1 /* $OpenBSD: rtld_machine.c,v 1.19 2013/06/13 04:13:47 brad Exp $ */ 2 3 /* 4 * Copyright (c) 2004 Dale Rahn 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 */ 28 29 #define _DYN_LOADER 30 31 #include <sys/types.h> 32 #include <sys/mman.h> 33 34 #include <nlist.h> 35 #include <link.h> 36 #include <signal.h> 37 38 #include "syscall.h" 39 #include "archdep.h" 40 #include "resolve.h" 41 42 void _dl_bind_start(void); /* XXX */ 43 Elf_Addr _dl_bind(elf_object_t *object, int reloff); 44 #define _RF_S 0x80000000 /* Resolve symbol */ 45 #define _RF_A 0x40000000 /* Use addend */ 46 #define _RF_P 0x20000000 /* Location relative */ 47 #define _RF_G 0x10000000 /* GOT offset */ 48 #define _RF_B 0x08000000 /* Load address relative */ 49 #define _RF_U 0x04000000 /* Unaligned */ 50 #define _RF_E 0x02000000 /* ERROR */ 51 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 52 #define _RF_RS(s) ((s) & 0xff) /* right shift */ 53 static int reloc_target_flags[] = { 54 0, /* 0 NONE */ 55 _RF_S|_RF_P|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 1 PC24 */ 56 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 2 ABS32 */ 57 _RF_S|_RF_P|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 3 REL32 */ 58 _RF_S|_RF_P|_RF_A| _RF_E, /* 4 REL13 */ 59 _RF_S|_RF_A| _RF_E, /* 5 ABS16 */ 60 _RF_S|_RF_A| _RF_E, /* 6 ABS12 */ 61 _RF_S|_RF_A| _RF_E, /* 7 T_ABS5 */ 62 _RF_S|_RF_A| _RF_E, /* 8 ABS8 */ 63 _RF_S|_RF_B|_RF_A| _RF_E, /* 9 SBREL32 */ 64 _RF_S|_RF_P|_RF_A| _RF_E, /* 10 T_PC22 */ 65 _RF_S|_RF_P|_RF_A| _RF_E, /* 11 T_PC8 */ 66 _RF_E, /* 12 Reserved */ 67 _RF_S|_RF_A| _RF_E, /* 13 SWI24 */ 68 _RF_S|_RF_A| _RF_E, /* 14 T_SWI8 */ 69 _RF_E, /* 15 OBSL */ 70 _RF_E, /* 16 OBSL */ 71 _RF_E, /* 17 UNUSED */ 72 _RF_E, /* 18 UNUSED */ 73 _RF_E, /* 19 UNUSED */ 74 _RF_S| _RF_SZ(32) | _RF_RS(0), /* 20 COPY */ 75 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 21 GLOB_DAT */ 76 _RF_S| _RF_SZ(32) | _RF_RS(0), /* 22 JUMP_SLOT */ 77 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* 23 RELATIVE */ 78 _RF_E, /* 24 GOTOFF */ 79 _RF_E, /* 25 GOTPC */ 80 _RF_E, /* 26 GOT32 */ 81 _RF_E, /* 27 PLT32 */ 82 _RF_E, /* 28 UNUSED */ 83 _RF_E, /* 29 UNUSED */ 84 _RF_E, /* 30 UNUSED */ 85 _RF_E, /* 31 UNUSED */ 86 _RF_E, /* 32 A_PCR 0 */ 87 _RF_E, /* 33 A_PCR 8 */ 88 _RF_E, /* 34 A_PCR 16 */ 89 _RF_E, /* 35 B_PCR 0 */ 90 _RF_E, /* 36 B_PCR 12 */ 91 _RF_E, /* 37 B_PCR 20 */ 92 _RF_E, /* 38 RELAB32 */ 93 _RF_E, /* 39 ROSGREL32 */ 94 _RF_E, /* 40 V4BX */ 95 _RF_E, /* 41 STKCHK */ 96 _RF_E /* 42 TSTKCHK */ 97 }; 98 99 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 100 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 101 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 102 #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 103 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 104 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 105 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 106 static int reloc_target_bitmask[] = { 107 #define _BM(x) (x == 32? ~0 : ~(-(1UL << (x)))) 108 _BM(0), /* 0 NONE */ 109 _BM(24), /* 1 PC24 */ 110 _BM(32), /* 2 ABS32 */ 111 _BM(32), /* 3 REL32 */ 112 _BM(0), /* 4 REL13 */ 113 _BM(0), /* 5 ABS16 */ 114 _BM(0), /* 6 ABS12 */ 115 _BM(0), /* 7 T_ABS5 */ 116 _BM(0), /* 8 ABS8 */ 117 _BM(32), /* 9 SBREL32 */ 118 _BM(0), /* 10 T_PC22 */ 119 _BM(0), /* 11 T_PC8 */ 120 _BM(0), /* 12 Reserved */ 121 _BM(0), /* 13 SWI24 */ 122 _BM(0), /* 14 T_SWI8 */ 123 _BM(0), /* 15 OBSL */ 124 _BM(0), /* 16 OBSL */ 125 _BM(0), /* 17 UNUSED */ 126 _BM(0), /* 18 UNUSED */ 127 _BM(0), /* 19 UNUSED */ 128 _BM(32), /* 20 COPY */ 129 _BM(32), /* 21 GLOB_DAT */ 130 _BM(32), /* 22 JUMP_SLOT */ 131 _BM(32), /* 23 RELATIVE */ 132 _BM(0), /* 24 GOTOFF */ 133 _BM(0), /* 25 GOTPC */ 134 _BM(0), /* 26 GOT32 */ 135 _BM(0), /* 27 PLT32 */ 136 _BM(0), /* 28 UNUSED */ 137 _BM(0), /* 29 UNUSED */ 138 _BM(0), /* 30 UNUSED */ 139 _BM(0), /* 31 UNUSED */ 140 _BM(0), /* 32 A_PCR 0 */ 141 _BM(0), /* 33 A_PCR 8 */ 142 _BM(0), /* 34 A_PCR 16 */ 143 _BM(0), /* 35 B_PCR 0 */ 144 _BM(0), /* 36 B_PCR 12 */ 145 _BM(0), /* 37 B_PCR 20 */ 146 _BM(0), /* 38 RELAB32 */ 147 _BM(0), /* 39 ROSGREL32 */ 148 _BM(0), /* 40 V4BX */ 149 _BM(0), /* 41 STKCHK */ 150 _BM(0) /* 42 TSTKCHK */ 151 #undef _BM 152 }; 153 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 154 155 #define R_TYPE(x) R_ARM_ ## x 156 157 void _dl_reloc_plt(Elf_Word *where, Elf_Addr value, Elf_Rel *rel); 158 159 int 160 _dl_md_reloc(elf_object_t *object, int rel, int relsz) 161 { 162 long i; 163 long numrel; 164 long relrel; 165 int fails = 0; 166 Elf_Addr loff; 167 Elf_Addr prev_value = 0; 168 const Elf_Sym *prev_sym = NULL; 169 Elf_Rel *rels; 170 struct load_list *llist; 171 172 loff = object->obj_base; 173 numrel = object->Dyn.info[relsz] / sizeof(Elf_Rel); 174 relrel = rel == DT_REL ? object->relcount : 0; 175 rels = (Elf_Rel *)(object->Dyn.info[rel]); 176 177 if (rels == NULL) 178 return(0); 179 180 if (relrel > numrel) { 181 _dl_printf("relcount > numrel: %ld > %ld\n", relrel, numrel); 182 _dl_exit(20); 183 } 184 185 /* 186 * unprotect some segments if we need it. 187 */ 188 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 189 for (llist = object->load_list; 190 llist != NULL; 191 llist = llist->next) { 192 if (!(llist->prot & PROT_WRITE)) 193 _dl_mprotect(llist->start, llist->size, 194 llist->prot|PROT_WRITE); 195 } 196 } 197 198 /* tight loop for leading RELATIVE relocs */ 199 for (i = 0; i < relrel; i++, rels++) { 200 Elf_Addr *where; 201 202 #ifdef DEBUG 203 if (ELF_R_TYPE(rels->r_info) != R_TYPE(RELATIVE)) { 204 _dl_printf("RELCOUNT wrong\n"); 205 _dl_exit(20); 206 } 207 #endif 208 where = (Elf_Addr *)(rels->r_offset + loff); 209 *where += loff; 210 } 211 for (; i < numrel; i++, rels++) { 212 Elf_Addr *where, value, ooff, mask; 213 Elf_Word type; 214 const Elf_Sym *sym, *this; 215 const char *symn; 216 217 type = ELF_R_TYPE(rels->r_info); 218 219 if (reloc_target_flags[type] & _RF_E) { 220 _dl_printf(" bad relocation %d %d\n", i, type); 221 _dl_exit(1); 222 } 223 if (type == R_TYPE(NONE)) 224 continue; 225 226 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL) 227 continue; 228 229 where = (Elf_Addr *)(rels->r_offset + loff); 230 231 if (RELOC_USE_ADDEND(type)) 232 #ifdef LDSO_ARCH_IS_RELA_ 233 value = rels->r_addend; 234 #else 235 value = *where & RELOC_VALUE_BITMASK(type); 236 #endif 237 else 238 value = 0; 239 240 sym = NULL; 241 symn = NULL; 242 if (RELOC_RESOLVE_SYMBOL(type)) { 243 sym = object->dyn.symtab; 244 sym += ELF_R_SYM(rels->r_info); 245 symn = object->dyn.strtab + sym->st_name; 246 247 if (sym->st_shndx != SHN_UNDEF && 248 ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 249 value += loff; 250 } else if (sym == prev_sym) { 251 value += prev_value; 252 } else { 253 this = NULL; 254 ooff = _dl_find_symbol_bysym(object, 255 ELF_R_SYM(rels->r_info), &this, 256 SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 257 ((type == R_TYPE(JUMP_SLOT)) ? 258 SYM_PLT : SYM_NOTPLT), 259 sym, NULL); 260 if (this == NULL) { 261 resolve_failed: 262 if (ELF_ST_BIND(sym->st_info) != 263 STB_WEAK) 264 fails++; 265 continue; 266 } 267 prev_sym = sym; 268 prev_value = (Elf_Addr)(ooff + this->st_value); 269 value += prev_value; 270 } 271 } 272 273 if (type == R_TYPE(JUMP_SLOT)) { 274 /* 275 _dl_reloc_plt((Elf_Word *)where, value, rels); 276 */ 277 *where = value; 278 continue; 279 } 280 281 if (type == R_TYPE(COPY)) { 282 void *dstaddr = where; 283 const void *srcaddr; 284 const Elf_Sym *dstsym = sym, *srcsym = NULL; 285 Elf_Addr soff; 286 287 soff = _dl_find_symbol(symn, &srcsym, 288 SYM_SEARCH_OTHER|SYM_WARNNOTFOUND|SYM_NOTPLT, 289 dstsym, object, NULL); 290 if (srcsym == NULL) 291 goto resolve_failed; 292 293 srcaddr = (void *)(soff + srcsym->st_value); 294 _dl_bcopy(srcaddr, dstaddr, dstsym->st_size); 295 continue; 296 } 297 298 if (RELOC_PC_RELATIVE(type)) 299 value -= (Elf_Addr)where; 300 if (RELOC_BASE_RELATIVE(type)) 301 value += loff; 302 303 mask = RELOC_VALUE_BITMASK(type); 304 value >>= RELOC_VALUE_RIGHTSHIFT(type); 305 value &= mask; 306 307 if (RELOC_UNALIGNED(type)) { 308 /* Handle unaligned relocations. */ 309 Elf_Addr tmp = 0; 310 char *ptr = (char *)where; 311 int i, size = RELOC_TARGET_SIZE(type)/8; 312 313 /* Read it in one byte at a time. */ 314 for (i=0; i<size; i++) 315 tmp = (tmp << 8) | ptr[i]; 316 317 tmp &= ~mask; 318 tmp |= value; 319 320 /* Write it back out. */ 321 for (i=0; i<size; i++) 322 ptr[i] = ((tmp >> (8*i)) & 0xff); 323 } else { 324 *where &= ~mask; 325 *where |= value; 326 } 327 } 328 329 /* reprotect the unprotected segments */ 330 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 331 for (llist = object->load_list; 332 llist != NULL; 333 llist = llist->next) { 334 if (!(llist->prot & PROT_WRITE)) 335 _dl_mprotect(llist->start, llist->size, 336 llist->prot); 337 } 338 } 339 340 return (fails); 341 } 342 343 /* 344 * Relocate the Global Offset Table (GOT). 345 * This is done by calling _dl_md_reloc on DT_JUMPREL for DL_BIND_NOW, 346 * otherwise the lazy binding plt initialization is performed. 347 */ 348 int 349 _dl_md_reloc_got(elf_object_t *object, int lazy) 350 { 351 int fails = 0; 352 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; 353 Elf_Addr ooff; 354 const Elf_Sym *this; 355 int i, num; 356 Elf_Rel *rel; 357 358 if (object->Dyn.info[DT_PLTREL] != DT_REL) 359 return (0); 360 361 object->got_addr = 0; 362 object->got_size = 0; 363 this = NULL; 364 ooff = _dl_find_symbol("__got_start", &this, 365 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 366 if (this != NULL) 367 object->got_addr = ooff + this->st_value; 368 369 this = NULL; 370 ooff = _dl_find_symbol("__got_end", &this, 371 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 372 if (this != NULL) 373 object->got_size = ooff + this->st_value - object->got_addr; 374 375 object->plt_size = 0; /* Text PLT on ARM */ 376 377 if (object->got_addr == 0) 378 object->got_start = 0; 379 else { 380 object->got_start = ELF_TRUNC(object->got_addr, _dl_pagesz); 381 object->got_size += object->got_addr - object->got_start; 382 object->got_size = ELF_ROUND(object->got_size, _dl_pagesz); 383 } 384 object->plt_start = 0; 385 386 if (object->traced) 387 lazy = 1; 388 389 if (!lazy) { 390 fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ); 391 } else { 392 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 393 num = (object->Dyn.info[DT_PLTRELSZ]); 394 395 for (i = 0; i < num/sizeof(Elf_Rel); i++, rel++) { 396 Elf_Addr *where; 397 where = (Elf_Addr *)(rel->r_offset + object->obj_base); 398 *where += object->obj_base; 399 } 400 401 pltgot[1] = (Elf_Addr)object; 402 pltgot[2] = (Elf_Addr)_dl_bind_start; 403 } 404 if (object->got_size != 0) 405 _dl_mprotect((void*)object->got_start, object->got_size, 406 PROT_READ); 407 if (object->plt_size != 0) 408 _dl_mprotect((void*)object->plt_start, object->plt_size, 409 PROT_READ|PROT_EXEC); 410 411 return (fails); 412 } 413 414 Elf_Addr 415 _dl_bind(elf_object_t *object, int relidx) 416 { 417 Elf_Rel *rel; 418 Elf_Word *addr; 419 const Elf_Sym *sym, *this; 420 const char *symn; 421 const elf_object_t *sobj; 422 Elf_Addr ooff, newval; 423 sigset_t savedmask; 424 425 rel = ((Elf_Rel *)object->Dyn.info[DT_JMPREL]) + (relidx); 426 427 sym = object->dyn.symtab; 428 sym += ELF_R_SYM(rel->r_info); 429 symn = object->dyn.strtab + sym->st_name; 430 431 this = NULL; 432 ooff = _dl_find_symbol(symn, &this, 433 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object, &sobj); 434 if (this == NULL) { 435 _dl_printf("lazy binding failed!\n"); 436 *(volatile int *)0 = 0; /* XXX */ 437 } 438 439 addr = (Elf_Addr *)(object->obj_base + rel->r_offset); 440 newval = ooff + this->st_value; 441 442 if (sobj->traced && _dl_trace_plt(sobj, symn)) 443 return newval; 444 445 /* if GOT is protected, allow the write */ 446 if (object->got_size != 0) { 447 _dl_thread_bind_lock(0, &savedmask); 448 _dl_mprotect((void*)object->got_start, object->got_size, 449 PROT_READ|PROT_WRITE); 450 } 451 452 if (*addr != newval) 453 *addr = newval; 454 455 /* put the GOT back to RO */ 456 if (object->got_size != 0) { 457 _dl_mprotect((void*)object->got_start, object->got_size, 458 PROT_READ); 459 _dl_thread_bind_lock(1, &savedmask); 460 } 461 return newval; 462 } 463