rtld_machine.c revision 1.27
1/* $OpenBSD: rtld_machine.c,v 1.27 2013/05/08 20:55:14 guenther 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/mman.h> 70 71#include <nlist.h> 72#include <link.h> 73#include <signal.h> 74 75#include "syscall.h" 76#include "archdep.h" 77#include "resolve.h" 78 79/* 80 * The following table holds for each relocation type: 81 * - the width in bits of the memory location the relocation 82 * applies to (not currently used) 83 * - the number of bits the relocation value must be shifted to the 84 * right (i.e. discard least significant bits) to fit into 85 * the appropriate field in the instruction word. 86 * - flags indicating whether 87 * * the relocation involves a symbol 88 * * the relocation is relative to the current position 89 * * the relocation is for a GOT entry 90 * * the relocation is relative to the load address 91 * 92 */ 93#define _RF_S 0x80000000 /* Resolve symbol */ 94#define _RF_A 0x40000000 /* Use addend */ 95#define _RF_P 0x20000000 /* Location relative */ 96#define _RF_G 0x10000000 /* GOT offset */ 97#define _RF_B 0x08000000 /* Load address relative */ 98#define _RF_U 0x04000000 /* Unaligned */ 99#define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 100#define _RF_RS(s) ((s) & 0xff) /* right shift */ 101static int reloc_target_flags[] = { 102 0, /* NONE */ 103 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32*/ 104 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC32 */ 105 _RF_G| _RF_SZ(32) | _RF_RS(00), /* GOT32 */ 106 _RF_A| _RF_SZ(32) | _RF_RS(0), /* PLT32 */ 107 _RF_S| _RF_SZ(32) | _RF_RS(0), /* COPY */ 108 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */ 109 _RF_S| _RF_SZ(32) | _RF_RS(0), /* JUMP_SLOT */ 110 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* RELATIVE */ 111 0, /* GOTOFF XXX */ 112 0, /* GOTPC XXX */ 113 0, /* DUMMY 11 */ 114 0, /* DUMMY 12 */ 115 0, /* DUMMY 13 */ 116 0, /* DUMMY 14 */ 117 0, /* DUMMY 15 */ 118 0, /* DUMMY 16 */ 119 0, /* DUMMY 17 */ 120 0, /* DUMMY 18 */ 121 0, /* DUMMY 19 */ 122 _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ 123 _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* PC_16 */ 124 _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ 125 _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* RELOC_PC8 */ 126}; 127 128#define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 129#define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 130#define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 131#define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 132#define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 133#define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 134#define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 135 136static long reloc_target_bitmask[] = { 137#define _BM(x) (~(-(1ULL << (x)))) 138 0, /* NONE */ 139 _BM(32), /* RELOC_32*/ 140 _BM(32), /* PC32 */ 141 _BM(32), /* GOT32 */ 142 _BM(32), /* PLT32 */ 143 0, /* COPY */ 144 _BM(32), /* GLOB_DAT */ 145 _BM(32), /* JUMP_SLOT */ 146 _BM(32), /* RELATIVE */ 147 0, /* GOTOFF XXX */ 148 0, /* GOTPC XXX */ 149 0, /* DUMMY 11 */ 150 0, /* DUMMY 12 */ 151 0, /* DUMMY 13 */ 152 0, /* DUMMY 14 */ 153 0, /* DUMMY 15 */ 154 0, /* DUMMY 16 */ 155 0, /* DUMMY 17 */ 156 0, /* DUMMY 18 */ 157 0, /* DUMMY 19 */ 158 _BM(16), /* RELOC_16 */ 159 _BM(8), /* PC_16 */ 160 _BM(8), /* RELOC_8 */ 161 _BM(8), /* RELOC_PC8 */ 162#undef _BM 163}; 164#define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 165 166void _dl_reloc_plt(Elf_Addr *where, Elf_Addr value); 167 168int 169_dl_md_reloc(elf_object_t *object, int rel, int relsz) 170{ 171 long i; 172 long numrel; 173 long relrel; 174 int fails = 0; 175 Elf_Addr loff; 176 Elf_Addr prev_value = 0; 177 const Elf_Sym *prev_sym = NULL; 178 Elf_Rel *rels; 179 struct load_list *llist; 180 181 loff = object->obj_base; 182 numrel = object->Dyn.info[relsz] / sizeof(Elf32_Rel); 183 relrel = rel == DT_REL ? object->relcount : 0; 184 rels = (Elf32_Rel *)(object->Dyn.info[rel]); 185 if (rels == NULL) 186 return(0); 187 188 if (relrel > numrel) { 189 _dl_printf("relcount > numrel: %ld > %ld\n", relrel, numrel); 190 _dl_exit(20); 191 } 192 193 /* 194 * unprotect some segments if we need it. 195 */ 196 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 197 for (llist = object->load_list; llist != NULL; llist = llist->next) { 198 if (!(llist->prot & PROT_WRITE)) 199 _dl_mprotect(llist->start, llist->size, 200 llist->prot|PROT_WRITE); 201 } 202 } 203 204 /* tight loop for leading RELATIVE relocs */ 205 for (i = 0; i < relrel; i++, rels++) { 206 Elf_Addr *where; 207 208#ifdef DEBUG 209 if (ELF_R_TYPE(rels->r_info) != R_TYPE(RELATIVE)) { 210 _dl_printf("RELCOUNT wrong\n"); 211 _dl_exit(20); 212 } 213#endif 214 where = (Elf_Addr *)(rels->r_offset + loff); 215 *where += loff; 216 } 217 for (; i < numrel; i++, rels++) { 218 Elf_Addr *where, value, ooff, mask; 219 Elf_Word type; 220 const Elf_Sym *sym, *this; 221 const char *symn; 222 223 type = ELF_R_TYPE(rels->r_info); 224 225 if (type == R_TYPE(NONE)) 226 continue; 227 228 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL) 229 continue; 230 231 where = (Elf_Addr *)(rels->r_offset + loff); 232 233 if (RELOC_USE_ADDEND(type)) 234 value = *where & RELOC_VALUE_BITMASK(type); 235 else 236 value = 0; 237 238 sym = NULL; 239 symn = NULL; 240 if (RELOC_RESOLVE_SYMBOL(type)) { 241 sym = object->dyn.symtab; 242 sym += ELF_R_SYM(rels->r_info); 243 symn = object->dyn.strtab + sym->st_name; 244 245 if (sym->st_shndx != SHN_UNDEF && 246 ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 247 value += loff; 248 } else if (sym == prev_sym) { 249 value += prev_value; 250 } else { 251 this = NULL; 252 ooff = _dl_find_symbol_bysym(object, 253 ELF_R_SYM(rels->r_info), &this, 254 SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 255 ((type == R_TYPE(JUMP_SLOT))? 256 SYM_PLT:SYM_NOTPLT), 257 sym, NULL); 258 if (this == NULL) { 259resolve_failed: 260 if (ELF_ST_BIND(sym->st_info) != 261 STB_WEAK) 262 fails++; 263 continue; 264 } 265 prev_sym = sym; 266 prev_value = (Elf_Addr)(ooff + this->st_value); 267 value += prev_value; 268 } 269 } 270 271 if (type == R_TYPE(JUMP_SLOT)) { 272 _dl_reloc_plt((Elf_Word *)where, value); 273 continue; 274 } 275 276 if (type == R_TYPE(COPY)) { 277 void *dstaddr = where; 278 const void *srcaddr; 279 const Elf_Sym *dstsym = sym, *srcsym = NULL; 280 size_t size = dstsym->st_size; 281 Elf_Addr soff; 282 283 soff = _dl_find_symbol(symn, &srcsym, 284 SYM_SEARCH_OTHER|SYM_WARNNOTFOUND| 285 ((type == R_TYPE(JUMP_SLOT)) ? SYM_PLT:SYM_NOTPLT), 286 sym, object, NULL); 287 if (srcsym == NULL) 288 goto resolve_failed; 289 290 srcaddr = (void *)(soff + srcsym->st_value); 291 _dl_bcopy(srcaddr, dstaddr, size); 292 continue; 293 } 294 295 if (RELOC_PC_RELATIVE(type)) 296 value -= (Elf_Addr)where; 297 if (RELOC_BASE_RELATIVE(type)) 298 value += loff; 299 300 mask = RELOC_VALUE_BITMASK(type); 301 value >>= RELOC_VALUE_RIGHTSHIFT(type); 302 value &= mask; 303 304 if (RELOC_UNALIGNED(type)) { 305 /* Handle unaligned relocations. */ 306 Elf_Addr tmp = 0; 307 char *ptr = (char *)where; 308 int i, size = RELOC_TARGET_SIZE(type)/8; 309 310 /* Read it in one byte at a time. */ 311 for (i=0; i<size; i++) 312 tmp = (tmp << 8) | ptr[i]; 313 314 tmp &= ~mask; 315 tmp |= value; 316 317 /* Write it back out. */ 318 for (i=0; i<size; i++) 319 ptr[i] = ((tmp >> (8*i)) & 0xff); 320 } else if (RELOC_TARGET_SIZE(type) > 32) { 321 *where &= ~mask; 322 *where |= value; 323 } else { 324 Elf32_Addr *where32 = (Elf32_Addr *)where; 325 326 *where32 &= ~mask; 327 *where32 |= value; 328 } 329 } 330 331 /* reprotect the unprotected segments */ 332 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 333 for (llist = object->load_list; llist != NULL; 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#if 0 344struct jmpslot { 345 u_short opcode; 346 u_short addr[2]; 347 u_short reloc_index; 348#define JMPSLOT_RELOC_MASK 0xffff 349}; 350#define JUMP 0xe990 /* NOP + JMP opcode */ 351#endif 352 353void 354_dl_reloc_plt(Elf_Addr *where, Elf_Addr value) 355{ 356 *where = value; 357} 358 359/* 360 * Resolve a symbol at run-time. 361 */ 362Elf_Addr 363_dl_bind(elf_object_t *object, int index) 364{ 365 Elf_Rel *rel; 366 Elf_Word *addr; 367 const Elf_Sym *sym, *this; 368 const char *symn; 369 Elf_Addr ooff; 370 sigset_t savedmask; 371 372 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 373 374 rel += index/sizeof(Elf_Rel); 375 376 sym = object->dyn.symtab; 377 sym += ELF_R_SYM(rel->r_info); 378 symn = object->dyn.strtab + sym->st_name; 379 380 addr = (Elf_Word *)(object->obj_base + rel->r_offset); 381 this = NULL; 382 ooff = _dl_find_symbol(symn, &this, 383 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object, NULL); 384 if (this == NULL) { 385 _dl_printf("lazy binding failed!\n"); 386 *((int *)0) = 0; /* XXX */ 387 } 388 389 /* if GOT is protected, allow the write */ 390 if (object->got_size != 0) { 391 _dl_thread_bind_lock(0, &savedmask); 392 _dl_mprotect((void*)object->got_start, object->got_size, 393 PROT_READ|PROT_WRITE); 394 } 395 396 _dl_reloc_plt(addr, ooff + this->st_value); 397 398 /* put the GOT back to RO */ 399 if (object->got_size != 0) { 400 _dl_mprotect((void*)object->got_start, object->got_size, 401 PROT_READ); 402 _dl_thread_bind_lock(1, &savedmask); 403 } 404 405 return((Elf_Addr)ooff + this->st_value); 406} 407 408int 409_dl_md_reloc_got(elf_object_t *object, int lazy) 410{ 411 extern void _dl_bind_start(void); /* XXX */ 412 int fails = 0; 413 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; 414 int i, num; 415 Elf_Rel *rel; 416 struct load_list *llist; 417 Elf_Addr ooff; 418 const Elf_Sym *this; 419 420 if (pltgot == NULL) 421 return (0); /* it is possible to have no PLT/GOT relocations */ 422 423 pltgot[1] = (Elf_Addr)object; 424 pltgot[2] = (Elf_Addr)&_dl_bind_start; 425 426 if (object->Dyn.info[DT_PLTREL] != DT_REL) 427 return (0); 428 429 object->got_addr = 0; 430 object->got_size = 0; 431 this = NULL; 432 ooff = _dl_find_symbol("__got_start", &this, 433 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 434 if (this != NULL) 435 object->got_addr = ooff + this->st_value; 436 437 this = NULL; 438 ooff = _dl_find_symbol("__got_end", &this, 439 SYM_SEARCH_OBJ|SYM_NOWARNNOTFOUND|SYM_PLT, NULL, object, NULL); 440 if (this != NULL) 441 object->got_size = ooff + this->st_value - object->got_addr; 442 443 if (object->got_addr == 0) 444 object->got_start = 0; 445 else { 446 object->got_start = ELF_TRUNC(object->got_addr, _dl_pagesz); 447 object->got_size += object->got_addr - object->got_start; 448 object->got_size = ELF_ROUND(object->got_size, _dl_pagesz); 449 } 450 451 if (!lazy) { 452 fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ); 453 } else { 454 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 455 num = (object->Dyn.info[DT_PLTRELSZ]); 456 for (llist = object->load_list; llist != NULL; 457 llist = llist->next) { 458 if (!(llist->prot & PROT_WRITE)) 459 _dl_mprotect(llist->start, llist->size, 460 llist->prot|PROT_WRITE); 461 } 462 for (i = 0; i < num/sizeof(Elf_Rel); i++, rel++) { 463 Elf_Addr *where; 464 where = (Elf_Addr *)(rel->r_offset + object->obj_base); 465 *where += object->obj_base; 466 } 467 for (llist = object->load_list; llist != NULL; 468 llist = llist->next) { 469 if (!(llist->prot & PROT_WRITE)) 470 _dl_mprotect(llist->start, llist->size, 471 llist->prot); 472 } 473 474 } 475 /* PLT is already RO on i386, no point in mprotecting it, just GOT */ 476 if (object->got_size != 0) 477 _dl_mprotect((void*)object->got_start, object->got_size, 478 PROT_READ); 479 480 return (fails); 481} 482