1 /*- 2 * Copyright 1996, 1997, 1998, 1999 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD$ 26 */ 27 28 /* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34 #include <sys/param.h> 35 #include <sys/mman.h> 36 #include <machine/segments.h> 37 #include <machine/sysarch.h> 38 39 #include <dlfcn.h> 40 #include <err.h> 41 #include <errno.h> 42 #include <fcntl.h> 43 #include <stdarg.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <unistd.h> 48 49 #include "debug.h" 50 #include "rtld.h" 51 52 /* 53 * Process the special R_386_COPY relocations in the main program. These 54 * copy data from a shared object into a region in the main program's BSS 55 * segment. 56 * 57 * Returns 0 on success, -1 on failure. 58 */ 59 int 60 do_copy_relocations(Obj_Entry *dstobj) 61 { 62 const Elf_Rel *rellim; 63 const Elf_Rel *rel; 64 65 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 66 67 rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize); 68 for (rel = dstobj->rel; rel < rellim; rel++) { 69 if (ELF_R_TYPE(rel->r_info) == R_386_COPY) { 70 void *dstaddr; 71 const Elf_Sym *dstsym; 72 const char *name; 73 size_t size; 74 const void *srcaddr; 75 const Elf_Sym *srcsym; 76 const Obj_Entry *srcobj, *defobj; 77 SymLook req; 78 int res; 79 80 dstaddr = (void *) (dstobj->relocbase + rel->r_offset); 81 dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info); 82 name = dstobj->strtab + dstsym->st_name; 83 size = dstsym->st_size; 84 symlook_init(&req, name); 85 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info)); 86 req.flags = SYMLOOK_EARLY; 87 88 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 89 res = symlook_obj(&req, srcobj); 90 if (res == 0) { 91 srcsym = req.sym_out; 92 defobj = req.defobj_out; 93 break; 94 } 95 } 96 97 if (srcobj == NULL) { 98 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 99 " relocation in %s", name, dstobj->path); 100 return -1; 101 } 102 103 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 104 memcpy(dstaddr, srcaddr, size); 105 } 106 } 107 108 return 0; 109 } 110 111 /* Initialize the special GOT entries. */ 112 void 113 init_pltgot(Obj_Entry *obj) 114 { 115 if (obj->pltgot != NULL) { 116 obj->pltgot[1] = (Elf_Addr) obj; 117 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 118 } 119 } 120 121 /* Process the non-PLT relocations. */ 122 int 123 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 124 RtldLockState *lockstate) 125 { 126 const Elf_Rel *rellim; 127 const Elf_Rel *rel; 128 SymCache *cache; 129 int r = -1; 130 131 /* 132 * The dynamic loader may be called from a thread, we have 133 * limited amounts of stack available so we cannot use alloca(). 134 */ 135 if (obj != obj_rtld) { 136 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 137 /* No need to check for NULL here */ 138 } else 139 cache = NULL; 140 141 rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize); 142 for (rel = obj->rel; rel < rellim; rel++) { 143 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 144 145 switch (ELF_R_TYPE(rel->r_info)) { 146 147 case R_386_NONE: 148 break; 149 150 case R_386_32: 151 { 152 const Elf_Sym *def; 153 const Obj_Entry *defobj; 154 155 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 156 flags, cache, lockstate); 157 if (def == NULL) 158 goto done; 159 160 *where += (Elf_Addr) (defobj->relocbase + def->st_value); 161 } 162 break; 163 164 case R_386_PC32: 165 /* 166 * I don't think the dynamic linker should ever see this 167 * type of relocation. But the binutils-2.6 tools sometimes 168 * generate it. 169 */ 170 { 171 const Elf_Sym *def; 172 const Obj_Entry *defobj; 173 174 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 175 flags, cache, lockstate); 176 if (def == NULL) 177 goto done; 178 179 *where += 180 (Elf_Addr) (defobj->relocbase + def->st_value) - 181 (Elf_Addr) where; 182 } 183 break; 184 185 case R_386_COPY: 186 /* 187 * These are deferred until all other relocations have 188 * been done. All we do here is make sure that the COPY 189 * relocation is not in a shared library. They are allowed 190 * only in executable files. 191 */ 192 if (!obj->mainprog) { 193 _rtld_error("%s: Unexpected R_386_COPY relocation" 194 " in shared library", obj->path); 195 goto done; 196 } 197 break; 198 199 case R_386_GLOB_DAT: 200 { 201 const Elf_Sym *def; 202 const Obj_Entry *defobj; 203 204 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 205 flags, cache, lockstate); 206 if (def == NULL) 207 goto done; 208 209 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 210 } 211 break; 212 213 case R_386_RELATIVE: 214 *where += (Elf_Addr) obj->relocbase; 215 break; 216 217 case R_386_TLS_TPOFF: 218 case R_386_TLS_TPOFF32: 219 { 220 const Elf_Sym *def; 221 const Obj_Entry *defobj; 222 Elf_Addr add; 223 224 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 225 flags, cache, lockstate); 226 if (def == NULL) 227 goto done; 228 229 /* 230 * We lazily allocate offsets for static TLS as we 231 * see the first relocation that references the 232 * TLS block. This allows us to support (small 233 * amounts of) static TLS in dynamically loaded 234 * modules. If we run out of space, we generate an 235 * error. 236 */ 237 if (!defobj->tls_done) { 238 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 239 _rtld_error("%s: No space available for static " 240 "Thread Local Storage", obj->path); 241 goto done; 242 } 243 } 244 add = (Elf_Addr) (def->st_value - defobj->tlsoffset); 245 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 246 *where += add; 247 else 248 *where -= add; 249 } 250 break; 251 252 case R_386_TLS_DTPMOD32: 253 { 254 const Elf_Sym *def; 255 const Obj_Entry *defobj; 256 257 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 258 flags, cache, lockstate); 259 if (def == NULL) 260 goto done; 261 262 *where += (Elf_Addr) defobj->tlsindex; 263 } 264 break; 265 266 case R_386_TLS_DTPOFF32: 267 { 268 const Elf_Sym *def; 269 const Obj_Entry *defobj; 270 271 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 272 flags, cache, lockstate); 273 if (def == NULL) 274 goto done; 275 276 *where += (Elf_Addr) def->st_value; 277 } 278 break; 279 280 default: 281 _rtld_error("%s: Unsupported relocation type %d" 282 " in non-PLT relocations\n", obj->path, 283 ELF_R_TYPE(rel->r_info)); 284 goto done; 285 } 286 } 287 r = 0; 288 done: 289 if (cache != NULL) 290 free(cache); 291 return (r); 292 } 293 294 /* Process the PLT relocations. */ 295 int 296 reloc_plt(Obj_Entry *obj) 297 { 298 const Elf_Rel *rellim; 299 const Elf_Rel *rel; 300 301 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 302 for (rel = obj->pltrel; rel < rellim; rel++) { 303 Elf_Addr *where/*, val*/; 304 305 switch (ELF_R_TYPE(rel->r_info)) { 306 case R_386_JMP_SLOT: 307 /* Relocate the GOT slot pointing into the PLT. */ 308 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 309 *where += (Elf_Addr)obj->relocbase; 310 break; 311 312 case R_386_IRELATIVE: 313 obj->irelative = true; 314 break; 315 316 default: 317 _rtld_error("Unknown relocation type %x in PLT", 318 ELF_R_TYPE(rel->r_info)); 319 return (-1); 320 } 321 } 322 return 0; 323 } 324 325 /* Relocate the jump slots in an object. */ 326 int 327 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 328 { 329 const Elf_Rel *rellim; 330 const Elf_Rel *rel; 331 332 if (obj->jmpslots_done) 333 return 0; 334 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 335 for (rel = obj->pltrel; rel < rellim; rel++) { 336 Elf_Addr *where, target; 337 const Elf_Sym *def; 338 const Obj_Entry *defobj; 339 340 switch (ELF_R_TYPE(rel->r_info)) { 341 case R_386_JMP_SLOT: 342 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 343 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 344 SYMLOOK_IN_PLT | flags, NULL, lockstate); 345 if (def == NULL) 346 return (-1); 347 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 348 obj->gnu_ifunc = true; 349 continue; 350 } 351 target = (Elf_Addr)(defobj->relocbase + def->st_value); 352 reloc_jmpslot(where, target, defobj, obj, rel); 353 break; 354 355 case R_386_IRELATIVE: 356 break; 357 358 default: 359 _rtld_error("Unknown relocation type %x in PLT", 360 ELF_R_TYPE(rel->r_info)); 361 return (-1); 362 } 363 } 364 365 obj->jmpslots_done = true; 366 return 0; 367 } 368 369 int 370 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 371 { 372 const Elf_Rel *rellim; 373 const Elf_Rel *rel; 374 Elf_Addr *where, target; 375 376 if (!obj->irelative) 377 return (0); 378 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 379 for (rel = obj->pltrel; rel < rellim; rel++) { 380 switch (ELF_R_TYPE(rel->r_info)) { 381 case R_386_IRELATIVE: 382 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 383 lock_release(rtld_bind_lock, lockstate); 384 target = ((Elf_Addr (*)(void))(obj->relocbase + *where))(); 385 wlock_acquire(rtld_bind_lock, lockstate); 386 *where = target; 387 break; 388 } 389 } 390 obj->irelative = false; 391 return (0); 392 } 393 394 int 395 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 396 { 397 const Elf_Rel *rellim; 398 const Elf_Rel *rel; 399 400 if (!obj->gnu_ifunc) 401 return (0); 402 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 403 for (rel = obj->pltrel; rel < rellim; rel++) { 404 Elf_Addr *where, target; 405 const Elf_Sym *def; 406 const Obj_Entry *defobj; 407 408 switch (ELF_R_TYPE(rel->r_info)) { 409 case R_386_JMP_SLOT: 410 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 411 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 412 SYMLOOK_IN_PLT | flags, NULL, lockstate); 413 if (def == NULL) 414 return (-1); 415 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 416 continue; 417 lock_release(rtld_bind_lock, lockstate); 418 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 419 wlock_acquire(rtld_bind_lock, lockstate); 420 reloc_jmpslot(where, target, defobj, obj, rel); 421 break; 422 } 423 } 424 425 obj->gnu_ifunc = false; 426 return (0); 427 } 428 429 void 430 allocate_initial_tls(Obj_Entry *objs) 431 { 432 void* tls; 433 434 /* 435 * Fix the size of the static TLS block by using the maximum 436 * offset allocated so far and adding a bit for dynamic modules to 437 * use. 438 */ 439 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 440 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 441 i386_set_gsbase(tls); 442 } 443 444 /* GNU ABI */ 445 __attribute__((__regparm__(1))) 446 void *___tls_get_addr(tls_index *ti) 447 { 448 Elf_Addr** segbase; 449 450 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 451 452 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 453 } 454 455 /* Sun ABI */ 456 void *__tls_get_addr(tls_index *ti) 457 { 458 Elf_Addr** segbase; 459 460 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 461 462 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 463 } 464