reloc.c revision 1.19
1 /* $NetBSD: reloc.c,v 1.19 1999/03/13 20:00:14 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 #ifndef RTLD_INHIBIT_COPY_RELOCS 56 static int _rtld_do_copy_relocation __P((const Obj_Entry *, const Elf_RelA *, 57 bool)); 58 59 /* 60 * XXX: These don't work for the alpha and i386; don't know about powerpc 61 * The alpha and the i386 avoid the problem by compiling everything PIC. 62 * These relocation are supposed to be writing the address of the 63 * function to be called on the bss.rel or bss.rela segment, but: 64 * - st_size == 0 65 * - on the i386 at least the call instruction is a direct call 66 * not an indirect call. 67 */ 68 static int 69 _rtld_do_copy_relocation(dstobj, rela, dodebug) 70 const Obj_Entry *dstobj; 71 const Elf_RelA *rela; 72 bool dodebug; 73 { 74 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 75 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 76 const char *name = dstobj->strtab + dstsym->st_name; 77 unsigned long hash = _rtld_elf_hash(name); 78 size_t size = dstsym->st_size; 79 const void *srcaddr; 80 const Elf_Sym *srcsym; 81 Obj_Entry *srcobj; 82 83 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 84 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, 85 false)) != NULL) 86 break; 87 88 if (srcobj == NULL) { 89 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 90 " relocation in %s", name, dstobj->path); 91 return (-1); 92 } 93 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 94 (void)memcpy(dstaddr, srcaddr, size); 95 rdbg(dodebug, ("COPY %s %s %s --> src=%p dst=%p *dst= %p size %ld", 96 dstobj->path, srcobj->path, name, (void *)srcaddr, 97 (void *)dstaddr, (void *)*(long *)dstaddr, (long)size)); 98 return (0); 99 } 100 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 101 102 103 /* 104 * Process the special R_xxx_COPY relocations in the main program. These 105 * copy data from a shared object into a region in the main program's BSS 106 * segment. 107 * 108 * Returns 0 on success, -1 on failure. 109 */ 110 int 111 _rtld_do_copy_relocations(dstobj, dodebug) 112 const Obj_Entry *dstobj; 113 bool dodebug; 114 { 115 #ifndef RTLD_INHIBIT_COPY_RELOCS 116 117 /* COPY relocations are invalid elsewhere */ 118 assert(dstobj->mainprog); 119 120 if (dstobj->rel != NULL) { 121 const Elf_Rel *rel; 122 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 123 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 124 Elf_RelA ourrela; 125 ourrela.r_info = rel->r_info; 126 ourrela.r_offset = rel->r_offset; 127 ourrela.r_addend = 0; 128 if (_rtld_do_copy_relocation(dstobj, 129 &ourrela, dodebug) < 0) 130 return (-1); 131 } 132 } 133 } 134 if (dstobj->rela != NULL) { 135 const Elf_RelA *rela; 136 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 137 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 138 if (_rtld_do_copy_relocation(dstobj, rela, 139 dodebug) < 0) 140 return (-1); 141 } 142 } 143 } 144 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 145 146 return (0); 147 } 148 149 150 #ifndef __sparc__ 151 int 152 _rtld_relocate_nonplt_object(obj, rela, dodebug) 153 const Obj_Entry *obj; 154 const Elf_RelA *rela; 155 bool dodebug; 156 { 157 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 158 const Elf_Sym *def; 159 const Obj_Entry *defobj; 160 #if defined(__i386__) || defined(__alpha__) 161 extern Elf_Addr _GLOBAL_OFFSET_TABLE_[]; 162 extern Elf_Dyn _DYNAMIC; 163 #endif 164 #if defined(__i386__) || defined(__alpha__) || defined(__powerpc__) 165 Elf_Addr tmp; 166 #endif 167 168 switch (ELF_R_TYPE(rela->r_info)) { 169 170 case R_TYPE(NONE): 171 break; 172 173 #ifdef __i386__ 174 case R_TYPE(GOT32): 175 176 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 177 &defobj, false); 178 if (def == NULL) 179 return -1; 180 181 tmp = (Elf_Addr)(defobj->relocbase + def->st_value); 182 if (*where != tmp) 183 *where = tmp; 184 rdbg(dodebug, ("GOT32 %s in %s --> %p in %s", 185 defobj->strtab + def->st_name, obj->path, 186 (void *)*where, defobj->path)); 187 break; 188 189 case R_TYPE(PC32): 190 /* 191 * I don't think the dynamic linker should ever see this 192 * type of relocation. But the binutils-2.6 tools sometimes 193 * generate it. 194 */ 195 196 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 197 &defobj, false); 198 if (def == NULL) 199 return -1; 200 201 *where += (Elf_Addr)(defobj->relocbase + def->st_value) - 202 (Elf_Addr)where; 203 rdbg(dodebug, ("PC32 %s in %s --> %p in %s", 204 defobj->strtab + def->st_name, obj->path, 205 (void *)*where, defobj->path)); 206 break; 207 208 case R_TYPE(32): 209 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 210 &defobj, false); 211 if (def == NULL) 212 return -1; 213 214 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 215 rdbg(dodebug, ("32 %s in %s --> %p in %s", 216 defobj->strtab + def->st_name, obj->path, 217 (void *)*where, defobj->path)); 218 break; 219 #endif /* __i386__ */ 220 221 #ifdef __alpha__ 222 case R_TYPE(REFQUAD): 223 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 224 &defobj, false); 225 if (def == NULL) 226 return -1; 227 228 tmp = (Elf_Addr)(defobj->relocbase + def->st_value) + 229 *where + rela->r_addend; 230 if (*where != tmp) 231 *where = tmp; 232 rdbg(dodebug, ("REFQUAD %s in %s --> %p in %s", 233 defobj->strtab + def->st_name, obj->path, 234 (void *)*where, defobj->path)); 235 break; 236 #endif /* __alpha__ */ 237 238 #if defined(__i386__) || defined(__alpha__) 239 case R_TYPE(GLOB_DAT): 240 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 241 &defobj, false); 242 if (def == NULL) 243 return -1; 244 245 if (*where != (Elf_Addr)(defobj->relocbase + def->st_value)) 246 *where = (Elf_Addr)(defobj->relocbase + def->st_value); 247 rdbg(dodebug, ("GLOB_DAT %s in %s --> %p in %s", 248 defobj->strtab + def->st_name, obj->path, 249 (void *)*where, defobj->path)); 250 break; 251 252 case R_TYPE(RELATIVE): 253 if (!dodebug || 254 (caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ || 255 (caddr_t)where >= (caddr_t)&_DYNAMIC) { 256 *where += (Elf_Addr)obj->relocbase; 257 rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path, 258 (void *)*where)); 259 } 260 else 261 rdbg(dodebug, ("RELATIVE in %s stays at %p", 262 obj->path, (void *)*where)); 263 break; 264 265 case R_TYPE(COPY): 266 /* 267 * These are deferred until all other relocations have 268 * been done. All we do here is make sure that the COPY 269 * relocation is not in a shared library. They are allowed 270 * only in executable files. 271 */ 272 if (!obj->mainprog) { 273 _rtld_error( 274 "%s: Unexpected R_COPY relocation in shared library", 275 obj->path); 276 return -1; 277 } 278 rdbg(dodebug, ("COPY (avoid in main)")); 279 break; 280 #endif /* __i386__ || __alpha__ */ 281 282 #ifdef __mips__ 283 case R_TYPE(REL32): 284 /* 32-bit PC-relative reference */ 285 def = obj->symtab + ELF_R_SYM(rela->r_info); 286 287 if (ELF_SYM_BIND(def->st_info) == Elf_estb_local && 288 (ELF_SYM_TYPE(def->st_info) == Elf_estt_section || 289 ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) { 290 *where += (Elf_Addr)obj->relocbase; 291 rdbg(dodebug, ("REL32 in %s --> %p", obj->path, 292 (void *)*where)); 293 } else { 294 /* XXX maybe do something re: bootstrapping? */ 295 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, 296 NULL, obj, &defobj, false); 297 if (def == NULL) 298 return -1; 299 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 300 rdbg(dodebug, ("REL32 %s in %s --> %p in %s", 301 defobj->strtab + def->st_name, obj->path, 302 (void *)*where, defobj->path)); 303 } 304 break; 305 306 #endif /* __mips__ */ 307 308 #ifdef __powerpc__ 309 case R_TYPE(32): /* word32 S + A */ 310 case R_TYPE(GLOB_DAT): /* word32 S + A */ 311 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 312 &defobj, false); 313 if (def == NULL) 314 return -1; 315 316 tmp = (Elf_Addr)(defobj->relocbase + def->st_value + 317 rela->r_addend); 318 319 if (*where != tmp) 320 *where = tmp; 321 rdbg(dodebug, ("32/GLOB_DAT %s in %s --> %p in %s", 322 defobj->strtab + def->st_name, obj->path, 323 (void *)*where, defobj->path)); 324 break; 325 326 case R_TYPE(COPY): 327 rdbg(dodebug, ("COPY")); 328 break; 329 330 case R_TYPE(JMP_SLOT): 331 rdbg(dodebug, ("JMP_SLOT")); 332 break; 333 334 case R_TYPE(RELATIVE): /* word32 B + A */ 335 tmp = (Elf_Addr)(obj->relocbase + rela->r_addend); 336 if (obj == &_rtld_objself && *where == tmp) 337 break; /* GOT - already done */ 338 339 *where = tmp; 340 rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path, 341 (void *)*where)); 342 break; 343 #endif /* __powerpc__ */ 344 345 default: 346 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 347 &defobj, true); 348 rdbg(dodebug, ("sym = %lu, type = %lu, offset = %p, " 349 "addend = %p, contents = %p, symbol = %s", 350 (u_long)ELF_R_SYM(rela->r_info), 351 (u_long)ELF_R_TYPE(rela->r_info), 352 (void *)rela->r_offset, (void *)rela->r_addend, 353 (void *)*where, 354 def ? defobj->strtab + def->st_name : "??")); 355 _rtld_error("%s: Unsupported relocation type %d" 356 "in non-PLT relocations\n", 357 obj->path, ELF_R_TYPE(rela->r_info)); 358 return -1; 359 } 360 return 0; 361 } 362 363 364 365 int 366 _rtld_relocate_plt_object(obj, rela, addrp, bind_now, dodebug) 367 const Obj_Entry *obj; 368 const Elf_RelA *rela; 369 caddr_t *addrp; 370 bool bind_now; 371 bool dodebug; 372 { 373 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 374 Elf_Addr new_value; 375 376 /* Fully resolve procedure addresses now */ 377 378 #if defined(__powerpc__) 379 return _rtld_reloc_powerpc_plt(obj, rela, bind_now); 380 #endif 381 382 #if defined(__alpha__) || defined(__i386__) 383 if (bind_now || obj->pltgot == NULL) { 384 const Elf_Sym *def; 385 const Obj_Entry *defobj; 386 387 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 388 389 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 390 &defobj, true); 391 if (def == NULL) 392 return -1; 393 394 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 395 rdbg(dodebug, ("bind now %d/fixup in %s --> old=%p new=%p", 396 (int)bind_now, 397 defobj->strtab + def->st_name, 398 (void *)*where, (void *)new_value)); 399 } else 400 #endif /* __alpha__ || __i386__ */ 401 if (!obj->mainprog) { 402 /* Just relocate the GOT slots pointing into the PLT */ 403 new_value = *where + (Elf_Addr)(obj->relocbase); 404 rdbg(dodebug, ("fixup !main in %s --> %p", obj->path, 405 (void *)*where)); 406 } else { 407 return 0; 408 } 409 /* 410 * Since this page is probably copy-on-write, let's not write 411 * it unless we really really have to. 412 */ 413 if (*where != new_value) 414 *where = new_value; 415 if (addrp != NULL) 416 *addrp = *(caddr_t *)(obj->relocbase + rela->r_offset); 417 return 0; 418 } 419 #endif /* __sparc__ */ 420 421 caddr_t 422 _rtld_bind(obj, reloff) 423 const Obj_Entry *obj; 424 Elf_Word reloff; 425 { 426 const Elf_RelA *rela; 427 Elf_RelA ourrela; 428 caddr_t addr; 429 430 if (obj->pltrel != NULL) { 431 const Elf_Rel *rel; 432 433 rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff); 434 ourrela.r_info = rel->r_info; 435 ourrela.r_offset = rel->r_offset; 436 rela = &ourrela; 437 } else { 438 rela = (const Elf_RelA *)((caddr_t) obj->pltrela + reloff); 439 } 440 441 if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0) 442 _rtld_die(); 443 444 return addr; 445 } 446 447 /* 448 * Relocate newly-loaded shared objects. The argument is a pointer to 449 * the Obj_Entry for the first such object. All objects from the first 450 * to the end of the list of objects are relocated. Returns 0 on success, 451 * or -1 on failure. 452 */ 453 int 454 _rtld_relocate_objects(first, bind_now, dodebug) 455 Obj_Entry *first; 456 bool bind_now; 457 bool dodebug; 458 { 459 Obj_Entry *obj; 460 int ok = 1; 461 462 for (obj = first; obj != NULL; obj = obj->next) { 463 if (obj->nbuckets == 0 || obj->nchains == 0 || 464 obj->buckets == NULL || obj->symtab == NULL || 465 obj->strtab == NULL) { 466 _rtld_error("%s: Shared object has no run-time" 467 " symbol table", obj->path); 468 return -1; 469 } 470 rdbg(dodebug, (" relocating %s (%ld/%ld rel/rela, " 471 "%ld/%ld plt rel/rela)", 472 obj->path, 473 (long)(obj->rellim - obj->rel), 474 (long)(obj->relalim - obj->rela), 475 (long)(obj->pltrellim - obj->pltrel), 476 (long)(obj->pltrelalim - obj->pltrela))); 477 478 if (obj->textrel) { 479 /* 480 * There are relocations to the write-protected text 481 * segment. 482 */ 483 if (mprotect(obj->mapbase, obj->textsize, 484 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 485 _rtld_error("%s: Cannot write-enable text " 486 "segment: %s", obj->path, xstrerror(errno)); 487 return -1; 488 } 489 } 490 if (obj->rel != NULL) { 491 /* Process the non-PLT relocations. */ 492 const Elf_Rel *rel; 493 for (rel = obj->rel; rel < obj->rellim; ++rel) { 494 Elf_RelA ourrela; 495 ourrela.r_info = rel->r_info; 496 ourrela.r_offset = rel->r_offset; 497 #if defined(__mips__) 498 /* rel->r_offset is not valid on mips? */ 499 if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE)) 500 ourrela.r_addend = 0; 501 else 502 #endif 503 ourrela.r_addend = 504 *(Elf_Word *)(obj->relocbase + 505 rel->r_offset); 506 507 if (_rtld_relocate_nonplt_object(obj, &ourrela, 508 dodebug) < 0) 509 ok = 0; 510 } 511 } 512 if (obj->rela != NULL) { 513 /* Process the non-PLT relocations. */ 514 const Elf_RelA *rela; 515 for (rela = obj->rela; rela < obj->relalim; ++rela) { 516 if (_rtld_relocate_nonplt_object(obj, rela, 517 dodebug) < 0) 518 ok = 0; 519 } 520 } 521 if (obj->textrel) { /* Re-protected the text segment. */ 522 if (mprotect(obj->mapbase, obj->textsize, 523 PROT_READ | PROT_EXEC) == -1) { 524 _rtld_error("%s: Cannot write-protect text " 525 "segment: %s", obj->path, xstrerror(errno)); 526 return -1; 527 } 528 } 529 /* Process the PLT relocations. */ 530 if (obj->pltrel != NULL) { 531 const Elf_Rel *rel; 532 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 533 Elf_RelA ourrela; 534 ourrela.r_info = rel->r_info; 535 ourrela.r_offset = rel->r_offset; 536 ourrela.r_addend = 537 *(Elf_Word *)(obj->relocbase + 538 rel->r_offset); 539 if (_rtld_relocate_plt_object(obj, &ourrela, 540 NULL, bind_now, dodebug) < 0) 541 ok = 0; 542 } 543 } 544 if (obj->pltrela != NULL) { 545 const Elf_RelA *rela; 546 for (rela = obj->pltrela; rela < obj->pltrelalim; 547 ++rela) { 548 if (_rtld_relocate_plt_object(obj, rela, 549 NULL, bind_now, dodebug) < 0) 550 ok = 0; 551 } 552 } 553 if (!ok) 554 return -1; 555 556 557 /* Set some sanity-checking numbers in the Obj_Entry. */ 558 obj->magic = RTLD_MAGIC; 559 obj->version = RTLD_VERSION; 560 561 /* Fill in the dynamic linker entry points. */ 562 obj->dlopen = _rtld_dlopen; 563 obj->dlsym = _rtld_dlsym; 564 obj->dlerror = _rtld_dlerror; 565 obj->dlclose = _rtld_dlclose; 566 567 /* Set the special PLTGOT entries. */ 568 if (obj->pltgot != NULL) { 569 #if defined(__i386__) 570 obj->pltgot[1] = (Elf_Addr) obj; 571 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 572 #endif 573 #if defined(__alpha__) 574 /* 575 * This function will be called to perform the 576 * relocation. 577 */ 578 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 579 /* Identify this shared object */ 580 obj->pltgot[3] = (Elf_Addr) obj; 581 #endif 582 #if defined(__mips__) 583 _rtld_relocate_mips_got(obj); 584 585 obj->pltgot[0] = (Elf_Addr) & _rtld_bind_start; 586 /* XXX only if obj->pltgot[1] & 0x80000000 ?? */ 587 obj->pltgot[1] |= (Elf_Addr) obj; 588 #endif 589 #if defined(__powerpc__) 590 _rtld_setup_powerpc_plt(obj); 591 #endif 592 #if defined(__sparc__) 593 /* 594 * PLTGOT is the PLT on the sparc. 595 * The first entry holds the call the dynamic linker. 596 * We construct a `call' sequence that transfers 597 * to `_rtld_bind_start()'. 598 * The second entry holds the object identification. 599 * Note: each PLT entry is three words long. 600 */ 601 #define SAVE 0x9de3bfc0 /* i.e. `save %sp,-64,%sp' */ 602 #define CALL 0x40000000 603 #define NOP 0x01000000 604 obj->pltgot[0] = SAVE; 605 obj->pltgot[1] = CALL | 606 ((Elf_Addr)&_rtld_bind_start - 607 (Elf_Addr)&obj->pltgot[1]) >> 2; 608 obj->pltgot[2] = NOP; 609 610 obj->pltgot[3] = (Elf_Addr) obj; 611 #endif 612 } 613 } 614 615 return 0; 616 } 617
Indexes created Mon Sep 29 21:09:56 GMT 2025