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 #include <machine/segments.h> 37 #include <machine/sysarch.h> 38 39 #include <dlfcn.h> 40 #include <err.h> 41 #include <errno.h> 42 #include <fcntl.h> 43 #include <stdarg.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <unistd.h> 48 49 #include "debug.h" 50 #include "rtld.h" 51 #include "rtld_tls.h" 52 53 /* 54 * Process the special R_386_COPY relocations in the main program. These 55 * copy data from a shared object into a region in the main program's BSS 56 * segment. 57 * 58 * Returns 0 on success, -1 on failure. 59 */ 60 int 61 do_copy_relocations(Obj_Entry *dstobj) 62 { 63 const Elf_Rel *rellim; 64 const Elf_Rel *rel; 65 66 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 67 68 rellim = (const Elf_Rel *)((const char *)dstobj->rel + dstobj->relsize); 69 for (rel = dstobj->rel; rel < rellim; rel++) { 70 if (ELF_R_TYPE(rel->r_info) == R_386_COPY) { 71 void *dstaddr; 72 const Elf_Sym *dstsym; 73 const char *name; 74 size_t size; 75 const void *srcaddr; 76 const Elf_Sym *srcsym; 77 const Obj_Entry *srcobj, *defobj; 78 SymLook req; 79 int res; 80 81 dstaddr = (void *)(dstobj->relocbase + rel->r_offset); 82 dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info); 83 name = dstobj->strtab + dstsym->st_name; 84 size = dstsym->st_size; 85 symlook_init(&req, name); 86 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info)); 87 req.flags = SYMLOOK_EARLY; 88 89 for (srcobj = globallist_next(dstobj); srcobj != NULL; 90 srcobj = globallist_next(srcobj)) { 91 res = symlook_obj(&req, srcobj); 92 if (res == 0) { 93 srcsym = req.sym_out; 94 defobj = req.defobj_out; 95 break; 96 } 97 } 98 99 if (srcobj == NULL) { 100 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 101 " relocation in %s", name, dstobj->path); 102 return -1; 103 } 104 105 srcaddr = (const void *)(defobj->relocbase + srcsym->st_value); 106 memcpy(dstaddr, srcaddr, size); 107 } 108 } 109 110 return 0; 111 } 112 113 /* Initialize the special GOT entries. */ 114 void 115 init_pltgot(Obj_Entry *obj) 116 { 117 if (obj->pltgot != NULL) { 118 obj->pltgot[1] = (Elf_Addr) obj; 119 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 120 } 121 } 122 123 /* Process the non-PLT relocations. */ 124 int 125 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 126 RtldLockState *lockstate) 127 { 128 const Elf_Rel *rellim; 129 const Elf_Rel *rel; 130 SymCache *cache; 131 const Elf_Sym *def; 132 const Obj_Entry *defobj; 133 Elf_Addr *where, symval, add; 134 int r; 135 136 r = -1; 137 /* 138 * The dynamic loader may be called from a thread, we have 139 * limited amounts of stack available so we cannot use alloca(). 140 */ 141 if (obj != obj_rtld) { 142 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 143 /* No need to check for NULL here */ 144 } else 145 cache = NULL; 146 147 /* Appease some compilers. */ 148 symval = 0; 149 def = NULL; 150 151 rellim = (const Elf_Rel *)((const char *)obj->rel + obj->relsize); 152 for (rel = obj->rel; rel < rellim; rel++) { 153 switch (ELF_R_TYPE(rel->r_info)) { 154 case R_386_32: 155 case R_386_PC32: 156 case R_386_GLOB_DAT: 157 case R_386_TLS_TPOFF: 158 case R_386_TLS_TPOFF32: 159 case R_386_TLS_DTPMOD32: 160 case R_386_TLS_DTPOFF32: 161 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 162 flags, cache, lockstate); 163 if (def == NULL) 164 goto done; 165 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 166 switch (ELF_R_TYPE(rel->r_info)) { 167 case R_386_32: 168 case R_386_PC32: 169 case R_386_GLOB_DAT: 170 if ((flags & SYMLOOK_IFUNC) == 0) { 171 obj->non_plt_gnu_ifunc = true; 172 continue; 173 } 174 symval = (Elf_Addr)rtld_resolve_ifunc( 175 defobj, def); 176 break; 177 case R_386_TLS_TPOFF: 178 case R_386_TLS_TPOFF32: 179 case R_386_TLS_DTPMOD32: 180 case R_386_TLS_DTPOFF32: 181 _rtld_error("%s: IFUNC for TLS reloc", 182 obj->path); 183 goto done; 184 } 185 } else { 186 if ((flags & SYMLOOK_IFUNC) != 0) 187 continue; 188 symval = (Elf_Addr)defobj->relocbase + 189 def->st_value; 190 } 191 break; 192 default: 193 if ((flags & SYMLOOK_IFUNC) != 0) 194 continue; 195 break; 196 } 197 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 198 199 switch (ELF_R_TYPE(rel->r_info)) { 200 case R_386_NONE: 201 break; 202 case R_386_32: 203 *where += symval; 204 break; 205 case R_386_PC32: 206 /* 207 * I don't think the dynamic linker should ever 208 * see this type of relocation. But the 209 * binutils-2.6 tools sometimes generate it. 210 */ 211 *where += symval - (Elf_Addr)where; 212 break; 213 case R_386_COPY: 214 /* 215 * These are deferred until all other 216 * relocations have been done. All we do here 217 * is make sure that the COPY relocation is 218 * not in a shared library. They are allowed 219 * only in executable files. 220 */ 221 if (!obj->mainprog) { 222 _rtld_error("%s: Unexpected R_386_COPY " 223 "relocation in shared library", obj->path); 224 goto done; 225 } 226 break; 227 case R_386_GLOB_DAT: 228 *where = symval; 229 break; 230 case R_386_RELATIVE: 231 *where += (Elf_Addr)obj->relocbase; 232 break; 233 case R_386_TLS_TPOFF: 234 case R_386_TLS_TPOFF32: 235 /* 236 * We lazily allocate offsets for static TLS 237 * as we see the first relocation that 238 * references the TLS block. This allows us to 239 * support (small amounts of) static TLS in 240 * dynamically loaded modules. If we run out 241 * of space, we generate an error. 242 */ 243 if (!defobj->tls_static) { 244 if (!allocate_tls_offset( 245 __DECONST(Obj_Entry *, defobj))) { 246 _rtld_error("%s: No space available " 247 "for static Thread Local Storage", 248 obj->path); 249 goto done; 250 } 251 } 252 add = (Elf_Addr)(def->st_value - defobj->tlsoffset); 253 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 254 *where += add; 255 else 256 *where -= add; 257 break; 258 case R_386_TLS_DTPMOD32: 259 *where += (Elf_Addr)defobj->tlsindex; 260 break; 261 case R_386_TLS_DTPOFF32: 262 *where += (Elf_Addr) def->st_value; 263 break; 264 case R_386_IRELATIVE: 265 obj->irelative_nonplt = true; 266 break; 267 default: 268 _rtld_error("%s: Unsupported relocation type %d" 269 " in non-PLT relocations\n", obj->path, 270 ELF_R_TYPE(rel->r_info)); 271 goto done; 272 } 273 } 274 r = 0; 275 done: 276 free(cache); 277 return (r); 278 } 279 280 /* Process the PLT relocations. */ 281 int 282 reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused) 283 { 284 const Elf_Rel *rellim; 285 const Elf_Rel *rel; 286 287 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 288 for (rel = obj->pltrel; rel < rellim; rel++) { 289 Elf_Addr *where/*, val*/; 290 291 switch (ELF_R_TYPE(rel->r_info)) { 292 case R_386_JMP_SLOT: 293 /* Relocate the GOT slot pointing into the PLT. */ 294 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 295 *where += (Elf_Addr)obj->relocbase; 296 break; 297 298 case R_386_IRELATIVE: 299 obj->irelative = true; 300 break; 301 302 default: 303 _rtld_error("Unknown relocation type %x in PLT", 304 ELF_R_TYPE(rel->r_info)); 305 return (-1); 306 } 307 } 308 return 0; 309 } 310 311 /* Relocate the jump slots in an object. */ 312 int 313 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 314 { 315 const Elf_Rel *rellim; 316 const Elf_Rel *rel; 317 318 if (obj->jmpslots_done) 319 return 0; 320 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 321 for (rel = obj->pltrel; rel < rellim; rel++) { 322 Elf_Addr *where, target; 323 const Elf_Sym *def; 324 const Obj_Entry *defobj; 325 326 switch (ELF_R_TYPE(rel->r_info)) { 327 case R_386_JMP_SLOT: 328 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 329 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 330 SYMLOOK_IN_PLT | flags, NULL, lockstate); 331 if (def == NULL) 332 return (-1); 333 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 334 obj->gnu_ifunc = true; 335 continue; 336 } 337 target = (Elf_Addr)(defobj->relocbase + def->st_value); 338 reloc_jmpslot(where, target, defobj, obj, rel); 339 break; 340 341 case R_386_IRELATIVE: 342 break; 343 344 default: 345 _rtld_error("Unknown relocation type %x in PLT", 346 ELF_R_TYPE(rel->r_info)); 347 return (-1); 348 } 349 } 350 351 obj->jmpslots_done = true; 352 return 0; 353 } 354 355 /* Fixup the jump slot at "where" to transfer control to "target". */ 356 Elf_Addr 357 reloc_jmpslot(Elf_Addr *where, Elf_Addr target, 358 const Obj_Entry *obj __unused, const Obj_Entry *refobj __unused, 359 const Elf_Rel *rel __unused) 360 { 361 #ifdef dbg 362 dbg("reloc_jmpslot: *%p = %p", where, (void *)target); 363 #endif 364 if (!ld_bind_not) 365 *where = target; 366 return (target); 367 } 368 369 static void 370 reloc_iresolve_one(Obj_Entry *obj, const Elf_Rel *rel, 371 RtldLockState *lockstate) 372 { 373 Elf_Addr *where, target; 374 375 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 376 lock_release(rtld_bind_lock, lockstate); 377 target = call_ifunc_resolver(obj->relocbase + *where); 378 wlock_acquire(rtld_bind_lock, lockstate); 379 *where = target; 380 } 381 382 int 383 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 384 { 385 const Elf_Rel *rellim; 386 const Elf_Rel *rel; 387 388 if (!obj->irelative) 389 return (0); 390 obj->irelative = false; 391 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 392 for (rel = obj->pltrel; rel < rellim; rel++) { 393 if (ELF_R_TYPE(rel->r_info) == R_386_IRELATIVE) 394 reloc_iresolve_one(obj, rel, lockstate); 395 } 396 return (0); 397 } 398 399 int 400 reloc_iresolve_nonplt(Obj_Entry *obj, RtldLockState *lockstate) 401 { 402 const Elf_Rel *rellim; 403 const Elf_Rel *rel; 404 405 if (!obj->irelative_nonplt) 406 return (0); 407 obj->irelative_nonplt = false; 408 rellim = (const Elf_Rel *)((const char *)obj->rel + obj->relsize); 409 for (rel = obj->rel; rel < rellim; rel++) { 410 if (ELF_R_TYPE(rel->r_info) == R_386_IRELATIVE) 411 reloc_iresolve_one(obj, rel, lockstate); 412 } 413 return (0); 414 } 415 416 int 417 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 418 { 419 const Elf_Rel *rellim; 420 const Elf_Rel *rel; 421 422 if (!obj->gnu_ifunc) 423 return (0); 424 rellim = (const Elf_Rel *)((const char *)obj->pltrel + obj->pltrelsize); 425 for (rel = obj->pltrel; rel < rellim; rel++) { 426 Elf_Addr *where, target; 427 const Elf_Sym *def; 428 const Obj_Entry *defobj; 429 430 switch (ELF_R_TYPE(rel->r_info)) { 431 case R_386_JMP_SLOT: 432 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 433 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 434 SYMLOOK_IN_PLT | flags, NULL, lockstate); 435 if (def == NULL) 436 return (-1); 437 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 438 continue; 439 lock_release(rtld_bind_lock, lockstate); 440 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 441 wlock_acquire(rtld_bind_lock, lockstate); 442 reloc_jmpslot(where, target, defobj, obj, rel); 443 break; 444 } 445 } 446 447 obj->gnu_ifunc = false; 448 return (0); 449 } 450 451 uint32_t cpu_feature, cpu_feature2, cpu_stdext_feature, cpu_stdext_feature2; 452 453 static void 454 rtld_cpuid_count(int idx, int cnt, u_int *p) 455 { 456 457 __asm __volatile( 458 " pushl %%ebx\n" 459 " cpuid\n" 460 " movl %%ebx,%1\n" 461 " popl %%ebx\n" 462 : "=a" (p[0]), "=r" (p[1]), "=c" (p[2]), "=d" (p[3]) 463 : "0" (idx), "2" (cnt)); 464 } 465 466 void 467 ifunc_init(Elf_Auxinfo aux_info[__min_size(AT_COUNT)] __unused) 468 { 469 u_int p[4], cpu_high; 470 int cpuid_supported; 471 472 __asm __volatile( 473 " pushfl\n" 474 " popl %%eax\n" 475 " movl %%eax,%%ecx\n" 476 " xorl $0x200000,%%eax\n" 477 " pushl %%eax\n" 478 " popfl\n" 479 " pushfl\n" 480 " popl %%eax\n" 481 " xorl %%eax,%%ecx\n" 482 " je 1f\n" 483 " movl $1,%0\n" 484 " jmp 2f\n" 485 "1: movl $0,%0\n" 486 "2:\n" 487 : "=r" (cpuid_supported) : : "eax", "ecx"); 488 if (!cpuid_supported) 489 return; 490 491 rtld_cpuid_count(1, 0, p); 492 cpu_feature = p[3]; 493 cpu_feature2 = p[2]; 494 rtld_cpuid_count(0, 0, p); 495 cpu_high = p[0]; 496 if (cpu_high >= 7) { 497 rtld_cpuid_count(7, 0, p); 498 cpu_stdext_feature = p[1]; 499 cpu_stdext_feature2 = p[2]; 500 } 501 } 502 503 void 504 allocate_initial_tls(Obj_Entry *objs) 505 { 506 void* tls; 507 508 /* 509 * Fix the size of the static TLS block by using the maximum 510 * offset allocated so far and adding a bit for dynamic modules to 511 * use. 512 */ 513 tls_static_space = tls_last_offset + ld_static_tls_extra; 514 tls = allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN); 515 _tcb_set(tls); 516 } 517 518 /* GNU ABI */ 519 __attribute__((__regparm__(1))) 520 void * 521 ___tls_get_addr(tls_index *ti) 522 { 523 uintptr_t **dtvp; 524 525 dtvp = &_tcb_get()->tcb_dtv; 526 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 527 } 528 529 /* Sun ABI */ 530 void * 531 __tls_get_addr(tls_index *ti) 532 { 533 uintptr_t **dtvp; 534 535 dtvp = &_tcb_get()->tcb_dtv; 536 return (tls_get_addr_common(dtvp, ti->ti_module, ti->ti_offset)); 537 } 538 539 size_t 540 calculate_tls_offset(size_t prev_offset, size_t prev_size __unused, 541 size_t size, size_t align, size_t offset) 542 { 543 size_t res; 544 545 /* 546 * res is the smallest integer satisfying res - prev_offset >= size 547 * and (-res) % p_align = p_vaddr % p_align (= p_offset % p_align). 548 */ 549 res = prev_offset + size + align - 1; 550 res -= (res + offset) & (align - 1); 551 return (res); 552 } 553 554 size_t 555 calculate_first_tls_offset(size_t size, size_t align, size_t offset) 556 { 557 return (calculate_tls_offset(0, 0, size, align, offset)); 558 } 559