1 /* 2 * Copyright (C) 2008, 2009 The Android Open Source Project 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 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <dlfcn.h> 30 #include <errno.h> 31 #include <fcntl.h> 32 #include <linux/auxvec.h> 33 #include <pthread.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <sys/atomics.h> 38 #include <sys/mman.h> 39 #include <sys/stat.h> 40 #include <unistd.h> 41 42 // Private C library headers. 43 #include <private/bionic_tls.h> 44 #include <private/KernelArgumentBlock.h> 45 #include <private/ScopedPthreadMutexLocker.h> 46 47 #include "linker.h" 48 #include "linker_debug.h" 49 #include "linker_environ.h" 50 #include "linker_phdr.h" 51 52 /* Assume average path length of 64 and max 8 paths */ 53 #define LDPATH_BUFSIZE 512 54 #define LDPATH_MAX 8 55 56 #define LDPRELOAD_BUFSIZE 512 57 #define LDPRELOAD_MAX 8 58 59 /* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< 60 * 61 * Do NOT use malloc() and friends or pthread_*() code here. 62 * Don't use printf() either; it's caused mysterious memory 63 * corruption in the past. 64 * The linker runs before we bring up libc and it's easiest 65 * to make sure it does not depend on any complex libc features 66 * 67 * open issues / todo: 68 * 69 * - are we doing everything we should for ARM_COPY relocations? 70 * - cleaner error reporting 71 * - after linking, set as much stuff as possible to READONLY 72 * and NOEXEC 73 */ 74 75 static bool soinfo_link_image(soinfo* si); 76 77 // We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous 78 // maps, each a single page in size. The pages are broken up into as many struct soinfo 79 // objects as will fit, and they're all threaded together on a free list. 80 #define SOINFO_PER_POOL ((PAGE_SIZE - sizeof(soinfo_pool_t*)) / sizeof(soinfo)) 81 struct soinfo_pool_t { 82 soinfo_pool_t* next; 83 soinfo info[SOINFO_PER_POOL]; 84 }; 85 static struct soinfo_pool_t* gSoInfoPools = NULL; 86 static soinfo* gSoInfoFreeList = NULL; 87 88 static soinfo* solist = &libdl_info; 89 static soinfo* sonext = &libdl_info; 90 static soinfo* somain; /* main process, always the one after libdl_info */ 91 92 static const char* const gSoPaths[] = { 93 "/vendor/lib", 94 "/system/lib", 95 NULL 96 }; 97 98 static char gLdPathsBuffer[LDPATH_BUFSIZE]; 99 static const char* gLdPaths[LDPATH_MAX + 1]; 100 101 static char gLdPreloadsBuffer[LDPRELOAD_BUFSIZE]; 102 static const char* gLdPreloadNames[LDPRELOAD_MAX + 1]; 103 104 static soinfo* gLdPreloads[LDPRELOAD_MAX + 1]; 105 106 __LIBC_HIDDEN__ int gLdDebugVerbosity; 107 108 __LIBC_HIDDEN__ abort_msg_t* gAbortMessage = NULL; // For debuggerd. 109 110 enum RelocationKind { 111 kRelocAbsolute = 0, 112 kRelocRelative, 113 kRelocCopy, 114 kRelocSymbol, 115 kRelocMax 116 }; 117 118 #if STATS 119 struct linker_stats_t { 120 int count[kRelocMax]; 121 }; 122 123 static linker_stats_t linker_stats; 124 125 static void count_relocation(RelocationKind kind) { 126 ++linker_stats.count[kind]; 127 } 128 #else 129 static void count_relocation(RelocationKind) { 130 } 131 #endif 132 133 #if COUNT_PAGES 134 static unsigned bitmask[4096]; 135 #define MARK(offset) \ 136 do { \ 137 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 138 } while(0) 139 #else 140 #define MARK(x) do {} while (0) 141 #endif 142 143 // You shouldn't try to call memory-allocating functions in the dynamic linker. 144 // Guard against the most obvious ones. 145 #define DISALLOW_ALLOCATION(return_type, name, ...) \ 146 return_type name __VA_ARGS__ \ 147 { \ 148 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 149 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 150 write(2, msg, strlen(msg)); \ 151 abort(); \ 152 } 153 #define UNUSED __attribute__((unused)) 154 DISALLOW_ALLOCATION(void*, malloc, (size_t u UNUSED)); 155 DISALLOW_ALLOCATION(void, free, (void* u UNUSED)); 156 DISALLOW_ALLOCATION(void*, realloc, (void* u1 UNUSED, size_t u2 UNUSED)); 157 DISALLOW_ALLOCATION(void*, calloc, (size_t u1 UNUSED, size_t u2 UNUSED)); 158 159 static char tmp_err_buf[768]; 160 static char __linker_dl_err_buf[768]; 161 162 char* linker_get_error_buffer() { 163 return &__linker_dl_err_buf[0]; 164 } 165 166 size_t linker_get_error_buffer_size() { 167 return sizeof(__linker_dl_err_buf); 168 } 169 170 /* 171 * This function is an empty stub where GDB locates a breakpoint to get notified 172 * about linker activity. 173 */ 174 extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 175 176 static r_debug _r_debug = {1, NULL, &rtld_db_dlactivity, RT_CONSISTENT, 0}; 177 static link_map_t* r_debug_tail = 0; 178 179 static pthread_mutex_t gDebugMutex = PTHREAD_MUTEX_INITIALIZER; 180 181 static void insert_soinfo_into_debug_map(soinfo * info) { 182 // Copy the necessary fields into the debug structure. 183 link_map_t* map = &(info->link_map); 184 map->l_addr = info->base; 185 map->l_name = (char*) info->name; 186 map->l_ld = (uintptr_t)info->dynamic; 187 188 /* Stick the new library at the end of the list. 189 * gdb tends to care more about libc than it does 190 * about leaf libraries, and ordering it this way 191 * reduces the back-and-forth over the wire. 192 */ 193 if (r_debug_tail) { 194 r_debug_tail->l_next = map; 195 map->l_prev = r_debug_tail; 196 map->l_next = 0; 197 } else { 198 _r_debug.r_map = map; 199 map->l_prev = 0; 200 map->l_next = 0; 201 } 202 r_debug_tail = map; 203 } 204 205 static void remove_soinfo_from_debug_map(soinfo* info) { 206 link_map_t* map = &(info->link_map); 207 208 if (r_debug_tail == map) { 209 r_debug_tail = map->l_prev; 210 } 211 212 if (map->l_prev) { 213 map->l_prev->l_next = map->l_next; 214 } 215 if (map->l_next) { 216 map->l_next->l_prev = map->l_prev; 217 } 218 } 219 220 static void notify_gdb_of_load(soinfo* info) { 221 if (info->flags & FLAG_EXE) { 222 // GDB already knows about the main executable 223 return; 224 } 225 226 ScopedPthreadMutexLocker locker(&gDebugMutex); 227 228 _r_debug.r_state = RT_ADD; 229 rtld_db_dlactivity(); 230 231 insert_soinfo_into_debug_map(info); 232 233 _r_debug.r_state = RT_CONSISTENT; 234 rtld_db_dlactivity(); 235 } 236 237 static void notify_gdb_of_unload(soinfo* info) { 238 if (info->flags & FLAG_EXE) { 239 // GDB already knows about the main executable 240 return; 241 } 242 243 ScopedPthreadMutexLocker locker(&gDebugMutex); 244 245 _r_debug.r_state = RT_DELETE; 246 rtld_db_dlactivity(); 247 248 remove_soinfo_from_debug_map(info); 249 250 _r_debug.r_state = RT_CONSISTENT; 251 rtld_db_dlactivity(); 252 } 253 254 void notify_gdb_of_libraries() { 255 _r_debug.r_state = RT_ADD; 256 rtld_db_dlactivity(); 257 _r_debug.r_state = RT_CONSISTENT; 258 rtld_db_dlactivity(); 259 } 260 261 static bool ensure_free_list_non_empty() { 262 if (gSoInfoFreeList != NULL) { 263 return true; 264 } 265 266 // Allocate a new pool. 267 soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool), 268 PROT_READ|PROT_WRITE, 269 MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); 270 if (pool == MAP_FAILED) { 271 return false; 272 } 273 274 // Add the pool to our list of pools. 275 pool->next = gSoInfoPools; 276 gSoInfoPools = pool; 277 278 // Chain the entries in the new pool onto the free list. 279 gSoInfoFreeList = &pool->info[0]; 280 soinfo* next = NULL; 281 for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) { 282 pool->info[i].next = next; 283 next = &pool->info[i]; 284 } 285 286 return true; 287 } 288 289 static void set_soinfo_pool_protection(int protection) { 290 for (soinfo_pool_t* p = gSoInfoPools; p != NULL; p = p->next) { 291 if (mprotect(p, sizeof(*p), protection) == -1) { 292 abort(); // Can't happen. 293 } 294 } 295 } 296 297 static soinfo* soinfo_alloc(const char* name) { 298 if (strlen(name) >= SOINFO_NAME_LEN) { 299 DL_ERR("library name \"%s\" too long", name); 300 return NULL; 301 } 302 303 if (!ensure_free_list_non_empty()) { 304 DL_ERR("out of memory when loading \"%s\"", name); 305 return NULL; 306 } 307 308 // Take the head element off the free list. 309 soinfo* si = gSoInfoFreeList; 310 gSoInfoFreeList = gSoInfoFreeList->next; 311 312 // Initialize the new element. 313 memset(si, 0, sizeof(soinfo)); 314 strlcpy(si->name, name, sizeof(si->name)); 315 sonext->next = si; 316 sonext = si; 317 318 TRACE("name %s: allocated soinfo @ %p", name, si); 319 return si; 320 } 321 322 static void soinfo_free(soinfo* si) 323 { 324 if (si == NULL) { 325 return; 326 } 327 328 soinfo *prev = NULL, *trav; 329 330 TRACE("name %s: freeing soinfo @ %p", si->name, si); 331 332 for (trav = solist; trav != NULL; trav = trav->next) { 333 if (trav == si) 334 break; 335 prev = trav; 336 } 337 if (trav == NULL) { 338 /* si was not in solist */ 339 DL_ERR("name \"%s\" is not in solist!", si->name); 340 return; 341 } 342 343 /* prev will never be NULL, because the first entry in solist is 344 always the static libdl_info. 345 */ 346 prev->next = si->next; 347 if (si == sonext) { 348 sonext = prev; 349 } 350 si->next = gSoInfoFreeList; 351 gSoInfoFreeList = si; 352 } 353 354 355 static void parse_path(const char* path, const char* delimiters, 356 const char** array, char* buf, size_t buf_size, size_t max_count) { 357 if (path == NULL) { 358 return; 359 } 360 361 size_t len = strlcpy(buf, path, buf_size); 362 363 size_t i = 0; 364 char* buf_p = buf; 365 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 366 if (*array[i] != '\0') { 367 ++i; 368 } 369 } 370 371 // Forget the last path if we had to truncate; this occurs if the 2nd to 372 // last char isn't '\0' (i.e. wasn't originally a delimiter). 373 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 374 array[i - 1] = NULL; 375 } else { 376 array[i] = NULL; 377 } 378 } 379 380 static void parse_LD_LIBRARY_PATH(const char* path) { 381 parse_path(path, ":", gLdPaths, 382 gLdPathsBuffer, sizeof(gLdPathsBuffer), LDPATH_MAX); 383 } 384 385 static void parse_LD_PRELOAD(const char* path) { 386 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 387 parse_path(path, " :", gLdPreloadNames, 388 gLdPreloadsBuffer, sizeof(gLdPreloadsBuffer), LDPRELOAD_MAX); 389 } 390 391 #ifdef ANDROID_ARM_LINKER 392 393 /* For a given PC, find the .so that it belongs to. 394 * Returns the base address of the .ARM.exidx section 395 * for that .so, and the number of 8-byte entries 396 * in that section (via *pcount). 397 * 398 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 399 * 400 * This function is exposed via dlfcn.cpp and libdl.so. 401 */ 402 _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount) 403 { 404 soinfo *si; 405 unsigned addr = (unsigned)pc; 406 407 for (si = solist; si != 0; si = si->next){ 408 if ((addr >= si->base) && (addr < (si->base + si->size))) { 409 *pcount = si->ARM_exidx_count; 410 return (_Unwind_Ptr)si->ARM_exidx; 411 } 412 } 413 *pcount = 0; 414 return NULL; 415 } 416 417 #elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER) 418 419 /* Here, we only have to provide a callback to iterate across all the 420 * loaded libraries. gcc_eh does the rest. */ 421 int 422 dl_iterate_phdr(int (*cb)(dl_phdr_info *info, size_t size, void *data), 423 void *data) 424 { 425 int rv = 0; 426 for (soinfo* si = solist; si != NULL; si = si->next) { 427 dl_phdr_info dl_info; 428 dl_info.dlpi_addr = si->link_map.l_addr; 429 dl_info.dlpi_name = si->link_map.l_name; 430 dl_info.dlpi_phdr = si->phdr; 431 dl_info.dlpi_phnum = si->phnum; 432 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 433 if (rv != 0) { 434 break; 435 } 436 } 437 return rv; 438 } 439 440 #endif 441 442 static Elf32_Sym* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 443 Elf32_Sym* s; 444 Elf32_Sym* symtab = si->symtab; 445 const char* strtab = si->strtab; 446 unsigned n; 447 448 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@0x%08x %08x %d", 449 name, si->name, si->base, hash, hash % si->nbucket); 450 n = hash % si->nbucket; 451 452 for (n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 453 s = symtab + n; 454 if (strcmp(strtab + s->st_name, name)) continue; 455 456 /* only concern ourselves with global and weak symbol definitions */ 457 switch(ELF32_ST_BIND(s->st_info)){ 458 case STB_GLOBAL: 459 case STB_WEAK: 460 if (s->st_shndx == SHN_UNDEF) { 461 continue; 462 } 463 464 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%08x) %d", 465 name, si->name, s->st_value, s->st_size); 466 return s; 467 } 468 } 469 470 return NULL; 471 } 472 473 static unsigned elfhash(const char* _name) { 474 const unsigned char* name = (const unsigned char*) _name; 475 unsigned h = 0, g; 476 477 while(*name) { 478 h = (h << 4) + *name++; 479 g = h & 0xf0000000; 480 h ^= g; 481 h ^= g >> 24; 482 } 483 return h; 484 } 485 486 static Elf32_Sym* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 487 unsigned elf_hash = elfhash(name); 488 Elf32_Sym* s = NULL; 489 490 if (si != NULL && somain != NULL) { 491 492 /* 493 * Local scope is executable scope. Just start looking into it right away 494 * for the shortcut. 495 */ 496 497 if (si == somain) { 498 s = soinfo_elf_lookup(si, elf_hash, name); 499 if (s != NULL) { 500 *lsi = si; 501 goto done; 502 } 503 } else { 504 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 505 506 /* 507 * If this object was built with symbolic relocations disabled, the 508 * first place to look to resolve external references is the main 509 * executable. 510 */ 511 512 if (!si->has_DT_SYMBOLIC) { 513 DEBUG("%s: looking up %s in executable %s", 514 si->name, name, somain->name); 515 s = soinfo_elf_lookup(somain, elf_hash, name); 516 if (s != NULL) { 517 *lsi = somain; 518 goto done; 519 } 520 } 521 522 /* Look for symbols in the local scope (the object who is 523 * searching). This happens with C++ templates on i386 for some 524 * reason. 525 * 526 * Notes on weak symbols: 527 * The ELF specs are ambiguous about treatment of weak definitions in 528 * dynamic linking. Some systems return the first definition found 529 * and some the first non-weak definition. This is system dependent. 530 * Here we return the first definition found for simplicity. */ 531 532 s = soinfo_elf_lookup(si, elf_hash, name); 533 if (s != NULL) { 534 *lsi = si; 535 goto done; 536 } 537 538 /* 539 * If this object was built with -Bsymbolic and symbol is not found 540 * in the local scope, try to find the symbol in the main executable. 541 */ 542 543 if (si->has_DT_SYMBOLIC) { 544 DEBUG("%s: looking up %s in executable %s after local scope", 545 si->name, name, somain->name); 546 s = soinfo_elf_lookup(somain, elf_hash, name); 547 if (s != NULL) { 548 *lsi = somain; 549 goto done; 550 } 551 } 552 } 553 } 554 555 /* Next, look for it in the preloads list */ 556 for (int i = 0; gLdPreloads[i] != NULL; i++) { 557 s = soinfo_elf_lookup(gLdPreloads[i], elf_hash, name); 558 if (s != NULL) { 559 *lsi = gLdPreloads[i]; 560 goto done; 561 } 562 } 563 564 for (int i = 0; needed[i] != NULL; i++) { 565 DEBUG("%s: looking up %s in %s", 566 si->name, name, needed[i]->name); 567 s = soinfo_elf_lookup(needed[i], elf_hash, name); 568 if (s != NULL) { 569 *lsi = needed[i]; 570 goto done; 571 } 572 } 573 574 done: 575 if (s != NULL) { 576 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = 0x%08x, " 577 "found in %s, base = 0x%08x, load bias = 0x%08x", 578 si->name, name, s->st_value, 579 (*lsi)->name, (*lsi)->base, (*lsi)->load_bias); 580 return s; 581 } 582 583 return NULL; 584 } 585 586 /* This is used by dlsym(3). It performs symbol lookup only within the 587 specified soinfo object and not in any of its dependencies. 588 589 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 590 that it should do a breadth first search through the dependency 591 tree. This agrees with the ELF spec (aka System V Application 592 Binary Interface) where in Chapter 5 it discuss resolving "Shared 593 Object Dependencies" in breadth first search order. 594 */ 595 Elf32_Sym* dlsym_handle_lookup(soinfo* si, const char* name) 596 { 597 return soinfo_elf_lookup(si, elfhash(name), name); 598 } 599 600 /* This is used by dlsym(3) to performs a global symbol lookup. If the 601 start value is null (for RTLD_DEFAULT), the search starts at the 602 beginning of the global solist. Otherwise the search starts at the 603 specified soinfo (for RTLD_NEXT). 604 */ 605 Elf32_Sym* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 606 unsigned elf_hash = elfhash(name); 607 608 if (start == NULL) { 609 start = solist; 610 } 611 612 Elf32_Sym* s = NULL; 613 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 614 s = soinfo_elf_lookup(si, elf_hash, name); 615 if (s != NULL) { 616 *found = si; 617 break; 618 } 619 } 620 621 if (s != NULL) { 622 TRACE_TYPE(LOOKUP, "%s s->st_value = 0x%08x, found->base = 0x%08x", 623 name, s->st_value, (*found)->base); 624 } 625 626 return s; 627 } 628 629 soinfo* find_containing_library(const void* p) { 630 Elf32_Addr address = reinterpret_cast<Elf32_Addr>(p); 631 for (soinfo* si = solist; si != NULL; si = si->next) { 632 if (address >= si->base && address - si->base < si->size) { 633 return si; 634 } 635 } 636 return NULL; 637 } 638 639 Elf32_Sym* dladdr_find_symbol(soinfo* si, const void* addr) { 640 Elf32_Addr soaddr = reinterpret_cast<Elf32_Addr>(addr) - si->base; 641 642 // Search the library's symbol table for any defined symbol which 643 // contains this address. 644 for (size_t i = 0; i < si->nchain; ++i) { 645 Elf32_Sym* sym = &si->symtab[i]; 646 if (sym->st_shndx != SHN_UNDEF && 647 soaddr >= sym->st_value && 648 soaddr < sym->st_value + sym->st_size) { 649 return sym; 650 } 651 } 652 653 return NULL; 654 } 655 656 #if 0 657 static void dump(soinfo* si) 658 { 659 Elf32_Sym* s = si->symtab; 660 for (unsigned n = 0; n < si->nchain; n++) { 661 TRACE("%04d> %08x: %02x %04x %08x %08x %s", n, s, 662 s->st_info, s->st_shndx, s->st_value, s->st_size, 663 si->strtab + s->st_name); 664 s++; 665 } 666 } 667 #endif 668 669 static int open_library_on_path(const char* name, const char* const paths[]) { 670 char buf[512]; 671 for (size_t i = 0; paths[i] != NULL; ++i) { 672 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 673 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 674 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 675 continue; 676 } 677 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 678 if (fd != -1) { 679 return fd; 680 } 681 } 682 return -1; 683 } 684 685 static int open_library(const char* name) { 686 TRACE("[ opening %s ]", name); 687 688 // If the name contains a slash, we should attempt to open it directly and not search the paths. 689 if (strchr(name, '/') != NULL) { 690 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 691 if (fd != -1) { 692 return fd; 693 } 694 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 695 } 696 697 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 698 int fd = open_library_on_path(name, gLdPaths); 699 if (fd == -1) { 700 fd = open_library_on_path(name, gSoPaths); 701 } 702 return fd; 703 } 704 705 static soinfo* load_library(const char* name) { 706 // Open the file. 707 int fd = open_library(name); 708 if (fd == -1) { 709 DL_ERR("library \"%s\" not found", name); 710 return NULL; 711 } 712 713 // Read the ELF header and load the segments. 714 ElfReader elf_reader(name, fd); 715 if (!elf_reader.Load()) { 716 return NULL; 717 } 718 719 const char* bname = strrchr(name, '/'); 720 soinfo* si = soinfo_alloc(bname ? bname + 1 : name); 721 if (si == NULL) { 722 return NULL; 723 } 724 si->base = elf_reader.load_start(); 725 si->size = elf_reader.load_size(); 726 si->load_bias = elf_reader.load_bias(); 727 si->flags = 0; 728 si->entry = 0; 729 si->dynamic = NULL; 730 si->phnum = elf_reader.phdr_count(); 731 si->phdr = elf_reader.loaded_phdr(); 732 return si; 733 } 734 735 static soinfo *find_loaded_library(const char *name) 736 { 737 soinfo *si; 738 const char *bname; 739 740 // TODO: don't use basename only for determining libraries 741 // http://code.google.com/p/android/issues/detail?id=6670 742 743 bname = strrchr(name, '/'); 744 bname = bname ? bname + 1 : name; 745 746 for (si = solist; si != NULL; si = si->next) { 747 if (!strcmp(bname, si->name)) { 748 return si; 749 } 750 } 751 return NULL; 752 } 753 754 static soinfo* find_library_internal(const char* name) { 755 if (name == NULL) { 756 return somain; 757 } 758 759 soinfo* si = find_loaded_library(name); 760 if (si != NULL) { 761 if (si->flags & FLAG_LINKED) { 762 return si; 763 } 764 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 765 return NULL; 766 } 767 768 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 769 si = load_library(name); 770 if (si == NULL) { 771 return NULL; 772 } 773 774 // At this point we know that whatever is loaded @ base is a valid ELF 775 // shared library whose segments are properly mapped in. 776 TRACE("[ init_library base=0x%08x sz=0x%08x name='%s' ]", 777 si->base, si->size, si->name); 778 779 if (!soinfo_link_image(si)) { 780 munmap(reinterpret_cast<void*>(si->base), si->size); 781 soinfo_free(si); 782 return NULL; 783 } 784 785 return si; 786 } 787 788 static soinfo* find_library(const char* name) { 789 soinfo* si = find_library_internal(name); 790 if (si != NULL) { 791 si->ref_count++; 792 } 793 return si; 794 } 795 796 static int soinfo_unload(soinfo* si) { 797 if (si->ref_count == 1) { 798 TRACE("unloading '%s'", si->name); 799 si->CallDestructors(); 800 801 for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 802 if (d->d_tag == DT_NEEDED) { 803 const char* library_name = si->strtab + d->d_un.d_val; 804 TRACE("%s needs to unload %s", si->name, library_name); 805 soinfo_unload(find_loaded_library(library_name)); 806 } 807 } 808 809 munmap(reinterpret_cast<void*>(si->base), si->size); 810 notify_gdb_of_unload(si); 811 soinfo_free(si); 812 si->ref_count = 0; 813 } else { 814 si->ref_count--; 815 TRACE("not unloading '%s', decrementing ref_count to %d", si->name, si->ref_count); 816 } 817 return 0; 818 } 819 820 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 821 if (!get_AT_SECURE()) { 822 parse_LD_LIBRARY_PATH(ld_library_path); 823 } 824 } 825 826 soinfo* do_dlopen(const char* name, int flags) { 827 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 828 DL_ERR("invalid flags to dlopen: %x", flags); 829 return NULL; 830 } 831 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 832 soinfo* si = find_library(name); 833 if (si != NULL) { 834 si->CallConstructors(); 835 } 836 set_soinfo_pool_protection(PROT_READ); 837 return si; 838 } 839 840 int do_dlclose(soinfo* si) { 841 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 842 int result = soinfo_unload(si); 843 set_soinfo_pool_protection(PROT_READ); 844 return result; 845 } 846 847 /* TODO: don't use unsigned for addrs below. It works, but is not 848 * ideal. They should probably be either uint32_t, Elf32_Addr, or unsigned 849 * long. 850 */ 851 static int soinfo_relocate(soinfo* si, Elf32_Rel* rel, unsigned count, 852 soinfo* needed[]) 853 { 854 Elf32_Sym* symtab = si->symtab; 855 const char* strtab = si->strtab; 856 Elf32_Sym* s; 857 Elf32_Rel* start = rel; 858 soinfo* lsi; 859 860 for (size_t idx = 0; idx < count; ++idx, ++rel) { 861 unsigned type = ELF32_R_TYPE(rel->r_info); 862 unsigned sym = ELF32_R_SYM(rel->r_info); 863 Elf32_Addr reloc = static_cast<Elf32_Addr>(rel->r_offset + si->load_bias); 864 Elf32_Addr sym_addr = 0; 865 char* sym_name = NULL; 866 867 DEBUG("Processing '%s' relocation at index %d", si->name, idx); 868 if (type == 0) { // R_*_NONE 869 continue; 870 } 871 if (sym != 0) { 872 sym_name = (char *)(strtab + symtab[sym].st_name); 873 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 874 if (s == NULL) { 875 /* We only allow an undefined symbol if this is a weak 876 reference.. */ 877 s = &symtab[sym]; 878 if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { 879 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 880 return -1; 881 } 882 883 /* IHI0044C AAELF 4.5.1.1: 884 885 Libraries are not searched to resolve weak references. 886 It is not an error for a weak reference to remain 887 unsatisfied. 888 889 During linking, the value of an undefined weak reference is: 890 - Zero if the relocation type is absolute 891 - The address of the place if the relocation is pc-relative 892 - The address of nominal base address if the relocation 893 type is base-relative. 894 */ 895 896 switch (type) { 897 #if defined(ANDROID_ARM_LINKER) 898 case R_ARM_JUMP_SLOT: 899 case R_ARM_GLOB_DAT: 900 case R_ARM_ABS32: 901 case R_ARM_RELATIVE: /* Don't care. */ 902 #elif defined(ANDROID_X86_LINKER) 903 case R_386_JMP_SLOT: 904 case R_386_GLOB_DAT: 905 case R_386_32: 906 case R_386_RELATIVE: /* Dont' care. */ 907 #endif /* ANDROID_*_LINKER */ 908 /* sym_addr was initialized to be zero above or relocation 909 code below does not care about value of sym_addr. 910 No need to do anything. */ 911 break; 912 913 #if defined(ANDROID_X86_LINKER) 914 case R_386_PC32: 915 sym_addr = reloc; 916 break; 917 #endif /* ANDROID_X86_LINKER */ 918 919 #if defined(ANDROID_ARM_LINKER) 920 case R_ARM_COPY: 921 /* Fall through. Can't really copy if weak symbol is 922 not found in run-time. */ 923 #endif /* ANDROID_ARM_LINKER */ 924 default: 925 DL_ERR("unknown weak reloc type %d @ %p (%d)", 926 type, rel, (int) (rel - start)); 927 return -1; 928 } 929 } else { 930 /* We got a definition. */ 931 #if 0 932 if ((base == 0) && (si->base != 0)) { 933 /* linking from libraries to main image is bad */ 934 DL_ERR("cannot locate \"%s\"...", 935 strtab + symtab[sym].st_name); 936 return -1; 937 } 938 #endif 939 sym_addr = static_cast<Elf32_Addr>(s->st_value + lsi->load_bias); 940 } 941 count_relocation(kRelocSymbol); 942 } else { 943 s = NULL; 944 } 945 946 /* TODO: This is ugly. Split up the relocations by arch into 947 * different files. 948 */ 949 switch(type){ 950 #if defined(ANDROID_ARM_LINKER) 951 case R_ARM_JUMP_SLOT: 952 count_relocation(kRelocAbsolute); 953 MARK(rel->r_offset); 954 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 955 *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; 956 break; 957 case R_ARM_GLOB_DAT: 958 count_relocation(kRelocAbsolute); 959 MARK(rel->r_offset); 960 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 961 *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; 962 break; 963 case R_ARM_ABS32: 964 count_relocation(kRelocAbsolute); 965 MARK(rel->r_offset); 966 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 967 *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; 968 break; 969 case R_ARM_REL32: 970 count_relocation(kRelocRelative); 971 MARK(rel->r_offset); 972 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 973 reloc, sym_addr, rel->r_offset, sym_name); 974 *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr - rel->r_offset; 975 break; 976 #elif defined(ANDROID_X86_LINKER) 977 case R_386_JMP_SLOT: 978 count_relocation(kRelocAbsolute); 979 MARK(rel->r_offset); 980 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 981 *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; 982 break; 983 case R_386_GLOB_DAT: 984 count_relocation(kRelocAbsolute); 985 MARK(rel->r_offset); 986 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 987 *reinterpret_cast<Elf32_Addr*>(reloc) = sym_addr; 988 break; 989 #elif defined(ANDROID_MIPS_LINKER) 990 case R_MIPS_REL32: 991 count_relocation(kRelocAbsolute); 992 MARK(rel->r_offset); 993 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x %s", 994 reloc, sym_addr, (sym_name) ? sym_name : "*SECTIONHDR*"); 995 if (s) { 996 *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; 997 } else { 998 *reinterpret_cast<Elf32_Addr*>(reloc) += si->base; 999 } 1000 break; 1001 #endif /* ANDROID_*_LINKER */ 1002 1003 #if defined(ANDROID_ARM_LINKER) 1004 case R_ARM_RELATIVE: 1005 #elif defined(ANDROID_X86_LINKER) 1006 case R_386_RELATIVE: 1007 #endif /* ANDROID_*_LINKER */ 1008 count_relocation(kRelocRelative); 1009 MARK(rel->r_offset); 1010 if (sym) { 1011 DL_ERR("odd RELATIVE form..."); 1012 return -1; 1013 } 1014 TRACE_TYPE(RELO, "RELO RELATIVE %08x <- +%08x", reloc, si->base); 1015 *reinterpret_cast<Elf32_Addr*>(reloc) += si->base; 1016 break; 1017 1018 #if defined(ANDROID_X86_LINKER) 1019 case R_386_32: 1020 count_relocation(kRelocRelative); 1021 MARK(rel->r_offset); 1022 1023 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1024 *reinterpret_cast<Elf32_Addr*>(reloc) += sym_addr; 1025 break; 1026 1027 case R_386_PC32: 1028 count_relocation(kRelocRelative); 1029 MARK(rel->r_offset); 1030 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1031 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1032 *reinterpret_cast<Elf32_Addr*>(reloc) += (sym_addr - reloc); 1033 break; 1034 #endif /* ANDROID_X86_LINKER */ 1035 1036 #ifdef ANDROID_ARM_LINKER 1037 case R_ARM_COPY: 1038 if ((si->flags & FLAG_EXE) == 0) { 1039 /* 1040 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1041 * 1042 * Section 4.7.1.10 "Dynamic relocations" 1043 * R_ARM_COPY may only appear in executable objects where e_type is 1044 * set to ET_EXEC. 1045 * 1046 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1047 * We should explicitly disallow ET_DYN executables from having 1048 * R_ARM_COPY relocations. 1049 */ 1050 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1051 return -1; 1052 } 1053 count_relocation(kRelocCopy); 1054 MARK(rel->r_offset); 1055 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1056 if (reloc == sym_addr) { 1057 Elf32_Sym *src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1058 1059 if (src == NULL) { 1060 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1061 return -1; 1062 } 1063 if (lsi->has_DT_SYMBOLIC) { 1064 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1065 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1066 return -1; 1067 } 1068 if (s->st_size < src->st_size) { 1069 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1070 si->name, s->st_size, src->st_size); 1071 return -1; 1072 } 1073 memcpy((void*)reloc, (void*)(src->st_value + lsi->load_bias), src->st_size); 1074 } else { 1075 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1076 return -1; 1077 } 1078 break; 1079 #endif /* ANDROID_ARM_LINKER */ 1080 1081 default: 1082 DL_ERR("unknown reloc type %d @ %p (%d)", 1083 type, rel, (int) (rel - start)); 1084 return -1; 1085 } 1086 } 1087 return 0; 1088 } 1089 1090 #ifdef ANDROID_MIPS_LINKER 1091 static int mips_relocate_got(soinfo* si, soinfo* needed[]) { 1092 unsigned *got; 1093 unsigned local_gotno, gotsym, symtabno; 1094 Elf32_Sym *symtab, *sym; 1095 unsigned g; 1096 1097 got = si->plt_got; 1098 local_gotno = si->mips_local_gotno; 1099 gotsym = si->mips_gotsym; 1100 symtabno = si->mips_symtabno; 1101 symtab = si->symtab; 1102 1103 /* 1104 * got[0] is address of lazy resolver function 1105 * got[1] may be used for a GNU extension 1106 * set it to a recognizable address in case someone calls it 1107 * (should be _rtld_bind_start) 1108 * FIXME: maybe this should be in a separate routine 1109 */ 1110 1111 if ((si->flags & FLAG_LINKER) == 0) { 1112 g = 0; 1113 got[g++] = 0xdeadbeef; 1114 if (got[g] & 0x80000000) { 1115 got[g++] = 0xdeadfeed; 1116 } 1117 /* 1118 * Relocate the local GOT entries need to be relocated 1119 */ 1120 for (; g < local_gotno; g++) { 1121 got[g] += si->load_bias; 1122 } 1123 } 1124 1125 /* Now for the global GOT entries */ 1126 sym = symtab + gotsym; 1127 got = si->plt_got + local_gotno; 1128 for (g = gotsym; g < symtabno; g++, sym++, got++) { 1129 const char* sym_name; 1130 Elf32_Sym* s; 1131 soinfo* lsi; 1132 1133 /* This is an undefined reference... try to locate it */ 1134 sym_name = si->strtab + sym->st_name; 1135 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1136 if (s == NULL) { 1137 /* We only allow an undefined symbol if this is a weak 1138 reference.. */ 1139 s = &symtab[g]; 1140 if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { 1141 DL_ERR("cannot locate \"%s\"...", sym_name); 1142 return -1; 1143 } 1144 *got = 0; 1145 } 1146 else { 1147 /* FIXME: is this sufficient? 1148 * For reference see NetBSD link loader 1149 * http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ld.elf_so/arch/mips/mips_reloc.c?rev=1.53&content-type=text/x-cvsweb-markup 1150 */ 1151 *got = lsi->load_bias + s->st_value; 1152 } 1153 } 1154 return 0; 1155 } 1156 #endif 1157 1158 void soinfo::CallArray(const char* array_name UNUSED, linker_function_t* functions, size_t count, bool reverse) { 1159 if (functions == NULL) { 1160 return; 1161 } 1162 1163 TRACE("[ Calling %s (size %d) @ %p for '%s' ]", array_name, count, functions, name); 1164 1165 int begin = reverse ? (count - 1) : 0; 1166 int end = reverse ? -1 : count; 1167 int step = reverse ? -1 : 1; 1168 1169 for (int i = begin; i != end; i += step) { 1170 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1171 CallFunction("function", functions[i]); 1172 } 1173 1174 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1175 } 1176 1177 void soinfo::CallFunction(const char* function_name UNUSED, linker_function_t function) { 1178 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1179 return; 1180 } 1181 1182 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1183 function(); 1184 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1185 1186 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1187 // are still writable. This happens with our debug malloc (see http://b/7941716). 1188 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 1189 } 1190 1191 void soinfo::CallPreInitConstructors() { 1192 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1193 // but ignored in a shared library. 1194 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1195 } 1196 1197 void soinfo::CallConstructors() { 1198 if (constructors_called) { 1199 return; 1200 } 1201 1202 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1203 // protect against recursive constructor calls. One simple example of constructor recursion 1204 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1205 // 1. The program depends on libc, so libc's constructor is called here. 1206 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1207 // 3. dlopen() calls the constructors on the newly created 1208 // soinfo for libc_malloc_debug_leak.so. 1209 // 4. The debug .so depends on libc, so CallConstructors is 1210 // called again with the libc soinfo. If it doesn't trigger the early- 1211 // out above, the libc constructor will be called again (recursively!). 1212 constructors_called = true; 1213 1214 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1215 // The GNU dynamic linker silently ignores these, but we warn the developer. 1216 PRINT("\"%s\": ignoring %d-entry DT_PREINIT_ARRAY in shared library!", 1217 name, preinit_array_count); 1218 } 1219 1220 if (dynamic != NULL) { 1221 for (Elf32_Dyn* d = dynamic; d->d_tag != DT_NULL; ++d) { 1222 if (d->d_tag == DT_NEEDED) { 1223 const char* library_name = strtab + d->d_un.d_val; 1224 TRACE("\"%s\": calling constructors in DT_NEEDED \"%s\"", name, library_name); 1225 find_loaded_library(library_name)->CallConstructors(); 1226 } 1227 } 1228 } 1229 1230 TRACE("\"%s\": calling constructors", name); 1231 1232 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1233 CallFunction("DT_INIT", init_func); 1234 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1235 } 1236 1237 void soinfo::CallDestructors() { 1238 TRACE("\"%s\": calling destructors", name); 1239 1240 // DT_FINI_ARRAY must be parsed in reverse order. 1241 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1242 1243 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1244 CallFunction("DT_FINI", fini_func); 1245 } 1246 1247 /* Force any of the closed stdin, stdout and stderr to be associated with 1248 /dev/null. */ 1249 static int nullify_closed_stdio() { 1250 int dev_null, i, status; 1251 int return_value = 0; 1252 1253 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1254 if (dev_null < 0) { 1255 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1256 return -1; 1257 } 1258 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1259 1260 /* If any of the stdio file descriptors is valid and not associated 1261 with /dev/null, dup /dev/null to it. */ 1262 for (i = 0; i < 3; i++) { 1263 /* If it is /dev/null already, we are done. */ 1264 if (i == dev_null) { 1265 continue; 1266 } 1267 1268 TRACE("[ Nullifying stdio file descriptor %d]", i); 1269 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1270 1271 /* If file is opened, we are good. */ 1272 if (status != -1) { 1273 continue; 1274 } 1275 1276 /* The only error we allow is that the file descriptor does not 1277 exist, in which case we dup /dev/null to it. */ 1278 if (errno != EBADF) { 1279 DL_ERR("fcntl failed: %s", strerror(errno)); 1280 return_value = -1; 1281 continue; 1282 } 1283 1284 /* Try dupping /dev/null to this stdio file descriptor and 1285 repeat if there is a signal. Note that any errors in closing 1286 the stdio descriptor are lost. */ 1287 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1288 if (status < 0) { 1289 DL_ERR("dup2 failed: %s", strerror(errno)); 1290 return_value = -1; 1291 continue; 1292 } 1293 } 1294 1295 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1296 if (dev_null > 2) { 1297 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1298 status = TEMP_FAILURE_RETRY(close(dev_null)); 1299 if (status == -1) { 1300 DL_ERR("close failed: %s", strerror(errno)); 1301 return_value = -1; 1302 } 1303 } 1304 1305 return return_value; 1306 } 1307 1308 static bool soinfo_link_image(soinfo* si) { 1309 /* "base" might wrap around UINT32_MAX. */ 1310 Elf32_Addr base = si->load_bias; 1311 const Elf32_Phdr *phdr = si->phdr; 1312 int phnum = si->phnum; 1313 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1314 1315 /* We can't debug anything until the linker is relocated */ 1316 if (!relocating_linker) { 1317 INFO("[ linking %s ]", si->name); 1318 DEBUG("si->base = 0x%08x si->flags = 0x%08x", si->base, si->flags); 1319 } 1320 1321 /* Extract dynamic section */ 1322 size_t dynamic_count; 1323 Elf32_Word dynamic_flags; 1324 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1325 &dynamic_count, &dynamic_flags); 1326 if (si->dynamic == NULL) { 1327 if (!relocating_linker) { 1328 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1329 } 1330 return false; 1331 } else { 1332 if (!relocating_linker) { 1333 DEBUG("dynamic = %p", si->dynamic); 1334 } 1335 } 1336 1337 #ifdef ANDROID_ARM_LINKER 1338 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1339 &si->ARM_exidx, &si->ARM_exidx_count); 1340 #endif 1341 1342 // Extract useful information from dynamic section. 1343 uint32_t needed_count = 0; 1344 for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1345 DEBUG("d = %p, d[0](tag) = 0x%08x d[1](val) = 0x%08x", d, d->d_tag, d->d_un.d_val); 1346 switch(d->d_tag){ 1347 case DT_HASH: 1348 si->nbucket = ((unsigned *) (base + d->d_un.d_ptr))[0]; 1349 si->nchain = ((unsigned *) (base + d->d_un.d_ptr))[1]; 1350 si->bucket = (unsigned *) (base + d->d_un.d_ptr + 8); 1351 si->chain = (unsigned *) (base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1352 break; 1353 case DT_STRTAB: 1354 si->strtab = (const char *) (base + d->d_un.d_ptr); 1355 break; 1356 case DT_SYMTAB: 1357 si->symtab = (Elf32_Sym *) (base + d->d_un.d_ptr); 1358 break; 1359 case DT_PLTREL: 1360 if (d->d_un.d_val != DT_REL) { 1361 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1362 return false; 1363 } 1364 break; 1365 case DT_JMPREL: 1366 si->plt_rel = (Elf32_Rel*) (base + d->d_un.d_ptr); 1367 break; 1368 case DT_PLTRELSZ: 1369 si->plt_rel_count = d->d_un.d_val / sizeof(Elf32_Rel); 1370 break; 1371 case DT_REL: 1372 si->rel = (Elf32_Rel*) (base + d->d_un.d_ptr); 1373 break; 1374 case DT_RELSZ: 1375 si->rel_count = d->d_un.d_val / sizeof(Elf32_Rel); 1376 break; 1377 case DT_PLTGOT: 1378 /* Save this in case we decide to do lazy binding. We don't yet. */ 1379 si->plt_got = (unsigned *)(base + d->d_un.d_ptr); 1380 break; 1381 case DT_DEBUG: 1382 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1383 // if the dynamic table is writable 1384 if ((dynamic_flags & PF_W) != 0) { 1385 d->d_un.d_val = (int) &_r_debug; 1386 } 1387 break; 1388 case DT_RELA: 1389 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1390 return false; 1391 case DT_INIT: 1392 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1393 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1394 break; 1395 case DT_FINI: 1396 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1397 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1398 break; 1399 case DT_INIT_ARRAY: 1400 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1401 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1402 break; 1403 case DT_INIT_ARRAYSZ: 1404 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); 1405 break; 1406 case DT_FINI_ARRAY: 1407 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1408 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1409 break; 1410 case DT_FINI_ARRAYSZ: 1411 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); 1412 break; 1413 case DT_PREINIT_ARRAY: 1414 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1415 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1416 break; 1417 case DT_PREINIT_ARRAYSZ: 1418 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(Elf32_Addr); 1419 break; 1420 case DT_TEXTREL: 1421 si->has_text_relocations = true; 1422 break; 1423 case DT_SYMBOLIC: 1424 si->has_DT_SYMBOLIC = true; 1425 break; 1426 case DT_NEEDED: 1427 ++needed_count; 1428 break; 1429 #if defined DT_FLAGS 1430 // TODO: why is DT_FLAGS not defined? 1431 case DT_FLAGS: 1432 if (d->d_un.d_val & DF_TEXTREL) { 1433 si->has_text_relocations = true; 1434 } 1435 if (d->d_un.d_val & DF_SYMBOLIC) { 1436 si->has_DT_SYMBOLIC = true; 1437 } 1438 break; 1439 #endif 1440 #if defined(ANDROID_MIPS_LINKER) 1441 case DT_STRSZ: 1442 case DT_SYMENT: 1443 case DT_RELENT: 1444 break; 1445 case DT_MIPS_RLD_MAP: 1446 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1447 { 1448 r_debug** dp = (r_debug**) d->d_un.d_ptr; 1449 *dp = &_r_debug; 1450 } 1451 break; 1452 case DT_MIPS_RLD_VERSION: 1453 case DT_MIPS_FLAGS: 1454 case DT_MIPS_BASE_ADDRESS: 1455 case DT_MIPS_UNREFEXTNO: 1456 break; 1457 1458 case DT_MIPS_SYMTABNO: 1459 si->mips_symtabno = d->d_un.d_val; 1460 break; 1461 1462 case DT_MIPS_LOCAL_GOTNO: 1463 si->mips_local_gotno = d->d_un.d_val; 1464 break; 1465 1466 case DT_MIPS_GOTSYM: 1467 si->mips_gotsym = d->d_un.d_val; 1468 break; 1469 1470 default: 1471 DEBUG("Unused DT entry: type 0x%08x arg 0x%08x", d->d_tag, d->d_un.d_val); 1472 break; 1473 #endif 1474 } 1475 } 1476 1477 DEBUG("si->base = 0x%08x, si->strtab = %p, si->symtab = %p", 1478 si->base, si->strtab, si->symtab); 1479 1480 // Sanity checks. 1481 if (relocating_linker && needed_count != 0) { 1482 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1483 return false; 1484 } 1485 if (si->nbucket == 0) { 1486 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1487 return false; 1488 } 1489 if (si->strtab == 0) { 1490 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1491 return false; 1492 } 1493 if (si->symtab == 0) { 1494 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1495 return false; 1496 } 1497 1498 /* if this is the main executable, then load all of the preloads now */ 1499 if (si->flags & FLAG_EXE) { 1500 memset(gLdPreloads, 0, sizeof(gLdPreloads)); 1501 for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) { 1502 soinfo* lsi = find_library(gLdPreloadNames[i]); 1503 if (lsi == NULL) { 1504 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1505 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1506 gLdPreloadNames[i], si->name, tmp_err_buf); 1507 return false; 1508 } 1509 gLdPreloads[i] = lsi; 1510 } 1511 } 1512 1513 soinfo** needed = (soinfo**) alloca((1 + needed_count) * sizeof(soinfo*)); 1514 soinfo** pneeded = needed; 1515 1516 for (Elf32_Dyn* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1517 if (d->d_tag == DT_NEEDED) { 1518 const char* library_name = si->strtab + d->d_un.d_val; 1519 DEBUG("%s needs %s", si->name, library_name); 1520 soinfo* lsi = find_library(library_name); 1521 if (lsi == NULL) { 1522 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1523 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1524 library_name, si->name, tmp_err_buf); 1525 return false; 1526 } 1527 *pneeded++ = lsi; 1528 } 1529 } 1530 *pneeded = NULL; 1531 1532 if (si->has_text_relocations) { 1533 /* Unprotect the segments, i.e. make them writable, to allow 1534 * text relocations to work properly. We will later call 1535 * phdr_table_protect_segments() after all of them are applied 1536 * and all constructors are run. 1537 */ 1538 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1539 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1540 si->name, strerror(errno)); 1541 return false; 1542 } 1543 } 1544 1545 if (si->plt_rel != NULL) { 1546 DEBUG("[ relocating %s plt ]", si->name ); 1547 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1548 return false; 1549 } 1550 } 1551 if (si->rel != NULL) { 1552 DEBUG("[ relocating %s ]", si->name ); 1553 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1554 return false; 1555 } 1556 } 1557 1558 #ifdef ANDROID_MIPS_LINKER 1559 if (mips_relocate_got(si, needed)) { 1560 return false; 1561 } 1562 #endif 1563 1564 si->flags |= FLAG_LINKED; 1565 DEBUG("[ finished linking %s ]", si->name); 1566 1567 if (si->has_text_relocations) { 1568 /* All relocations are done, we can protect our segments back to 1569 * read-only. */ 1570 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1571 DL_ERR("can't protect segments for \"%s\": %s", 1572 si->name, strerror(errno)); 1573 return false; 1574 } 1575 } 1576 1577 /* We can also turn on GNU RELRO protection */ 1578 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1579 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1580 si->name, strerror(errno)); 1581 return false; 1582 } 1583 1584 // If this is a setuid/setgid program, close the security hole described in 1585 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 1586 if (get_AT_SECURE()) { 1587 nullify_closed_stdio(); 1588 } 1589 notify_gdb_of_load(si); 1590 return true; 1591 } 1592 1593 /* 1594 * This code is called after the linker has linked itself and 1595 * fixed it's own GOT. It is safe to make references to externs 1596 * and other non-local data at this point. 1597 */ 1598 static Elf32_Addr __linker_init_post_relocation(KernelArgumentBlock& args, Elf32_Addr linker_base) { 1599 /* NOTE: we store the args pointer on a special location 1600 * of the temporary TLS area in order to pass it to 1601 * the C Library's runtime initializer. 1602 * 1603 * The initializer must clear the slot and reset the TLS 1604 * to point to a different location to ensure that no other 1605 * shared library constructor can access it. 1606 */ 1607 __libc_init_tls(args); 1608 1609 #if TIMING 1610 struct timeval t0, t1; 1611 gettimeofday(&t0, 0); 1612 #endif 1613 1614 // Initialize environment functions, and get to the ELF aux vectors table. 1615 linker_env_init(args); 1616 1617 debuggerd_init(); 1618 1619 // Get a few environment variables. 1620 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 1621 if (LD_DEBUG != NULL) { 1622 gLdDebugVerbosity = atoi(LD_DEBUG); 1623 } 1624 1625 // Normally, these are cleaned by linker_env_init, but the test 1626 // doesn't cost us anything. 1627 const char* ldpath_env = NULL; 1628 const char* ldpreload_env = NULL; 1629 if (!get_AT_SECURE()) { 1630 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 1631 ldpreload_env = linker_env_get("LD_PRELOAD"); 1632 } 1633 1634 INFO("[ android linker & debugger ]"); 1635 1636 soinfo* si = soinfo_alloc(args.argv[0]); 1637 if (si == NULL) { 1638 exit(EXIT_FAILURE); 1639 } 1640 1641 /* bootstrap the link map, the main exe always needs to be first */ 1642 si->flags |= FLAG_EXE; 1643 link_map_t* map = &(si->link_map); 1644 1645 map->l_addr = 0; 1646 map->l_name = args.argv[0]; 1647 map->l_prev = NULL; 1648 map->l_next = NULL; 1649 1650 _r_debug.r_map = map; 1651 r_debug_tail = map; 1652 1653 /* gdb expects the linker to be in the debug shared object list. 1654 * Without this, gdb has trouble locating the linker's ".text" 1655 * and ".plt" sections. Gdb could also potentially use this to 1656 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1657 * Don't use soinfo_alloc(), because the linker shouldn't 1658 * be on the soinfo list. 1659 */ 1660 { 1661 static soinfo linker_soinfo; 1662 strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name)); 1663 linker_soinfo.flags = 0; 1664 linker_soinfo.base = linker_base; 1665 1666 /* 1667 * Set the dynamic field in the link map otherwise gdb will complain with 1668 * the following: 1669 * warning: .dynamic section for "/system/bin/linker" is not at the 1670 * expected address (wrong library or version mismatch?) 1671 */ 1672 Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_base; 1673 Elf32_Phdr *phdr = (Elf32_Phdr*)((unsigned char*) linker_base + elf_hdr->e_phoff); 1674 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 1675 &linker_soinfo.dynamic, NULL, NULL); 1676 insert_soinfo_into_debug_map(&linker_soinfo); 1677 } 1678 1679 // Extract information passed from the kernel. 1680 si->phdr = reinterpret_cast<Elf32_Phdr*>(args.getauxval(AT_PHDR)); 1681 si->phnum = args.getauxval(AT_PHNUM); 1682 si->entry = args.getauxval(AT_ENTRY); 1683 1684 /* Compute the value of si->base. We can't rely on the fact that 1685 * the first entry is the PHDR because this will not be true 1686 * for certain executables (e.g. some in the NDK unit test suite) 1687 */ 1688 si->base = 0; 1689 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1690 si->load_bias = 0; 1691 for (size_t i = 0; i < si->phnum; ++i) { 1692 if (si->phdr[i].p_type == PT_PHDR) { 1693 si->load_bias = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_vaddr; 1694 si->base = reinterpret_cast<Elf32_Addr>(si->phdr) - si->phdr[i].p_offset; 1695 break; 1696 } 1697 } 1698 si->dynamic = NULL; 1699 si->ref_count = 1; 1700 1701 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 1702 parse_LD_LIBRARY_PATH(ldpath_env); 1703 parse_LD_PRELOAD(ldpreload_env); 1704 1705 somain = si; 1706 1707 if (!soinfo_link_image(si)) { 1708 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 1709 exit(EXIT_FAILURE); 1710 } 1711 1712 si->CallPreInitConstructors(); 1713 1714 for (size_t i = 0; gLdPreloads[i] != NULL; ++i) { 1715 gLdPreloads[i]->CallConstructors(); 1716 } 1717 1718 /* After the link_image, the si->load_bias is initialized. 1719 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 1720 * We need to update this value for so exe here. So Unwind_Backtrace 1721 * for some arch like x86 could work correctly within so exe. 1722 */ 1723 map->l_addr = si->load_bias; 1724 si->CallConstructors(); 1725 1726 #if TIMING 1727 gettimeofday(&t1,NULL); 1728 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 1729 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 1730 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec) 1731 )); 1732 #endif 1733 #if STATS 1734 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 1735 linker_stats.count[kRelocAbsolute], 1736 linker_stats.count[kRelocRelative], 1737 linker_stats.count[kRelocCopy], 1738 linker_stats.count[kRelocSymbol]); 1739 #endif 1740 #if COUNT_PAGES 1741 { 1742 unsigned n; 1743 unsigned i; 1744 unsigned count = 0; 1745 for (n = 0; n < 4096; n++) { 1746 if (bitmask[n]) { 1747 unsigned x = bitmask[n]; 1748 for (i = 0; i < 8; i++) { 1749 if (x & 1) { 1750 count++; 1751 } 1752 x >>= 1; 1753 } 1754 } 1755 } 1756 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 1757 } 1758 #endif 1759 1760 #if TIMING || STATS || COUNT_PAGES 1761 fflush(stdout); 1762 #endif 1763 1764 TRACE("[ Ready to execute '%s' @ 0x%08x ]", si->name, si->entry); 1765 return si->entry; 1766 } 1767 1768 /* Compute the load-bias of an existing executable. This shall only 1769 * be used to compute the load bias of an executable or shared library 1770 * that was loaded by the kernel itself. 1771 * 1772 * Input: 1773 * elf -> address of ELF header, assumed to be at the start of the file. 1774 * Return: 1775 * load bias, i.e. add the value of any p_vaddr in the file to get 1776 * the corresponding address in memory. 1777 */ 1778 static Elf32_Addr get_elf_exec_load_bias(const Elf32_Ehdr* elf) { 1779 Elf32_Addr offset = elf->e_phoff; 1780 const Elf32_Phdr* phdr_table = (const Elf32_Phdr*)((char*)elf + offset); 1781 const Elf32_Phdr* phdr_end = phdr_table + elf->e_phnum; 1782 1783 for (const Elf32_Phdr* phdr = phdr_table; phdr < phdr_end; phdr++) { 1784 if (phdr->p_type == PT_LOAD) { 1785 return reinterpret_cast<Elf32_Addr>(elf) + phdr->p_offset - phdr->p_vaddr; 1786 } 1787 } 1788 return 0; 1789 } 1790 1791 /* 1792 * This is the entry point for the linker, called from begin.S. This 1793 * method is responsible for fixing the linker's own relocations, and 1794 * then calling __linker_init_post_relocation(). 1795 * 1796 * Because this method is called before the linker has fixed it's own 1797 * relocations, any attempt to reference an extern variable, extern 1798 * function, or other GOT reference will generate a segfault. 1799 */ 1800 extern "C" Elf32_Addr __linker_init(void* raw_args) { 1801 KernelArgumentBlock args(raw_args); 1802 1803 Elf32_Addr linker_addr = args.getauxval(AT_BASE); 1804 1805 Elf32_Ehdr* elf_hdr = (Elf32_Ehdr*) linker_addr; 1806 Elf32_Phdr* phdr = (Elf32_Phdr*)((unsigned char*) linker_addr + elf_hdr->e_phoff); 1807 1808 soinfo linker_so; 1809 memset(&linker_so, 0, sizeof(soinfo)); 1810 1811 linker_so.base = linker_addr; 1812 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 1813 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 1814 linker_so.dynamic = NULL; 1815 linker_so.phdr = phdr; 1816 linker_so.phnum = elf_hdr->e_phnum; 1817 linker_so.flags |= FLAG_LINKER; 1818 1819 if (!soinfo_link_image(&linker_so)) { 1820 // It would be nice to print an error message, but if the linker 1821 // can't link itself, there's no guarantee that we'll be able to 1822 // call write() (because it involves a GOT reference). 1823 // 1824 // This situation should never occur unless the linker itself 1825 // is corrupt. 1826 exit(EXIT_FAILURE); 1827 } 1828 1829 // We have successfully fixed our own relocations. It's safe to run 1830 // the main part of the linker now. 1831 args.abort_message_ptr = &gAbortMessage; 1832 Elf32_Addr start_address = __linker_init_post_relocation(args, linker_addr); 1833 1834 set_soinfo_pool_protection(PROT_READ); 1835 1836 // Return the address that the calling assembly stub should jump to. 1837 return start_address; 1838 } 1839
