reloc.c revision 1.11
1 /* $NetBSD: reloc.c,v 1.11 1999/02/24 18:31:00 christos Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by John Polstra. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 /* 35 * Dynamic linker for ELF. 36 * 37 * John Polstra <jdp (at) polstra.com>. 38 */ 39 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 #include <sys/types.h> 49 #include <sys/mman.h> 50 #include <dirent.h> 51 52 #include "debug.h" 53 #include "rtld.h" 54 55 #if defined(__alpha__) || defined(__powerpc__) || defined(__i386__) 56 /* 57 * XXX: These don't work for the alpha and i386; don't know about powerpc 58 * The alpha and the i386 avoid the problem by compiling everything PIC. 59 * These relocation are supposed to be writing the address of the 60 * function to be called on the bss.rel or bss.rela segment, but: 61 * - st_size == 0 62 * - on the i386 at least the call instruction is a direct call 63 * not an indirect call. 64 */ 65 static int 66 _rtld_do_copy_relocation( 67 const Obj_Entry *dstobj, 68 const Elf_RelA *rela, 69 bool dodebug) 70 { 71 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 72 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 73 const char *name = dstobj->strtab + dstsym->st_name; 74 unsigned long hash = _rtld_elf_hash(name); 75 size_t size = dstsym->st_size; 76 const void *srcaddr; 77 const Elf_Sym *srcsym; 78 Obj_Entry *srcobj; 79 80 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 81 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, 82 false)) != NULL) 83 break; 84 85 if (srcobj == NULL) { 86 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 87 " relocation in %s", name, dstobj->path); 88 return -1; 89 } 90 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 91 (void)memcpy(dstaddr, srcaddr, size); 92 rdbg(dodebug, "COPY %s %s %s --> src=%p dst=%p *dst= %p size %d", 93 dstobj->path, srcobj->path, name, (void *)srcaddr, 94 (void *)dstaddr, (void *)*(long *)dstaddr, size); 95 return 0; 96 } 97 #endif /* __alpha__ || __powerpc__ || __i386__ */ 98 99 100 /* 101 * Process the special R_xxx_COPY relocations in the main program. These 102 * copy data from a shared object into a region in the main program's BSS 103 * segment. 104 * 105 * Returns 0 on success, -1 on failure. 106 */ 107 int 108 _rtld_do_copy_relocations( 109 const Obj_Entry *dstobj, 110 bool dodebug) 111 { 112 assert(dstobj->mainprog); /* COPY relocations are invalid 113 * elsewhere */ 114 115 #if defined(__alpha__) || defined(__powerpc__) || defined(__i386__) 116 if (dstobj->rel != NULL) { 117 const Elf_Rel *rel; 118 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 119 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 120 Elf_RelA ourrela; 121 ourrela.r_info = rel->r_info; 122 ourrela.r_offset = rel->r_offset; 123 ourrela.r_addend = 0; 124 if (_rtld_do_copy_relocation(dstobj, 125 &ourrela, dodebug) < 0) 126 return -1; 127 } 128 } 129 } 130 if (dstobj->rela != NULL) { 131 const Elf_RelA *rela; 132 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 133 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 134 if (_rtld_do_copy_relocation(dstobj, rela, 135 dodebug) < 0) 136 return -1; 137 } 138 } 139 } 140 #endif /* __alpha__ || __powerpc__ || __i386__ */ 141 142 return 0; 143 } 144 145 146 #ifndef __sparc__ 147 int 148 _rtld_relocate_nonplt_object( 149 const Obj_Entry * obj, 150 const Elf_RelA * rela, 151 bool dodebug) 152 { 153 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 154 const Elf_Sym *def; 155 const Obj_Entry *defobj; 156 extern Elf_Addr _GLOBAL_OFFSET_TABLE_[]; 157 extern Elf_Dyn _DYNAMIC; 158 Elf_Addr tmp; 159 160 switch (ELF_R_TYPE(rela->r_info)) { 161 162 case R_TYPE(NONE): 163 break; 164 165 #ifdef __i386__ 166 case R_TYPE(GOT32): 167 168 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 169 &defobj, false); 170 if (def == NULL) 171 return -1; 172 173 tmp = (Elf_Addr)(defobj->relocbase + def->st_value); 174 if (*where != tmp) 175 *where = tmp; 176 rdbg(dodebug, "GOT32 %s in %s --> %p in %s", 177 defobj->strtab + def->st_name, obj->path, 178 (void *)*where, defobj->path); 179 break; 180 181 case R_TYPE(PC32): 182 /* 183 * I don't think the dynamic linker should ever see this 184 * type of relocation. But the binutils-2.6 tools sometimes 185 * generate it. 186 */ 187 188 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 189 &defobj, false); 190 if (def == NULL) 191 return -1; 192 193 *where += (Elf_Addr)(defobj->relocbase + def->st_value) - 194 (Elf_Addr)where; 195 rdbg(dodebug, "PC32 %s in %s --> %p in %s", 196 defobj->strtab + def->st_name, obj->path, 197 (void *)*where, defobj->path); 198 break; 199 200 case R_TYPE(32): 201 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 202 &defobj, false); 203 if (def == NULL) 204 return -1; 205 206 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 207 rdbg(dodebug, "32 %s in %s --> %p in %s", 208 defobj->strtab + def->st_name, obj->path, 209 (void *)*where, defobj->path); 210 break; 211 #endif /* __i386__ */ 212 213 #ifdef __alpha__ 214 case R_TYPE(REFQUAD): 215 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 216 &defobj, false); 217 if (def == NULL) 218 return -1; 219 220 tmp = (Elf_Addr)(defobj->relocbase + def->st_value) + 221 *where + rela->r_addend; 222 if (*where != tmp_value) 223 *where = tmp_value; 224 rdbg(dodebug, "REFQUAD %s in %s --> %p in %s", 225 defobj->strtab + def->st_name, obj->path, 226 (void *)*where, defobj->path); 227 break; 228 #endif /* __alpha__ */ 229 230 #if defined(__i386__) || defined(__alpha__) 231 case R_TYPE(GLOB_DAT): 232 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 233 &defobj, false); 234 if (def == NULL) 235 return -1; 236 237 if (*where != (Elf_Addr)(defobj->relocbase + def->st_value)) 238 *where = (Elf_Addr)(defobj->relocbase + def->st_value); 239 rdbg(dodebug, "GLOB_DAT %s in %s --> %p in %s", 240 defobj->strtab + def->st_name, obj->path, 241 (void *)*where, defobj->path); 242 break; 243 244 case R_TYPE(RELATIVE): 245 if (obj != &_rtld_objself || 246 (caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ || 247 (caddr_t)where >= (caddr_t)&_DYNAMIC) { 248 *where += (Elf_Addr)obj->relocbase; 249 rdbg(dodebug, "RELATIVE in %s --> %p", obj->path, 250 (void *)*where); 251 } 252 else 253 rdbg(dodebug, "RELATIVE in %s stays at %p", 254 obj->path, (void *)*where); 255 break; 256 257 case R_TYPE(COPY): 258 /* 259 * These are deferred until all other relocations have 260 * been done. All we do here is make sure that the COPY 261 * relocation is not in a shared library. They are allowed 262 * only in executable files. 263 */ 264 if (!obj->mainprog) { 265 _rtld_error( 266 "%s: Unexpected R_COPY relocation in shared library", 267 obj->path); 268 return -1; 269 } 270 rdbg(dodebug, "COPY (avoid in main)"); 271 break; 272 #endif /* __i386__ || __alpha__ */ 273 274 #ifdef __mips__ 275 case R_TYPE(REL32): 276 /* 32-bit PC-relative reference */ 277 def = obj->symtab + ELF_R_SYM(rela->r_info); 278 279 if (ELF_SYM_BIND(def->st_info) == Elf_estb_local && 280 (ELF_SYM_TYPE(def->st_info) == Elf_estt_section || 281 ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) { 282 *where += (Elf_Addr)obj->relocbase; 283 rdbg(dodebug, "REL32 in %s --> %p", obj->path, 284 (void *)*where); 285 } else { 286 /* XXX maybe do something re: bootstrapping? */ 287 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, 288 NULL, obj, &defobj, false); 289 if (def == NULL) 290 return -1; 291 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 292 rdbg(dodebug, "REL32 %s in %s --> %p in %s", 293 defobj->strtab + def->st_name, obj->path, 294 (void *)*where, defobj->path); 295 } 296 break; 297 298 #endif /* __mips__ */ 299 300 #ifdef __powerpc__ 301 case R_TYPE(32): /* word32 S + A */ 302 case R_TYPE(GLOB_DAT): /* word32 S + A */ 303 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 304 &defobj, false); 305 if (def == NULL) 306 return -1; 307 308 tmp = (Elf_Addr)(defobj->relocbase + def->st_value + 309 rela->r_addend); 310 311 if (*where != tmp) 312 *where = tmp; 313 rdbg(dodebug, "32/GLOB_DAT %s in %s --> %p in %s", 314 defobj->strtab + def->st_name, obj->path, 315 (void *)*where, defobj->path); 316 break; 317 318 case R_TYPE(COPY): 319 rdbg(dodebug, "COPY"); 320 break; 321 322 case R_TYPE(JMP_SLOT): 323 rdbg(dodebug, "JMP_SLOT"); 324 break; 325 326 case R_TYPE(RELATIVE): /* word32 B + A */ 327 tmp = (Elf_Addr)(obj->relocbase + rela->r_addend); 328 if (obj == &_rtld_objself && *where == tmp; 329 break; /* GOT - already done */ 330 331 *where = tmp; 332 rdbg(dodebug, "RELATIVE in %s --> %p", obj->path, 333 (void *)*where); 334 break; 335 #endif /* __powerpc__ */ 336 337 default: 338 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 339 &defobj, true); 340 rdbg(dodebug, "sym = %lu, type = %lu, offset = %p, " 341 "addend = %p, contents = %p, symbol = %s", 342 (u_long)ELF_R_SYM(rela->r_info), 343 (u_long)ELF_R_TYPE(rela->r_info), 344 (void *)rela->r_offset, (void *)rela->r_addend, 345 (void *)*where, 346 def ? defobj->strtab + def->st_name : "??"); 347 _rtld_error("%s: Unsupported relocation type %d" 348 "in non-PLT relocations\n", 349 obj->path, ELF_R_TYPE(rela->r_info)); 350 return -1; 351 } 352 return 0; 353 } 354 355 356 357 int 358 _rtld_relocate_plt_object( 359 const Obj_Entry * obj, 360 const Elf_RelA * rela, 361 caddr_t *addrp, 362 bool bind_now, 363 bool dodebug) 364 { 365 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 366 Elf_Addr new_value; 367 368 /* Fully resolve procedure addresses now */ 369 370 #if defined(__powerpc__) 371 return _rtld_reloc_powerpc_plt(obj, rela, bind_now); 372 #endif 373 374 #if defined(__alpha__) || defined(__i386__) 375 if (bind_now || obj->pltgot == NULL) { 376 const Elf_Sym *def; 377 const Obj_Entry *defobj; 378 379 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 380 381 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 382 &defobj, true); 383 if (def == NULL) 384 return -1; 385 386 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 387 rdbg(dodebug, "bind now %d/fixup in %s --> old=%p new=%p", 388 (int)bind_now, 389 defobj->strtab + def->st_name, 390 (void *)*where, (void *)new_value); 391 } else 392 #endif /* __alpha__ || __i386__ */ 393 if (!obj->mainprog) { 394 /* Just relocate the GOT slots pointing into the PLT */ 395 new_value = *where + (Elf_Addr)(obj->relocbase); 396 rdbg(dodebug, "fixup !main in %s --> %p", obj->path, 397 (void *)*where); 398 } else { 399 return 0; 400 } 401 /* 402 * Since this page is probably copy-on-write, let's not write 403 * it unless we really really have to. 404 */ 405 if (*where != new_value) 406 *where = new_value; 407 if (addrp != NULL) 408 *addrp = *(caddr_t *)(obj->relocbase + rela->r_offset); 409 return 0; 410 } 411 #endif /* __sparc__ */ 412 413 caddr_t 414 _rtld_bind( 415 const Obj_Entry *obj, 416 Elf_Word reloff) 417 { 418 const Elf_RelA *rela; 419 Elf_RelA ourrela; 420 caddr_t addr; 421 422 if (obj->pltrel != NULL) { 423 const Elf_Rel *rel; 424 425 rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff); 426 ourrela.r_info = rel->r_info; 427 ourrela.r_offset = rel->r_offset; 428 rela = &ourrela; 429 } else { 430 rela = (const Elf_RelA *)((caddr_t) obj->pltrela + reloff); 431 } 432 433 if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0) 434 _rtld_die(); 435 436 return addr; 437 } 438 439 /* 440 * Relocate newly-loaded shared objects. The argument is a pointer to 441 * the Obj_Entry for the first such object. All objects from the first 442 * to the end of the list of objects are relocated. Returns 0 on success, 443 * or -1 on failure. 444 */ 445 int 446 _rtld_relocate_objects( 447 Obj_Entry * first, 448 bool bind_now, 449 bool dodebug) 450 { 451 Obj_Entry *obj; 452 int ok = 1; 453 454 for (obj = first; obj != NULL; obj = obj->next) { 455 if (obj->nbuckets == 0 || obj->nchains == 0 456 || obj->buckets == NULL || obj->symtab == NULL 457 || obj->strtab == NULL) { 458 _rtld_error("%s: Shared object has no run-time" 459 " symbol table", obj->path); 460 return -1; 461 } 462 rdbg(dodebug, " relocating %s (%ld/%ld rel/rela, " 463 "%ld/%ld plt rel/rela)", 464 obj->path, 465 (long)(obj->rellim - obj->rel), 466 (long)(obj->relalim - obj->rela), 467 (long)(obj->pltrellim - obj->pltrel), 468 (long)(obj->pltrelalim - obj->pltrela)); 469 470 if (obj->textrel) { 471 /* 472 * There are relocations to the write-protected text 473 * segment. 474 */ 475 if (mprotect(obj->mapbase, obj->textsize, 476 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 477 _rtld_error("%s: Cannot write-enable text " 478 "segment: %s", obj->path, xstrerror(errno)); 479 return -1; 480 } 481 } 482 if (obj->rel != NULL) { 483 /* Process the non-PLT relocations. */ 484 const Elf_Rel *rel; 485 for (rel = obj->rel; rel < obj->rellim; ++rel) { 486 Elf_RelA ourrela; 487 ourrela.r_info = rel->r_info; 488 ourrela.r_offset = rel->r_offset; 489 #if defined(__mips__) 490 /* rel->r_offset is not valid on mips? */ 491 if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE)) 492 ourrela.r_addend = 0; 493 else 494 #endif 495 ourrela.r_addend = 496 *(Elf_Word *)(obj->relocbase + 497 rel->r_offset); 498 499 if (_rtld_relocate_nonplt_object(obj, &ourrela, 500 dodebug) < 0) 501 ok = 0; 502 } 503 } 504 if (obj->rela != NULL) { 505 /* Process the non-PLT relocations. */ 506 const Elf_RelA *rela; 507 for (rela = obj->rela; rela < obj->relalim; ++rela) { 508 if (_rtld_relocate_nonplt_object(obj, rela, 509 dodebug) < 0) 510 ok = 0; 511 } 512 } 513 if (obj->textrel) { /* Re-protected the text segment. */ 514 if (mprotect(obj->mapbase, obj->textsize, 515 PROT_READ | PROT_EXEC) == -1) { 516 _rtld_error("%s: Cannot write-protect text " 517 "segment: %s", obj->path, xstrerror(errno)); 518 return -1; 519 } 520 } 521 /* Process the PLT relocations. */ 522 if (obj->pltrel != NULL) { 523 const Elf_Rel *rel; 524 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 525 Elf_RelA ourrela; 526 ourrela.r_info = rel->r_info; 527 ourrela.r_offset = rel->r_offset; 528 ourrela.r_addend = 529 *(Elf_Word *)(obj->relocbase + 530 rel->r_offset); 531 if (_rtld_relocate_plt_object(obj, &ourrela, 532 NULL, bind_now, dodebug) < 0) 533 ok = 0; 534 } 535 } 536 if (obj->pltrela != NULL) { 537 const Elf_RelA *rela; 538 for (rela = obj->pltrela; rela < obj->pltrelalim; 539 ++rela) { 540 if (_rtld_relocate_plt_object(obj, rela, 541 NULL, bind_now, dodebug) < 0) 542 ok = 0; 543 } 544 } 545 if (!ok) 546 return -1; 547 548 549 /* Set some sanity-checking numbers in the Obj_Entry. */ 550 obj->magic = RTLD_MAGIC; 551 obj->version = RTLD_VERSION; 552 553 /* Fill in the dynamic linker entry points. */ 554 obj->dlopen = _rtld_dlopen; 555 obj->dlsym = _rtld_dlsym; 556 obj->dlerror = _rtld_dlerror; 557 obj->dlclose = _rtld_dlclose; 558 559 /* Set the special PLTGOT entries. */ 560 if (obj->pltgot != NULL) { 561 #if defined(__i386__) 562 obj->pltgot[1] = (Elf_Addr) obj; 563 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 564 #endif 565 #if defined(__alpha__) 566 /* 567 * This function will be called to perform the 568 * relocation. 569 */ 570 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 571 /* Identify this shared object */ 572 obj->pltgot[3] = (Elf_Addr) obj; 573 #endif 574 #if defined(__mips__) 575 _rtld_relocate_mips_got(obj); 576 577 obj->pltgot[0] = (Elf_Addr) & _rtld_bind_start; 578 /* XXX only if obj->pltgot[1] & 0x80000000 ?? */ 579 obj->pltgot[1] |= (Elf_Addr) obj; 580 #endif 581 #if defined(__powerpc__) 582 _rtld_setup_powerpc_plt(obj); 583 #endif 584 #if defined(__sparc__) 585 /* 586 * PLTGOT is the PLT on the sparc. 587 * The first entry holds the call the dynamic linker. 588 * We construct a `call' instruction that transfers 589 * to `_rtld_bind_start()'. 590 * The second entry holds the object identification. 591 * Note: each PLT entry is three words long. 592 */ 593 obj->pltgot[1] = 0x40000000 | 594 ((Elf_Addr)&_rtld_bind_start - 595 (Elf_Addr)&obj->pltgot[1]); 596 obj->pltgot[3] = (Elf_Addr) obj; 597 #endif 598 } 599 } 600 601 return 0; 602 } 603
Indexes created Tue Sep 30 07:10:03 GMT 2025