1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 28 /* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34 #define _WANT_P_OSREL 35 #include <sys/param.h> 36 #include <sys/mman.h> 37 #include <machine/cpufunc.h> 38 #include <machine/specialreg.h> 39 #include <machine/sysarch.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 #include "rtld_tls.h" 54 55 /* 56 * Process the special R_X86_64_COPY relocations in the main program. These 57 * copy data from a shared object into a region in the main program's BSS 58 * segment. 59 * 60 * Returns 0 on success, -1 on failure. 61 */ 62 int 63 do_copy_relocations(Obj_Entry *dstobj) 64 { 65 const Elf_Rela *relalim; 66 const Elf_Rela *rela; 67 68 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 69 70 relalim = (const Elf_Rela *)((const char *) dstobj->rela + dstobj->relasize); 71 for (rela = dstobj->rela; rela < relalim; rela++) { 72 if (ELF_R_TYPE(rela->r_info) == R_X86_64_COPY) { 73 void *dstaddr; 74 const Elf_Sym *dstsym; 75 const char *name; 76 size_t size; 77 const void *srcaddr; 78 const Elf_Sym *srcsym; 79 const Obj_Entry *srcobj, *defobj; 80 SymLook req; 81 int res; 82 83 dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 84 dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 85 name = dstobj->strtab + dstsym->st_name; 86 size = dstsym->st_size; 87 symlook_init(&req, name); 88 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rela->r_info)); 89 req.flags = SYMLOOK_EARLY; 90 91 for (srcobj = globallist_next(dstobj); srcobj != NULL; 92 srcobj = globallist_next(srcobj)) { 93 res = symlook_obj(&req, srcobj); 94 if (res == 0) { 95 srcsym = req.sym_out; 96 defobj = req.defobj_out; 97 break; 98 } 99 } 100 101 if (srcobj == NULL) { 102 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 103 " relocation in %s", name, dstobj->path); 104 return -1; 105 } 106 107 srcaddr = (const void *)(defobj->relocbase + srcsym->st_value); 108 memcpy(dstaddr, srcaddr, size); 109 } 110 } 111 112 return 0; 113 } 114 115 /* Initialize the special GOT entries. */ 116 void 117 init_pltgot(Obj_Entry *obj) 118 { 119 if (obj->pltgot != NULL) { 120 obj->pltgot[1] = (Elf_Addr) obj; 121 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 122 } 123 } 124 125 /* Process the non-PLT relocations. */ 126 int 127 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 128 RtldLockState *lockstate) 129 { 130 const Elf_Rela *relalim; 131 const Elf_Rela *rela; 132 SymCache *cache; 133 const Elf_Sym *def; 134 const Obj_Entry *defobj; 135 Elf_Addr *where, symval; 136 Elf32_Addr *where32; 137 int r; 138 139 r = -1; 140 symval = 0; 141 def = NULL; 142 143 /* 144 * The dynamic loader may be called from a thread, we have 145 * limited amounts of stack available so we cannot use alloca(). 146 */ 147 if (obj != obj_rtld) { 148 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 149 /* No need to check for NULL here */ 150 } else 151 cache = NULL; 152 153 relalim = (const Elf_Rela *)((const char*)obj->rela + obj->relasize); 154 for (rela = obj->rela; rela < relalim; rela++) { 155 /* 156 * First, resolve symbol for relocations which 157 * reference symbols. 158 */ 159 switch (ELF_R_TYPE(rela->r_info)) { 160 case R_X86_64_64: 161 case R_X86_64_PC32: 162 case R_X86_64_GLOB_DAT: 163 case R_X86_64_TPOFF64: 164 case R_X86_64_TPOFF32: 165 case R_X86_64_DTPMOD64: 166 case R_X86_64_DTPOFF64: 167 case R_X86_64_DTPOFF32: 168 def = find_symdef(ELF_R_SYM(rela->r_info), obj, 169 &defobj, flags, cache, lockstate); 170 if (def == NULL) 171 goto done; 172 /* 173 * If symbol is IFUNC, only perform relocation 174 * when caller allowed it by passing 175 * SYMLOOK_IFUNC flag. Skip the relocations 176 * otherwise. 177 * 178 * Also error out in case IFUNC relocations 179 * are specified for TLS, which cannot be 180 * usefully interpreted. 181 */ 182 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 183 switch (ELF_R_TYPE(rela->r_info)) { 184 case R_X86_64_64: 185 case R_X86_64_PC32: 186 case R_X86_64_GLOB_DAT: 187 if ((flags & SYMLOOK_IFUNC) == 0) { 188 obj->non_plt_gnu_ifunc = true; 189 continue; 190 } 191 symval = (Elf_Addr)rtld_resolve_ifunc( 192 defobj, def); 193 break; 194 case R_X86_64_TPOFF64: 195 case R_X86_64_TPOFF32: 196 case R_X86_64_DTPMOD64: 197 case R_X86_64_DTPOFF64: 198 case R_X86_64_DTPOFF32: 199 _rtld_error("%s: IFUNC for TLS reloc", 200 obj->path); 201 goto done; 202 } 203 } else { 204 if ((flags & SYMLOOK_IFUNC) != 0) 205 continue; 206 symval = (Elf_Addr)defobj->relocbase + 207 def->st_value; 208 } 209 break; 210 default: 211 if ((flags & SYMLOOK_IFUNC) != 0) 212 continue; 213 break; 214 } 215 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 216 where32 = (Elf32_Addr *)where; 217 218 switch (ELF_R_TYPE(rela->r_info)) { 219 case R_X86_64_NONE: 220 break; 221 case R_X86_64_64: 222 *where = symval + rela->r_addend; 223 break; 224 case R_X86_64_PC32: 225 /* 226 * I don't think the dynamic linker should 227 * ever see this type of relocation. But the 228 * binutils-2.6 tools sometimes generate it. 229 */ 230 *where32 = (Elf32_Addr)(unsigned long)(symval + 231 rela->r_addend - (Elf_Addr)where); 232 break; 233 /* missing: R_X86_64_GOT32 R_X86_64_PLT32 */ 234 case R_X86_64_COPY: 235 /* 236 * These are deferred until all other relocations have 237 * been done. All we do here is make sure that the COPY 238 * relocation is not in a shared library. They are 239 * allowed only in executable files. 240 */ 241 if (!obj->mainprog) { 242 _rtld_error("%s: Unexpected R_X86_64_COPY " 243 "relocation in shared library", obj->path); 244 goto done; 245 } 246 break; 247 case R_X86_64_GLOB_DAT: 248 *where = symval; 249 break; 250 case R_X86_64_TPOFF64: 251 /* 252 * We lazily allocate offsets for static TLS 253 * as we see the first relocation that 254 * references the TLS block. This allows us to 255 * support (small amounts of) static TLS in 256 * dynamically loaded modules. If we run out 257 * of space, we generate an error. 258 */ 259 if (!defobj->tls_static) { 260 if (!allocate_tls_offset( 261 __DECONST(Obj_Entry *, defobj))) { 262 _rtld_error("%s: No space available " 263 "for static Thread Local Storage", 264 obj->path); 265 goto done; 266 } 267 } 268 *where = (Elf_Addr)(def->st_value - defobj->tlsoffset + 269 rela->r_addend); 270 break; 271 case R_X86_64_TPOFF32: 272 /* 273 * We lazily allocate offsets for static TLS 274 * as we see the first relocation that 275 * references the TLS block. This allows us to 276 * support (small amounts of) static TLS in 277 * dynamically loaded modules. If we run out 278 * of space, we generate an error. 279 */ 280 if (!defobj->tls_static) { 281 if (!allocate_tls_offset( 282 __DECONST(Obj_Entry *, defobj))) { 283 _rtld_error("%s: No space available " 284 "for static Thread Local Storage", 285 obj->path); 286 goto done; 287 } 288 } 289 *where32 = (Elf32_Addr)(def->st_value - 290 defobj->tlsoffset + rela->r_addend); 291 break; 292 case R_X86_64_DTPMOD64: 293 *where += (Elf_Addr)defobj->tlsindex; 294 break; 295 case R_X86_64_DTPOFF64: 296 *where += (Elf_Addr)(def->st_value + rela->r_addend); 297 break; 298 case R_X86_64_DTPOFF32: 299 *where32 += (Elf32_Addr)(def->st_value + 300 rela->r_addend); 301 break; 302 case R_X86_64_RELATIVE: 303 *where = (Elf_Addr)(obj->relocbase + rela->r_addend); 304 break; 305 case R_X86_64_IRELATIVE: 306 obj->irelative_nonplt = true; 307 break; 308 309 /* 310 * missing: 311 * R_X86_64_GOTPCREL, R_X86_64_32, R_X86_64_32S, R_X86_64_16, 312 * R_X86_64_PC16, R_X86_64_8, R_X86_64_PC8 313 */ 314 default: 315 _rtld_error("%s: Unsupported relocation type %u" 316 " in non-PLT relocations\n", obj->path, 317 (unsigned int)ELF_R_TYPE(rela->r_info)); 318 goto done; 319 } 320 } 321 r = 0; 322 done: 323 free(cache); 324 return (r); 325 } 326 327 /* Process the PLT relocations. */ 328 int 329 reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused) 330 { 331 const Elf_Rela *relalim; 332 const Elf_Rela *rela; 333 334 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 335 for (rela = obj->pltrela; rela < relalim; rela++) { 336 Elf_Addr *where; 337 338 switch(ELF_R_TYPE(rela->r_info)) { 339 case R_X86_64_JMP_SLOT: 340 /* Relocate the GOT slot pointing into the PLT. */ 341 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 342 *where += (Elf_Addr)obj->relocbase; 343 break; 344 345 case R_X86_64_IRELATIVE: 346 obj->irelative = true; 347 break; 348 349 default: 350 _rtld_error("Unknown relocation type %x in PLT", 351 (unsigned int)ELF_R_TYPE(rela->r_info)); 352 return (-1); 353 } 354 } 355 return 0; 356 } 357 358 /* Relocate the jump slots in an object. */ 359 int 360 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 361 { 362 const Elf_Rela *relalim; 363 const Elf_Rela *rela; 364 365 if (obj->jmpslots_done) 366 return 0; 367 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 368 for (rela = obj->pltrela; rela < relalim; rela++) { 369 Elf_Addr *where, target; 370 const Elf_Sym *def; 371 const Obj_Entry *defobj; 372 373 switch (ELF_R_TYPE(rela->r_info)) { 374 case R_X86_64_JMP_SLOT: 375 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 376 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 377 SYMLOOK_IN_PLT | flags, NULL, lockstate); 378 if (def == NULL) 379 return (-1); 380 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 381 obj->gnu_ifunc = true; 382 continue; 383 } 384 target = (Elf_Addr)(defobj->relocbase + def->st_value + rela->r_addend); 385 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 386 break; 387 388 case R_X86_64_IRELATIVE: 389 break; 390 391 default: 392 _rtld_error("Unknown relocation type %x in PLT", 393 (unsigned int)ELF_R_TYPE(rela->r_info)); 394 return (-1); 395 } 396 } 397 obj->jmpslots_done = true; 398 return 0; 399 } 400 401 /* Fixup the jump slot at "where" to transfer control to "target". */ 402 Elf_Addr 403 reloc_jmpslot(Elf_Addr *where, Elf_Addr target, 404 const struct Struct_Obj_Entry *obj __unused, 405 const struct Struct_Obj_Entry *refobj __unused, 406 const Elf_Rel *rel __unused) 407 { 408 #ifdef dbg 409 dbg("reloc_jmpslot: *%p = %p", where, (void *)target); 410 #endif 411 if (!ld_bind_not) 412 *where = target; 413 return (target); 414 } 415 416 static void 417 reloc_iresolve_one(Obj_Entry *obj, const Elf_Rela *rela, 418 RtldLockState *lockstate) 419 { 420 Elf_Addr *where, target, *ptr; 421 422 ptr = (Elf_Addr *)(obj->relocbase + rela->r_addend); 423 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 424 lock_release(rtld_bind_lock, lockstate); 425 target = call_ifunc_resolver(ptr); 426 wlock_acquire(rtld_bind_lock, lockstate); 427 *where = target; 428 } 429 430 int 431 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 432 { 433 const Elf_Rela *relalim; 434 const Elf_Rela *rela; 435 436 if (!obj->irelative) 437 return (0); 438 obj->irelative = false; 439 relalim = (const Elf_Rela *)((const char *)obj->pltrela + 440 obj->pltrelasize); 441 for (rela = obj->pltrela; rela < relalim; rela++) { 442 if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE) 443 reloc_iresolve_one(obj, rela, lockstate); 444 } 445 return (0); 446 } 447 448 int 449 reloc_iresolve_nonplt(Obj_Entry *obj, RtldLockState *lockstate) 450 { 451 const Elf_Rela *relalim; 452 const Elf_Rela *rela; 453 454 if (!obj->irelative_nonplt) 455 return (0); 456 obj->irelative_nonplt = false; 457 relalim = (const Elf_Rela *)((const char *)obj->rela + obj->relasize); 458 for (rela = obj->rela; rela < relalim; rela++) { 459 if (ELF_R_TYPE(rela->r_info) == R_X86_64_IRELATIVE) 460 reloc_iresolve_one(obj, rela, lockstate); 461 } 462 return (0); 463 } 464 465 int 466 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 467 { 468 const Elf_Rela *relalim; 469 const Elf_Rela *rela; 470 471 if (!obj->gnu_ifunc) 472 return (0); 473 relalim = (const Elf_Rela *)((const char *)obj->pltrela + obj->pltrelasize); 474 for (rela = obj->pltrela; rela < relalim; rela++) { 475 Elf_Addr *where, target; 476 const Elf_Sym *def; 477 const Obj_Entry *defobj; 478 479 switch (ELF_R_TYPE(rela->r_info)) { 480 case R_X86_64_JMP_SLOT: 481 where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 482 def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, 483 SYMLOOK_IN_PLT | flags, NULL, lockstate); 484 if (def == NULL) 485 return (-1); 486 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 487 continue; 488 lock_release(rtld_bind_lock, lockstate); 489 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 490 wlock_acquire(rtld_bind_lock, lockstate); 491 reloc_jmpslot(where, target, defobj, obj, (const Elf_Rel *)rela); 492 break; 493 } 494 } 495 obj->gnu_ifunc = false; 496 return (0); 497 } 498 499 uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2; 500 501 void 502 ifunc_init(Elf_Auxinfo aux_info[__min_size(AT_COUNT)] __unused) 503 { 504 u_int p[4], cpu_high; 505 506 do_cpuid(1, p); 507 cpu_feature = p[3]; 508 cpu_feature2 = p[2]; 509 do_cpuid(0, p); 510 cpu_high = p[0]; 511 if (cpu_high >= 7) { 512 cpuid_count(7, 0, p); 513 cpu_stdext_feature = p[1]; 514 cpu_stdext_feature2 = p[2]; 515 } 516 } 517 518 int __getosreldate(void); 519 520 void 521 allocate_initial_tls(Obj_Entry *objs) 522 { 523 void *addr; 524 525 /* 526 * Fix the size of the static TLS block by using the maximum 527 * offset allocated so far and adding a bit for dynamic 528 * modules to use. 529 */ 530 tls_static_space = tls_last_offset + ld_static_tls_extra; 531 532 addr = allocate_tls(objs, 0, TLS_TCB_SIZE, TLS_TCB_ALIGN); 533 534 /* 535 * This does not use _tcb_set() as it calls amd64_set_fsbase() 536 * which is an ifunc and rtld must not use ifuncs. 537 */ 538 if (__getosreldate() >= P_OSREL_WRFSBASE && 539 (cpu_stdext_feature & CPUID_STDEXT_FSGSBASE) != 0) 540 wrfsbase((uintptr_t)addr); 541 else 542 sysarch(AMD64_SET_FSBASE, &addr); 543 } 544 545 void * 546 __tls_get_addr(tls_index *ti) 547 { 548 uintptr_t **dtvp; 549 550 dtvp = &_tcb_get()->tcb_dtv; 551 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 552 } 553 554 size_t 555 calculate_tls_offset(size_t prev_offset, size_t prev_size __unused, 556 size_t size, size_t align, size_t offset) 557 { 558 size_t res; 559 560 /* 561 * res is the smallest integer satisfying res - prev_offset >= size 562 * and (-res) % p_align = p_vaddr % p_align (= p_offset % p_align). 563 */ 564 res = prev_offset + size + align - 1; 565 res -= (res + offset) & (align - 1); 566 return (res); 567 } 568 569 size_t 570 calculate_first_tls_offset(size_t size, size_t align, size_t offset) 571 { 572 return (calculate_tls_offset(0, 0, size, align, offset)); 573 } 574