reloc.c revision 1.15
1 /* $NetBSD: reloc.c,v 1.15 1999/02/27 21:38:04 scottr 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 #ifndef RTLD_INHIBIT_COPY_RELOCS 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 /* RTLD_INHIBIT_COPY_RELOCS */ 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 #ifndef RTLD_INHIBIT_COPY_RELOCS 113 114 /* COPY relocations are invalid elsewhere */ 115 assert(dstobj->mainprog); 116 117 if (dstobj->rel != NULL) { 118 const Elf_Rel *rel; 119 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 120 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 121 Elf_RelA ourrela; 122 ourrela.r_info = rel->r_info; 123 ourrela.r_offset = rel->r_offset; 124 ourrela.r_addend = 0; 125 if (_rtld_do_copy_relocation(dstobj, 126 &ourrela, dodebug) < 0) 127 return (-1); 128 } 129 } 130 } 131 if (dstobj->rela != NULL) { 132 const Elf_RelA *rela; 133 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 134 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 135 if (_rtld_do_copy_relocation(dstobj, rela, 136 dodebug) < 0) 137 return (-1); 138 } 139 } 140 } 141 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 142 143 return (0); 144 } 145 146 147 #ifndef __sparc__ 148 int 149 _rtld_relocate_nonplt_object( 150 const Obj_Entry * obj, 151 const Elf_RelA * rela, 152 bool dodebug) 153 { 154 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 155 const Elf_Sym *def; 156 const Obj_Entry *defobj; 157 #if defined(__i386__) || defined(__alpha__) 158 extern Elf_Addr _GLOBAL_OFFSET_TABLE_[]; 159 extern Elf_Dyn _DYNAMIC; 160 #endif 161 Elf_Addr tmp; 162 163 switch (ELF_R_TYPE(rela->r_info)) { 164 165 case R_TYPE(NONE): 166 break; 167 168 #ifdef __i386__ 169 case R_TYPE(GOT32): 170 171 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 172 &defobj, false); 173 if (def == NULL) 174 return -1; 175 176 tmp = (Elf_Addr)(defobj->relocbase + def->st_value); 177 if (*where != tmp) 178 *where = tmp; 179 rdbg(dodebug, "GOT32 %s in %s --> %p in %s", 180 defobj->strtab + def->st_name, obj->path, 181 (void *)*where, defobj->path); 182 break; 183 184 case R_TYPE(PC32): 185 /* 186 * I don't think the dynamic linker should ever see this 187 * type of relocation. But the binutils-2.6 tools sometimes 188 * generate it. 189 */ 190 191 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 192 &defobj, false); 193 if (def == NULL) 194 return -1; 195 196 *where += (Elf_Addr)(defobj->relocbase + def->st_value) - 197 (Elf_Addr)where; 198 rdbg(dodebug, "PC32 %s in %s --> %p in %s", 199 defobj->strtab + def->st_name, obj->path, 200 (void *)*where, defobj->path); 201 break; 202 203 case R_TYPE(32): 204 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 205 &defobj, false); 206 if (def == NULL) 207 return -1; 208 209 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 210 rdbg(dodebug, "32 %s in %s --> %p in %s", 211 defobj->strtab + def->st_name, obj->path, 212 (void *)*where, defobj->path); 213 break; 214 #endif /* __i386__ */ 215 216 #ifdef __alpha__ 217 case R_TYPE(REFQUAD): 218 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 219 &defobj, false); 220 if (def == NULL) 221 return -1; 222 223 tmp = (Elf_Addr)(defobj->relocbase + def->st_value) + 224 *where + rela->r_addend; 225 if (*where != tmp) 226 *where = tmp; 227 rdbg(dodebug, "REFQUAD %s in %s --> %p in %s", 228 defobj->strtab + def->st_name, obj->path, 229 (void *)*where, defobj->path); 230 break; 231 #endif /* __alpha__ */ 232 233 #if defined(__i386__) || defined(__alpha__) 234 case R_TYPE(GLOB_DAT): 235 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 236 &defobj, false); 237 if (def == NULL) 238 return -1; 239 240 if (*where != (Elf_Addr)(defobj->relocbase + def->st_value)) 241 *where = (Elf_Addr)(defobj->relocbase + def->st_value); 242 rdbg(dodebug, "GLOB_DAT %s in %s --> %p in %s", 243 defobj->strtab + def->st_name, obj->path, 244 (void *)*where, defobj->path); 245 break; 246 247 case R_TYPE(RELATIVE): 248 if ((caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ || 249 (caddr_t)where >= (caddr_t)&_DYNAMIC) { 250 *where += (Elf_Addr)obj->relocbase; 251 rdbg(dodebug, "RELATIVE in %s --> %p", obj->path, 252 (void *)*where); 253 } 254 else 255 rdbg(dodebug, "RELATIVE in %s stays at %p", 256 obj->path, (void *)*where); 257 break; 258 259 case R_TYPE(COPY): 260 /* 261 * These are deferred until all other relocations have 262 * been done. All we do here is make sure that the COPY 263 * relocation is not in a shared library. They are allowed 264 * only in executable files. 265 */ 266 if (!obj->mainprog) { 267 _rtld_error( 268 "%s: Unexpected R_COPY relocation in shared library", 269 obj->path); 270 return -1; 271 } 272 rdbg(dodebug, "COPY (avoid in main)"); 273 break; 274 #endif /* __i386__ || __alpha__ */ 275 276 #ifdef __mips__ 277 case R_TYPE(REL32): 278 /* 32-bit PC-relative reference */ 279 def = obj->symtab + ELF_R_SYM(rela->r_info); 280 281 if (ELF_SYM_BIND(def->st_info) == Elf_estb_local && 282 (ELF_SYM_TYPE(def->st_info) == Elf_estt_section || 283 ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) { 284 *where += (Elf_Addr)obj->relocbase; 285 rdbg(dodebug, "REL32 in %s --> %p", obj->path, 286 (void *)*where); 287 } else { 288 /* XXX maybe do something re: bootstrapping? */ 289 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, 290 NULL, obj, &defobj, false); 291 if (def == NULL) 292 return -1; 293 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 294 rdbg(dodebug, "REL32 %s in %s --> %p in %s", 295 defobj->strtab + def->st_name, obj->path, 296 (void *)*where, defobj->path); 297 } 298 break; 299 300 #endif /* __mips__ */ 301 302 #ifdef __powerpc__ 303 case R_TYPE(32): /* word32 S + A */ 304 case R_TYPE(GLOB_DAT): /* word32 S + A */ 305 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 306 &defobj, false); 307 if (def == NULL) 308 return -1; 309 310 tmp = (Elf_Addr)(defobj->relocbase + def->st_value + 311 rela->r_addend); 312 313 if (*where != tmp) 314 *where = tmp; 315 rdbg(dodebug, "32/GLOB_DAT %s in %s --> %p in %s", 316 defobj->strtab + def->st_name, obj->path, 317 (void *)*where, defobj->path); 318 break; 319 320 case R_TYPE(COPY): 321 rdbg(dodebug, "COPY"); 322 break; 323 324 case R_TYPE(JMP_SLOT): 325 rdbg(dodebug, "JMP_SLOT"); 326 break; 327 328 case R_TYPE(RELATIVE): /* word32 B + A */ 329 tmp = (Elf_Addr)(obj->relocbase + rela->r_addend); 330 if (obj == &_rtld_objself && *where == tmp) 331 break; /* GOT - already done */ 332 333 *where = tmp; 334 rdbg(dodebug, "RELATIVE in %s --> %p", obj->path, 335 (void *)*where); 336 break; 337 #endif /* __powerpc__ */ 338 339 default: 340 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 341 &defobj, true); 342 rdbg(dodebug, "sym = %lu, type = %lu, offset = %p, " 343 "addend = %p, contents = %p, symbol = %s", 344 (u_long)ELF_R_SYM(rela->r_info), 345 (u_long)ELF_R_TYPE(rela->r_info), 346 (void *)rela->r_offset, (void *)rela->r_addend, 347 (void *)*where, 348 def ? defobj->strtab + def->st_name : "??"); 349 _rtld_error("%s: Unsupported relocation type %d" 350 "in non-PLT relocations\n", 351 obj->path, ELF_R_TYPE(rela->r_info)); 352 return -1; 353 } 354 return 0; 355 } 356 357 358 359 int 360 _rtld_relocate_plt_object( 361 const Obj_Entry * obj, 362 const Elf_RelA * rela, 363 caddr_t *addrp, 364 bool bind_now, 365 bool dodebug) 366 { 367 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 368 Elf_Addr new_value; 369 370 /* Fully resolve procedure addresses now */ 371 372 #if defined(__powerpc__) 373 return _rtld_reloc_powerpc_plt(obj, rela, bind_now); 374 #endif 375 376 #if defined(__alpha__) || defined(__i386__) 377 if (bind_now || obj->pltgot == NULL) { 378 const Elf_Sym *def; 379 const Obj_Entry *defobj; 380 381 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 382 383 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 384 &defobj, true); 385 if (def == NULL) 386 return -1; 387 388 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 389 rdbg(dodebug, "bind now %d/fixup in %s --> old=%p new=%p", 390 (int)bind_now, 391 defobj->strtab + def->st_name, 392 (void *)*where, (void *)new_value); 393 } else 394 #endif /* __alpha__ || __i386__ */ 395 if (!obj->mainprog) { 396 /* Just relocate the GOT slots pointing into the PLT */ 397 new_value = *where + (Elf_Addr)(obj->relocbase); 398 rdbg(dodebug, "fixup !main in %s --> %p", obj->path, 399 (void *)*where); 400 } else { 401 return 0; 402 } 403 /* 404 * Since this page is probably copy-on-write, let's not write 405 * it unless we really really have to. 406 */ 407 if (*where != new_value) 408 *where = new_value; 409 if (addrp != NULL) 410 *addrp = *(caddr_t *)(obj->relocbase + rela->r_offset); 411 return 0; 412 } 413 #endif /* __sparc__ */ 414 415 caddr_t 416 _rtld_bind( 417 const Obj_Entry *obj, 418 Elf_Word reloff) 419 { 420 const Elf_RelA *rela; 421 Elf_RelA ourrela; 422 caddr_t addr; 423 424 if (obj->pltrel != NULL) { 425 const Elf_Rel *rel; 426 427 rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff); 428 ourrela.r_info = rel->r_info; 429 ourrela.r_offset = rel->r_offset; 430 rela = &ourrela; 431 } else { 432 rela = (const Elf_RelA *)((caddr_t) obj->pltrela + reloff); 433 } 434 435 if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0) 436 _rtld_die(); 437 438 return addr; 439 } 440 441 /* 442 * Relocate newly-loaded shared objects. The argument is a pointer to 443 * the Obj_Entry for the first such object. All objects from the first 444 * to the end of the list of objects are relocated. Returns 0 on success, 445 * or -1 on failure. 446 */ 447 int 448 _rtld_relocate_objects( 449 Obj_Entry * first, 450 bool bind_now, 451 bool dodebug) 452 { 453 Obj_Entry *obj; 454 int ok = 1; 455 456 for (obj = first; obj != NULL; obj = obj->next) { 457 if (obj->nbuckets == 0 || obj->nchains == 0 458 || obj->buckets == NULL || obj->symtab == NULL 459 || obj->strtab == NULL) { 460 _rtld_error("%s: Shared object has no run-time" 461 " symbol table", obj->path); 462 return -1; 463 } 464 rdbg(dodebug, " relocating %s (%ld/%ld rel/rela, " 465 "%ld/%ld plt rel/rela)", 466 obj->path, 467 (long)(obj->rellim - obj->rel), 468 (long)(obj->relalim - obj->rela), 469 (long)(obj->pltrellim - obj->pltrel), 470 (long)(obj->pltrelalim - obj->pltrela)); 471 472 if (obj->textrel) { 473 /* 474 * There are relocations to the write-protected text 475 * segment. 476 */ 477 if (mprotect(obj->mapbase, obj->textsize, 478 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 479 _rtld_error("%s: Cannot write-enable text " 480 "segment: %s", obj->path, xstrerror(errno)); 481 return -1; 482 } 483 } 484 if (obj->rel != NULL) { 485 /* Process the non-PLT relocations. */ 486 const Elf_Rel *rel; 487 for (rel = obj->rel; rel < obj->rellim; ++rel) { 488 Elf_RelA ourrela; 489 ourrela.r_info = rel->r_info; 490 ourrela.r_offset = rel->r_offset; 491 #if defined(__mips__) 492 /* rel->r_offset is not valid on mips? */ 493 if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE)) 494 ourrela.r_addend = 0; 495 else 496 #endif 497 ourrela.r_addend = 498 *(Elf_Word *)(obj->relocbase + 499 rel->r_offset); 500 501 if (_rtld_relocate_nonplt_object(obj, &ourrela, 502 dodebug) < 0) 503 ok = 0; 504 } 505 } 506 if (obj->rela != NULL) { 507 /* Process the non-PLT relocations. */ 508 const Elf_RelA *rela; 509 for (rela = obj->rela; rela < obj->relalim; ++rela) { 510 if (_rtld_relocate_nonplt_object(obj, rela, 511 dodebug) < 0) 512 ok = 0; 513 } 514 } 515 if (obj->textrel) { /* Re-protected the text segment. */ 516 if (mprotect(obj->mapbase, obj->textsize, 517 PROT_READ | PROT_EXEC) == -1) { 518 _rtld_error("%s: Cannot write-protect text " 519 "segment: %s", obj->path, xstrerror(errno)); 520 return -1; 521 } 522 } 523 /* Process the PLT relocations. */ 524 if (obj->pltrel != NULL) { 525 const Elf_Rel *rel; 526 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 527 Elf_RelA ourrela; 528 ourrela.r_info = rel->r_info; 529 ourrela.r_offset = rel->r_offset; 530 ourrela.r_addend = 531 *(Elf_Word *)(obj->relocbase + 532 rel->r_offset); 533 if (_rtld_relocate_plt_object(obj, &ourrela, 534 NULL, bind_now, dodebug) < 0) 535 ok = 0; 536 } 537 } 538 if (obj->pltrela != NULL) { 539 const Elf_RelA *rela; 540 for (rela = obj->pltrela; rela < obj->pltrelalim; 541 ++rela) { 542 if (_rtld_relocate_plt_object(obj, rela, 543 NULL, bind_now, dodebug) < 0) 544 ok = 0; 545 } 546 } 547 if (!ok) 548 return -1; 549 550 551 /* Set some sanity-checking numbers in the Obj_Entry. */ 552 obj->magic = RTLD_MAGIC; 553 obj->version = RTLD_VERSION; 554 555 /* Fill in the dynamic linker entry points. */ 556 obj->dlopen = _rtld_dlopen; 557 obj->dlsym = _rtld_dlsym; 558 obj->dlerror = _rtld_dlerror; 559 obj->dlclose = _rtld_dlclose; 560 561 /* Set the special PLTGOT entries. */ 562 if (obj->pltgot != NULL) { 563 #if defined(__i386__) 564 obj->pltgot[1] = (Elf_Addr) obj; 565 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 566 #endif 567 #if defined(__alpha__) 568 /* 569 * This function will be called to perform the 570 * relocation. 571 */ 572 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 573 /* Identify this shared object */ 574 obj->pltgot[3] = (Elf_Addr) obj; 575 #endif 576 #if defined(__mips__) 577 _rtld_relocate_mips_got(obj); 578 579 obj->pltgot[0] = (Elf_Addr) & _rtld_bind_start; 580 /* XXX only if obj->pltgot[1] & 0x80000000 ?? */ 581 obj->pltgot[1] |= (Elf_Addr) obj; 582 #endif 583 #if defined(__powerpc__) 584 _rtld_setup_powerpc_plt(obj); 585 #endif 586 #if defined(__sparc__) 587 /* 588 * PLTGOT is the PLT on the sparc. 589 * The first entry holds the call the dynamic linker. 590 * We construct a `call' sequence that transfers 591 * to `_rtld_bind_start()'. 592 * The second entry holds the object identification. 593 * Note: each PLT entry is three words long. 594 */ 595 #define SAVE 0x9de3bfc0 /* i.e. `save %sp,-64,%sp' */ 596 #define CALL 0x40000000 597 #define NOP 0x01000000 598 obj->pltgot[0] = SAVE; 599 obj->pltgot[1] = CALL | 600 ((Elf_Addr)&_rtld_bind_start - 601 (Elf_Addr)&obj->pltgot[1]) >> 2; 602 obj->pltgot[2] = NOP; 603 604 obj->pltgot[3] = (Elf_Addr) obj; 605 #endif 606 } 607 } 608 609 return 0; 610 } 611
Indexes created Tue Sep 30 11:09:46 GMT 2025