next = object->dep_next->dep_next; 167 _dl_free(depobj); 168 } 169 _dl_free(object); 170 } 171 172 173 elf_object_t * 174 _dl_lookup_object(const char *name) 175 { 176 elf_object_t *object; 177 178 object = _dl_objects; 179 while (object) { 180 if (_dl_strcmp(name, object->load_name) == 0) 181 return(object); 182 object = object->next; 183 } 184 return(0); 185 } 186 187 int find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash, 188 int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym, 189 elf_object_t **weak_object); 190 191 sym_cache *_dl_symcache; 192 int _dl_symcachestat_hits; 193 int _dl_symcachestat_lookups; 194 195 Elf_Addr 196 _dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx, 197 elf_object_t *startlook, const Elf_Sym **ref, int flags, int req_size) 198 { 199 Elf_Addr ret; 200 const Elf_Sym *sym; 201 const char *symn; 202 203 _dl_symcachestat_lookups ++; 204 if ((_dl_symcache != NULL) && 205 (symidx < req_obj->nchains) && 206 (_dl_symcache[symidx].sym != NULL) && 207 (_dl_symcache[symidx].flags == flags)) { 208 209 _dl_symcachestat_hits++; 210 *ref = _dl_symcache[symidx].sym; 211 return _dl_symcache[symidx].offset; 212 } 213 214 sym = req_obj->dyn.symtab; 215 sym += symidx; 216 symn = req_obj->dyn.strtab + sym->st_name; 217 218 ret = _dl_find_symbol(symn, startlook, ref, flags, req_size, req_obj); 219 220 if ((_dl_symcache != NULL) && 221 (symidx < req_obj->nchains)) { 222 _dl_symcache[symidx].sym = *ref; 223 _dl_symcache[symidx].offset = ret; 224 _dl_symcache[symidx].flags = flags; 225 } 226 227 return ret; 228 } 229 230 Elf_Addr 231 _dl_find_symbol(const char *name, elf_object_t *startlook, 232 const Elf_Sym **ref, int flags, int req_size, elf_object_t *req_obj) 233 { 234 const Elf_Sym *weak_sym = NULL; 235 unsigned long h = 0; 236 const char *p = name; 237 elf_object_t *object, *weak_object = NULL; 238 int found = 0; 239 int lastchance = 0; 240 241 while (*p) { 242 unsigned long g; 243 h = (h << 4) + *p++; 244 if ((g = h & 0xf0000000)) 245 h ^= g >> 24; 246 h &= ~g; 247 } 248 249 if (req_obj->dyn.symbolic) 250 if (find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym, 251 &weak_object)) { 252 object = req_obj; 253 found = 1; 254 goto found; 255 } 256 257 retry_nonglobal_dlo: 258 for (object = startlook; object; 259 object = ((flags & SYM_SEARCH_SELF) ? 0 : object->next)) { 260 261 if ((lastchance == 0) && 262 ((object->obj_flags & RTLD_GLOBAL) == 0) && 263 (object->obj_type == OBJTYPE_DLO) && 264 (object != req_obj)) 265 continue; 266 267 if (find_symbol_obj(object, name, h, flags, ref, &weak_sym, 268 &weak_object)) { 269 found = 1; 270 break; 271 } 272 } 273 274 found: 275 if (weak_object != NULL && found == 0) { 276 object=weak_object; 277 *ref = weak_sym; 278 found = 1; 279 } 280 281 if (found == 0) { 282 if (lastchance == 0) { 283 lastchance = 1; 284 goto retry_nonglobal_dlo; 285 } 286 if (flags & SYM_WARNNOTFOUND) 287 _dl_printf("%s:%s: undefined symbol '%s'\n", 288 _dl_progname, req_obj->load_name, name); 289 return (0); 290 } 291 292 if (req_size != (*ref)->st_size && req_size != 0 && 293 (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) { 294 _dl_printf("%s:%s: %s : WARNING: " 295 "symbol(%s) size mismatch, relink your program\n", 296 _dl_progname, req_obj->load_name, 297 object->load_name, name); 298 } 299 300 return (object->load_offs); 301 } 302 303 int 304 find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash, 305 int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym, 306 elf_object_t **weak_object) 307 { 308 const Elf_Sym *symt = object->dyn.symtab; 309 const char *strt = object->dyn.strtab; 310 long si; 311 const char *symn; 312 313 for (si = object->buckets[hash % object->nbuckets]; 314 si != STN_UNDEF; si = object->chains[si]) { 315 const Elf_Sym *sym = symt + si; 316 317 if (sym->st_value == 0) 318 continue; 319 320 if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE && 321 ELF_ST_TYPE(sym->st_info) != STT_OBJECT && 322 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 323 continue; 324 325 symn = strt + sym->st_name; 326 if (sym != *ref && _dl_strcmp(symn, name)) 327 continue; 328 329 /* allow this symbol if we are referring to a function 330 * which has a value, even if section is UNDEF. 331 * this allows &func to refer to PLT as per the 332 * ELF spec. st_value is checked above. 333 * if flags has SYM_PLT set, we must have actual 334 * symbol, so this symbol is skipped. 335 */ 336 if (sym->st_shndx == SHN_UNDEF) { 337 if ((flags & SYM_PLT) || sym->st_value == 0 || 338 ELF_ST_TYPE(sym->st_info) != STT_FUNC) 339 continue; 340 } 341 342 if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) { 343 *ref = sym; 344 return 1; 345 } else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) { 346 if (!*weak_sym) { 347 *weak_sym = sym; 348 *weak_object = object; 349 } 350 } 351 } 352 return 0; 353 } 354