1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright 1996, 1997, 1998, 1999 John D. Polstra. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 * 27 * $FreeBSD$ 28 */ 29 30 /* 31 * Dynamic linker for ELF. 32 * 33 * John Polstra <jdp@polstra.com>. 34 */ 35 36 #define _WANT_P_OSREL 37 #include <sys/param.h> 38 #include <sys/mman.h> 39 #include <machine/cpufunc.h> 40 #include <machine/specialreg.h> 41 #include <machine/sysarch.h> 42 43 #include <dlfcn.h> 44 #include <err.h> 45 #include <errno.h> 46 #include <fcntl.h> 47 #include <stdarg.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <unistd.h> 52 53 #include "debug.h" 54 #include "rtld.h" 55 #include "rtld_tls.h" 56 57 /* 58 * Process the special R_X86_64_COPY relocations in the main program. These 59 * copy data from a shared object into a region in the main program's BSS 60 * segment. 61 * 62 * Returns 0 on success, -1 on failure. 63 */ 64 int 65 do_copy_relocations(Obj_Entry *dstobj) 66 { 67 const Elf_Rela *relalim; 68 const Elf_Rela *rela; 69 70 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 71 72 relalim = (const Elf_Rela *)((const char *) dstobj->rela + dstobj->relasize); 73 for (rela = dstobj->rela; rela < relalim; rela++) { 74 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 75 void *dstaddr; 76 const Elf_Sym *dstsym; 77 const char *name; 78 size_t size; 79 const void *srcaddr; 80 const Elf_Sym *srcsym; 81 const Obj_Entry *srcobj, *defobj; 82 SymLook req; 83 int res; 84 85 dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 86 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 87 name = dstobj->strtab + dstsym->st_name; 88 size = dstsym->st_size; 89 symlook_init(&req, name); 90 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info)); 91 req.flags = SYMLOOK_EARLY; 92 93 for (srcobj = globallist_next(dstobj); srcobj != NULL; 94 srcobj = globallist_next(srcobj)) { 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 return -1; 107 } 108 109 srcaddr = (const void *)(defobj->relocbase + srcsym->st_value); 110 memcpy(dstaddr, srcaddr, size); 111 } 112 } 113 114 return 0; 115 } 116 117 /* Initialize the special GOT entries. */ 118 void 119 init_pltgot(Obj_Entry *obj) 120 { 121 if (obj->pltgot != NULL) { 122 obj->pltgot[1] = (Elf_Addr) obj; 123 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 124 } 125 } 126 127 /* Process the non-PLT relocations. */ 128 int 129 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 130 RtldLockState *lockstate) 131 { 132 const Elf_Rela *relalim; 133 const Elf_Rela *rela; 134 SymCache *cache; 135 const Elf_Sym *def; 136 const Obj_Entry *defobj; 137 Elf_Addr *where, symval; 138 Elf32_Addr *where32; 139 int r; 140 141 r = -1; 142 symval = 0; 143 def = NULL; 144 145 /* 146 * The dynamic loader may be called from a thread, we have 147 * limited amounts of stack available so we cannot use alloca(). 148 */ 149 if (obj != obj_rtld) { 150 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 151 /* No need to check for NULL here */ 152 } else 153 cache = NULL; 154 155 relalim = (const Elf_Rela *)((const char*)obj->rela + obj->relasize); 156 for (rela = obj->rela; rela < relalim; rela++) { 157 /* 158 * First, resolve symbol for relocations which 159 * reference symbols. 160 */ 161 switch (ELF_R_TYPE(rela->r_info)) { 162 case R_X86_64_64: 163 case R_X86_64_PC32: 164 case R_X86_64_GLOB_DAT: 165 case R_X86_64_TPOFF64: 166 case R_X86_64_TPOFF32: 167 case R_X86_64_DTPMOD64: 168 case R_X86_64_DTPOFF64: 169 case R_X86_64_DTPOFF32: 170 def = find_symdef(ELF_R_SYM(rela->r_info), obj, 171 &defobj, flags, cache, lockstate); 172 if (def == NULL) 173 goto done; 174 /* 175 * If symbol is IFUNC, only perform relocation 176 * when caller allowed it by passing 177 * SYMLOOK_IFUNC flag. Skip the relocations 178 * otherwise. 179 * 180 * Also error out in case IFUNC relocations 181 * are specified for TLS, which cannot be 182 * usefully interpreted. 183 */ 184 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 185 switch (ELF_R_TYPE(rela->r_info)) { 186 case R_X86_64_64: 187 case R_X86_64_PC32: 188 case R_X86_64_GLOB_DAT: 189 if ((flags & SYMLOOK_IFUNC) == 0) { 190 obj->non_plt_gnu_ifunc = true; 191 continue; 192 } 193 symval = (Elf_Addr)rtld_resolve_ifunc( 194 defobj, def); 195 break; 196 case R_X86_64_TPOFF64: 197 case R_X86_64_TPOFF32: 198 case R_X86_64_DTPMOD64: 199 case R_X86_64_DTPOFF64: 200 case R_X86_64_DTPOFF32: 201 _rtld_error("%s: IFUNC for TLS reloc", 202 obj->path); 203 goto done; 204 } 205 } else { 206 if ((flags & SYMLOOK_IFUNC) != 0) 207 continue; 208 symval = (Elf_Addr)defobj->relocbase + 209 def->st_value; 210 } 211 break; 212 default: 213 if ((flags & SYMLOOK_IFUNC) != 0) 214 continue; 215 break; 216 } 217 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 218 where32 = (Elf32_Addr *)where; 219 220 switch (ELF_R_TYPE(rela->r_info)) { 221 case R_X86_64_NONE: 222 break; 223 case R_X86_64_64: 224 *where = symval + rela->r_addend; 225 break; 226 case R_X86_64_PC32: 227 /* 228 * I don't think the dynamic linker should 229 * ever see this type of relocation. But the 230 * binutils-2.6 tools sometimes generate it. 231 */ 232 *where32 = (Elf32_Addr)(unsigned long)(symval + 233 rela->r_addend - (Elf_Addr)where); 234 break; 235 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 236 case R_X86_64_COPY: 237 /* 238 * These are deferred until all other relocations have 239 * been done. All we do here is make sure that the COPY 240 * relocation is not in a shared library. They are 241 * allowed only in executable files. 242 */ 243 if (!obj->mainprog) { 244 _rtld_error("%s: Unexpected R_X86_64_COPY " 245 "relocation in shared library", obj->path); 246 goto done; 247 } 248 break; 249 case R_X86_64_GLOB_DAT: 250 *where = symval; 251 break; 252 case R_X86_64_TPOFF64: 253 /* 254 * We lazily allocate offsets for static TLS 255 * as we see the first relocation that 256 * references the TLS block. This allows us to 257 * support (small amounts of) static TLS in 258 * dynamically loaded modules. If we run out 259 * of space, we generate an error. 260 */ 261 if (!defobj->tls_done) { 262 if (!allocate_tls_offset( 263 __DECONST(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( 284 __DECONST(Obj_Entry *, defobj))) { 285 _rtld_error("%s: No space available " 286 "for static Thread Local Storage", 287 obj->path); 288 goto done; 289 } 290 } 291 *where32 = (Elf32_Addr)(def->st_value - 292 defobj->tlsoffset + rela->r_addend); 293 break; 294 case R_X86_64_DTPMOD64: 295 *where += (Elf_Addr)defobj->tlsindex; 296 break; 297 case R_X86_64_DTPOFF64: 298 *where += (Elf_Addr)(def->st_value + rela->r_addend); 299 break; 300 case R_X86_64_DTPOFF32: 301 *where32 += (Elf32_Addr)(def->st_value + 302 rela->r_addend); 303 break; 304 case R_X86_64_RELATIVE: 305 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 306 break; 307 case R_X86_64_IRELATIVE: 308 obj->irelative_nonplt = true; 309 break; 310 311 /* 312 * missing: 313 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, 314 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 315 */ 316 default: 317 _rtld_error("%s: Unsupported relocation type %u" 318 " in non-PLT relocations\n", obj->path, 319 (unsigned int)ELF_R_TYPE(rela->r_info)); 320 goto done; 321 } 322 } 323 r = 0; 324 done: 325 free(cache); 326 return (r); 327 } 328 329 /* Process the PLT relocations. */ 330 int 331 reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused) 332 { 333 const Elf_Rela *relalim; 334 const Elf_Rela *rela; 335 336 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 337 for (rela = obj->pltrela; rela < relalim; rela++) { 338 Elf_Addr *where; 339 340 switch(ELF_R_TYPE(rela->r_info)) { 341 case R_X86_64_JMP_SLOT: 342 /* Relocate the GOT slot pointing into the PLT. */ 343 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 344 *where += (Elf_Addr)obj->relocbase; 345 break; 346 347 case R_X86_64_IRELATIVE: 348 obj->irelative = true; 349 break; 350 351 default: 352 _rtld_error("Unknown relocation type %x in PLT", 353 (unsigned int)ELF_R_TYPE(rela->r_info)); 354 return (-1); 355 } 356 } 357 return 0; 358 } 359 360 /* Relocate the jump slots in an object. */ 361 int 362 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 363 { 364 const Elf_Rela *relalim; 365 const Elf_Rela *rela; 366 367 if (obj->jmpslots_done) 368 return 0; 369 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 370 for (rela = obj->pltrela; rela < relalim; rela++) { 371 Elf_Addr *where, target; 372 const Elf_Sym *def; 373 const Obj_Entry *defobj; 374 375 switch (ELF_R_TYPE(rela->r_info)) { 376 case R_X86_64_JMP_SLOT: 377 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 378 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 379 SYMLOOK_IN_PLT | flags, NULL, lockstate); 380 if (def == NULL) 381 return (-1); 382 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 383 obj->gnu_ifunc = true; 384 continue; 385 } 386 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 387 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 388 break; 389 390 case R_X86_64_IRELATIVE: 391 break; 392 393 default: 394 _rtld_error("Unknown relocation type %x in PLT", 395 (unsigned int)ELF_R_TYPE(rela->r_info)); 396 return (-1); 397 } 398 } 399 obj->jmpslots_done = true; 400 return 0; 401 } 402 403 /* Fixup the jump slot at "where" to transfer control to "target". */ 404 Elf_Addr 405 reloc_jmpslot(Elf_Addr *where, Elf_Addr target, 406 const struct Struct_Obj_Entry *obj __unused, 407 const struct Struct_Obj_Entry *refobj __unused, 408 const Elf_Rel *rel __unused) 409 { 410 #ifdef dbg 411 dbg("reloc_jmpslot: *%p = %p", where, (void *)target); 412 #endif 413 if (!ld_bind_not) 414 *where = target; 415 return (target); 416 } 417 418 static void 419 reloc_iresolve_one(Obj_Entry *obj, const Elf_Rela *rela, 420 RtldLockState *lockstate) 421 { 422 Elf_Addr *where, target, *ptr; 423 424 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend); 425 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 426 lock_release(rtld_bind_lock, lockstate); 427 target = call_ifunc_resolver(ptr); 428 wlock_acquire(rtld_bind_lock, lockstate); 429 *where = target; 430 } 431 432 int 433 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 434 { 435 const Elf_Rela *relalim; 436 const Elf_Rela *rela; 437 438 if (!obj->irelative) 439 return (0); 440 obj->irelative = false; 441 relalim = (const Elf_Rela *)((const char *)obj->pltrela + 442 obj->pltrelasize); 443 for (rela = obj->pltrela; rela < relalim; rela++) { 444 if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE) 445 reloc_iresolve_one(obj, rela, lockstate); 446 } 447 return (0); 448 } 449 450 int 451 reloc_iresolve_nonplt(Obj_Entry *obj, RtldLockState *lockstate) 452 { 453 const Elf_Rela *relalim; 454 const Elf_Rela *rela; 455 456 if (!obj->irelative_nonplt) 457 return (0); 458 obj->irelative_nonplt = false; 459 relalim = (const Elf_Rela *)((const char *)obj->rela + obj->relasize); 460 for (rela = obj->rela; rela < relalim; rela++) { 461 if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE) 462 reloc_iresolve_one(obj, rela, lockstate); 463 } 464 return (0); 465 } 466 467 int 468 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 469 { 470 const Elf_Rela *relalim; 471 const Elf_Rela *rela; 472 473 if (!obj->gnu_ifunc) 474 return (0); 475 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 476 for (rela = obj->pltrela; rela < relalim; rela++) { 477 Elf_Addr *where, target; 478 const Elf_Sym *def; 479 const Obj_Entry *defobj; 480 481 switch (ELF_R_TYPE(rela->r_info)) { 482 case R_X86_64_JMP_SLOT: 483 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 484 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 485 SYMLOOK_IN_PLT | flags, NULL, lockstate); 486 if (def == NULL) 487 return (-1); 488 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 489 continue; 490 lock_release(rtld_bind_lock, lockstate); 491 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 492 wlock_acquire(rtld_bind_lock, lockstate); 493 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 494 break; 495 } 496 } 497 obj->gnu_ifunc = false; 498 return (0); 499 } 500 501 uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2; 502 503 void 504 ifunc_init(Elf_Auxinfo aux_info[__min_size(AT_COUNT)] __unused) 505 { 506 u_int p[4], cpu_high; 507 508 do_cpuid(1, p); 509 cpu_feature = p[3]; 510 cpu_feature2 = p[2]; 511 do_cpuid(0, p); 512 cpu_high = p[0]; 513 if (cpu_high >= 7) { 514 cpuid_count(7, 0, p); 515 cpu_stdext_feature = p[1]; 516 cpu_stdext_feature2 = p[2]; 517 } 518 } 519 520 int __getosreldate(void); 521 522 void 523 allocate_initial_tls(Obj_Entry *objs) 524 { 525 void *addr; 526 527 /* 528 * Fix the size of the static TLS block by using the maximum 529 * offset allocated so far and adding a bit for dynamic 530 * modules to use. 531 */ 532 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 533 534 addr = allocate_tls(objs, 0, TLS_TCB_SIZE, TLS_TCB_ALIGN); 535 536 /* 537 * This does not use _tcb_set() as it calls amd64_set_fsbase() 538 * which is an ifunc and rtld must not use ifuncs. 539 */ 540 if (__getosreldate() >= P_OSREL_WRFSBASE && 541 (cpu_stdext_feature & CPUID_STDEXT_FSGSBASE) != 0) 542 wrfsbase((uintptr_t)addr); 543 else 544 sysarch(AMD64_SET_FSBASE, &addr); 545 } 546 547 void * 548 __tls_get_addr(tls_index *ti) 549 { 550 uintptr_t **dtvp; 551 552 dtvp = &_tcb_get()->tcb_dtv; 553 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 554 } 555 556 size_t 557 calculate_tls_offset(size_t prev_offset, size_t prev_size __unused, 558 size_t size, size_t align, size_t offset) 559 { 560 size_t res; 561 562 /* 563 * res is the smallest integer satisfying res - prev_offset >= size 564 * and (-res) % p_align = p_vaddr % p_align (= p_offset % p_align). 565 */ 566 res = prev_offset + size + align - 1; 567 res -= (res + offset) & (align - 1); 568 return (res); 569 } 570 571 size_t 572 calculate_first_tls_offset(size_t size, size_t align, size_t offset) 573 { 574 return (calculate_tls_offset(0, 0, size, align, offset)); 575 } 576