reloc.c revision 1.6
1 /* $NetBSD: reloc.c,v 1.6 1999/02/07 17:24:05 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 { 70 void *dstaddr = (void *) (dstobj->relocbase + rela->r_offset); 71 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 72 const char *name = dstobj->strtab + dstsym->st_name; 73 unsigned long hash = _rtld_elf_hash(name); 74 size_t size = dstsym->st_size; 75 const void *srcaddr; 76 const Elf_Sym *srcsym; 77 Obj_Entry *srcobj; 78 79 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 80 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, false)) != NULL) 81 break; 82 83 if (srcobj == NULL) { 84 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 85 " relocation in %s", name, dstobj->path); 86 return -1; 87 } 88 89 srcaddr = (const void *) (srcobj->relocbase + srcsym->st_value); 90 memcpy(dstaddr, srcaddr, size); 91 #ifdef RTLD_DEBUG_RELOC 92 dbg("COPY %s %s %s --> src=%p dst=%p *dst= %p size %d", 93 dstobj->path, srcobj->path, name, (void *)srcaddr, (void *)dstaddr, 94 (void *)*(long *)dstaddr, size); 95 #endif 96 return 0; 97 } 98 #endif /* __alpha__ || __powerpc__ || __i386__ */ 99 100 /* 102 * Process the special R_xxx_COPY relocations in the main program. These 103 * copy data from a shared object into a region in the main program's BSS 104 * segment. 105 * 106 * Returns 0 on success, -1 on failure. 107 */ 108 int 109 _rtld_do_copy_relocations( 110 const Obj_Entry *dstobj) 111 { 112 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 113 114 #if defined(__alpha__) || defined(__powerpc__) || defined(__i386__) 115 if (dstobj->rel != NULL) { 116 const Elf_Rel *rel; 117 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 118 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 119 Elf_RelA ourrela; 120 ourrela.r_info = rel->r_info; 121 ourrela.r_offset = rel->r_offset; 122 ourrela.r_addend = 0; 123 if (_rtld_do_copy_relocation(dstobj, &ourrela) < 0) 124 return -1; 125 } 126 } 127 } 128 129 if (dstobj->rela != NULL) { 130 const Elf_RelA *rela; 131 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 132 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 133 if (_rtld_do_copy_relocation(dstobj, rela) < 0) 134 return -1; 135 } 136 } 137 } 138 #endif /* __alpha__ || __powerpc__ || __i386__ */ 139 140 return 0; 141 } 142 143 static int 145 _rtld_relocate_nonplt_object( 146 const Obj_Entry *obj, 147 const Elf_RelA *rela) 148 { 149 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset); 150 151 switch (ELF_R_TYPE(rela->r_info)) { 152 153 case R_TYPE(NONE): 154 break; 155 156 #ifdef __i386__ 157 case R_TYPE(GOT32): { 158 const Elf_Sym *def; 159 const Obj_Entry *defobj; 160 161 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 162 if (def == NULL) 163 return -1; 164 165 if (*where != (Elf_Addr) (defobj->relocbase + def->st_value)) 166 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 167 #ifdef RTLD_DEBUG_RELOC 168 dbg("GOT32 %s in %s --> %p in %s", 169 defobj->strtab + def->st_name, obj->path, 170 (void *)*where, defobj->path); 171 #endif 172 break; 173 } 174 175 case R_TYPE(PC32): 176 /* 177 * I don't think the dynamic linker should ever see this 178 * type of relocation. But the binutils-2.6 tools sometimes 179 * generate it. 180 */ 181 { 182 const Elf_Sym *def; 183 const Obj_Entry *defobj; 184 185 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 186 if (def == NULL) 187 return -1; 188 189 *where += (Elf_Addr) (defobj->relocbase + def->st_value) 190 - (Elf_Addr) where; 191 #ifdef RTLD_DEBUG_RELOC 192 dbg("PC32 %s in %s --> %p in %s", 193 defobj->strtab + def->st_name, obj->path, 194 (void *)*where, defobj->path); 195 #endif 196 break; 197 } 198 199 case R_TYPE(32): { 200 const Elf_Sym *def; 201 const Obj_Entry *defobj; 202 203 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 204 if (def == NULL) 205 return -1; 206 207 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 208 #ifdef RTLD_DEBUG_RELOC 209 dbg("32 %s in %s --> %p in %s", 210 defobj->strtab + def->st_name, obj->path, 211 (void *)*where, defobj->path); 212 #endif 213 break; 214 } 215 #endif /* __i386__ */ 216 217 #ifdef __alpha__ 218 case R_ALPHA_REFQUAD: { 219 const Elf_Sym *def; 220 const Obj_Entry *defobj; 221 Elf_Addr tmp_value; 222 223 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 224 if (def == NULL) 225 return -1; 226 227 tmp_value = (Elf_Addr) (defobj->relocbase + def->st_value) 228 + *where + rela->r_addend; 229 if (*where != tmp_value) 230 *where = tmp_value; 231 #ifdef RTLD_DEBUG_RELOC 232 dbg("REFQUAD %s in %s --> %p in %s", 233 defobj->strtab + def->st_name, obj->path, 234 (void *)*where, defobj->path); 235 #endif 236 break; 237 } 238 #endif /* __alpha__ */ 239 240 #if defined(__i386__) || defined(__alpha__) 241 case R_TYPE(GLOB_DAT): 242 { 243 const Elf_Sym *def; 244 const Obj_Entry *defobj; 245 246 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 247 if (def == NULL) 248 return -1; 249 250 if (*where != (Elf_Addr) (defobj->relocbase + def->st_value)) 251 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 252 #ifdef RTLD_DEBUG_RELOC 253 dbg("GLOB_DAT %s in %s --> %p in %s", 254 defobj->strtab + def->st_name, obj->path, 255 (void *)*where, defobj->path); 256 #endif 257 break; 258 } 259 260 case R_TYPE(RELATIVE): { 261 extern Elf_Addr _GLOBAL_OFFSET_TABLE_[]; 262 extern Elf_Dyn _DYNAMIC; 263 264 if (obj != &_rtld_objself || 265 (caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ || 266 (caddr_t)where >= (caddr_t)&_DYNAMIC) { 267 *where += (Elf_Addr) obj->relocbase; 268 #ifdef RTLD_DEBUG_RELOC 269 dbg("RELATIVE in %s --> %p", obj->path, (void *)*where); 270 #endif 271 } 272 #ifdef RTLD_DEBUG_RELOC 273 else 274 dbg("RELATIVE in %s stays at %p", obj->path, (void *)*where); 275 #endif 276 break; 277 } 278 279 case R_TYPE(COPY): { 280 /* 281 * These are deferred until all other relocations have 282 * been done. All we do here is make sure that the COPY 283 * relocation is not in a shared library. They are allowed 284 * only in executable files. 285 */ 286 if (!obj->mainprog) { 287 _rtld_error("%s: Unexpected R_COPY relocation in shared library", 288 obj->path); 289 return -1; 290 } 291 #ifdef RTLD_DEBUG_RELOC 292 dbg("COPY (avoid in main)"); 293 #endif 294 break; 295 } 296 #endif /* __i386__ || __alpha__ */ 297 298 #ifdef __mips__ 299 case R_TYPE(REL32): { 300 /* 32-bit PC-relative reference */ 301 302 const Elf_Sym *def; 303 const Obj_Entry *defobj; 304 305 def = obj->symtab + ELF_R_SYM(rela->r_info); 306 307 if (ELF_SYM_BIND(def->st_info) == Elf_estb_local && 308 (ELF_SYM_TYPE(def->st_info) == Elf_estt_section || 309 ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) { 310 *where += (Elf_Addr) obj->relocbase; 311 #ifdef RTLD_DEBUG_RELOC 312 dbg("REL32 in %s --> %p", obj->path, (void *)*where); 313 #endif 314 } else { 315 /* XXX maybe do something re: bootstrapping? */ 316 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 317 &defobj, false); 318 if (def == NULL) 319 return -1; 320 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 321 #ifdef RTLD_DEBUG_RELOC 322 dbg("REL32 %s in %s --> %p in %s", 323 defobj->strtab + def->st_name, obj->path, 324 (void *)*where, defobj->path); 325 #endif 326 } 327 break; 328 } 329 330 #endif /* mips */ 331 332 #ifdef __powerpc__ 333 case R_TYPE(32): /* word32 S + A */ 334 case R_TYPE(GLOB_DAT): { /* word32 S + A */ 335 const Elf_Sym *def; 336 const Obj_Entry *defobj; 337 Elf_Addr x; 338 339 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false); 340 if (def == NULL) 341 return -1; 342 343 x = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 344 345 if (*where != x) 346 *where = x; 347 #ifdef RTLD_DEBUG_RELOC 348 dbg("32/GLOB_DAT %s in %s --> %p in %s", 349 defobj->strtab + def->st_name, obj->path, 350 (void *)*where, defobj->path); 351 #endif 352 break; 353 } 354 355 case R_TYPE(COPY): 356 #ifdef RTLD_DEBUG_RELOC 357 dbg("COPY"); 358 #endif 359 break; 360 361 case R_TYPE(JMP_SLOT): 362 #ifdef RTLD_DEBUG_RELOC 363 dbg("JMP_SLOT"); 364 #endif 365 break; 366 367 case R_TYPE(RELATIVE): { /* word32 B + A */ 368 if (obj == &_rtld_objself && 369 *where == (Elf_Addr)obj->relocbase + rela->r_addend) 370 break; /* GOT - already done */ 371 372 *where = (Elf_Addr)obj->relocbase + rela->r_addend; 373 #ifdef RTLD_DEBUG_RELOC 374 dbg("RELATIVE in %s --> %p", obj->path, (void *)*where); 375 #endif 376 break; 377 } 378 #endif /* __powerpc__ */ 379 380 default: { 381 const Elf_Sym *def; 382 const Obj_Entry *defobj; 383 384 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, true); 385 dbg("sym = %lu, type = %lu, offset = %p, addend = %p, contents = %p, symbol = %s", 386 (u_long)ELF_R_SYM(rela->r_info), (u_long)ELF_R_TYPE(rela->r_info), 387 (void *)rela->r_offset, (void *)rela->r_addend, (void *)*where, 388 def ? defobj->strtab + def->st_name : "??"); 389 _rtld_error("%s: Unsupported relocation type %d in non-PLT relocations\n", 390 obj->path, ELF_R_TYPE(rela->r_info)); 391 return -1; 392 } 393 } 394 return 0; 395 } 396 397 static int 399 _rtld_relocate_plt_object( 400 const Obj_Entry *obj, 401 const Elf_RelA *rela, 402 bool bind_now) 403 { 404 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset); 405 Elf_Addr new_value; 406 407 /* Fully resolve procedure addresses now */ 408 409 #if defined(__powerpc__) 410 return _rtld_reloc_powerpc_plt(obj, rela, bind_now); 411 #endif 412 413 #if defined(__alpha__) || defined(__i386__) /* (jrs) */ 414 if (bind_now || obj->pltgot == NULL) { 415 const Elf_Sym *def; 416 const Obj_Entry *defobj; 417 418 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 419 420 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, true); 421 if (def == NULL) 422 return -1; 423 424 new_value = (Elf_Addr) (defobj->relocbase + def->st_value); 425 #ifdef RTLD_DEBUG_RELOC 426 dbg("bind now %d/fixup in %s --> old=%p new=%p", 427 (int)bind_now, 428 defobj->strtab + def->st_name, 429 (void *)*where, (void *)new_value); 430 #endif 431 } else 432 #endif /* __alpha__ (jrs) */ 433 if (!obj->mainprog) { 434 /* Just relocate the GOT slots pointing into the PLT */ 435 new_value = *where + (Elf_Addr) (obj->relocbase); 436 #ifdef RTLD_DEBUG_RELOC 437 dbg("fixup !main in %s --> %p", obj->path, (void *)*where); 438 #endif 439 } else { 440 #ifdef __i386__ 441 new_value = *where + (Elf_Addr) (obj->relocbase); 442 #ifdef RTLD_DEBUG_RELOC 443 dbg("fixup main in %s --> %p", obj->path, (void *)*where); 444 #endif 445 #endif 446 } 447 /* 448 * Since this page is probably copy-on-write, let's not write 449 * it unless we really really have to. 450 */ 451 if (*where != new_value) 452 *where = new_value; 453 return 0; 454 } 455 456 caddr_t 458 _rtld_bind( 459 const Obj_Entry *obj, 460 Elf_Word reloff) 461 { 462 const Elf_RelA *rela; 463 Elf_RelA ourrela; 464 465 if (obj->pltrel != NULL) { 466 ourrela.r_info = ((const Elf_Rel *) ((caddr_t) obj->pltrel + reloff))->r_info; 467 ourrela.r_offset = ((const Elf_Rel *) ((caddr_t) obj->pltrel + reloff))->r_offset; 468 rela = &ourrela; 469 } else { 470 rela = (const Elf_RelA *) ((caddr_t) obj->pltrela + reloff); 471 } 472 473 if (_rtld_relocate_plt_object(obj, rela, true) < 0) 474 _rtld_die(); 475 476 return *(caddr_t *)(obj->relocbase + rela->r_offset); 477 } 478 479 /* 481 * Relocate newly-loaded shared objects. The argument is a pointer to 482 * the Obj_Entry for the first such object. All objects from the first 483 * to the end of the list of objects are relocated. Returns 0 on success, 484 * or -1 on failure. 485 */ 486 int 487 _rtld_relocate_objects( 488 Obj_Entry *first, 489 bool bind_now) 490 { 491 Obj_Entry *obj; 492 int ok = 1; 493 494 for (obj = first; obj != NULL; obj = obj->next) { 495 496 if (obj->nbuckets == 0 || obj->nchains == 0 497 || obj->buckets == NULL || obj->symtab == NULL 498 || obj->strtab == NULL) { 499 _rtld_error("%s: Shared object has no run-time symbol table", 500 obj->path); 501 return -1; 502 } 503 504 dbg(" relocating %s (%ld/%ld rel/rela, %ld/%ld plt rel/rela)", 505 obj->path, 506 (long)(obj->rellim - obj->rel), (long)(obj->relalim - obj->rela), 507 (long)(obj->pltrellim - obj->pltrel), 508 (long)(obj->pltrelalim - obj->pltrela)); 509 510 if (obj->textrel) { 511 /* There are relocations to the write-protected text segment. */ 512 if (mprotect(obj->mapbase, obj->textsize, 513 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 514 _rtld_error("%s: Cannot write-enable text segment: %s", 515 obj->path, xstrerror(errno)); 516 return -1; 517 } 518 } 519 520 if (obj->rel != NULL) { 521 /* Process the non-PLT relocations. */ 522 const Elf_Rel *rel; 523 for (rel = obj->rel; rel < obj->rellim; ++rel) { 524 Elf_RelA ourrela; 525 ourrela.r_info = rel->r_info; 526 ourrela.r_offset = rel->r_offset; 527 #if defined(__mips__) 528 /* rel->r_offset is not valid on mips? */ 529 if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE)) 530 ourrela.r_addend = 0; 531 else 532 #endif 533 ourrela.r_addend = *(Elf_Word *) (obj->relocbase + rel->r_offset); 534 535 if (_rtld_relocate_nonplt_object(obj, &ourrela) < 0) 536 ok = 0; 537 } 538 } 539 540 if (obj->rela != NULL) { 541 /* Process the non-PLT relocations. */ 542 const Elf_RelA *rela; 543 for (rela = obj->rela; rela < obj->relalim; ++rela) { 544 if (_rtld_relocate_nonplt_object(obj, rela) < 0) 545 ok = 0; 546 } 547 } 548 549 if (obj->textrel) { /* Re-protected the text segment. */ 550 if (mprotect(obj->mapbase, obj->textsize, 551 PROT_READ|PROT_EXEC) == -1) { 552 _rtld_error("%s: Cannot write-protect text segment: %s", 553 obj->path, xstrerror(errno)); 554 return -1; 555 } 556 } 557 558 /* Process the PLT relocations. */ 559 if (obj->pltrel != NULL) { 560 const Elf_Rel *rel; 561 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 562 Elf_RelA ourrela; 563 ourrela.r_info = rel->r_info; 564 ourrela.r_offset = rel->r_offset; 565 ourrela.r_addend = *(Elf_Word *) (obj->relocbase + rel->r_offset); 566 if (_rtld_relocate_plt_object(obj, &ourrela, bind_now) < 0) 567 ok = 0; 568 } 569 } 570 571 if (obj->pltrela != NULL) { 572 const Elf_RelA *rela; 573 for (rela = obj->pltrela; rela < obj->pltrelalim; ++rela) { 574 if (_rtld_relocate_plt_object(obj, rela, bind_now) < 0) 575 ok = 0; 576 } 577 } 578 579 if (!ok) 580 return -1; 581 582 583 /* Set some sanity-checking numbers in the Obj_Entry. */ 584 obj->magic = RTLD_MAGIC; 585 obj->version = RTLD_VERSION; 586 587 /* Fill in the dynamic linker entry points. */ 588 obj->dlopen = _rtld_dlopen; 589 obj->dlsym = _rtld_dlsym; 590 obj->dlerror = _rtld_dlerror; 591 obj->dlclose = _rtld_dlclose; 592 593 /* Set the special PLTGOT entries. */ 594 if (obj->pltgot != NULL) { 595 #if defined(__i386__) 596 obj->pltgot[1] = (Elf_Addr) obj; 597 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 598 #endif 599 #if defined(__alpha__) 600 /* This function will be called to perform the relocation. */ 601 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 602 /* Identify this shared object */ 603 obj->pltgot[3] = (Elf_Addr) obj; 604 #endif 605 #if defined(__mips__) 606 _rtld_relocate_mips_got(obj); 607 608 obj->pltgot[0] = (Elf_Addr) &_rtld_bind_start; 609 /* XXX only if obj->pltgot[1] & 0x80000000 ?? */ 610 obj->pltgot[1] |= (Elf_Addr) obj; 611 #endif 612 #if defined(__powerpc__) 613 _rtld_setup_powerpc_plt(obj); 614 #endif 615 } 616 } 617 618 return 0; 619 } 620
Indexes created Tue Sep 30 11:09:46 GMT 2025