1 /*- 2 * Copyright 1996, 1997, 1998, 1999 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD$ 26 */ 27 28 /* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34 #include <sys/param.h> 35 #include <sys/mman.h> 36 #include <sys/tls.h> 37 38 #include <machine/sysarch.h> 39 #include <machine/tls.h> 40 41 #include <dlfcn.h> 42 #include <err.h> 43 #include <errno.h> 44 #include <fcntl.h> 45 #include <stdarg.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #include <unistd.h> 50 51 #include "debug.h" 52 #include "rtld.h" 53 54 /* 55 * Process the special R_X86_64_COPY relocations in the main program. These 56 * copy data from a shared object into a region in the main program's BSS 57 * segment. 58 * 59 * Returns 0 on success, -1 on failure. 60 */ 61 int 62 do_copy_relocations(Obj_Entry *dstobj) 63 { 64 const Elf_Rela *relalim; 65 const Elf_Rela *rela; 66 int error = 0; 67 68 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 69 70 if (dstobj->relro_protected) 71 mprotect(dstobj->relro_page, dstobj->relro_size, PROT_READ | PROT_WRITE); 72 73 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize); 74 for (rela = dstobj->rela; rela < relalim; rela++) { 75 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 76 void *dstaddr; 77 const Elf_Sym *dstsym; 78 const char *name; 79 size_t size; 80 const void *srcaddr; 81 const Elf_Sym *srcsym; 82 const Obj_Entry *srcobj, *defobj; 83 SymLook req; 84 int res; 85 86 dstaddr = (void *) (dstobj->relocbase + rela->r_offset); 87 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 88 name = dstobj->strtab + dstsym->st_name; 89 size = dstsym->st_size; 90 symlook_init(&req, name); 91 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info)); 92 req.flags = SYMLOOK_EARLY; 93 94 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 95 res = symlook_obj(&req, srcobj); 96 if (res == 0) { 97 srcsym = req.sym_out; 98 defobj = req.defobj_out; 99 break; 100 } 101 } 102 103 if (srcobj == NULL) { 104 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 105 " relocation in %s", name, dstobj->path); 106 error = -1; 107 break; 108 } 109 110 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 111 memcpy(dstaddr, srcaddr, size); 112 } 113 } 114 115 if (dstobj->relro_protected) 116 mprotect(dstobj->relro_page, dstobj->relro_size, PROT_READ); 117 118 return error; 119 } 120 121 /* Initialize the special GOT entries. */ 122 void 123 init_pltgot(Obj_Entry *obj) 124 { 125 if (obj->pltgot != NULL) { 126 obj->pltgot[1] = (Elf_Addr) obj; 127 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 128 } 129 } 130 131 /* Process the non-PLT relocations. */ 132 int 133 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 134 RtldLockState *lockstate) 135 { 136 const Elf_Rela *relalim; 137 const Elf_Rela *rela; 138 SymCache *cache; 139 const Elf_Sym *def; 140 const Obj_Entry *defobj; 141 Elf_Addr *where, symval; 142 Elf32_Addr *where32; 143 int r; 144 145 r = -1; 146 /* 147 * The dynamic loader may be called from a thread, we have 148 * limited amounts of stack available so we cannot use alloca(). 149 */ 150 if (obj != obj_rtld) { 151 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 152 /* No need to check for NULL here */ 153 } else 154 cache = NULL; 155 156 relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize); 157 for (rela = obj->rela; rela < relalim; rela++) { 158 /* 159 * First, resolve symbol for relocations which 160 * reference symbols. 161 */ 162 switch (ELF_R_TYPE(rela->r_info)) { 163 case R_X86_64_64: 164 case R_X86_64_PC32: 165 case R_X86_64_GLOB_DAT: 166 case R_X86_64_TPOFF64: 167 case R_X86_64_TPOFF32: 168 case R_X86_64_DTPMOD64: 169 case R_X86_64_DTPOFF64: 170 case R_X86_64_DTPOFF32: 171 def = find_symdef(ELF_R_SYM(rela->r_info), obj, 172 &defobj, flags, cache, lockstate); 173 if (def == NULL) 174 goto done; 175 /* 176 * If symbol is IFUNC, only perform relocation 177 * when caller allowed it by passing 178 * SYMLOOK_IFUNC flag. Skip the relocations 179 * otherwise. 180 * 181 * Also error out in case IFUNC relocations 182 * are specified for TLS, which cannot be 183 * usefully interpreted. 184 */ 185 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 186 switch (ELF_R_TYPE(rela->r_info)) { 187 case R_X86_64_64: 188 case R_X86_64_PC32: 189 case R_X86_64_GLOB_DAT: 190 if ((flags & SYMLOOK_IFUNC) == 0) { 191 obj->non_plt_gnu_ifunc = true; 192 continue; 193 } 194 symval = (Elf_Addr)rtld_resolve_ifunc( 195 defobj, def); 196 break; 197 case R_X86_64_TPOFF64: 198 case R_X86_64_TPOFF32: 199 case R_X86_64_DTPMOD64: 200 case R_X86_64_DTPOFF64: 201 case R_X86_64_DTPOFF32: 202 _rtld_error("%s: IFUNC for TLS reloc", 203 obj->path); 204 goto done; 205 } 206 } else { 207 if ((flags & SYMLOOK_IFUNC) != 0) 208 continue; 209 symval = (Elf_Addr)defobj->relocbase + 210 def->st_value; 211 } 212 break; 213 default: 214 if ((flags & SYMLOOK_IFUNC) != 0) 215 continue; 216 break; 217 } 218 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 219 where32 = (Elf32_Addr *)where; 220 221 switch (ELF_R_TYPE(rela->r_info)) { 222 case R_X86_64_NONE: 223 break; 224 case R_X86_64_64: 225 *where = symval + rela->r_addend; 226 break; 227 case R_X86_64_PC32: 228 /* 229 * I don't think the dynamic linker should 230 * ever see this type of relocation. But the 231 * binutils-2.6 tools sometimes generate it. 232 */ 233 *where32 = (Elf32_Addr)(unsigned long)(symval + 234 rela->r_addend - (Elf_Addr)where); 235 break; 236 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 237 case R_X86_64_COPY: 238 /* 239 * These are deferred until all other relocations have 240 * been done. All we do here is make sure that the COPY 241 * relocation is not in a shared library. They are allowed 242 * only in executable files. 243 */ 244 if (!obj->mainprog) { 245 _rtld_error("%s: Unexpected R_X86_64_COPY " 246 "relocation in shared library", obj->path); 247 goto done; 248 } 249 break; 250 case R_X86_64_GLOB_DAT: 251 *where = symval; 252 break; 253 case R_X86_64_TPOFF64: 254 /* 255 * We lazily allocate offsets for static TLS 256 * as we see the first relocation that 257 * references the TLS block. This allows us to 258 * support (small amounts of) static TLS in 259 * dynamically loaded modules. If we run out 260 * of space, we generate an error. 261 */ 262 if (!defobj->tls_done) { 263 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 264 _rtld_error("%s: No space available " 265 "for static Thread Local Storage", 266 obj->path); 267 goto done; 268 } 269 } 270 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset + 271 rela->r_addend); 272 break; 273 case R_X86_64_TPOFF32: 274 /* 275 * We lazily allocate offsets for static TLS 276 * as we see the first relocation that 277 * references the TLS block. This allows us to 278 * support (small amounts of) static TLS in 279 * dynamically loaded modules. If we run out 280 * of space, we generate an error. 281 */ 282 if (!defobj->tls_done) { 283 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 284 _rtld_error("%s: No space available " 285 "for static Thread Local Storage", 286 obj->path); 287 goto done; 288 } 289 } 290 *where32 = (Elf32_Addr)(def->st_value - 291 defobj->tlsoffset + rela->r_addend); 292 break; 293 case R_X86_64_DTPMOD64: 294 *where += (Elf_Addr)defobj->tlsindex; 295 break; 296 case R_X86_64_DTPOFF64: 297 *where += (Elf_Addr)(def->st_value + rela->r_addend); 298 break; 299 case R_X86_64_DTPOFF32: 300 *where32 += (Elf32_Addr)(def->st_value + 301 rela->r_addend); 302 break; 303 case R_X86_64_RELATIVE: 304 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 305 break; 306 /* 307 * missing: 308 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, 309 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 310 */ 311 default: 312 _rtld_error("%s: Unsupported relocation type %u" 313 " in non-PLT relocations\n", obj->path, 314 (unsigned int)ELF_R_TYPE(rela->r_info)); 315 goto done; 316 } 317 } 318 r = 0; 319 done: 320 free(cache); 321 return (r); 322 } 323 324 /* Process the PLT relocations. */ 325 int 326 reloc_plt(Obj_Entry *obj) 327 { 328 const Elf_Rela *relalim; 329 const Elf_Rela *rela; 330 331 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 332 for (rela = obj->pltrela; rela < relalim; rela++) { 333 Elf_Addr *where; 334 335 switch(ELF_R_TYPE(rela->r_info)) { 336 case R_X86_64_JMP_SLOT: 337 /* Relocate the GOT slot pointing into the PLT. */ 338 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 339 *where += (Elf_Addr)obj->relocbase; 340 break; 341 342 case R_X86_64_IRELATIVE: 343 obj->irelative = true; 344 break; 345 346 default: 347 _rtld_error("Unknown relocation type %x in PLT", 348 (unsigned int)ELF_R_TYPE(rela->r_info)); 349 return (-1); 350 } 351 } 352 return 0; 353 } 354 355 /* Relocate the jump slots in an object. */ 356 int 357 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 358 { 359 const Elf_Rela *relalim; 360 const Elf_Rela *rela; 361 362 if (obj->jmpslots_done) 363 return 0; 364 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 365 for (rela = obj->pltrela; rela < relalim; rela++) { 366 Elf_Addr *where, target; 367 const Elf_Sym *def; 368 const Obj_Entry *defobj; 369 370 switch (ELF_R_TYPE(rela->r_info)) { 371 case R_X86_64_JMP_SLOT: 372 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 373 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 374 SYMLOOK_IN_PLT | flags, NULL, lockstate); 375 if (def == NULL) 376 return (-1); 377 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 378 obj->gnu_ifunc = true; 379 continue; 380 } 381 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 382 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 383 break; 384 385 case R_X86_64_IRELATIVE: 386 break; 387 388 default: 389 _rtld_error("Unknown relocation type %x in PLT", 390 (unsigned int)ELF_R_TYPE(rela->r_info)); 391 return (-1); 392 } 393 } 394 obj->jmpslots_done = true; 395 return 0; 396 } 397 398 int 399 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 400 { 401 const Elf_Rela *relalim; 402 const Elf_Rela *rela; 403 404 if (!obj->irelative) 405 return (0); 406 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 407 for (rela = obj->pltrela; rela < relalim; rela++) { 408 Elf_Addr *where, target, *ptr; 409 410 switch (ELF_R_TYPE(rela->r_info)) { 411 case R_X86_64_JMP_SLOT: 412 break; 413 414 case R_X86_64_IRELATIVE: 415 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend); 416 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 417 lock_release(rtld_bind_lock, lockstate); 418 target = ((Elf_Addr (*)(void))ptr)(); 419 wlock_acquire(rtld_bind_lock, lockstate); 420 *where = target; 421 break; 422 } 423 } 424 obj->irelative = false; 425 return (0); 426 } 427 428 int 429 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 430 { 431 const Elf_Rela *relalim; 432 const Elf_Rela *rela; 433 434 if (!obj->gnu_ifunc) 435 return (0); 436 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 437 for (rela = obj->pltrela; rela < relalim; rela++) { 438 Elf_Addr *where, target; 439 const Elf_Sym *def; 440 const Obj_Entry *defobj; 441 442 switch (ELF_R_TYPE(rela->r_info)) { 443 case R_X86_64_JMP_SLOT: 444 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 445 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 446 SYMLOOK_IN_PLT | flags, NULL, lockstate); 447 if (def == NULL) 448 return (-1); 449 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 450 continue; 451 lock_release(rtld_bind_lock, lockstate); 452 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 453 wlock_acquire(rtld_bind_lock, lockstate); 454 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 455 break; 456 } 457 } 458 obj->gnu_ifunc = false; 459 return (0); 460 } 461 462 void *__tls_get_addr(tls_index *ti) 463 { 464 struct tls_tcb *tcb; 465 466 tcb = tls_get_tcb(); 467 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset); 468 } 469 470 void * 471 __tls_get_addr_tcb(struct tls_tcb *tcb, tls_index *ti) 472 { 473 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset); 474 } 475