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 req.flags = SYMLOOK_EARLY; 87 88 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 89 res = symlook_obj(&req, srcobj); 90 if (res == 0) { 91 srcsym = req.sym_out; 92 defobj = req.defobj_out; 93 break; 94 } 95 } 96 97 if (srcobj == NULL) { 98 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 99 " relocation in %s", name, dstobj->path); 100 return -1; 101 } 102 103 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 104 memcpy(dstaddr, srcaddr, size); 105 } 106 } 107 108 return 0; 109 } 110 111 /* Initialize the special GOT entries. */ 112 void 113 init_pltgot(Obj_Entry *obj) 114 { 115 if (obj->pltgot != NULL) { 116 obj->pltgot[1] = (Elf_Addr) obj; 117 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 118 } 119 } 120 121 /* Process the non-PLT relocations. */ 122 int 123 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 124 RtldLockState *lockstate) 125 { 126 const Elf_Rel *rellim; 127 const Elf_Rel *rel; 128 SymCache *cache; 129 const Elf_Sym *def; 130 const Obj_Entry *defobj; 131 Elf_Addr *where, symval, add; 132 int r; 133 134 r = -1; 135 /* 136 * The dynamic loader may be called from a thread, we have 137 * limited amounts of stack available so we cannot use alloca(). 138 */ 139 if (obj != obj_rtld) { 140 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 141 /* No need to check for NULL here */ 142 } else 143 cache = NULL; 144 145 rellim = (const Elf_Rel *)((caddr_t) obj->rel + obj->relsize); 146 for (rel = obj->rel; rel < rellim; rel++) { 147 switch (ELF_R_TYPE(rel->r_info)) { 148 case R_386_32: 149 case R_386_PC32: 150 case R_386_GLOB_DAT: 151 case R_386_TLS_TPOFF: 152 case R_386_TLS_TPOFF32: 153 case R_386_TLS_DTPMOD32: 154 case R_386_TLS_DTPOFF32: 155 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 156 flags, cache, lockstate); 157 if (def == NULL) 158 goto done; 159 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 160 switch (ELF_R_TYPE(rel->r_info)) { 161 case R_386_32: 162 case R_386_PC32: 163 case R_386_GLOB_DAT: 164 if ((flags & SYMLOOK_IFUNC) == 0) { 165 obj->non_plt_gnu_ifunc = true; 166 continue; 167 } 168 symval = (Elf_Addr)rtld_resolve_ifunc( 169 defobj, def); 170 break; 171 case R_386_TLS_TPOFF: 172 case R_386_TLS_TPOFF32: 173 case R_386_TLS_DTPMOD32: 174 case R_386_TLS_DTPOFF32: 175 _rtld_error("%s: IFUNC for TLS reloc", 176 obj->path); 177 goto done; 178 } 179 } else { 180 if ((flags & SYMLOOK_IFUNC) != 0) 181 continue; 182 symval = (Elf_Addr)defobj->relocbase + 183 def->st_value; 184 } 185 break; 186 default: 187 if ((flags & SYMLOOK_IFUNC) != 0) 188 continue; 189 break; 190 } 191 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 192 193 switch (ELF_R_TYPE(rel->r_info)) { 194 case R_386_NONE: 195 break; 196 case R_386_32: 197 *where += symval; 198 break; 199 case R_386_PC32: 200 /* 201 * I don't think the dynamic linker should ever 202 * see this type of relocation. But the 203 * binutils-2.6 tools sometimes generate it. 204 */ 205 *where += symval - (Elf_Addr)where; 206 break; 207 case R_386_COPY: 208 /* 209 * These are deferred until all other 210 * relocations have been done. All we do here 211 * is make sure that the COPY relocation is 212 * not in a shared library. They are allowed 213 * only in executable files. 214 */ 215 if (!obj->mainprog) { 216 _rtld_error("%s: Unexpected R_386_COPY " 217 "relocation in shared library", obj->path); 218 goto done; 219 } 220 break; 221 case R_386_GLOB_DAT: 222 *where = symval; 223 break; 224 case R_386_RELATIVE: 225 *where += (Elf_Addr)obj->relocbase; 226 break; 227 case R_386_TLS_TPOFF: 228 case R_386_TLS_TPOFF32: 229 /* 230 * We lazily allocate offsets for static TLS 231 * as we see the first relocation that 232 * references the TLS block. This allows us to 233 * support (small amounts of) static TLS in 234 * dynamically loaded modules. If we run out 235 * of space, we generate an error. 236 */ 237 if (!defobj->tls_done) { 238 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 239 _rtld_error("%s: No space available " 240 "for static Thread Local Storage", 241 obj->path); 242 goto done; 243 } 244 } 245 add = (Elf_Addr)(def->st_value - defobj->tlsoffset); 246 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 247 *where += add; 248 else 249 *where -= add; 250 break; 251 case R_386_TLS_DTPMOD32: 252 *where += (Elf_Addr)defobj->tlsindex; 253 break; 254 case R_386_TLS_DTPOFF32: 255 *where += (Elf_Addr) def->st_value; 256 break; 257 default: 258 _rtld_error("%s: Unsupported relocation type %d" 259 " in non-PLT relocations\n", obj->path, 260 ELF_R_TYPE(rel->r_info)); 261 goto done; 262 } 263 } 264 r = 0; 265 done: 266 free(cache); 267 return (r); 268 } 269 270 /* Process the PLT relocations. */ 271 int 272 reloc_plt(Obj_Entry *obj) 273 { 274 const Elf_Rel *rellim; 275 const Elf_Rel *rel; 276 277 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 278 for (rel = obj->pltrel; rel < rellim; rel++) { 279 Elf_Addr *where/*, val*/; 280 281 switch (ELF_R_TYPE(rel->r_info)) { 282 case R_386_JMP_SLOT: 283 /* Relocate the GOT slot pointing into the PLT. */ 284 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 285 *where += (Elf_Addr)obj->relocbase; 286 break; 287 288 case R_386_IRELATIVE: 289 obj->irelative = true; 290 break; 291 292 default: 293 _rtld_error("Unknown relocation type %x in PLT", 294 ELF_R_TYPE(rel->r_info)); 295 return (-1); 296 } 297 } 298 return 0; 299 } 300 301 /* Relocate the jump slots in an object. */ 302 int 303 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 304 { 305 const Elf_Rel *rellim; 306 const Elf_Rel *rel; 307 308 if (obj->jmpslots_done) 309 return 0; 310 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 311 for (rel = obj->pltrel; rel < rellim; rel++) { 312 Elf_Addr *where, target; 313 const Elf_Sym *def; 314 const Obj_Entry *defobj; 315 316 switch (ELF_R_TYPE(rel->r_info)) { 317 case R_386_JMP_SLOT: 318 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 319 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 320 SYMLOOK_IN_PLT | flags, NULL, lockstate); 321 if (def == NULL) 322 return (-1); 323 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 324 obj->gnu_ifunc = true; 325 continue; 326 } 327 target = (Elf_Addr)(defobj->relocbase + def->st_value); 328 reloc_jmpslot(where, target, defobj, obj, rel); 329 break; 330 331 case R_386_IRELATIVE: 332 break; 333 334 default: 335 _rtld_error("Unknown relocation type %x in PLT", 336 ELF_R_TYPE(rel->r_info)); 337 return (-1); 338 } 339 } 340 341 obj->jmpslots_done = true; 342 return 0; 343 } 344 345 int 346 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 347 { 348 const Elf_Rel *rellim; 349 const Elf_Rel *rel; 350 Elf_Addr *where, target; 351 352 if (!obj->irelative) 353 return (0); 354 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 355 for (rel = obj->pltrel; rel < rellim; rel++) { 356 switch (ELF_R_TYPE(rel->r_info)) { 357 case R_386_IRELATIVE: 358 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 359 lock_release(rtld_bind_lock, lockstate); 360 target = ((Elf_Addr (*)(void))(obj->relocbase + *where))(); 361 wlock_acquire(rtld_bind_lock, lockstate); 362 *where = target; 363 break; 364 } 365 } 366 obj->irelative = false; 367 return (0); 368 } 369 370 int 371 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 372 { 373 const Elf_Rel *rellim; 374 const Elf_Rel *rel; 375 376 if (!obj->gnu_ifunc) 377 return (0); 378 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 379 for (rel = obj->pltrel; rel < rellim; rel++) { 380 Elf_Addr *where, target; 381 const Elf_Sym *def; 382 const Obj_Entry *defobj; 383 384 switch (ELF_R_TYPE(rel->r_info)) { 385 case R_386_JMP_SLOT: 386 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 387 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 388 SYMLOOK_IN_PLT | flags, NULL, lockstate); 389 if (def == NULL) 390 return (-1); 391 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 392 continue; 393 lock_release(rtld_bind_lock, lockstate); 394 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 395 wlock_acquire(rtld_bind_lock, lockstate); 396 reloc_jmpslot(where, target, defobj, obj, rel); 397 break; 398 } 399 } 400 401 obj->gnu_ifunc = false; 402 return (0); 403 } 404 405 void 406 allocate_initial_tls(Obj_Entry *objs) 407 { 408 void* tls; 409 410 /* 411 * Fix the size of the static TLS block by using the maximum 412 * offset allocated so far and adding a bit for dynamic modules to 413 * use. 414 */ 415 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 416 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 417 i386_set_gsbase(tls); 418 } 419 420 /* GNU ABI */ 421 __attribute__((__regparm__(1))) 422 void *___tls_get_addr(tls_index *ti) 423 { 424 Elf_Addr** segbase; 425 426 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 427 428 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 429 } 430 431 /* Sun ABI */ 432 void *__tls_get_addr(tls_index *ti) 433 { 434 Elf_Addr** segbase; 435 436 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 437 438 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 439 } 440