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/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 52 /* 53 * Process the special R_386_COPY relocations in the main program. These 54 * copy data from a shared object into a region in the main program's BSS 55 * segment. 56 * 57 * Returns 0 on success, -1 on failure. 58 */ 59 int 60 do_copy_relocations(Obj_Entry *dstobj) 61 { 62 const Elf_Rel *rellim; 63 const Elf_Rel *rel; 64 65 assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */ 66 67 rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize); 68 for (rel = dstobj->rel; rel < rellim; rel++) { 69 if (ELF_R_TYPE(rel->r_info) == R_386_COPY) { 70 void *dstaddr; 71 const Elf_Sym *dstsym; 72 const char *name; 73 size_t size; 74 const void *srcaddr; 75 const Elf_Sym *srcsym; 76 const Obj_Entry *srcobj, *defobj; 77 SymLook req; 78 int res; 79 80 dstaddr = (void *) (dstobj->relocbase + rel->r_offset); 81 dstsym = dstobj->symtab + ELF_R_SYM(rel->r_info); 82 name = dstobj->strtab + dstsym->st_name; 83 size = dstsym->st_size; 84 symlook_init(&req, name); 85 req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info)); 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, RtldLockState *lockstate) 123 { 124 const Elf_Rel *rellim; 125 const Elf_Rel *rel; 126 SymCache *cache; 127 int r = -1; 128 129 /* 130 * The dynamic loader may be called from a thread, we have 131 * limited amounts of stack available so we cannot use alloca(). 132 */ 133 if (obj != obj_rtld) { 134 cache = calloc(obj->nchains, sizeof(SymCache)); 135 /* No need to check for NULL here */ 136 } else 137 cache = NULL; 138 139 rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize); 140 for (rel = obj->rel; rel < rellim; rel++) { 141 Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 142 143 switch (ELF_R_TYPE(rel->r_info)) { 144 145 case R_386_NONE: 146 break; 147 148 case R_386_32: 149 { 150 const Elf_Sym *def; 151 const Obj_Entry *defobj; 152 153 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 154 false, cache, lockstate); 155 if (def == NULL) 156 goto done; 157 158 *where += (Elf_Addr) (defobj->relocbase + def->st_value); 159 } 160 break; 161 162 case R_386_PC32: 163 /* 164 * I don't think the dynamic linker should ever see this 165 * type of relocation. But the binutils-2.6 tools sometimes 166 * generate it. 167 */ 168 { 169 const Elf_Sym *def; 170 const Obj_Entry *defobj; 171 172 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 173 false, cache, lockstate); 174 if (def == NULL) 175 goto done; 176 177 *where += 178 (Elf_Addr) (defobj->relocbase + def->st_value) - 179 (Elf_Addr) where; 180 } 181 break; 182 183 case R_386_COPY: 184 /* 185 * These are deferred until all other relocations have 186 * been done. All we do here is make sure that the COPY 187 * relocation is not in a shared library. They are allowed 188 * only in executable files. 189 */ 190 if (!obj->mainprog) { 191 _rtld_error("%s: Unexpected R_386_COPY relocation" 192 " in shared library", obj->path); 193 goto done; 194 } 195 break; 196 197 case R_386_GLOB_DAT: 198 { 199 const Elf_Sym *def; 200 const Obj_Entry *defobj; 201 202 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 203 false, cache, lockstate); 204 if (def == NULL) 205 goto done; 206 207 *where = (Elf_Addr) (defobj->relocbase + def->st_value); 208 } 209 break; 210 211 case R_386_RELATIVE: 212 *where += (Elf_Addr) obj->relocbase; 213 break; 214 215 case R_386_TLS_TPOFF: 216 case R_386_TLS_TPOFF32: 217 { 218 const Elf_Sym *def; 219 const Obj_Entry *defobj; 220 Elf_Addr add; 221 222 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 223 false, cache, lockstate); 224 if (def == NULL) 225 goto done; 226 227 /* 228 * We lazily allocate offsets for static TLS as we 229 * see the first relocation that references the 230 * TLS block. This allows us to support (small 231 * amounts of) static TLS in dynamically loaded 232 * modules. If we run out of space, we generate an 233 * error. 234 */ 235 if (!defobj->tls_done) { 236 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 237 _rtld_error("%s: No space available for static " 238 "Thread Local Storage", obj->path); 239 goto done; 240 } 241 } 242 add = (Elf_Addr) (def->st_value - defobj->tlsoffset); 243 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 244 *where += add; 245 else 246 *where -= add; 247 } 248 break; 249 250 case R_386_TLS_DTPMOD32: 251 { 252 const Elf_Sym *def; 253 const Obj_Entry *defobj; 254 255 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 256 false, cache, lockstate); 257 if (def == NULL) 258 goto done; 259 260 *where += (Elf_Addr) defobj->tlsindex; 261 } 262 break; 263 264 case R_386_TLS_DTPOFF32: 265 { 266 const Elf_Sym *def; 267 const Obj_Entry *defobj; 268 269 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 270 false, cache, lockstate); 271 if (def == NULL) 272 goto done; 273 274 *where += (Elf_Addr) def->st_value; 275 } 276 break; 277 278 default: 279 _rtld_error("%s: Unsupported relocation type %d" 280 " in non-PLT relocations\n", obj->path, 281 ELF_R_TYPE(rel->r_info)); 282 goto done; 283 } 284 } 285 r = 0; 286 done: 287 if (cache != NULL) 288 free(cache); 289 return(r); 290 } 291 292 /* Process the PLT relocations. */ 293 int 294 reloc_plt(Obj_Entry *obj) 295 { 296 const Elf_Rel *rellim; 297 const Elf_Rel *rel; 298 299 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 300 for (rel = obj->pltrel; rel < rellim; rel++) { 301 Elf_Addr *where/*, val*/; 302 303 switch (ELF_R_TYPE(rel->r_info)) { 304 case R_386_JMP_SLOT: 305 /* Relocate the GOT slot pointing into the PLT. */ 306 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 307 *where += (Elf_Addr)obj->relocbase; 308 break; 309 310 case R_386_IRELATIVE: 311 obj->irelative = true; 312 break; 313 314 default: 315 _rtld_error("Unknown relocation type %x in PLT", 316 ELF_R_TYPE(rel->r_info)); 317 return (-1); 318 } 319 } 320 return 0; 321 } 322 323 /* Relocate the jump slots in an object. */ 324 int 325 reloc_jmpslots(Obj_Entry *obj, RtldLockState *lockstate) 326 { 327 const Elf_Rel *rellim; 328 const Elf_Rel *rel; 329 330 if (obj->jmpslots_done) 331 return 0; 332 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 333 for (rel = obj->pltrel; rel < rellim; rel++) { 334 Elf_Addr *where, target; 335 const Elf_Sym *def; 336 const Obj_Entry *defobj; 337 338 switch (ELF_R_TYPE(rel->r_info)) { 339 case R_386_JMP_SLOT: 340 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 341 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL, 342 lockstate); 343 if (def == NULL) 344 return (-1); 345 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 346 obj->gnu_ifunc = true; 347 continue; 348 } 349 target = (Elf_Addr)(defobj->relocbase + def->st_value); 350 reloc_jmpslot(where, target, defobj, obj, rel); 351 break; 352 353 case R_386_IRELATIVE: 354 break; 355 356 default: 357 _rtld_error("Unknown relocation type %x in PLT", 358 ELF_R_TYPE(rel->r_info)); 359 return (-1); 360 } 361 } 362 363 obj->jmpslots_done = true; 364 return 0; 365 } 366 367 int 368 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 369 { 370 const Elf_Rel *rellim; 371 const Elf_Rel *rel; 372 Elf_Addr *where, target; 373 374 if (!obj->irelative) 375 return (0); 376 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 377 for (rel = obj->pltrel; rel < rellim; rel++) { 378 switch (ELF_R_TYPE(rel->r_info)) { 379 case R_386_IRELATIVE: 380 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 381 lock_release(rtld_bind_lock, lockstate); 382 target = ((Elf_Addr (*)(void))(obj->relocbase + *where))(); 383 wlock_acquire(rtld_bind_lock, lockstate); 384 *where = target; 385 break; 386 } 387 } 388 obj->irelative = false; 389 return (0); 390 } 391 392 int 393 reloc_gnu_ifunc(Obj_Entry *obj, RtldLockState *lockstate) 394 { 395 const Elf_Rel *rellim; 396 const Elf_Rel *rel; 397 398 if (!obj->gnu_ifunc) 399 return (0); 400 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 401 for (rel = obj->pltrel; rel < rellim; rel++) { 402 Elf_Addr *where, target; 403 const Elf_Sym *def; 404 const Obj_Entry *defobj; 405 406 switch (ELF_R_TYPE(rel->r_info)) { 407 case R_386_JMP_SLOT: 408 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 409 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL, 410 lockstate); 411 if (def == NULL) 412 return (-1); 413 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 414 continue; 415 lock_release(rtld_bind_lock, lockstate); 416 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 417 wlock_acquire(rtld_bind_lock, lockstate); 418 reloc_jmpslot(where, target, defobj, obj, rel); 419 break; 420 } 421 } 422 423 obj->gnu_ifunc = false; 424 return (0); 425 } 426 427 void 428 allocate_initial_tls(Obj_Entry *objs) 429 { 430 void* tls; 431 432 /* 433 * Fix the size of the static TLS block by using the maximum 434 * offset allocated so far and adding a bit for dynamic modules to 435 * use. 436 */ 437 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 438 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 439 i386_set_gsbase(tls); 440 } 441 442 /* GNU ABI */ 443 __attribute__((__regparm__(1))) 444 void *___tls_get_addr(tls_index *ti) 445 { 446 Elf_Addr** segbase; 447 Elf_Addr* dtv; 448 449 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 450 dtv = segbase[1]; 451 452 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 453 } 454 455 /* Sun ABI */ 456 void *__tls_get_addr(tls_index *ti) 457 { 458 Elf_Addr** segbase; 459 Elf_Addr* dtv; 460 461 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 462 dtv = segbase[1]; 463 464 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 465 } 466