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