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 #include <sys/param.h> 35 #include <sys/mman.h> 36 37 #include <machine/segments.h> 38 #include <machine/sysarch.h> 39 40 #include <dlfcn.h> 41 #include <err.h> 42 #include <errno.h> 43 #include <fcntl.h> 44 #include <stdarg.h> 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include <unistd.h> 49 50 #include "debug.h" 51 #include "rtld.h" 52 #include "rtld_tls.h" 53 54 /* 55 * Process the special R_386_COPY relocations in the main program. These 56 * copy data from a shared object into a region in the main program's BSS 57 * segment. 58 * 59 * Returns 0 on success, -1 on failure. 60 */ 61 int 62 do_copy_relocations(Obj_Entry *dstobj) 63 { 64 const Elf_Rel *rellim; 65 const Elf_Rel *rel; 66 67 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 68 69 rellim = (const Elf_Rel *)((const char *)dstobj->rel + dstobj->relsize); 70 for (rel = dstobj->rel; rel < rellim; rel++) { 71 if (ELF_R_TYPE(rel->r_info) == R_386_COPY) { 72 void *dstaddr; 73 const Elf_Sym *dstsym; 74 const char *name; 75 size_t size; 76 const void *srcaddr; 77 const Elf_Sym *srcsym; 78 const Obj_Entry *srcobj, *defobj; 79 SymLook req; 80 int res; 81 82 dstaddr = (void *)(dstobj->relocbase + rel->r_offset); 83 dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info); 84 name = dstobj->strtab + dstsym->st_name; 85 size = dstsym->st_size; 86 symlook_init(&req, name); 87 req.ventry = fetch_ventry(dstobj, 88 ELF_R_SYM(rel->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( 103 "Undefined symbol \"%s\" referenced from COPY" 104 " relocation in %s", 105 name, dstobj->path); 106 return (-1); 107 } 108 109 srcaddr = (const void *)(defobj->relocbase + 110 srcsym->st_value); 111 memcpy(dstaddr, srcaddr, size); 112 } 113 } 114 115 return (0); 116 } 117 118 /* Initialize the special GOT entries. */ 119 void 120 init_pltgot(Obj_Entry *obj) 121 { 122 if (obj->pltgot != NULL) { 123 obj->pltgot[1] = (Elf_Addr)obj; 124 obj->pltgot[2] = (Elf_Addr)&_rtld_bind_start; 125 } 126 } 127 128 /* Process the non-PLT relocations. */ 129 int 130 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 131 RtldLockState *lockstate) 132 { 133 const Elf_Rel *rellim; 134 const Elf_Rel *rel; 135 SymCache *cache; 136 const Elf_Sym *def; 137 const Obj_Entry *defobj; 138 Elf_Addr *where, symval, add; 139 int r; 140 141 r = -1; 142 /* 143 * The dynamic loader may be called from a thread, we have 144 * limited amounts of stack available so we cannot use alloca(). 145 */ 146 if (obj != obj_rtld) { 147 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 148 /* No need to check for NULL here */ 149 } else { 150 cache = NULL; 151 } 152 153 /* Appease some compilers. */ 154 symval = 0; 155 def = NULL; 156 157 rellim = (const Elf_Rel *)((const char *)obj->rel + obj->relsize); 158 for (rel = obj->rel; rel < rellim; rel++) { 159 switch (ELF_R_TYPE(rel->r_info)) { 160 case R_386_32: 161 case R_386_PC32: 162 case R_386_GLOB_DAT: 163 case R_386_TLS_TPOFF: 164 case R_386_TLS_TPOFF32: 165 case R_386_TLS_DTPMOD32: 166 case R_386_TLS_DTPOFF32: 167 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 168 flags, cache, lockstate); 169 if (def == NULL) 170 goto done; 171 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 172 switch (ELF_R_TYPE(rel->r_info)) { 173 case R_386_32: 174 case R_386_PC32: 175 case R_386_GLOB_DAT: 176 if ((flags & SYMLOOK_IFUNC) == 0) { 177 obj->non_plt_gnu_ifunc = true; 178 continue; 179 } 180 symval = (Elf_Addr) 181 rtld_resolve_ifunc(defobj, def); 182 break; 183 case R_386_TLS_TPOFF: 184 case R_386_TLS_TPOFF32: 185 case R_386_TLS_DTPMOD32: 186 case R_386_TLS_DTPOFF32: 187 _rtld_error("%s: IFUNC for TLS reloc", 188 obj->path); 189 goto done; 190 } 191 } else { 192 if ((flags & SYMLOOK_IFUNC) != 0) 193 continue; 194 symval = (Elf_Addr)defobj->relocbase + 195 def->st_value; 196 } 197 break; 198 default: 199 if ((flags & SYMLOOK_IFUNC) != 0) 200 continue; 201 break; 202 } 203 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 204 205 switch (ELF_R_TYPE(rel->r_info)) { 206 case R_386_NONE: 207 break; 208 case R_386_32: 209 *where += symval; 210 break; 211 case R_386_PC32: 212 /* 213 * I don't think the dynamic linker should ever 214 * see this type of relocation. But the 215 * binutils-2.6 tools sometimes generate it. 216 */ 217 *where += symval - (Elf_Addr)where; 218 break; 219 case R_386_COPY: 220 /* 221 * These are deferred until all other 222 * relocations have been done. All we do here 223 * is make sure that the COPY relocation is 224 * not in a shared library. They are allowed 225 * only in executable files. 226 */ 227 if (!obj->mainprog) { 228 _rtld_error( 229 "%s: Unexpected R_386_COPY relocation in shared library", 230 obj->path); 231 goto done; 232 } 233 break; 234 case R_386_GLOB_DAT: 235 *where = symval; 236 break; 237 case R_386_RELATIVE: 238 *where += (Elf_Addr)obj->relocbase; 239 break; 240 case R_386_TLS_TPOFF: 241 case R_386_TLS_TPOFF32: 242 /* 243 * We lazily allocate offsets for static TLS 244 * as we see the first relocation that 245 * references the TLS block. This allows us to 246 * support (small amounts of) static TLS in 247 * dynamically loaded modules. If we run out 248 * of space, we generate an error. 249 */ 250 if (!defobj->tls_static) { 251 if (!allocate_tls_offset( 252 __DECONST(Obj_Entry *, defobj))) { 253 _rtld_error( 254 "%s: No space available for static Thread Local Storage", 255 obj->path); 256 goto done; 257 } 258 } 259 add = (Elf_Addr)(def->st_value - defobj->tlsoffset); 260 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 261 *where += add; 262 else 263 *where -= add; 264 break; 265 case R_386_TLS_DTPMOD32: 266 *where += (Elf_Addr)defobj->tlsindex; 267 break; 268 case R_386_TLS_DTPOFF32: 269 *where += (Elf_Addr)def->st_value; 270 break; 271 case R_386_IRELATIVE: 272 obj->irelative_nonplt = true; 273 break; 274 default: 275 _rtld_error( 276 "%s: Unsupported relocation type %d in non-PLT relocations", 277 obj->path, ELF_R_TYPE(rel->r_info)); 278 goto done; 279 } 280 } 281 r = 0; 282 done: 283 free(cache); 284 return (r); 285 } 286 287 /* Process the PLT relocations. */ 288 int 289 reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused) 290 { 291 const Elf_Rel *rellim; 292 const Elf_Rel *rel; 293 294 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 295 for (rel = obj->pltrel; rel < rellim; rel++) { 296 Elf_Addr *where; 297 298 switch (ELF_R_TYPE(rel->r_info)) { 299 case R_386_JMP_SLOT: 300 /* Relocate the GOT slot pointing into the PLT. */ 301 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 302 *where += (Elf_Addr)obj->relocbase; 303 break; 304 305 case R_386_IRELATIVE: 306 obj->irelative = true; 307 break; 308 309 default: 310 _rtld_error("Unknown relocation type %x in PLT", 311 ELF_R_TYPE(rel->r_info)); 312 return (-1); 313 } 314 } 315 return (0); 316 } 317 318 /* Relocate the jump slots in an object. */ 319 int 320 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 321 { 322 const Elf_Rel *rellim; 323 const Elf_Rel *rel; 324 325 if (obj->jmpslots_done) 326 return (0); 327 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 328 for (rel = obj->pltrel; rel < rellim; rel++) { 329 Elf_Addr *where, target; 330 const Elf_Sym *def; 331 const Obj_Entry *defobj; 332 333 switch (ELF_R_TYPE(rel->r_info)) { 334 case R_386_JMP_SLOT: 335 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 336 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 337 SYMLOOK_IN_PLT | flags, NULL, lockstate); 338 if (def == NULL) 339 return (-1); 340 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 341 obj->gnu_ifunc = true; 342 continue; 343 } 344 target = (Elf_Addr)(defobj->relocbase + def->st_value); 345 reloc_jmpslot(where, target, defobj, obj, rel); 346 break; 347 348 case R_386_IRELATIVE: 349 break; 350 351 default: 352 _rtld_error("Unknown relocation type %x in PLT", 353 ELF_R_TYPE(rel->r_info)); 354 return (-1); 355 } 356 } 357 358 obj->jmpslots_done = true; 359 return (0); 360 } 361 362 /* Fixup the jump slot at "where" to transfer control to "target". */ 363 Elf_Addr 364 reloc_jmpslot(Elf_Addr *where, Elf_Addr target, const Obj_Entry *obj __unused, 365 const Obj_Entry *refobj __unused, const Elf_Rel *rel __unused) 366 { 367 dbg("reloc_jmpslot: *%p = %p", where, (void *)target); 368 if (!ld_bind_not) 369 *where = target; 370 return (target); 371 } 372 373 static void 374 reloc_iresolve_one(Obj_Entry *obj, const Elf_Rel *rel, RtldLockState *lockstate) 375 { 376 Elf_Addr *where, target; 377 378 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 379 lock_release(rtld_bind_lock, lockstate); 380 target = call_ifunc_resolver(obj->relocbase + *where); 381 wlock_acquire(rtld_bind_lock, lockstate); 382 *where = target; 383 } 384 385 int 386 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 387 { 388 const Elf_Rel *rellim; 389 const Elf_Rel *rel; 390 391 if (!obj->irelative) 392 return (0); 393 obj->irelative = false; 394 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 395 for (rel = obj->pltrel; rel < rellim; rel++) { 396 if (ELF_R_TYPE(rel->r_info) == R_386_IRELATIVE) 397 reloc_iresolve_one(obj, rel, lockstate); 398 } 399 return (0); 400 } 401 402 int 403 reloc_iresolve_nonplt(Obj_Entry *obj, RtldLockState *lockstate) 404 { 405 const Elf_Rel *rellim; 406 const Elf_Rel *rel; 407 408 if (!obj->irelative_nonplt) 409 return (0); 410 obj->irelative_nonplt = false; 411 rellim = (const Elf_Rel *)((const char *)obj->rel + obj->relsize); 412 for (rel = obj->rel; rel < rellim; rel++) { 413 if (ELF_R_TYPE(rel->r_info) == R_386_IRELATIVE) 414 reloc_iresolve_one(obj, rel, lockstate); 415 } 416 return (0); 417 } 418 419 int 420 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 421 { 422 const Elf_Rel *rellim; 423 const Elf_Rel *rel; 424 425 if (!obj->gnu_ifunc) 426 return (0); 427 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 428 for (rel = obj->pltrel; rel < rellim; rel++) { 429 Elf_Addr *where, target; 430 const Elf_Sym *def; 431 const Obj_Entry *defobj; 432 433 switch (ELF_R_TYPE(rel->r_info)) { 434 case R_386_JMP_SLOT: 435 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 436 def = find_symdef(ELF_R_SYM(rel->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, rel); 446 break; 447 } 448 } 449 450 obj->gnu_ifunc = false; 451 return (0); 452 } 453 454 uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2; 455 456 static void 457 rtld_cpuid_count(int idx, int cnt, u_int *p) 458 { 459 __asm __volatile( 460 " pushl %%ebx\n" 461 " cpuid\n" 462 " movl %%ebx,%1\n" 463 " popl %%ebx\n" 464 : "=a"(p[0]), "=r"(p[1]), "=c"(p[2]), "=d"(p[3]) 465 : "0"(idx), "2"(cnt)); 466 } 467 468 void 469 ifunc_init(Elf_Auxinfo *aux_info[__min_size(AT_COUNT)] __unused) 470 { 471 u_int p[4], cpu_high; 472 int cpuid_supported; 473 474 __asm __volatile( 475 " pushfl\n" 476 " popl %%eax\n" 477 " movl %%eax,%%ecx\n" 478 " xorl $0x200000,%%eax\n" 479 " pushl %%eax\n" 480 " popfl\n" 481 " pushfl\n" 482 " popl %%eax\n" 483 " xorl %%eax,%%ecx\n" 484 " je 1f\n" 485 " movl $1,%0\n" 486 " jmp 2f\n" 487 "1: movl $0,%0\n" 488 "2:\n" 489 : "=r"(cpuid_supported) 490 : 491 : "eax", "ecx"); 492 if (!cpuid_supported) 493 return; 494 495 rtld_cpuid_count(1, 0, p); 496 cpu_feature = p[3]; 497 cpu_feature2 = p[2]; 498 rtld_cpuid_count(0, 0, p); 499 cpu_high = p[0]; 500 if (cpu_high >= 7) { 501 rtld_cpuid_count(7, 0, p); 502 cpu_stdext_feature = p[1]; 503 cpu_stdext_feature2 = p[2]; 504 } 505 } 506 507 void 508 allocate_initial_tls(Obj_Entry *objs) 509 { 510 void *tls; 511 512 /* 513 * Fix the size of the static TLS block by using the maximum 514 * offset allocated so far and adding a bit for dynamic modules to 515 * use. 516 */ 517 tls_static_space = tls_last_offset + ld_static_tls_extra; 518 tls = allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN); 519 _tcb_set(tls); 520 } 521 522 /* GNU ABI */ 523 __attribute__((__regparm__(1))) void * 524 ___tls_get_addr(tls_index *ti) 525 { 526 uintptr_t **dtvp; 527 528 dtvp = &_tcb_get()->tcb_dtv; 529 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 530 } 531 532 /* Sun ABI */ 533 void * 534 __tls_get_addr(tls_index *ti) 535 { 536 uintptr_t **dtvp; 537 538 dtvp = &_tcb_get()->tcb_dtv; 539 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 540 } 541 542 size_t 543 calculate_tls_offset(size_t prev_offset, size_t prev_size __unused, size_t size, 544 size_t align, size_t offset) 545 { 546 size_t res; 547 548 /* 549 * res is the smallest integer satisfying res - prev_offset >= size 550 * and (-res) % p_align = p_vaddr % p_align (= p_offset % p_align). 551 */ 552 res = prev_offset + size + align - 1; 553 res -= (res + offset) & (align - 1); 554 return (res); 555 } 556 557 size_t 558 calculate_first_tls_offset(size_t size, size_t align, size_t offset) 559 { 560 return (calculate_tls_offset(0, 0, size, align, offset)); 561 } 562