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 <machine/sysarch.h> 37 38 #include <dlfcn.h> 39 #include <err.h> 40 #include <errno.h> 41 #include <fcntl.h> 42 #include <stdarg.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <unistd.h> 47 48 #include "debug.h" 49 #include "rtld.h" 50 #include "rtld_tls.h" 51 52 /* 53 * Process the special R_X86_64_COPY relocations in the main program. These 54 * copy data from a shared object into a region in the main program's BSS 55 * segment. 56 * 57 * Returns 0 on success, -1 on failure. 58 */ 59 int 60 do_copy_relocations(Obj_Entry *dstobj) 61 { 62 const Elf_Rela *relalim; 63 const Elf_Rela *rela; 64 65 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 66 67 relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela + dstobj->relasize); 68 for (rela = dstobj->rela; rela < relalim; rela++) { 69 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 70 void *dstaddr; 71 const Elf_Sym *dstsym; 72 const char *name; 73 size_t size; 74 const void *srcaddr; 75 const Elf_Sym *srcsym; 76 const Obj_Entry *srcobj, *defobj; 77 SymLook req; 78 int res; 79 80 dstaddr = (void *) (dstobj->relocbase + rela->r_offset); 81 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 82 name = dstobj->strtab + dstsym->st_name; 83 size = dstsym->st_size; 84 symlook_init(&req, name); 85 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info)); 86 req.flags = SYMLOOK_EARLY; 87 88 for (srcobj = globallist_next(dstobj); srcobj != NULL; 89 srcobj = globallist_next(srcobj)) { 90 res = symlook_obj(&req, srcobj); 91 if (res == 0) { 92 srcsym = req.sym_out; 93 defobj = req.defobj_out; 94 break; 95 } 96 } 97 98 if (srcobj == NULL) { 99 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 100 " relocation in %s", name, dstobj->path); 101 return -1; 102 } 103 104 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 105 memcpy(dstaddr, srcaddr, size); 106 } 107 } 108 109 return 0; 110 } 111 112 /* Initialize the special GOT entries. */ 113 void 114 init_pltgot(Obj_Entry *obj) 115 { 116 if (obj->pltgot != NULL) { 117 obj->pltgot[1] = (Elf_Addr) obj; 118 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 119 } 120 } 121 122 /* Process the non-PLT relocations. */ 123 int 124 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 125 RtldLockState *lockstate) 126 { 127 const Elf_Rela *relalim; 128 const Elf_Rela *rela; 129 SymCache *cache; 130 const Elf_Sym *def; 131 const Obj_Entry *defobj; 132 Elf_Addr *where, symval; 133 Elf32_Addr *where32; 134 int r; 135 136 r = -1; 137 /* 138 * The dynamic loader may be called from a thread, we have 139 * limited amounts of stack available so we cannot use alloca(). 140 */ 141 if (obj != obj_rtld) { 142 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 143 /* No need to check for NULL here */ 144 } else 145 cache = NULL; 146 147 relalim = (const Elf_Rela *)((caddr_t)obj->rela + obj->relasize); 148 for (rela = obj->rela; rela < relalim; rela++) { 149 /* 150 * First, resolve symbol for relocations which 151 * reference symbols. 152 */ 153 switch (ELF_R_TYPE(rela->r_info)) { 154 case R_X86_64_64: 155 case R_X86_64_PC32: 156 case R_X86_64_GLOB_DAT: 157 case R_X86_64_TPOFF64: 158 case R_X86_64_TPOFF32: 159 case R_X86_64_DTPMOD64: 160 case R_X86_64_DTPOFF64: 161 case R_X86_64_DTPOFF32: 162 def = find_symdef(ELF_R_SYM(rela->r_info), obj, 163 &defobj, flags, cache, lockstate); 164 if (def == NULL) 165 goto done; 166 /* 167 * If symbol is IFUNC, only perform relocation 168 * when caller allowed it by passing 169 * SYMLOOK_IFUNC flag. Skip the relocations 170 * otherwise. 171 * 172 * Also error out in case IFUNC relocations 173 * are specified for TLS, which cannot be 174 * usefully interpreted. 175 */ 176 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 177 switch (ELF_R_TYPE(rela->r_info)) { 178 case R_X86_64_64: 179 case R_X86_64_PC32: 180 case R_X86_64_GLOB_DAT: 181 if ((flags & SYMLOOK_IFUNC) == 0) { 182 obj->non_plt_gnu_ifunc = true; 183 continue; 184 } 185 symval = (Elf_Addr)rtld_resolve_ifunc( 186 defobj, def); 187 break; 188 case R_X86_64_TPOFF64: 189 case R_X86_64_TPOFF32: 190 case R_X86_64_DTPMOD64: 191 case R_X86_64_DTPOFF64: 192 case R_X86_64_DTPOFF32: 193 _rtld_error("%s: IFUNC for TLS reloc", 194 obj->path); 195 goto done; 196 } 197 } else { 198 if ((flags & SYMLOOK_IFUNC) != 0) 199 continue; 200 symval = (Elf_Addr)defobj->relocbase + 201 def->st_value; 202 } 203 break; 204 default: 205 if ((flags & SYMLOOK_IFUNC) != 0) 206 continue; 207 break; 208 } 209 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 210 where32 = (Elf32_Addr *)where; 211 212 switch (ELF_R_TYPE(rela->r_info)) { 213 case R_X86_64_NONE: 214 break; 215 case R_X86_64_64: 216 *where = symval + rela->r_addend; 217 break; 218 case R_X86_64_PC32: 219 /* 220 * I don't think the dynamic linker should 221 * ever see this type of relocation. But the 222 * binutils-2.6 tools sometimes generate it. 223 */ 224 *where32 = (Elf32_Addr)(unsigned long)(symval + 225 rela->r_addend - (Elf_Addr)where); 226 break; 227 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 228 case R_X86_64_COPY: 229 /* 230 * These are deferred until all other relocations have 231 * been done. All we do here is make sure that the COPY 232 * relocation is not in a shared library. They are 233 * allowed only in executable files. 234 */ 235 if (!obj->mainprog) { 236 _rtld_error("%s: Unexpected R_X86_64_COPY " 237 "relocation in shared library", obj->path); 238 goto done; 239 } 240 break; 241 case R_X86_64_GLOB_DAT: 242 *where = symval; 243 break; 244 case R_X86_64_TPOFF64: 245 /* 246 * We lazily allocate offsets for static TLS 247 * as we see the first relocation that 248 * references the TLS block. This allows us to 249 * support (small amounts of) static TLS in 250 * dynamically loaded modules. If we run out 251 * of space, we generate an error. 252 */ 253 if (!defobj->tls_done) { 254 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 255 _rtld_error("%s: No space available " 256 "for static Thread Local Storage", 257 obj->path); 258 goto done; 259 } 260 } 261 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset + 262 rela->r_addend); 263 break; 264 case R_X86_64_TPOFF32: 265 /* 266 * We lazily allocate offsets for static TLS 267 * as we see the first relocation that 268 * references the TLS block. This allows us to 269 * support (small amounts of) static TLS in 270 * dynamically loaded modules. If we run out 271 * of space, we generate an error. 272 */ 273 if (!defobj->tls_done) { 274 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 275 _rtld_error("%s: No space available " 276 "for static Thread Local Storage", 277 obj->path); 278 goto done; 279 } 280 } 281 *where32 = (Elf32_Addr)(def->st_value - 282 defobj->tlsoffset + rela->r_addend); 283 break; 284 case R_X86_64_DTPMOD64: 285 *where += (Elf_Addr)defobj->tlsindex; 286 break; 287 case R_X86_64_DTPOFF64: 288 *where += (Elf_Addr)(def->st_value + rela->r_addend); 289 break; 290 case R_X86_64_DTPOFF32: 291 *where32 += (Elf32_Addr)(def->st_value + 292 rela->r_addend); 293 break; 294 case R_X86_64_RELATIVE: 295 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 296 break; 297 /* 298 * missing: 299 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, 300 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 301 */ 302 default: 303 _rtld_error("%s: Unsupported relocation type %u" 304 " in non-PLT relocations\n", obj->path, 305 (unsigned int)ELF_R_TYPE(rela->r_info)); 306 goto done; 307 } 308 } 309 r = 0; 310 done: 311 free(cache); 312 return (r); 313 } 314 315 /* Process the PLT relocations. */ 316 int 317 reloc_plt(Obj_Entry *obj) 318 { 319 const Elf_Rela *relalim; 320 const Elf_Rela *rela; 321 322 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 323 for (rela = obj->pltrela; rela < relalim; rela++) { 324 Elf_Addr *where; 325 326 switch(ELF_R_TYPE(rela->r_info)) { 327 case R_X86_64_JMP_SLOT: 328 /* Relocate the GOT slot pointing into the PLT. */ 329 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 330 *where += (Elf_Addr)obj->relocbase; 331 break; 332 333 case R_X86_64_IRELATIVE: 334 obj->irelative = true; 335 break; 336 337 default: 338 _rtld_error("Unknown relocation type %x in PLT", 339 (unsigned int)ELF_R_TYPE(rela->r_info)); 340 return (-1); 341 } 342 } 343 return 0; 344 } 345 346 /* Relocate the jump slots in an object. */ 347 int 348 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 349 { 350 const Elf_Rela *relalim; 351 const Elf_Rela *rela; 352 353 if (obj->jmpslots_done) 354 return 0; 355 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 356 for (rela = obj->pltrela; rela < relalim; rela++) { 357 Elf_Addr *where, target; 358 const Elf_Sym *def; 359 const Obj_Entry *defobj; 360 361 switch (ELF_R_TYPE(rela->r_info)) { 362 case R_X86_64_JMP_SLOT: 363 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 364 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 365 SYMLOOK_IN_PLT | flags, NULL, lockstate); 366 if (def == NULL) 367 return (-1); 368 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 369 obj->gnu_ifunc = true; 370 continue; 371 } 372 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 373 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 374 break; 375 376 case R_X86_64_IRELATIVE: 377 break; 378 379 default: 380 _rtld_error("Unknown relocation type %x in PLT", 381 (unsigned int)ELF_R_TYPE(rela->r_info)); 382 return (-1); 383 } 384 } 385 obj->jmpslots_done = true; 386 return 0; 387 } 388 389 int 390 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 391 { 392 const Elf_Rela *relalim; 393 const Elf_Rela *rela; 394 395 if (!obj->irelative) 396 return (0); 397 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 398 for (rela = obj->pltrela; rela < relalim; rela++) { 399 Elf_Addr *where, target, *ptr; 400 401 switch (ELF_R_TYPE(rela->r_info)) { 402 case R_X86_64_JMP_SLOT: 403 break; 404 405 case R_X86_64_IRELATIVE: 406 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend); 407 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 408 lock_release(rtld_bind_lock, lockstate); 409 target = ((Elf_Addr (*)(void))ptr)(); 410 wlock_acquire(rtld_bind_lock, lockstate); 411 *where = target; 412 break; 413 } 414 } 415 obj->irelative = false; 416 return (0); 417 } 418 419 int 420 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 421 { 422 const Elf_Rela *relalim; 423 const Elf_Rela *rela; 424 425 if (!obj->gnu_ifunc) 426 return (0); 427 relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize); 428 for (rela = obj->pltrela; rela < relalim; rela++) { 429 Elf_Addr *where, target; 430 const Elf_Sym *def; 431 const Obj_Entry *defobj; 432 433 switch (ELF_R_TYPE(rela->r_info)) { 434 case R_X86_64_JMP_SLOT: 435 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 436 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 437 SYMLOOK_IN_PLT | flags, NULL, lockstate); 438 if (def == NULL) 439 return (-1); 440 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 441 continue; 442 lock_release(rtld_bind_lock, lockstate); 443 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 444 wlock_acquire(rtld_bind_lock, lockstate); 445 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 446 break; 447 } 448 } 449 obj->gnu_ifunc = false; 450 return (0); 451 } 452 453 void 454 allocate_initial_tls(Obj_Entry *objs) 455 { 456 /* 457 * Fix the size of the static TLS block by using the maximum 458 * offset allocated so far and adding a bit for dynamic modules to 459 * use. 460 */ 461 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 462 amd64_set_fsbase(allocate_tls(objs, 0, 463 3*sizeof(Elf_Addr), sizeof(Elf_Addr))); 464 } 465 466 void *__tls_get_addr(tls_index *ti) 467 { 468 Elf_Addr** segbase; 469 470 __asm __volatile("movq %%fs:0, %0" : "=r" (segbase)); 471 472 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 473 } 474