1 /* $OpenBSD: rtld_machine.c,v 1.25 2011/04/06 11:36:25 miod Exp $ */ 2 3 /* 4 * Copyright (c) 2002 Dale Rahn 5 * Copyright (c) 2001 Niklas Hallqvist 6 * Copyright (c) 2001 Artur Grabowski 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 18 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 /*- 30 * Copyright (c) 2000 Eduardo Horvath. 31 * Copyright (c) 1999 The NetBSD Foundation, Inc. 32 * All rights reserved. 33 * 34 * This code is derived from software contributed to The NetBSD Foundation 35 * by Paul Kranenburg. 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. All advertising materials mentioning features or use of this software 46 * must display the following acknowledgement: 47 * This product includes software developed by the NetBSD 48 * Foundation, Inc. and its contributors. 49 * 4. Neither the name of The NetBSD Foundation nor the names of its 50 * contributors may be used to endorse or promote products derived 51 * from this software without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 54 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 56 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 57 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 58 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 59 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 60 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 61 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 62 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 63 * POSSIBILITY OF SUCH DAMAGE. 64 */ 65 66 #define _DYN_LOADER 67 68 #include <sys/types.h> 69 #include <sys/cdefs.h> 70 #include <sys/mman.h> 71 72 #include <nlist.h> 73 #include <link.h> 74 #include <signal.h> 75 76 #include "syscall.h" 77 #include "archdep.h" 78 #include "resolve.h" 79 80 /* 81 * The following table holds for each relocation type: 82 * - the width in bits of the memory location the relocation 83 * applies to (not currently used) 84 * - the number of bits the relocation value must be shifted to the 85 * right (i.e. discard least significant bits) to fit into 86 * the appropriate field in the instruction word. 87 * - flags indicating whether 88 * * the relocation involves a symbol 89 * * the relocation is relative to the current position 90 * * the relocation is for a GOT entry 91 * * the relocation is relative to the load address 92 * 93 */ 94 #define _RF_S 0x80000000 /* Resolve symbol */ 95 #define _RF_A 0x40000000 /* Use addend */ 96 #define _RF_P 0x20000000 /* Location relative */ 97 #define _RF_G 0x10000000 /* GOT offset */ 98 #define _RF_B 0x08000000 /* Load address relative */ 99 #define _RF_U 0x04000000 /* Unaligned */ 100 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 101 #define _RF_RS(s) ((s) & 0xff) /* right shift */ 102 static int reloc_target_flags[] = { 103 0, /* NONE */ 104 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32*/ 105 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC32 */ 106 _RF_G| _RF_SZ(32) | _RF_RS(00), /* GOT32 */ 107 _RF_A| _RF_SZ(32) | _RF_RS(0), /* PLT32 */ 108 _RF_S| _RF_SZ(32) | _RF_RS(0), /* COPY */ 109 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */ 110 _RF_S| _RF_SZ(32) | _RF_RS(0), /* JUMP_SLOT */ 111 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* RELATIVE */ 112 0, /* GOTOFF XXX */ 113 0, /* GOTPC XXX */ 114 0, /* DUMMY 11 */ 115 0, /* DUMMY 12 */ 116 0, /* DUMMY 13 */ 117 0, /* DUMMY 14 */ 118 0, /* DUMMY 15 */ 119 0, /* DUMMY 16 */ 120 0, /* DUMMY 17 */ 121 0, /* DUMMY 18 */ 122 0, /* DUMMY 19 */ 123 _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ 124 _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* PC_16 */ 125 _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ 126 _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* RELOC_PC8 */ 127 }; 128 129 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 130 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 131 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 132 #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 133 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 134 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 135 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 136 137 static long reloc_target_bitmask[] = { 138 #define _BM(x) (~(-(1ULL << (x)))) 139 0, /* NONE */ 140 _BM(32), /* RELOC_32*/ 141 _BM(32), /* PC32 */ 142 _BM(32), /* GOT32 */ 143 _BM(32), /* PLT32 */ 144 0, /* COPY */ 145 _BM(32), /* GLOB_DAT */ 146 _BM(32), /* JUMP_SLOT */ 147 _BM(32), /* RELATIVE */ 148 0, /* GOTOFF XXX */ 149 0, /* GOTPC XXX */ 150 0, /* DUMMY 11 */ 151 0, /* DUMMY 12 */ 152 0, /* DUMMY 13 */ 153 0, /* DUMMY 14 */ 154 0, /* DUMMY 15 */ 155 0, /* DUMMY 16 */ 156 0, /* DUMMY 17 */ 157 0, /* DUMMY 18 */ 158 0, /* DUMMY 19 */ 159 _BM(16), /* RELOC_16 */ 160 _BM(8), /* PC_16 */ 161 _BM(8), /* RELOC_8 */ 162 _BM(8), /* RELOC_PC8 */ 163 #undef _BM 164 }; 165 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 166 167 void _dl_reloc_plt(Elf_Addr *where, Elf_Addr value); 168 169 int 170 _dl_md_reloc(elf_object_t *object, int rel, int relsz) 171 { 172 long i; 173 long numrel; 174 int fails = 0; 175 Elf_Addr loff; 176 Elf_Rel *rels; 177 struct load_list *llist; 178 179 loff = object->obj_base; 180 numrel = object->Dyn.info[relsz] / sizeof(Elf32_Rel); 181 rels = (Elf32_Rel *)(object->Dyn.info[rel]); 182 if (rels == NULL) 183 return(0); 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; llist != NULL; llist = llist->next) { 190 if (!(llist->prot & PROT_WRITE)) 191 _dl_mprotect(llist->start, llist->size, 192 llist->prot|PROT_WRITE); 193 } 194 } 195 196 for (i = 0; i < numrel; i++, rels++) { 197 Elf_Addr *where, value, ooff, mask; 198 Elf_Word type; 199 const Elf_Sym *sym, *this; 200 const char *symn; 201 202 type = ELF_R_TYPE(rels->r_info); 203 204 if (type == R_TYPE(NONE)) 205 continue; 206 207 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL) 208 continue; 209 210 where = (Elf_Addr *)(rels->r_offset + loff); 211 212 if (RELOC_USE_ADDEND(type)) 213 value = *where & RELOC_VALUE_BITMASK(type); 214 else 215 value = 0; 216 217 sym = NULL; 218 symn = NULL; 219 if (RELOC_RESOLVE_SYMBOL(type)) { 220 sym = object->dyn.symtab; 221 sym += ELF_R_SYM(rels->r_info); 222 symn = object->dyn.strtab + sym->st_name; 223 224 if (sym->st_shndx != SHN_UNDEF && 225 ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 226 value += loff; 227 } else { 228 this = NULL; 229 ooff = _dl_find_symbol_bysym(object, 230 ELF_R_SYM(rels->r_info), &this, 231 SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 232 ((type == R_TYPE(JUMP_SLOT))? 233 SYM_PLT:SYM_NOTPLT), 234 sym, NULL); 235 if (this == NULL) { 236 resolve_failed: 237 if (ELF_ST_BIND(sym->st_info) != 238 STB_WEAK) 239 fails++; 240 continue; 241 } 242 value += (Elf_Addr)(ooff + this->st_value); 243 } 244 } 245 246 if (type == R_TYPE(JUMP_SLOT)) { 247 _dl_reloc_plt((Elf_Word *)where, value); 248 continue; 249 } 250 251 if (type == R_TYPE(COPY)) { 252 void *dstaddr = where; 253 const void *srcaddr; 254 const Elf_Sym *dstsym = sym, *srcsym = NULL; 255 size_t size = dstsym->st_size; 256 Elf_Addr soff; 257 258 soff = _dl_find_symbol(symn, &srcsym, 259 SYM_SEARCH_OTHER|SYM_WARNNOTFOUND| 260 ((type == R_TYPE(JUMP_SLOT)) ? SYM_PLT:SYM_NOTPLT), 261 sym, object, NULL); 262 if (srcsym == NULL) 263 goto resolve_failed; 264 265 srcaddr = (void *)(soff + srcsym->st_value); 266 _dl_bcopy(srcaddr, dstaddr, size); 267 continue; 268 } 269 270 if (RELOC_PC_RELATIVE(type)) 271 value -= (Elf_Addr)where; 272 if (RELOC_BASE_RELATIVE(type)) 273 value += loff; 274 275 mask = RELOC_VALUE_BITMASK(type); 276 value >>= RELOC_VALUE_RIGHTSHIFT(type); 277 value &= mask; 278 279 if (RELOC_UNALIGNED(type)) { 280 /* Handle unaligned relocations. */ 281 Elf_Addr tmp = 0; 282 char *ptr = (char *)where; 283 int i, size = RELOC_TARGET_SIZE(type)/8; 284 285 /* Read it in one byte at a time. */ 286 for (i=0; i<size; i++) 287 tmp = (tmp << 8) | ptr[i]; 288 289 tmp &= ~mask; 290 tmp |= value; 291 292 /* Write it back out. */ 293 for (i=0; i<size; i++) 294 ptr[i] = ((tmp >> (8*i)) & 0xff); 295 } else if (RELOC_TARGET_SIZE(type) > 32) { 296 *where &= ~mask; 297 *where |= value; 298 } else { 299 Elf32_Addr *where32 = (Elf32_Addr *)where; 300 301 *where32 &= ~mask; 302 *where32 |= value; 303 } 304 } 305 306 /* reprotect the unprotected segments */ 307 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 308 for (llist = object->load_list; llist != NULL; llist = llist->next) { 309 if (!(llist->prot & PROT_WRITE)) 310 _dl_mprotect(llist->start, llist->size, 311 llist->prot); 312 } 313 } 314 315 return (fails); 316 } 317 318 #if 0 319 struct jmpslot { 320 u_short opcode; 321 u_short addr[2]; 322 u_short reloc_index; 323 #define JMPSLOT_RELOC_MASK 0xffff 324 }; 325 #define JUMP 0xe990 /* NOP + JMP opcode */ 326 #endif 327 328 void 329 _dl_reloc_plt(Elf_Addr *where, Elf_Addr value) 330 { 331 *where = value; 332 } 333 334 /* 335 * Resolve a symbol at run-time. 336 */ 337 Elf_Addr 338 _dl_bind(elf_object_t *object, int index) 339 { 340 Elf_Rel *rel; 341 Elf_Word *addr; 342 const Elf_Sym *sym, *this; 343 const char *symn; 344 Elf_Addr ooff; 345 sigset_t savedmask; 346 347 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 348 349 rel += index/sizeof(Elf_Rel); 350 351 sym = object->dyn.symtab; 352 sym += ELF_R_SYM(rel->r_info); 353 symn = object->dyn.strtab + sym->st_name; 354 355 addr = (Elf_Word *)(object->obj_base + rel->r_offset); 356 this = NULL; 357 ooff = _dl_find_symbol(symn, &this, 358 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object, NULL); 359 if (this == NULL) { 360 _dl_printf("lazy binding failed!\n"); 361 *((int *)0) = 0; /* XXX */ 362 } 363 364 /* if GOT is protected, allow the write */ 365 if (object->got_size != 0) { 366 _dl_thread_bind_lock(0, &savedmask); 367 _dl_mprotect((void*)object->got_start, object->got_size, 368 PROT_READ|PROT_WRITE); 369 } 370 371 _dl_reloc_plt(addr, ooff + this->st_value); 372 373 /* put the GOT back to RO */ 374 if (object->got_size != 0) { 375 _dl_mprotect((void*)object->got_start, object->got_size, 376 PROT_READ); 377 _dl_thread_bind_lock(1, &savedmask); 378 } 379 380 return((Elf_Addr)ooff + this->st_value); 381 } 382 383 int 384 _dl_md_reloc_got(elf_object_t *object, int lazy) 385 { 386 extern void _dl_bind_start(void); /* XXX */ 387 int fails = 0; 388 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; 389 int i, num; 390 Elf_Rel *rel; 391 struct load_list *llist; 392 Elf_Addr ooff; 393 const Elf_Sym *this; 394 395 if (pltgot == NULL) 396 return (0); /* it is possible to have no PLT/GOT relocations */ 397 398 pltgot[1] = (Elf_Addr)object; 399 pltgot[2] = (Elf_Addr)&_dl_bind_start; 400 401 if (object->Dyn.info[DT_PLTREL] != DT_REL) 402 return (0); 403 404 object->got_addr = 0; 405 object->got_size = 0; 406 this = NULL; 407 ooff = _dl_find_symbol("__got_start", &this, 408 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 409 if (this != NULL) 410 object->got_addr = ooff + this->st_value; 411 412 this = NULL; 413 ooff = _dl_find_symbol("__got_end", &this, 414 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 415 if (this != NULL) 416 object->got_size = ooff + this->st_value - object->got_addr; 417 418 if (object->got_addr == 0) 419 object->got_start = 0; 420 else { 421 object->got_start = ELF_TRUNC(object->got_addr, _dl_pagesz); 422 object->got_size += object->got_addr - object->got_start; 423 object->got_size = ELF_ROUND(object->got_size, _dl_pagesz); 424 } 425 426 if (!lazy) { 427 fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ); 428 } else { 429 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 430 num = (object->Dyn.info[DT_PLTRELSZ]); 431 for (llist = object->load_list; llist != NULL; 432 llist = llist->next) { 433 if (!(llist->prot & PROT_WRITE)) 434 _dl_mprotect(llist->start, llist->size, 435 llist->prot|PROT_WRITE); 436 } 437 for (i = 0; i < num/sizeof(Elf_Rel); i++, rel++) { 438 Elf_Addr *where; 439 where = (Elf_Addr *)(rel->r_offset + object->obj_base); 440 *where += object->obj_base; 441 } 442 for (llist = object->load_list; llist != NULL; 443 llist = llist->next) { 444 if (!(llist->prot & PROT_WRITE)) 445 _dl_mprotect(llist->start, llist->size, 446 llist->prot); 447 } 448 449 } 450 /* PLT is already RO on i386, no point in mprotecting it, just GOT */ 451 if (object->got_size != 0) 452 _dl_mprotect((void*)object->got_start, object->got_size, 453 PROT_READ); 454 455 return (fails); 456 } 457