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