rtld_machine.c revision 1.14
1/* $OpenBSD: rtld_machine.c,v 1.14 2004/05/25 15:56:18 deraadt 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 80void 81_dl_bcopy(const void *src, void *dest, int size) 82{ 83 const unsigned char *psrc = src; 84 unsigned char *pdest = dest; 85 int i; 86 87 for (i = 0; i < size; i++) 88 pdest[i] = psrc[i]; 89} 90 91/* 92 * The following table holds for each relocation type: 93 * - the width in bits of the memory location the relocation 94 * applies to (not currently used) 95 * - the number of bits the relocation value must be shifted to the 96 * right (i.e. discard least significant bits) to fit into 97 * the appropriate field in the instruction word. 98 * - flags indicating whether 99 * * the relocation involves a symbol 100 * * the relocation is relative to the current position 101 * * the relocation is for a GOT entry 102 * * the relocation is relative to the load address 103 * 104 */ 105#define _RF_S 0x80000000 /* Resolve symbol */ 106#define _RF_A 0x40000000 /* Use addend */ 107#define _RF_P 0x20000000 /* Location relative */ 108#define _RF_G 0x10000000 /* GOT offset */ 109#define _RF_B 0x08000000 /* Load address relative */ 110#define _RF_U 0x04000000 /* Unaligned */ 111#define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 112#define _RF_RS(s) ((s) & 0xff) /* right shift */ 113static int reloc_target_flags[] = { 114 0, /* NONE */ 115 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* RELOC_32*/ 116 _RF_S|_RF_A|_RF_P| _RF_SZ(32) | _RF_RS(0), /* PC32 */ 117 _RF_G| _RF_SZ(32) | _RF_RS(00), /* GOT32 */ 118 _RF_A| _RF_SZ(32) | _RF_RS(0), /* PLT32 */ 119 _RF_S| _RF_SZ(32) | _RF_RS(0), /* COPY */ 120 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* GLOB_DAT */ 121 _RF_S| _RF_SZ(32) | _RF_RS(0), /* JUMP_SLOT */ 122 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* RELATIVE */ 123 0, /* GOTOFF XXX */ 124 0, /* GOTPC XXX */ 125 0, /* DUMMY 11 */ 126 0, /* DUMMY 12 */ 127 0, /* DUMMY 13 */ 128 0, /* DUMMY 14 */ 129 0, /* DUMMY 15 */ 130 0, /* DUMMY 16 */ 131 0, /* DUMMY 17 */ 132 0, /* DUMMY 18 */ 133 0, /* DUMMY 19 */ 134 _RF_S|_RF_A| _RF_SZ(16) | _RF_RS(0), /* RELOC_16 */ 135 _RF_S|_RF_A|_RF_P| _RF_SZ(16) | _RF_RS(0), /* PC_16 */ 136 _RF_S|_RF_A| _RF_SZ(8) | _RF_RS(0), /* RELOC_8 */ 137 _RF_S|_RF_A|_RF_P| _RF_SZ(8) | _RF_RS(0), /* RELOC_PC8 */ 138}; 139 140#define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 141#define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 142#define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 143#define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 144#define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 145#define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 146#define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 147 148static long reloc_target_bitmask[] = { 149#define _BM(x) (~(-(1ULL << (x)))) 150 0, /* NONE */ 151 _BM(32), /* RELOC_32*/ 152 _BM(32), /* PC32 */ 153 _BM(32), /* GOT32 */ 154 _BM(32), /* PLT32 */ 155 0, /* COPY */ 156 _BM(32), /* GLOB_DAT */ 157 _BM(32), /* JUMP_SLOT */ 158 _BM(32), /* RELATIVE */ 159 0, /* GOTOFF XXX */ 160 0, /* GOTPC XXX */ 161 0, /* DUMMY 11 */ 162 0, /* DUMMY 12 */ 163 0, /* DUMMY 13 */ 164 0, /* DUMMY 14 */ 165 0, /* DUMMY 15 */ 166 0, /* DUMMY 16 */ 167 0, /* DUMMY 17 */ 168 0, /* DUMMY 18 */ 169 0, /* DUMMY 19 */ 170 _BM(16), /* RELOC_16 */ 171 _BM(8), /* PC_16 */ 172 _BM(8), /* RELOC_8 */ 173 _BM(8), /* RELOC_PC8 */ 174#undef _BM 175}; 176#define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 177 178void _dl_reloc_plt(Elf_Addr *where, Elf_Addr value); 179 180int 181_dl_md_reloc(elf_object_t *object, int rel, int relsz) 182{ 183 long i; 184 long numrel; 185 long fails = 0; 186 Elf_Addr loff; 187 Elf_Rel *rels; 188 struct load_list *llist; 189 190 loff = object->load_offs; 191 numrel = object->Dyn.info[relsz] / sizeof(Elf32_Rel); 192 rels = (Elf32_Rel *)(object->Dyn.info[rel]); 193 if (rels == NULL) 194 return(0); 195 196 /* 197 * unprotect some segments if we need it. 198 */ 199 if ((rel == DT_REL || rel == DT_RELA)) { 200 for (llist = object->load_list; llist != NULL; llist = llist->next) { 201 if (!(llist->prot & PROT_WRITE)) 202 _dl_mprotect(llist->start, llist->size, 203 llist->prot|PROT_WRITE); 204 } 205 } 206 207 for (i = 0; i < numrel; i++, rels++) { 208 Elf_Addr *where, value, ooff, mask; 209 Elf_Word type; 210 const Elf_Sym *sym, *this; 211 const char *symn; 212 213 type = ELF_R_TYPE(rels->r_info); 214 215 if (type == R_TYPE(NONE)) 216 continue; 217 218 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL) 219 continue; 220 221 where = (Elf_Addr *)(rels->r_offset + loff); 222 223 if (RELOC_USE_ADDEND(type)) 224 value = *where & RELOC_VALUE_BITMASK(type); 225 else 226 value = 0; 227 228 sym = NULL; 229 symn = NULL; 230 if (RELOC_RESOLVE_SYMBOL(type)) { 231 sym = object->dyn.symtab; 232 sym += ELF_R_SYM(rels->r_info); 233 symn = object->dyn.strtab + sym->st_name; 234 235 if (sym->st_shndx != SHN_UNDEF && 236 ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 237 value += loff; 238 } else { 239 this = NULL; 240 ooff = _dl_find_symbol_bysym(object, 241 ELF_R_SYM(rels->r_info), _dl_objects, 242 &this, SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 243 ((type == R_TYPE(JUMP_SLOT))? 244 SYM_PLT:SYM_NOTPLT), 245 sym->st_size); 246 if (this == NULL) { 247resolve_failed: 248 _dl_printf("%s: %s: can't resolve " 249 "reference '%s'\n", 250 _dl_progname, object->load_name, 251 symn); 252 fails++; 253 continue; 254 } 255 value += (Elf_Addr)(ooff + this->st_value); 256 } 257 } 258 259 if (type == R_TYPE(JUMP_SLOT)) { 260 _dl_reloc_plt((Elf_Word *)where, value); 261 continue; 262 } 263 264 if (type == R_TYPE(COPY)) { 265 void *dstaddr = where; 266 const void *srcaddr; 267 const Elf_Sym *dstsym = sym, *srcsym = NULL; 268 size_t size = dstsym->st_size; 269 Elf_Addr soff; 270 271 soff = _dl_find_symbol(symn, object->next, &srcsym, 272 SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 273 ((type == R_TYPE(JUMP_SLOT)) ? SYM_PLT:SYM_NOTPLT), 274 size, object); 275 if (srcsym == NULL) 276 goto resolve_failed; 277 278 srcaddr = (void *)(soff + srcsym->st_value); 279 _dl_bcopy(srcaddr, dstaddr, size); 280 continue; 281 } 282 283 if (RELOC_PC_RELATIVE(type)) 284 value -= (Elf_Addr)where; 285 if (RELOC_BASE_RELATIVE(type)) 286 value += loff; 287 288 mask = RELOC_VALUE_BITMASK(type); 289 value >>= RELOC_VALUE_RIGHTSHIFT(type); 290 value &= mask; 291 292 if (RELOC_UNALIGNED(type)) { 293 /* Handle unaligned relocations. */ 294 Elf_Addr tmp = 0; 295 char *ptr = (char *)where; 296 int i, size = RELOC_TARGET_SIZE(type)/8; 297 298 /* Read it in one byte at a time. */ 299 for (i=0; i<size; i++) 300 tmp = (tmp << 8) | ptr[i]; 301 302 tmp &= ~mask; 303 tmp |= value; 304 305 /* Write it back out. */ 306 for (i=0; i<size; i++) 307 ptr[i] = ((tmp >> (8*i)) & 0xff); 308 } else if (RELOC_TARGET_SIZE(type) > 32) { 309 *where &= ~mask; 310 *where |= value; 311 } else { 312 Elf32_Addr *where32 = (Elf32_Addr *)where; 313 314 *where32 &= ~mask; 315 *where32 |= value; 316 } 317 } 318 319 /* reprotect the unprotected segments */ 320 if ((rel == DT_REL || rel == DT_RELA)) { 321 for (llist = object->load_list; llist != NULL; llist = llist->next) { 322 if (!(llist->prot & PROT_WRITE)) 323 _dl_mprotect(llist->start, llist->size, 324 llist->prot); 325 } 326 } 327 328 return (fails); 329} 330 331#if 0 332struct jmpslot { 333 u_short opcode; 334 u_short addr[2]; 335 u_short reloc_index; 336#define JMPSLOT_RELOC_MASK 0xffff 337}; 338#define JUMP 0xe990 /* NOP + JMP opcode */ 339#endif 340 341void 342_dl_reloc_plt(Elf_Addr *where, Elf_Addr value) 343{ 344 *where = value; 345} 346 347/* 348 * Resolve a symbol at run-time. 349 */ 350Elf_Addr 351_dl_bind(elf_object_t *object, int index) 352{ 353 Elf_Rel *rel; 354 Elf_Word *addr; 355 const Elf_Sym *sym, *this; 356 const char *symn; 357 Elf_Addr ooff; 358 sigset_t omask, nmask; 359 360 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 361 362 rel += index/sizeof(Elf_Rel); 363 364 sym = object->dyn.symtab; 365 sym += ELF_R_SYM(rel->r_info); 366 symn = object->dyn.strtab + sym->st_name; 367 368 addr = (Elf_Word *)(object->load_offs + rel->r_offset); 369 this = NULL; 370 ooff = _dl_find_symbol(symn, _dl_objects, &this, 371 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym->st_size, object); 372 if (this == NULL) { 373 _dl_printf("lazy binding failed!\n"); 374 *((int *)0) = 0; /* XXX */ 375 } 376 377 /* if GOT is protected, allow the write */ 378 if (object->got_size != 0) { 379 sigfillset(&nmask); 380 _dl_sigprocmask(SIG_BLOCK, &nmask, &omask); 381 _dl_mprotect((void*)object->got_start, object->got_size, 382 PROT_READ|PROT_WRITE); 383 } 384 385 _dl_reloc_plt(addr, ooff + this->st_value); 386 387 /* put the GOT back to RO */ 388 if (object->got_size != 0) { 389 _dl_mprotect((void*)object->got_start, object->got_size, 390 PROT_READ); 391 _dl_sigprocmask(SIG_SETMASK, &omask, NULL); 392 } 393 394 return((Elf_Addr)ooff + this->st_value); 395} 396 397void 398_dl_md_reloc_got(elf_object_t *object, int lazy) 399{ 400 extern void _dl_bind_start(void); /* XXX */ 401 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; 402 int i, num; 403 Elf_Rel *rel; 404 struct load_list *llist; 405 Elf_Addr ooff; 406 const Elf_Sym *this; 407 408 if (pltgot == NULL) 409 return; /* it is possible to have no PLT/GOT relocations */ 410 411 pltgot[1] = (Elf_Addr)object; 412 pltgot[2] = (Elf_Addr)&_dl_bind_start; 413 414 if (object->Dyn.info[DT_PLTREL] != DT_REL) 415 return; 416 417 object->got_addr = NULL; 418 object->got_size = 0; 419 this = NULL; 420 ooff = _dl_find_symbol("__got_start", object, &this, 421 SYM_SEARCH_SELF|SYM_NOWARNNOTFOUND|SYM_PLT, 0, object); 422 if (this != NULL) 423 object->got_addr = ooff + this->st_value; 424 425 this = NULL; 426 ooff = _dl_find_symbol("__got_end", object, &this, 427 SYM_SEARCH_SELF|SYM_NOWARNNOTFOUND|SYM_PLT, 0, object); 428 if (this != NULL) 429 object->got_size = ooff + this->st_value - object->got_addr; 430 431 if (object->got_addr == NULL) 432 object->got_start = NULL; 433 else { 434 object->got_start = ELF_TRUNC(object->got_addr, _dl_pagesz); 435 object->got_size += object->got_addr - object->got_start; 436 object->got_size = ELF_ROUND(object->got_size, _dl_pagesz); 437 } 438 439 if (!lazy) { 440 _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ); 441 } else { 442 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 443 num = (object->Dyn.info[DT_PLTRELSZ]); 444 for (llist = object->load_list; llist != NULL; 445 llist = llist->next) { 446 if (!(llist->prot & PROT_WRITE)) 447 _dl_mprotect(llist->start, llist->size, 448 llist->prot|PROT_WRITE); 449 } 450 for (i = 0; i < num/sizeof(Elf_Rel); i++, rel++) { 451 Elf_Addr *where; 452 where = (Elf_Addr *)(rel->r_offset + object->load_offs); 453 *where += object->load_offs; 454 } 455 for (llist = object->load_list; llist != NULL; 456 llist = llist->next) { 457 if (!(llist->prot & PROT_WRITE)) 458 _dl_mprotect(llist->start, llist->size, 459 llist->prot); 460 } 461 462 } 463 /* PLT is already RO on i386, no point in mprotecting it, just GOT */ 464 if (object->got_size != 0) 465 _dl_mprotect((void*)object->got_start, object->got_size, 466 PROT_READ); 467} 468