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 #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 *) ((caddr_t) 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 = dstobj->next; srcobj != NULL; srcobj = srcobj->next) { 90 res = symlook_obj(&req, srcobj); 91 if (res == 0) { 92 srcsym = req.sym_out; 93 defobj = req.defobj_out; 94 break; 95 } 96 } 97 98 if (srcobj == NULL) { 99 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 100 " relocation in %s", name, dstobj->path); 101 return -1; 102 } 103 104 srcaddr = (const void *) (defobj->relocbase + srcsym->st_value); 105 memcpy(dstaddr, srcaddr, size); 106 } 107 } 108 109 return 0; 110 } 111 112 /* Initialize the special GOT entries. */ 113 void 114 init_pltgot(Obj_Entry *obj) 115 { 116 if (obj->pltgot != NULL) { 117 obj->pltgot[1] = (Elf_Addr) obj; 118 obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start; 119 } 120 } 121 122 /* Process the non-PLT relocations. */ 123 int 124 reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags, 125 RtldLockState *lockstate) 126 { 127 const Elf_Rel *rellim; 128 const Elf_Rel *rel; 129 SymCache *cache; 130 const Elf_Sym *def; 131 const Obj_Entry *defobj; 132 Elf_Addr *where, symval, add; 133 int r; 134 135 r = -1; 136 /* 137 * The dynamic loader may be called from a thread, we have 138 * limited amounts of stack available so we cannot use alloca(). 139 */ 140 if (obj != obj_rtld) { 141 cache = calloc(obj->dynsymcount, sizeof(SymCache)); 142 /* No need to check for NULL here */ 143 } else 144 cache = NULL; 145 146 rellim = (const Elf_Rel *)((caddr_t) obj->rel + obj->relsize); 147 for (rel = obj->rel; rel < rellim; rel++) { 148 switch (ELF_R_TYPE(rel->r_info)) { 149 case R_386_32: 150 case R_386_PC32: 151 case R_386_GLOB_DAT: 152 case R_386_TLS_TPOFF: 153 case R_386_TLS_TPOFF32: 154 case R_386_TLS_DTPMOD32: 155 case R_386_TLS_DTPOFF32: 156 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 157 flags, cache, lockstate); 158 if (def == NULL) 159 goto done; 160 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 161 switch (ELF_R_TYPE(rel->r_info)) { 162 case R_386_32: 163 case R_386_PC32: 164 case R_386_GLOB_DAT: 165 if ((flags & SYMLOOK_IFUNC) == 0) { 166 obj->non_plt_gnu_ifunc = true; 167 continue; 168 } 169 symval = (Elf_Addr)rtld_resolve_ifunc( 170 defobj, def); 171 break; 172 case R_386_TLS_TPOFF: 173 case R_386_TLS_TPOFF32: 174 case R_386_TLS_DTPMOD32: 175 case R_386_TLS_DTPOFF32: 176 _rtld_error("%s: IFUNC for TLS reloc", 177 obj->path); 178 goto done; 179 } 180 } else { 181 if ((flags & SYMLOOK_IFUNC) != 0) 182 continue; 183 symval = (Elf_Addr)defobj->relocbase + 184 def->st_value; 185 } 186 break; 187 default: 188 if ((flags & SYMLOOK_IFUNC) != 0) 189 continue; 190 break; 191 } 192 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 193 194 switch (ELF_R_TYPE(rel->r_info)) { 195 case R_386_NONE: 196 break; 197 case R_386_32: 198 *where += symval; 199 break; 200 case R_386_PC32: 201 /* 202 * I don't think the dynamic linker should ever 203 * see this type of relocation. But the 204 * binutils-2.6 tools sometimes generate it. 205 */ 206 *where += symval - (Elf_Addr)where; 207 break; 208 case R_386_COPY: 209 /* 210 * These are deferred until all other 211 * relocations have been done. All we do here 212 * is make sure that the COPY relocation is 213 * not in a shared library. They are allowed 214 * only in executable files. 215 */ 216 if (!obj->mainprog) { 217 _rtld_error("%s: Unexpected R_386_COPY " 218 "relocation in shared library", obj->path); 219 goto done; 220 } 221 break; 222 case R_386_GLOB_DAT: 223 *where = symval; 224 break; 225 case R_386_RELATIVE: 226 *where += (Elf_Addr)obj->relocbase; 227 break; 228 case R_386_TLS_TPOFF: 229 case R_386_TLS_TPOFF32: 230 /* 231 * We lazily allocate offsets for static TLS 232 * as we see the first relocation that 233 * references the TLS block. This allows us to 234 * support (small amounts of) static TLS in 235 * dynamically loaded modules. If we run out 236 * of space, we generate an error. 237 */ 238 if (!defobj->tls_done) { 239 if (!allocate_tls_offset((Obj_Entry*) defobj)) { 240 _rtld_error("%s: No space available " 241 "for static Thread Local Storage", 242 obj->path); 243 goto done; 244 } 245 } 246 add = (Elf_Addr)(def->st_value - defobj->tlsoffset); 247 if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF) 248 *where += add; 249 else 250 *where -= add; 251 break; 252 case R_386_TLS_DTPMOD32: 253 *where += (Elf_Addr)defobj->tlsindex; 254 break; 255 case R_386_TLS_DTPOFF32: 256 *where += (Elf_Addr) def->st_value; 257 break; 258 default: 259 _rtld_error("%s: Unsupported relocation type %d" 260 " in non-PLT relocations\n", obj->path, 261 ELF_R_TYPE(rel->r_info)); 262 goto done; 263 } 264 } 265 r = 0; 266 done: 267 free(cache); 268 return (r); 269 } 270 271 /* Process the PLT relocations. */ 272 int 273 reloc_plt(Obj_Entry *obj) 274 { 275 const Elf_Rel *rellim; 276 const Elf_Rel *rel; 277 278 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 279 for (rel = obj->pltrel; rel < rellim; rel++) { 280 Elf_Addr *where/*, val*/; 281 282 switch (ELF_R_TYPE(rel->r_info)) { 283 case R_386_JMP_SLOT: 284 /* Relocate the GOT slot pointing into the PLT. */ 285 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 286 *where += (Elf_Addr)obj->relocbase; 287 break; 288 289 case R_386_IRELATIVE: 290 obj->irelative = true; 291 break; 292 293 default: 294 _rtld_error("Unknown relocation type %x in PLT", 295 ELF_R_TYPE(rel->r_info)); 296 return (-1); 297 } 298 } 299 return 0; 300 } 301 302 /* Relocate the jump slots in an object. */ 303 int 304 reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate) 305 { 306 const Elf_Rel *rellim; 307 const Elf_Rel *rel; 308 309 if (obj->jmpslots_done) 310 return 0; 311 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 312 for (rel = obj->pltrel; rel < rellim; rel++) { 313 Elf_Addr *where, target; 314 const Elf_Sym *def; 315 const Obj_Entry *defobj; 316 317 switch (ELF_R_TYPE(rel->r_info)) { 318 case R_386_JMP_SLOT: 319 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 320 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 321 SYMLOOK_IN_PLT | flags, NULL, lockstate); 322 if (def == NULL) 323 return (-1); 324 if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) { 325 obj->gnu_ifunc = true; 326 continue; 327 } 328 target = (Elf_Addr)(defobj->relocbase + def->st_value); 329 reloc_jmpslot(where, target, defobj, obj, rel); 330 break; 331 332 case R_386_IRELATIVE: 333 break; 334 335 default: 336 _rtld_error("Unknown relocation type %x in PLT", 337 ELF_R_TYPE(rel->r_info)); 338 return (-1); 339 } 340 } 341 342 obj->jmpslots_done = true; 343 return 0; 344 } 345 346 int 347 reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate) 348 { 349 const Elf_Rel *rellim; 350 const Elf_Rel *rel; 351 Elf_Addr *where, target; 352 353 if (!obj->irelative) 354 return (0); 355 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 356 for (rel = obj->pltrel; rel < rellim; rel++) { 357 switch (ELF_R_TYPE(rel->r_info)) { 358 case R_386_IRELATIVE: 359 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 360 lock_release(rtld_bind_lock, lockstate); 361 target = ((Elf_Addr (*)(void))(obj->relocbase + *where))(); 362 wlock_acquire(rtld_bind_lock, lockstate); 363 *where = target; 364 break; 365 } 366 } 367 obj->irelative = false; 368 return (0); 369 } 370 371 int 372 reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate) 373 { 374 const Elf_Rel *rellim; 375 const Elf_Rel *rel; 376 377 if (!obj->gnu_ifunc) 378 return (0); 379 rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize); 380 for (rel = obj->pltrel; rel < rellim; rel++) { 381 Elf_Addr *where, target; 382 const Elf_Sym *def; 383 const Obj_Entry *defobj; 384 385 switch (ELF_R_TYPE(rel->r_info)) { 386 case R_386_JMP_SLOT: 387 where = (Elf_Addr *)(obj->relocbase + rel->r_offset); 388 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, 389 SYMLOOK_IN_PLT | flags, NULL, lockstate); 390 if (def == NULL) 391 return (-1); 392 if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC) 393 continue; 394 lock_release(rtld_bind_lock, lockstate); 395 target = (Elf_Addr)rtld_resolve_ifunc(defobj, def); 396 wlock_acquire(rtld_bind_lock, lockstate); 397 reloc_jmpslot(where, target, defobj, obj, rel); 398 break; 399 } 400 } 401 402 obj->gnu_ifunc = false; 403 return (0); 404 } 405 406 void 407 allocate_initial_tls(Obj_Entry *objs) 408 { 409 void* tls; 410 411 /* 412 * Fix the size of the static TLS block by using the maximum 413 * offset allocated so far and adding a bit for dynamic modules to 414 * use. 415 */ 416 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 417 tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr)); 418 i386_set_gsbase(tls); 419 } 420 421 /* GNU ABI */ 422 __attribute__((__regparm__(1))) 423 void *___tls_get_addr(tls_index *ti) 424 { 425 Elf_Addr** segbase; 426 427 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 428 429 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 430 } 431 432 /* Sun ABI */ 433 void *__tls_get_addr(tls_index *ti) 434 { 435 Elf_Addr** segbase; 436 437 __asm __volatile("movl %%gs:0, %0" : "=r" (segbase)); 438 439 return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset); 440 } 441