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 67 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 68 69 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize); 70 for (rela = dstobj->rela; rela < relalim; rela++) { 71 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 72 void *dstaddr; 73 const Elf_Sym *dstsym; 74 const char *name; 75 size_t size; 76 const void *srcaddr; 77 const Elf_Sym *srcsym; 78 const Obj_Entry *srcobj, *defobj; 79 SymLook req; 80 int res; 81 82 dstaddr = (void *) (dstobj->relocbase + rela->r_offset); 83 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 84 name = dstobj->strtab + dstsym->st_name; 85 size = dstsym->st_size; 86 symlook_init(&req, name); 87 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info)); 88 req.flags = SYMLOOK_EARLY; 89 90 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 91 res = symlook_obj(&req, srcobj); 92 if (res == 0) { 93 srcsym = req.sym_out; 94 defobj = req.defobj_out; 95 break; 96 } 97 } 98 99 if (srcobj == NULL) { 100 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 101 " relocation in %s", name, dstobj->path); 102 return -1; 103 } 104 105 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 106 memcpy(dstaddr, srcaddr, size); 107 } 108 } 109 110 return 0; 111 } 112 113 /* Initialize the special GOT entries. */ 114 void 115 init_pltgot(Obj_Entry *obj) 116 { 117 if (obj->pltgot != NULL) { 118 obj->pltgot[1] = (Elf_Addr) obj; 119 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 120 } 121 } 122 123 /* Process the non-PLT relocations. */ 124 int 125 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 126 RtldLockState *lockstate) 127 { 128 const Elf_Rela *relalim; 129 const Elf_Rela *rela; 130 SymCache *cache; 131 const Elf_Sym *def; 132 const Obj_Entry *defobj; 133 Elf_Addr *where, symval; 134 Elf32_Addr *where32; 135 int r; 136 137 r = -1; 138 /* 139 * The dynamic loader may be called from a thread, we have 140 * limited amounts of stack available so we cannot use alloca(). 141 */ 142 if (obj != obj_rtld) { 143 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 144 /* No need to check for NULL here */ 145 } else 146 cache = NULL; 147 148 relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize); 149 for (rela = obj->rela; rela < relalim; rela++) { 150 /* 151 * First, resolve symbol for relocations which 152 * reference symbols. 153 */ 154 switch (ELF_R_TYPE(rela->r_info)) { 155 case R_X86_64_64: 156 case R_X86_64_PC32: 157 case R_X86_64_GLOB_DAT: 158 case R_X86_64_TPOFF64: 159 case R_X86_64_TPOFF32: 160 case R_X86_64_DTPMOD64: 161 case R_X86_64_DTPOFF64: 162 case R_X86_64_DTPOFF32: 163 def = find_symdef(ELF_R_SYM(rela->r_info), obj, 164 &defobj, flags, cache, lockstate); 165 if (def == NULL) 166 goto done; 167 /* 168 * If symbol is IFUNC, only perform relocation 169 * when caller allowed it by passing 170 * SYMLOOK_IFUNC flag. Skip the relocations 171 * otherwise. 172 * 173 * Also error out in case IFUNC relocations 174 * are specified for TLS, which cannot be 175 * usefully interpreted. 176 */ 177 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 178 switch (ELF_R_TYPE(rela->r_info)) { 179 case R_X86_64_64: 180 case R_X86_64_PC32: 181 case R_X86_64_GLOB_DAT: 182 if ((flags & SYMLOOK_IFUNC) == 0) { 183 obj->non_plt_gnu_ifunc = true; 184 continue; 185 } 186 symval = (Elf_Addr)rtld_resolve_ifunc( 187 defobj, def); 188 break; 189 case R_X86_64_TPOFF64: 190 case R_X86_64_TPOFF32: 191 case R_X86_64_DTPMOD64: 192 case R_X86_64_DTPOFF64: 193 case R_X86_64_DTPOFF32: 194 _rtld_error("%s: IFUNC for TLS reloc", 195 obj->path); 196 goto done; 197 } 198 } else { 199 if ((flags & SYMLOOK_IFUNC) != 0) 200 continue; 201 symval = (Elf_Addr)defobj->relocbase + 202 def->st_value; 203 } 204 break; 205 default: 206 if ((flags & SYMLOOK_IFUNC) != 0) 207 continue; 208 break; 209 } 210 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 211 where32 = (Elf32_Addr *)where; 212 213 switch (ELF_R_TYPE(rela->r_info)) { 214 case R_X86_64_NONE: 215 break; 216 case R_X86_64_64: 217 *where = symval + rela->r_addend; 218 break; 219 case R_X86_64_PC32: 220 /* 221 * I don't think the dynamic linker should 222 * ever see this type of relocation. But the 223 * binutils-2.6 tools sometimes generate it. 224 */ 225 *where32 = (Elf32_Addr)(unsigned long)(symval + 226 rela->r_addend - (Elf_Addr)where); 227 break; 228 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 229 case R_X86_64_COPY: 230 /* 231 * These are deferred until all other relocations have 232 * been done. All we do here is make sure that the COPY 233 * relocation is not in a shared library. They are allowed 234 * only in executable files. 235 */ 236 if (!obj->mainprog) { 237 _rtld_error("%s: Unexpected R_X86_64_COPY " 238 "relocation in shared library", obj->path); 239 goto done; 240 } 241 break; 242 case R_X86_64_GLOB_DAT: 243 *where = symval; 244 break; 245 case R_X86_64_TPOFF64: 246 /* 247 * We lazily allocate offsets for static TLS 248 * as we see the first relocation that 249 * references the TLS block. This allows us to 250 * support (small amounts of) static TLS in 251 * dynamically loaded modules. If we run out 252 * of space, we generate an error. 253 */ 254 if (!defobj->tls_done) { 255 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 256 _rtld_error("%s: No space available " 257 "for static Thread Local Storage", 258 obj->path); 259 goto done; 260 } 261 } 262 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset + 263 rela->r_addend); 264 break; 265 case R_X86_64_TPOFF32: 266 /* 267 * We lazily allocate offsets for static TLS 268 * as we see the first relocation that 269 * references the TLS block. This allows us to 270 * support (small amounts of) static TLS in 271 * dynamically loaded modules. If we run out 272 * of space, we generate an error. 273 */ 274 if (!defobj->tls_done) { 275 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 276 _rtld_error("%s: No space available " 277 "for static Thread Local Storage", 278 obj->path); 279 goto done; 280 } 281 } 282 *where32 = (Elf32_Addr)(def->st_value - 283 defobj->tlsoffset + rela->r_addend); 284 break; 285 case R_X86_64_DTPMOD64: 286 *where += (Elf_Addr)defobj->tlsindex; 287 break; 288 case R_X86_64_DTPOFF64: 289 *where += (Elf_Addr)(def->st_value + rela->r_addend); 290 break; 291 case R_X86_64_DTPOFF32: 292 *where32 += (Elf32_Addr)(def->st_value + 293 rela->r_addend); 294 break; 295 case R_X86_64_RELATIVE: 296 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 297 break; 298 /* 299 * missing: 300 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, 301 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 302 */ 303 default: 304 _rtld_error("%s: Unsupported relocation type %u" 305 " in non-PLT relocations\n", obj->path, 306 (unsigned int)ELF_R_TYPE(rela->r_info)); 307 goto done; 308 } 309 } 310 r = 0; 311 done: 312 free(cache); 313 return (r); 314 } 315 316 /* Process the PLT relocations. */ 317 int 318 reloc_plt(Obj_Entry *obj) 319 { 320 const Elf_Rela *relalim; 321 const Elf_Rela *rela; 322 323 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 324 for (rela = obj->pltrela; rela < relalim; rela++) { 325 Elf_Addr *where; 326 327 switch(ELF_R_TYPE(rela->r_info)) { 328 case R_X86_64_JMP_SLOT: 329 /* Relocate the GOT slot pointing into the PLT. */ 330 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 331 *where += (Elf_Addr)obj->relocbase; 332 break; 333 334 case R_X86_64_IRELATIVE: 335 obj->irelative = true; 336 break; 337 338 default: 339 _rtld_error("Unknown relocation type %x in PLT", 340 (unsigned int)ELF_R_TYPE(rela->r_info)); 341 return (-1); 342 } 343 } 344 return 0; 345 } 346 347 /* Relocate the jump slots in an object. */ 348 int 349 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 350 { 351 const Elf_Rela *relalim; 352 const Elf_Rela *rela; 353 354 if (obj->jmpslots_done) 355 return 0; 356 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 357 for (rela = obj->pltrela; rela < relalim; rela++) { 358 Elf_Addr *where, target; 359 const Elf_Sym *def; 360 const Obj_Entry *defobj; 361 362 switch (ELF_R_TYPE(rela->r_info)) { 363 case R_X86_64_JMP_SLOT: 364 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 365 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 366 SYMLOOK_IN_PLT | flags, NULL, lockstate); 367 if (def == NULL) 368 return (-1); 369 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 370 obj->gnu_ifunc = true; 371 continue; 372 } 373 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 374 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 375 break; 376 377 case R_X86_64_IRELATIVE: 378 break; 379 380 default: 381 _rtld_error("Unknown relocation type %x in PLT", 382 (unsigned int)ELF_R_TYPE(rela->r_info)); 383 return (-1); 384 } 385 } 386 obj->jmpslots_done = true; 387 return 0; 388 } 389 390 int 391 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 392 { 393 const Elf_Rela *relalim; 394 const Elf_Rela *rela; 395 396 if (!obj->irelative) 397 return (0); 398 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 399 for (rela = obj->pltrela; rela < relalim; rela++) { 400 Elf_Addr *where, target, *ptr; 401 402 switch (ELF_R_TYPE(rela->r_info)) { 403 case R_X86_64_JMP_SLOT: 404 break; 405 406 case R_X86_64_IRELATIVE: 407 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend); 408 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 409 lock_release(rtld_bind_lock, lockstate); 410 target = ((Elf_Addr (*)(void))ptr)(); 411 wlock_acquire(rtld_bind_lock, lockstate); 412 *where = target; 413 break; 414 } 415 } 416 obj->irelative = false; 417 return (0); 418 } 419 420 int 421 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 422 { 423 const Elf_Rela *relalim; 424 const Elf_Rela *rela; 425 426 if (!obj->gnu_ifunc) 427 return (0); 428 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 429 for (rela = obj->pltrela; rela < relalim; rela++) { 430 Elf_Addr *where, target; 431 const Elf_Sym *def; 432 const Obj_Entry *defobj; 433 434 switch (ELF_R_TYPE(rela->r_info)) { 435 case R_X86_64_JMP_SLOT: 436 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 437 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 438 SYMLOOK_IN_PLT | flags, NULL, lockstate); 439 if (def == NULL) 440 return (-1); 441 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 442 continue; 443 lock_release(rtld_bind_lock, lockstate); 444 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 445 wlock_acquire(rtld_bind_lock, lockstate); 446 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 447 break; 448 } 449 } 450 obj->gnu_ifunc = false; 451 return (0); 452 } 453 454 void *__tls_get_addr(tls_index *ti) 455 { 456 struct tls_tcb *tcb; 457 458 tcb = tls_get_tcb(); 459 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset); 460 } 461 462 void * 463 __tls_get_addr_tcb(struct tls_tcb *tcb, tls_index *ti) 464 { 465 return tls_get_addr_common((Elf_Addr **)&tcb->tcb_dtv, ti->ti_module, ti->ti_offset); 466 } 467