reloc.c revision 1.20
1 /* $NetBSD: reloc.c,v 1.20 1999/04/29 15:06:41 kleink 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(__alpha__) || defined(__i386__) || defined(__m68k__) 161 extern Elf_Addr _GLOBAL_OFFSET_TABLE_[]; 162 extern Elf_Dyn _DYNAMIC; 163 #endif 164 #if defined(__alpha__) || defined(__i386__) || defined(__m68k__) || \ 165 defined(__powerpc__) 166 Elf_Addr tmp; 167 #endif 168 169 switch (ELF_R_TYPE(rela->r_info)) { 170 171 case R_TYPE(NONE): 172 break; 173 174 #if defined(__i386__) || defined(__m68k__) 175 case R_TYPE(GOT32): 176 177 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 178 &defobj, false); 179 if (def == NULL) 180 return -1; 181 182 tmp = (Elf_Addr)(defobj->relocbase + def->st_value); 183 if (*where != tmp) 184 *where = tmp; 185 rdbg(dodebug, ("GOT32 %s in %s --> %p in %s", 186 defobj->strtab + def->st_name, obj->path, 187 (void *)*where, defobj->path)); 188 break; 189 190 case R_TYPE(PC32): 191 /* 192 * I don't think the dynamic linker should ever see this 193 * type of relocation. But the binutils-2.6 tools sometimes 194 * generate it. 195 */ 196 197 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 198 &defobj, false); 199 if (def == NULL) 200 return -1; 201 202 *where += (Elf_Addr)(defobj->relocbase + def->st_value) - 203 (Elf_Addr)where; 204 rdbg(dodebug, ("PC32 %s in %s --> %p in %s", 205 defobj->strtab + def->st_name, obj->path, 206 (void *)*where, defobj->path)); 207 break; 208 209 case R_TYPE(32): 210 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 211 &defobj, false); 212 if (def == NULL) 213 return -1; 214 215 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 216 rdbg(dodebug, ("32 %s in %s --> %p in %s", 217 defobj->strtab + def->st_name, obj->path, 218 (void *)*where, defobj->path)); 219 break; 220 #endif /* __i386__ || __m68k__ */ 221 222 #ifdef __alpha__ 223 case R_TYPE(REFQUAD): 224 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 225 &defobj, false); 226 if (def == NULL) 227 return -1; 228 229 tmp = (Elf_Addr)(defobj->relocbase + def->st_value) + 230 *where + rela->r_addend; 231 if (*where != tmp) 232 *where = tmp; 233 rdbg(dodebug, ("REFQUAD %s in %s --> %p in %s", 234 defobj->strtab + def->st_name, obj->path, 235 (void *)*where, defobj->path)); 236 break; 237 #endif /* __alpha__ */ 238 239 #if defined(__alpha__) || defined(__i386__) || defined(__m68k__) 240 case R_TYPE(GLOB_DAT): 241 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 242 &defobj, false); 243 if (def == NULL) 244 return -1; 245 246 if (*where != (Elf_Addr)(defobj->relocbase + def->st_value)) 247 *where = (Elf_Addr)(defobj->relocbase + def->st_value); 248 rdbg(dodebug, ("GLOB_DAT %s in %s --> %p in %s", 249 defobj->strtab + def->st_name, obj->path, 250 (void *)*where, defobj->path)); 251 break; 252 253 case R_TYPE(RELATIVE): 254 if (!dodebug || 255 (caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ || 256 (caddr_t)where >= (caddr_t)&_DYNAMIC) { 257 *where += (Elf_Addr)obj->relocbase; 258 rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path, 259 (void *)*where)); 260 } 261 else 262 rdbg(dodebug, ("RELATIVE in %s stays at %p", 263 obj->path, (void *)*where)); 264 break; 265 266 case R_TYPE(COPY): 267 /* 268 * These are deferred until all other relocations have 269 * been done. All we do here is make sure that the COPY 270 * relocation is not in a shared library. They are allowed 271 * only in executable files. 272 */ 273 if (!obj->mainprog) { 274 _rtld_error( 275 "%s: Unexpected R_COPY relocation in shared library", 276 obj->path); 277 return -1; 278 } 279 rdbg(dodebug, ("COPY (avoid in main)")); 280 break; 281 #endif /* __i386__ || __alpha__ */ 282 283 #ifdef __mips__ 284 case R_TYPE(REL32): 285 /* 32-bit PC-relative reference */ 286 def = obj->symtab + ELF_R_SYM(rela->r_info); 287 288 if (ELF_SYM_BIND(def->st_info) == Elf_estb_local && 289 (ELF_SYM_TYPE(def->st_info) == Elf_estt_section || 290 ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) { 291 *where += (Elf_Addr)obj->relocbase; 292 rdbg(dodebug, ("REL32 in %s --> %p", obj->path, 293 (void *)*where)); 294 } else { 295 /* XXX maybe do something re: bootstrapping? */ 296 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, 297 NULL, obj, &defobj, false); 298 if (def == NULL) 299 return -1; 300 *where += (Elf_Addr)(defobj->relocbase + def->st_value); 301 rdbg(dodebug, ("REL32 %s in %s --> %p in %s", 302 defobj->strtab + def->st_name, obj->path, 303 (void *)*where, defobj->path)); 304 } 305 break; 306 307 #endif /* __mips__ */ 308 309 #ifdef __powerpc__ 310 case R_TYPE(32): /* word32 S + A */ 311 case R_TYPE(GLOB_DAT): /* word32 S + A */ 312 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 313 &defobj, false); 314 if (def == NULL) 315 return -1; 316 317 tmp = (Elf_Addr)(defobj->relocbase + def->st_value + 318 rela->r_addend); 319 320 if (*where != tmp) 321 *where = tmp; 322 rdbg(dodebug, ("32/GLOB_DAT %s in %s --> %p in %s", 323 defobj->strtab + def->st_name, obj->path, 324 (void *)*where, defobj->path)); 325 break; 326 327 case R_TYPE(COPY): 328 rdbg(dodebug, ("COPY")); 329 break; 330 331 case R_TYPE(JMP_SLOT): 332 rdbg(dodebug, ("JMP_SLOT")); 333 break; 334 335 case R_TYPE(RELATIVE): /* word32 B + A */ 336 tmp = (Elf_Addr)(obj->relocbase + rela->r_addend); 337 if (obj == &_rtld_objself && *where == tmp) 338 break; /* GOT - already done */ 339 340 *where = tmp; 341 rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path, 342 (void *)*where)); 343 break; 344 #endif /* __powerpc__ */ 345 346 default: 347 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 348 &defobj, true); 349 rdbg(dodebug, ("sym = %lu, type = %lu, offset = %p, " 350 "addend = %p, contents = %p, symbol = %s", 351 (u_long)ELF_R_SYM(rela->r_info), 352 (u_long)ELF_R_TYPE(rela->r_info), 353 (void *)rela->r_offset, (void *)rela->r_addend, 354 (void *)*where, 355 def ? defobj->strtab + def->st_name : "??")); 356 _rtld_error("%s: Unsupported relocation type %d" 357 "in non-PLT relocations\n", 358 obj->path, ELF_R_TYPE(rela->r_info)); 359 return -1; 360 } 361 return 0; 362 } 363 364 365 366 int 367 _rtld_relocate_plt_object(obj, rela, addrp, bind_now, dodebug) 368 const Obj_Entry *obj; 369 const Elf_RelA *rela; 370 caddr_t *addrp; 371 bool bind_now; 372 bool dodebug; 373 { 374 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 375 Elf_Addr new_value; 376 377 /* Fully resolve procedure addresses now */ 378 379 #if defined(__powerpc__) 380 return _rtld_reloc_powerpc_plt(obj, rela, bind_now); 381 #endif 382 383 #if defined(__alpha__) || defined(__i386__) || defined(__m68k__) 384 if (bind_now || obj->pltgot == NULL) { 385 const Elf_Sym *def; 386 const Obj_Entry *defobj; 387 388 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 389 390 def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, 391 &defobj, true); 392 if (def == NULL) 393 return -1; 394 395 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 396 rdbg(dodebug, ("bind now %d/fixup in %s --> old=%p new=%p", 397 (int)bind_now, 398 defobj->strtab + def->st_name, 399 (void *)*where, (void *)new_value)); 400 } else 401 #endif /* __alpha__ || __i386__ || __m68k__ */ 402 if (!obj->mainprog) { 403 /* Just relocate the GOT slots pointing into the PLT */ 404 new_value = *where + (Elf_Addr)(obj->relocbase); 405 rdbg(dodebug, ("fixup !main in %s --> %p", obj->path, 406 (void *)*where)); 407 } else { 408 return 0; 409 } 410 /* 411 * Since this page is probably copy-on-write, let's not write 412 * it unless we really really have to. 413 */ 414 if (*where != new_value) 415 *where = new_value; 416 if (addrp != NULL) 417 *addrp = *(caddr_t *)(obj->relocbase + rela->r_offset); 418 return 0; 419 } 420 #endif /* __sparc__ */ 421 422 caddr_t 423 _rtld_bind(obj, reloff) 424 const Obj_Entry *obj; 425 Elf_Word reloff; 426 { 427 const Elf_RelA *rela; 428 Elf_RelA ourrela; 429 caddr_t addr; 430 431 if (obj->pltrel != NULL) { 432 const Elf_Rel *rel; 433 434 rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff); 435 ourrela.r_info = rel->r_info; 436 ourrela.r_offset = rel->r_offset; 437 rela = &ourrela; 438 } else { 439 rela = (const Elf_RelA *)((caddr_t) obj->pltrela + reloff); 440 } 441 442 if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0) 443 _rtld_die(); 444 445 return addr; 446 } 447 448 /* 449 * Relocate newly-loaded shared objects. The argument is a pointer to 450 * the Obj_Entry for the first such object. All objects from the first 451 * to the end of the list of objects are relocated. Returns 0 on success, 452 * or -1 on failure. 453 */ 454 int 455 _rtld_relocate_objects(first, bind_now, dodebug) 456 Obj_Entry *first; 457 bool bind_now; 458 bool dodebug; 459 { 460 Obj_Entry *obj; 461 int ok = 1; 462 463 for (obj = first; obj != NULL; obj = obj->next) { 464 if (obj->nbuckets == 0 || obj->nchains == 0 || 465 obj->buckets == NULL || obj->symtab == NULL || 466 obj->strtab == NULL) { 467 _rtld_error("%s: Shared object has no run-time" 468 " symbol table", obj->path); 469 return -1; 470 } 471 rdbg(dodebug, (" relocating %s (%ld/%ld rel/rela, " 472 "%ld/%ld plt rel/rela)", 473 obj->path, 474 (long)(obj->rellim - obj->rel), 475 (long)(obj->relalim - obj->rela), 476 (long)(obj->pltrellim - obj->pltrel), 477 (long)(obj->pltrelalim - obj->pltrela))); 478 479 if (obj->textrel) { 480 /* 481 * There are relocations to the write-protected text 482 * segment. 483 */ 484 if (mprotect(obj->mapbase, obj->textsize, 485 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 486 _rtld_error("%s: Cannot write-enable text " 487 "segment: %s", obj->path, xstrerror(errno)); 488 return -1; 489 } 490 } 491 if (obj->rel != NULL) { 492 /* Process the non-PLT relocations. */ 493 const Elf_Rel *rel; 494 for (rel = obj->rel; rel < obj->rellim; ++rel) { 495 Elf_RelA ourrela; 496 ourrela.r_info = rel->r_info; 497 ourrela.r_offset = rel->r_offset; 498 #if defined(__mips__) 499 /* rel->r_offset is not valid on mips? */ 500 if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE)) 501 ourrela.r_addend = 0; 502 else 503 #endif 504 ourrela.r_addend = 505 *(Elf_Word *)(obj->relocbase + 506 rel->r_offset); 507 508 if (_rtld_relocate_nonplt_object(obj, &ourrela, 509 dodebug) < 0) 510 ok = 0; 511 } 512 } 513 if (obj->rela != NULL) { 514 /* Process the non-PLT relocations. */ 515 const Elf_RelA *rela; 516 for (rela = obj->rela; rela < obj->relalim; ++rela) { 517 if (_rtld_relocate_nonplt_object(obj, rela, 518 dodebug) < 0) 519 ok = 0; 520 } 521 } 522 if (obj->textrel) { /* Re-protected the text segment. */ 523 if (mprotect(obj->mapbase, obj->textsize, 524 PROT_READ | PROT_EXEC) == -1) { 525 _rtld_error("%s: Cannot write-protect text " 526 "segment: %s", obj->path, xstrerror(errno)); 527 return -1; 528 } 529 } 530 /* Process the PLT relocations. */ 531 if (obj->pltrel != NULL) { 532 const Elf_Rel *rel; 533 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 534 Elf_RelA ourrela; 535 ourrela.r_info = rel->r_info; 536 ourrela.r_offset = rel->r_offset; 537 ourrela.r_addend = 538 *(Elf_Word *)(obj->relocbase + 539 rel->r_offset); 540 if (_rtld_relocate_plt_object(obj, &ourrela, 541 NULL, bind_now, dodebug) < 0) 542 ok = 0; 543 } 544 } 545 if (obj->pltrela != NULL) { 546 const Elf_RelA *rela; 547 for (rela = obj->pltrela; rela < obj->pltrelalim; 548 ++rela) { 549 if (_rtld_relocate_plt_object(obj, rela, 550 NULL, bind_now, dodebug) < 0) 551 ok = 0; 552 } 553 } 554 if (!ok) 555 return -1; 556 557 558 /* Set some sanity-checking numbers in the Obj_Entry. */ 559 obj->magic = RTLD_MAGIC; 560 obj->version = RTLD_VERSION; 561 562 /* Fill in the dynamic linker entry points. */ 563 obj->dlopen = _rtld_dlopen; 564 obj->dlsym = _rtld_dlsym; 565 obj->dlerror = _rtld_dlerror; 566 obj->dlclose = _rtld_dlclose; 567 568 /* Set the special PLTGOT entries. */ 569 if (obj->pltgot != NULL) { 570 #if defined(__i386__) || defined(__m68k__) 571 obj->pltgot[1] = (Elf_Addr) obj; 572 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 573 #endif 574 #if defined(__alpha__) 575 /* 576 * This function will be called to perform the 577 * relocation. 578 */ 579 obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start; 580 /* Identify this shared object */ 581 obj->pltgot[3] = (Elf_Addr) obj; 582 #endif 583 #if defined(__mips__) 584 _rtld_relocate_mips_got(obj); 585 586 obj->pltgot[0] = (Elf_Addr) & _rtld_bind_start; 587 /* XXX only if obj->pltgot[1] & 0x80000000 ?? */ 588 obj->pltgot[1] |= (Elf_Addr) obj; 589 #endif 590 #if defined(__powerpc__) 591 _rtld_setup_powerpc_plt(obj); 592 #endif 593 #if defined(__sparc__) 594 /* 595 * PLTGOT is the PLT on the sparc. 596 * The first entry holds the call the dynamic linker. 597 * We construct a `call' sequence that transfers 598 * to `_rtld_bind_start()'. 599 * The second entry holds the object identification. 600 * Note: each PLT entry is three words long. 601 */ 602 #define SAVE 0x9de3bfc0 /* i.e. `save %sp,-64,%sp' */ 603 #define CALL 0x40000000 604 #define NOP 0x01000000 605 obj->pltgot[0] = SAVE; 606 obj->pltgot[1] = CALL | 607 ((Elf_Addr)&_rtld_bind_start - 608 (Elf_Addr)&obj->pltgot[1]) >> 2; 609 obj->pltgot[2] = NOP; 610 611 obj->pltgot[3] = (Elf_Addr) obj; 612 #endif 613 } 614 } 615 616 return 0; 617 } 618
Indexes created Mon Sep 29 21:09:56 GMT 2025