linker.cpp revision d59e50063ad708509f3ad83350be33f5612c4f54
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 <inttypes.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#include "linker_allocator.h" 52 53/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< 54 * 55 * Do NOT use malloc() and friends or pthread_*() code here. 56 * Don't use printf() either; it's caused mysterious memory 57 * corruption in the past. 58 * The linker runs before we bring up libc and it's easiest 59 * to make sure it does not depend on any complex libc features 60 * 61 * open issues / todo: 62 * 63 * - cleaner error reporting 64 * - after linking, set as much stuff as possible to READONLY 65 * and NOEXEC 66 */ 67 68static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 69static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 70 71static LinkerAllocator<soinfo> g_soinfo_allocator; 72static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator; 73 74static soinfo* solist; 75static soinfo* sonext; 76static soinfo* somain; /* main process, always the one after libdl_info */ 77 78static const char* const kDefaultLdPaths[] = { 79#if defined(__LP64__) 80 "/vendor/lib64", 81 "/system/lib64", 82#else 83 "/vendor/lib", 84 "/system/lib", 85#endif 86 NULL 87}; 88 89#define LDPATH_BUFSIZE (LDPATH_MAX*64) 90#define LDPATH_MAX 8 91 92#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 93#define LDPRELOAD_MAX 8 94 95static char g_ld_library_paths_buffer[LDPATH_BUFSIZE]; 96static const char* g_ld_library_paths[LDPATH_MAX + 1]; 97 98static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE]; 99static const char* g_ld_preload_names[LDPRELOAD_MAX + 1]; 100 101static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1]; 102 103__LIBC_HIDDEN__ int g_ld_debug_verbosity; 104 105__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd. 106 107enum RelocationKind { 108 kRelocAbsolute = 0, 109 kRelocRelative, 110 kRelocCopy, 111 kRelocSymbol, 112 kRelocMax 113}; 114 115#if STATS 116struct linker_stats_t { 117 int count[kRelocMax]; 118}; 119 120static linker_stats_t linker_stats; 121 122static void count_relocation(RelocationKind kind) { 123 ++linker_stats.count[kind]; 124} 125#else 126static void count_relocation(RelocationKind) { 127} 128#endif 129 130#if COUNT_PAGES 131static unsigned bitmask[4096]; 132#if defined(__LP64__) 133#define MARK(offset) \ 134 do { \ 135 if ((((offset) >> 12) >> 5) < 4096) \ 136 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 137 } while (0) 138#else 139#define MARK(offset) \ 140 do { \ 141 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 142 } while (0) 143#endif 144#else 145#define MARK(x) do {} while (0) 146#endif 147 148// You shouldn't try to call memory-allocating functions in the dynamic linker. 149// Guard against the most obvious ones. 150#define DISALLOW_ALLOCATION(return_type, name, ...) \ 151 return_type name __VA_ARGS__ \ 152 { \ 153 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 154 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 155 write(2, msg, strlen(msg)); \ 156 abort(); \ 157 } 158DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 159DISALLOW_ALLOCATION(void, free, (void* u __unused)); 160DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 161DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 162 163static char tmp_err_buf[768]; 164static char __linker_dl_err_buf[768]; 165 166char* linker_get_error_buffer() { 167 return &__linker_dl_err_buf[0]; 168} 169 170size_t linker_get_error_buffer_size() { 171 return sizeof(__linker_dl_err_buf); 172} 173 174/* 175 * This function is an empty stub where GDB locates a breakpoint to get notified 176 * about linker activity. 177 */ 178extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 179 180static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 181static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 182static link_map* r_debug_tail = 0; 183 184static void insert_soinfo_into_debug_map(soinfo* info) { 185 // Copy the necessary fields into the debug structure. 186 link_map* map = &(info->link_map_head); 187 map->l_addr = info->load_bias; 188 map->l_name = reinterpret_cast<char*>(info->name); 189 map->l_ld = info->dynamic; 190 191 /* Stick the new library at the end of the list. 192 * gdb tends to care more about libc than it does 193 * about leaf libraries, and ordering it this way 194 * reduces the back-and-forth over the wire. 195 */ 196 if (r_debug_tail) { 197 r_debug_tail->l_next = map; 198 map->l_prev = r_debug_tail; 199 map->l_next = 0; 200 } else { 201 _r_debug.r_map = map; 202 map->l_prev = 0; 203 map->l_next = 0; 204 } 205 r_debug_tail = map; 206} 207 208static void remove_soinfo_from_debug_map(soinfo* info) { 209 link_map* map = &(info->link_map_head); 210 211 if (r_debug_tail == map) { 212 r_debug_tail = map->l_prev; 213 } 214 215 if (map->l_prev) { 216 map->l_prev->l_next = map->l_next; 217 } 218 if (map->l_next) { 219 map->l_next->l_prev = map->l_prev; 220 } 221} 222 223static void notify_gdb_of_load(soinfo* info) { 224 if (info->flags & FLAG_EXE) { 225 // GDB already knows about the main executable 226 return; 227 } 228 229 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 230 231 _r_debug.r_state = r_debug::RT_ADD; 232 rtld_db_dlactivity(); 233 234 insert_soinfo_into_debug_map(info); 235 236 _r_debug.r_state = r_debug::RT_CONSISTENT; 237 rtld_db_dlactivity(); 238} 239 240static void notify_gdb_of_unload(soinfo* info) { 241 if (info->flags & FLAG_EXE) { 242 // GDB already knows about the main executable 243 return; 244 } 245 246 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 247 248 _r_debug.r_state = r_debug::RT_DELETE; 249 rtld_db_dlactivity(); 250 251 remove_soinfo_from_debug_map(info); 252 253 _r_debug.r_state = r_debug::RT_CONSISTENT; 254 rtld_db_dlactivity(); 255} 256 257void notify_gdb_of_libraries() { 258 _r_debug.r_state = r_debug::RT_ADD; 259 rtld_db_dlactivity(); 260 _r_debug.r_state = r_debug::RT_CONSISTENT; 261 rtld_db_dlactivity(); 262} 263 264LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 265 return g_soinfo_links_allocator.alloc(); 266} 267 268void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 269 g_soinfo_links_allocator.free(entry); 270} 271 272static void protect_data(int protection) { 273 g_soinfo_allocator.protect_all(protection); 274 g_soinfo_links_allocator.protect_all(protection); 275} 276 277static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 278 if (strlen(name) >= SOINFO_NAME_LEN) { 279 DL_ERR("library name \"%s\" too long", name); 280 return NULL; 281 } 282 283 soinfo* si = g_soinfo_allocator.alloc(); 284 285 // Initialize the new element. 286 memset(si, 0, sizeof(soinfo)); 287 strlcpy(si->name, name, sizeof(si->name)); 288 si->flags = FLAG_NEW_SOINFO; 289 290 if (file_stat != NULL) { 291 si->set_st_dev(file_stat->st_dev); 292 si->set_st_ino(file_stat->st_ino); 293 } 294 295 sonext->next = si; 296 sonext = si; 297 298 TRACE("name %s: allocated soinfo @ %p", name, si); 299 return si; 300} 301 302static void soinfo_free(soinfo* si) { 303 if (si == NULL) { 304 return; 305 } 306 307 if (si->base != 0 && si->size != 0) { 308 munmap(reinterpret_cast<void*>(si->base), si->size); 309 } 310 311 soinfo *prev = NULL, *trav; 312 313 TRACE("name %s: freeing soinfo @ %p", si->name, si); 314 315 for (trav = solist; trav != NULL; trav = trav->next) { 316 if (trav == si) 317 break; 318 prev = trav; 319 } 320 if (trav == NULL) { 321 /* si was not in solist */ 322 DL_ERR("name \"%s\" is not in solist!", si->name); 323 return; 324 } 325 326 // clear links to/from si 327 si->remove_all_links(); 328 329 /* prev will never be NULL, because the first entry in solist is 330 always the static libdl_info. 331 */ 332 prev->next = si->next; 333 if (si == sonext) { 334 sonext = prev; 335 } 336 337 g_soinfo_allocator.free(si); 338} 339 340 341static void parse_path(const char* path, const char* delimiters, 342 const char** array, char* buf, size_t buf_size, size_t max_count) { 343 if (path == NULL) { 344 return; 345 } 346 347 size_t len = strlcpy(buf, path, buf_size); 348 349 size_t i = 0; 350 char* buf_p = buf; 351 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 352 if (*array[i] != '\0') { 353 ++i; 354 } 355 } 356 357 // Forget the last path if we had to truncate; this occurs if the 2nd to 358 // last char isn't '\0' (i.e. wasn't originally a delimiter). 359 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 360 array[i - 1] = NULL; 361 } else { 362 array[i] = NULL; 363 } 364} 365 366static void parse_LD_LIBRARY_PATH(const char* path) { 367 parse_path(path, ":", g_ld_library_paths, 368 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 369} 370 371static void parse_LD_PRELOAD(const char* path) { 372 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 373 parse_path(path, " :", g_ld_preload_names, 374 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 375} 376 377#if defined(__arm__) 378 379/* For a given PC, find the .so that it belongs to. 380 * Returns the base address of the .ARM.exidx section 381 * for that .so, and the number of 8-byte entries 382 * in that section (via *pcount). 383 * 384 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 385 * 386 * This function is exposed via dlfcn.cpp and libdl.so. 387 */ 388_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 389 unsigned addr = (unsigned)pc; 390 391 for (soinfo* si = solist; si != 0; si = si->next) { 392 if ((addr >= si->base) && (addr < (si->base + si->size))) { 393 *pcount = si->ARM_exidx_count; 394 return (_Unwind_Ptr)si->ARM_exidx; 395 } 396 } 397 *pcount = 0; 398 return NULL; 399} 400 401#endif 402 403/* Here, we only have to provide a callback to iterate across all the 404 * loaded libraries. gcc_eh does the rest. */ 405int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 406 int rv = 0; 407 for (soinfo* si = solist; si != NULL; si = si->next) { 408 dl_phdr_info dl_info; 409 dl_info.dlpi_addr = si->link_map_head.l_addr; 410 dl_info.dlpi_name = si->link_map_head.l_name; 411 dl_info.dlpi_phdr = si->phdr; 412 dl_info.dlpi_phnum = si->phnum; 413 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 414 if (rv != 0) { 415 break; 416 } 417 } 418 return rv; 419} 420 421static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 422 ElfW(Sym)* symtab = si->symtab; 423 const char* strtab = si->strtab; 424 425 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 426 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 427 428 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 429 ElfW(Sym)* s = symtab + n; 430 if (strcmp(strtab + s->st_name, name)) continue; 431 432 /* only concern ourselves with global and weak symbol definitions */ 433 switch (ELF_ST_BIND(s->st_info)) { 434 case STB_GLOBAL: 435 case STB_WEAK: 436 if (s->st_shndx == SHN_UNDEF) { 437 continue; 438 } 439 440 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 441 name, si->name, reinterpret_cast<void*>(s->st_value), 442 static_cast<size_t>(s->st_size)); 443 return s; 444 } 445 } 446 447 return NULL; 448} 449 450static unsigned elfhash(const char* _name) { 451 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 452 unsigned h = 0, g; 453 454 while (*name) { 455 h = (h << 4) + *name++; 456 g = h & 0xf0000000; 457 h ^= g; 458 h ^= g >> 24; 459 } 460 return h; 461} 462 463static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 464 unsigned elf_hash = elfhash(name); 465 ElfW(Sym)* s = NULL; 466 467 if (si != NULL && somain != NULL) { 468 /* 469 * Local scope is executable scope. Just start looking into it right away 470 * for the shortcut. 471 */ 472 473 if (si == somain) { 474 s = soinfo_elf_lookup(si, elf_hash, name); 475 if (s != NULL) { 476 *lsi = si; 477 goto done; 478 } 479 } else { 480 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 481 482 /* 483 * If this object was built with symbolic relocations disabled, the 484 * first place to look to resolve external references is the main 485 * executable. 486 */ 487 488 if (!si->has_DT_SYMBOLIC) { 489 DEBUG("%s: looking up %s in executable %s", 490 si->name, name, somain->name); 491 s = soinfo_elf_lookup(somain, elf_hash, name); 492 if (s != NULL) { 493 *lsi = somain; 494 goto done; 495 } 496 } 497 498 /* Look for symbols in the local scope (the object who is 499 * searching). This happens with C++ templates on x86 for some 500 * reason. 501 * 502 * Notes on weak symbols: 503 * The ELF specs are ambiguous about treatment of weak definitions in 504 * dynamic linking. Some systems return the first definition found 505 * and some the first non-weak definition. This is system dependent. 506 * Here we return the first definition found for simplicity. */ 507 508 s = soinfo_elf_lookup(si, elf_hash, name); 509 if (s != NULL) { 510 *lsi = si; 511 goto done; 512 } 513 514 /* 515 * If this object was built with -Bsymbolic and symbol is not found 516 * in the local scope, try to find the symbol in the main executable. 517 */ 518 519 if (si->has_DT_SYMBOLIC) { 520 DEBUG("%s: looking up %s in executable %s after local scope", 521 si->name, name, somain->name); 522 s = soinfo_elf_lookup(somain, elf_hash, name); 523 if (s != NULL) { 524 *lsi = somain; 525 goto done; 526 } 527 } 528 } 529 } 530 531 /* Next, look for it in the preloads list */ 532 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 533 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name); 534 if (s != NULL) { 535 *lsi = g_ld_preloads[i]; 536 goto done; 537 } 538 } 539 540 for (int i = 0; needed[i] != NULL; i++) { 541 DEBUG("%s: looking up %s in %s", 542 si->name, name, needed[i]->name); 543 s = soinfo_elf_lookup(needed[i], elf_hash, name); 544 if (s != NULL) { 545 *lsi = needed[i]; 546 goto done; 547 } 548 } 549 550done: 551 if (s != NULL) { 552 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 553 "found in %s, base = %p, load bias = %p", 554 si->name, name, reinterpret_cast<void*>(s->st_value), 555 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 556 reinterpret_cast<void*>((*lsi)->load_bias)); 557 return s; 558 } 559 560 return NULL; 561} 562 563/* This is used by dlsym(3). It performs symbol lookup only within the 564 specified soinfo object and not in any of its dependencies. 565 566 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 567 that it should do a breadth first search through the dependency 568 tree. This agrees with the ELF spec (aka System V Application 569 Binary Interface) where in Chapter 5 it discuss resolving "Shared 570 Object Dependencies" in breadth first search order. 571 */ 572ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) { 573 return soinfo_elf_lookup(si, elfhash(name), name); 574} 575 576/* This is used by dlsym(3) to performs a global symbol lookup. If the 577 start value is null (for RTLD_DEFAULT), the search starts at the 578 beginning of the global solist. Otherwise the search starts at the 579 specified soinfo (for RTLD_NEXT). 580 */ 581ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 582 unsigned elf_hash = elfhash(name); 583 584 if (start == NULL) { 585 start = solist; 586 } 587 588 ElfW(Sym)* s = NULL; 589 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 590 s = soinfo_elf_lookup(si, elf_hash, name); 591 if (s != NULL) { 592 *found = si; 593 break; 594 } 595 } 596 597 if (s != NULL) { 598 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 599 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 600 } 601 602 return s; 603} 604 605soinfo* find_containing_library(const void* p) { 606 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 607 for (soinfo* si = solist; si != NULL; si = si->next) { 608 if (address >= si->base && address - si->base < si->size) { 609 return si; 610 } 611 } 612 return NULL; 613} 614 615ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 616 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 617 618 // Search the library's symbol table for any defined symbol which 619 // contains this address. 620 for (size_t i = 0; i < si->nchain; ++i) { 621 ElfW(Sym)* sym = &si->symtab[i]; 622 if (sym->st_shndx != SHN_UNDEF && 623 soaddr >= sym->st_value && 624 soaddr < sym->st_value + sym->st_size) { 625 return sym; 626 } 627 } 628 629 return NULL; 630} 631 632static int open_library_on_path(const char* name, const char* const paths[]) { 633 char buf[512]; 634 for (size_t i = 0; paths[i] != NULL; ++i) { 635 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 636 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 637 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 638 continue; 639 } 640 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 641 if (fd != -1) { 642 return fd; 643 } 644 } 645 return -1; 646} 647 648static int open_library(const char* name) { 649 TRACE("[ opening %s ]", name); 650 651 // If the name contains a slash, we should attempt to open it directly and not search the paths. 652 if (strchr(name, '/') != NULL) { 653 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 654 if (fd != -1) { 655 return fd; 656 } 657 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 658#if defined(__LP64__) 659 return -1; 660#endif 661 } 662 663 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 664 int fd = open_library_on_path(name, g_ld_library_paths); 665 if (fd == -1) { 666 fd = open_library_on_path(name, kDefaultLdPaths); 667 } 668 return fd; 669} 670 671static soinfo* load_library(const char* name, const android_dlextinfo* extinfo) { 672 // Open the file. 673 int fd = open_library(name); 674 if (fd == -1) { 675 DL_ERR("library \"%s\" not found", name); 676 return NULL; 677 } 678 679 ElfReader elf_reader(name, fd); 680 681 struct stat file_stat; 682 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 683 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 684 return NULL; 685 } 686 687 // Check for symlink and other situations where 688 // file can have different names. 689 for (soinfo* si = solist; si != NULL; si = si->next) { 690 if (si->get_st_dev() != 0 && 691 si->get_st_ino() != 0 && 692 si->get_st_dev() == file_stat.st_dev && 693 si->get_st_ino() == file_stat.st_ino) { 694 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 695 return si; 696 } 697 } 698 699 // Read the ELF header and load the segments. 700 if (!elf_reader.Load(extinfo)) { 701 return NULL; 702 } 703 704 const char* bname = strrchr(name, '/'); 705 soinfo* si = soinfo_alloc(bname ? bname + 1 : name, &file_stat); 706 if (si == NULL) { 707 return NULL; 708 } 709 si->base = elf_reader.load_start(); 710 si->size = elf_reader.load_size(); 711 si->load_bias = elf_reader.load_bias(); 712 si->phnum = elf_reader.phdr_count(); 713 si->phdr = elf_reader.loaded_phdr(); 714 715 // At this point we know that whatever is loaded @ base is a valid ELF 716 // shared library whose segments are properly mapped in. 717 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 718 reinterpret_cast<void*>(si->base), si->size, si->name); 719 720 if (!soinfo_link_image(si, extinfo)) { 721 soinfo_free(si); 722 return NULL; 723 } 724 725 return si; 726} 727 728static soinfo *find_loaded_library(const char* name) { 729 // TODO: don't use basename only for determining libraries 730 // http://code.google.com/p/android/issues/detail?id=6670 731 732 const char* bname = strrchr(name, '/'); 733 bname = bname ? bname + 1 : name; 734 735 for (soinfo* si = solist; si != NULL; si = si->next) { 736 if (!strcmp(bname, si->name)) { 737 return si; 738 } 739 } 740 return NULL; 741} 742 743static soinfo* find_library_internal(const char* name, const android_dlextinfo* extinfo) { 744 if (name == NULL) { 745 return somain; 746 } 747 748 soinfo* si = find_loaded_library(name); 749 if (si != NULL) { 750 if (si->flags & FLAG_LINKED) { 751 return si; 752 } 753 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 754 return NULL; 755 } 756 757 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 758 return load_library(name, extinfo); 759} 760 761static soinfo* find_library(const char* name, const android_dlextinfo* extinfo) { 762 soinfo* si = find_library_internal(name, extinfo); 763 if (si != NULL) { 764 si->ref_count++; 765 } 766 return si; 767} 768 769static int soinfo_unload(soinfo* si) { 770 if (si->ref_count == 1) { 771 TRACE("unloading '%s'", si->name); 772 si->CallDestructors(); 773 774 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 775 si->get_children().for_each([&] (soinfo* child) { 776 TRACE("%s needs to unload %s", si->name, child->name); 777 soinfo_unload(child); 778 }); 779 } else { 780 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 781 if (d->d_tag == DT_NEEDED) { 782 const char* library_name = si->strtab + d->d_un.d_val; 783 TRACE("%s needs to unload %s", si->name, library_name); 784 soinfo_unload(find_loaded_library(library_name)); 785 } 786 } 787 } 788 789 notify_gdb_of_unload(si); 790 si->ref_count = 0; 791 soinfo_free(si); 792 } else { 793 si->ref_count--; 794 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 795 } 796 return 0; 797} 798 799void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 800 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 801} 802 803void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 804 if (!get_AT_SECURE()) { 805 parse_LD_LIBRARY_PATH(ld_library_path); 806 } 807} 808 809soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 810 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 811 DL_ERR("invalid flags to dlopen: %x", flags); 812 return NULL; 813 } 814 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 815 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 816 return NULL; 817 } 818 protect_data(PROT_READ | PROT_WRITE); 819 soinfo* si = find_library(name, extinfo); 820 if (si != NULL) { 821 si->CallConstructors(); 822 somain->add_child(si); 823 } 824 protect_data(PROT_READ); 825 return si; 826} 827 828int do_dlclose(soinfo* si) { 829 protect_data(PROT_READ | PROT_WRITE); 830 int result = soinfo_unload(si); 831 protect_data(PROT_READ); 832 return result; 833} 834 835#if defined(USE_RELA) 836static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 837 ElfW(Sym)* s; 838 soinfo* lsi; 839 840 for (size_t idx = 0; idx < count; ++idx, ++rela) { 841 unsigned type = ELFW(R_TYPE)(rela->r_info); 842 unsigned sym = ELFW(R_SYM)(rela->r_info); 843 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 844 ElfW(Addr) sym_addr = 0; 845 const char* sym_name = NULL; 846 847 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 848 if (type == 0) { // R_*_NONE 849 continue; 850 } 851 if (sym != 0) { 852 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 853 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 854 if (s == NULL) { 855 // We only allow an undefined symbol if this is a weak reference... 856 s = &si->symtab[sym]; 857 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 858 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 859 return -1; 860 } 861 862 /* IHI0044C AAELF 4.5.1.1: 863 864 Libraries are not searched to resolve weak references. 865 It is not an error for a weak reference to remain unsatisfied. 866 867 During linking, the value of an undefined weak reference is: 868 - Zero if the relocation type is absolute 869 - The address of the place if the relocation is pc-relative 870 - The address of nominal base address if the relocation 871 type is base-relative. 872 */ 873 874 switch (type) { 875#if defined(__aarch64__) 876 case R_AARCH64_JUMP_SLOT: 877 case R_AARCH64_GLOB_DAT: 878 case R_AARCH64_ABS64: 879 case R_AARCH64_ABS32: 880 case R_AARCH64_ABS16: 881 case R_AARCH64_RELATIVE: 882 /* 883 * The sym_addr was initialized to be zero above, or the relocation 884 * code below does not care about value of sym_addr. 885 * No need to do anything. 886 */ 887 break; 888#elif defined(__x86_64__) 889 case R_X86_64_JUMP_SLOT: 890 case R_X86_64_GLOB_DAT: 891 case R_X86_64_32: 892 case R_X86_64_RELATIVE: 893 // No need to do anything. 894 break; 895 case R_X86_64_PC32: 896 sym_addr = reloc; 897 break; 898#endif 899 default: 900 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 901 return -1; 902 } 903 } else { 904 // We got a definition. 905 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 906 } 907 count_relocation(kRelocSymbol); 908 } else { 909 s = NULL; 910 } 911 912 switch (type) { 913#if defined(__aarch64__) 914 case R_AARCH64_JUMP_SLOT: 915 count_relocation(kRelocAbsolute); 916 MARK(rela->r_offset); 917 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 918 reloc, (sym_addr + rela->r_addend), sym_name); 919 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 920 break; 921 case R_AARCH64_GLOB_DAT: 922 count_relocation(kRelocAbsolute); 923 MARK(rela->r_offset); 924 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 925 reloc, (sym_addr + rela->r_addend), sym_name); 926 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 927 break; 928 case R_AARCH64_ABS64: 929 count_relocation(kRelocAbsolute); 930 MARK(rela->r_offset); 931 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 932 reloc, (sym_addr + rela->r_addend), sym_name); 933 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 934 break; 935 case R_AARCH64_ABS32: 936 count_relocation(kRelocAbsolute); 937 MARK(rela->r_offset); 938 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 939 reloc, (sym_addr + rela->r_addend), sym_name); 940 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 941 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 942 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 943 } else { 944 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 945 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 946 static_cast<ElfW(Addr)>(INT32_MIN), 947 static_cast<ElfW(Addr)>(UINT32_MAX)); 948 return -1; 949 } 950 break; 951 case R_AARCH64_ABS16: 952 count_relocation(kRelocAbsolute); 953 MARK(rela->r_offset); 954 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 955 reloc, (sym_addr + rela->r_addend), sym_name); 956 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 957 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 958 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 959 } else { 960 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 961 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 962 static_cast<ElfW(Addr)>(INT16_MIN), 963 static_cast<ElfW(Addr)>(UINT16_MAX)); 964 return -1; 965 } 966 break; 967 case R_AARCH64_PREL64: 968 count_relocation(kRelocRelative); 969 MARK(rela->r_offset); 970 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 971 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 972 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 973 break; 974 case R_AARCH64_PREL32: 975 count_relocation(kRelocRelative); 976 MARK(rela->r_offset); 977 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 978 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 979 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 980 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 981 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 982 } else { 983 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 984 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 985 static_cast<ElfW(Addr)>(INT32_MIN), 986 static_cast<ElfW(Addr)>(UINT32_MAX)); 987 return -1; 988 } 989 break; 990 case R_AARCH64_PREL16: 991 count_relocation(kRelocRelative); 992 MARK(rela->r_offset); 993 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 994 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 995 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 996 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 997 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 998 } else { 999 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1000 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1001 static_cast<ElfW(Addr)>(INT16_MIN), 1002 static_cast<ElfW(Addr)>(UINT16_MAX)); 1003 return -1; 1004 } 1005 break; 1006 1007 case R_AARCH64_RELATIVE: 1008 count_relocation(kRelocRelative); 1009 MARK(rela->r_offset); 1010 if (sym) { 1011 DL_ERR("odd RELATIVE form..."); 1012 return -1; 1013 } 1014 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1015 reloc, (si->base + rela->r_addend)); 1016 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1017 break; 1018 1019 case R_AARCH64_COPY: 1020 /* 1021 * ET_EXEC is not supported so this should not happen. 1022 * 1023 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1024 * 1025 * Section 4.7.1.10 "Dynamic relocations" 1026 * R_AARCH64_COPY may only appear in executable objects where e_type is 1027 * set to ET_EXEC. 1028 */ 1029 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1030 return -1; 1031 case R_AARCH64_TLS_TPREL64: 1032 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1033 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1034 break; 1035 case R_AARCH64_TLS_DTPREL32: 1036 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1037 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1038 break; 1039#elif defined(__x86_64__) 1040 case R_X86_64_JUMP_SLOT: 1041 count_relocation(kRelocAbsolute); 1042 MARK(rela->r_offset); 1043 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1044 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1045 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1046 break; 1047 case R_X86_64_GLOB_DAT: 1048 count_relocation(kRelocAbsolute); 1049 MARK(rela->r_offset); 1050 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1051 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1052 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1053 break; 1054 case R_X86_64_RELATIVE: 1055 count_relocation(kRelocRelative); 1056 MARK(rela->r_offset); 1057 if (sym) { 1058 DL_ERR("odd RELATIVE form..."); 1059 return -1; 1060 } 1061 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1062 static_cast<size_t>(si->base)); 1063 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1064 break; 1065 case R_X86_64_32: 1066 count_relocation(kRelocRelative); 1067 MARK(rela->r_offset); 1068 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1069 static_cast<size_t>(sym_addr), sym_name); 1070 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1071 break; 1072 case R_X86_64_64: 1073 count_relocation(kRelocRelative); 1074 MARK(rela->r_offset); 1075 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1076 static_cast<size_t>(sym_addr), sym_name); 1077 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1078 break; 1079 case R_X86_64_PC32: 1080 count_relocation(kRelocRelative); 1081 MARK(rela->r_offset); 1082 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1083 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1084 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1085 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1086 break; 1087#endif 1088 1089 default: 1090 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1091 return -1; 1092 } 1093 } 1094 return 0; 1095} 1096 1097#else // REL, not RELA. 1098 1099static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1100 ElfW(Sym)* s; 1101 soinfo* lsi; 1102 1103 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1104 unsigned type = ELFW(R_TYPE)(rel->r_info); 1105 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1106 unsigned sym = ELFW(R_SYM)(rel->r_info); 1107 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1108 ElfW(Addr) sym_addr = 0; 1109 const char* sym_name = NULL; 1110 1111 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1112 if (type == 0) { // R_*_NONE 1113 continue; 1114 } 1115 if (sym != 0) { 1116 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1117 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1118 if (s == NULL) { 1119 // We only allow an undefined symbol if this is a weak reference... 1120 s = &si->symtab[sym]; 1121 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1122 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1123 return -1; 1124 } 1125 1126 /* IHI0044C AAELF 4.5.1.1: 1127 1128 Libraries are not searched to resolve weak references. 1129 It is not an error for a weak reference to remain 1130 unsatisfied. 1131 1132 During linking, the value of an undefined weak reference is: 1133 - Zero if the relocation type is absolute 1134 - The address of the place if the relocation is pc-relative 1135 - The address of nominal base address if the relocation 1136 type is base-relative. 1137 */ 1138 1139 switch (type) { 1140#if defined(__arm__) 1141 case R_ARM_JUMP_SLOT: 1142 case R_ARM_GLOB_DAT: 1143 case R_ARM_ABS32: 1144 case R_ARM_RELATIVE: /* Don't care. */ 1145 // sym_addr was initialized to be zero above or relocation 1146 // code below does not care about value of sym_addr. 1147 // No need to do anything. 1148 break; 1149#elif defined(__i386__) 1150 case R_386_JMP_SLOT: 1151 case R_386_GLOB_DAT: 1152 case R_386_32: 1153 case R_386_RELATIVE: /* Don't care. */ 1154 // sym_addr was initialized to be zero above or relocation 1155 // code below does not care about value of sym_addr. 1156 // No need to do anything. 1157 break; 1158 case R_386_PC32: 1159 sym_addr = reloc; 1160 break; 1161#endif 1162 1163#if defined(__arm__) 1164 case R_ARM_COPY: 1165 // Fall through. Can't really copy if weak symbol is not found at run-time. 1166#endif 1167 default: 1168 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1169 return -1; 1170 } 1171 } else { 1172 // We got a definition. 1173 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1174 } 1175 count_relocation(kRelocSymbol); 1176 } else { 1177 s = NULL; 1178 } 1179 1180 switch (type) { 1181#if defined(__arm__) 1182 case R_ARM_JUMP_SLOT: 1183 count_relocation(kRelocAbsolute); 1184 MARK(rel->r_offset); 1185 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1186 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1187 break; 1188 case R_ARM_GLOB_DAT: 1189 count_relocation(kRelocAbsolute); 1190 MARK(rel->r_offset); 1191 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1192 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1193 break; 1194 case R_ARM_ABS32: 1195 count_relocation(kRelocAbsolute); 1196 MARK(rel->r_offset); 1197 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1198 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1199 break; 1200 case R_ARM_REL32: 1201 count_relocation(kRelocRelative); 1202 MARK(rel->r_offset); 1203 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1204 reloc, sym_addr, rel->r_offset, sym_name); 1205 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1206 break; 1207 case R_ARM_COPY: 1208 /* 1209 * ET_EXEC is not supported so this should not happen. 1210 * 1211 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1212 * 1213 * Section 4.7.1.10 "Dynamic relocations" 1214 * R_ARM_COPY may only appear in executable objects where e_type is 1215 * set to ET_EXEC. 1216 */ 1217 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1218 return -1; 1219#elif defined(__i386__) 1220 case R_386_JMP_SLOT: 1221 count_relocation(kRelocAbsolute); 1222 MARK(rel->r_offset); 1223 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1224 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1225 break; 1226 case R_386_GLOB_DAT: 1227 count_relocation(kRelocAbsolute); 1228 MARK(rel->r_offset); 1229 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1230 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1231 break; 1232 case R_386_32: 1233 count_relocation(kRelocRelative); 1234 MARK(rel->r_offset); 1235 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1236 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1237 break; 1238 case R_386_PC32: 1239 count_relocation(kRelocRelative); 1240 MARK(rel->r_offset); 1241 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1242 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1243 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1244 break; 1245#elif defined(__mips__) 1246 case R_MIPS_REL32: 1247#if defined(__LP64__) 1248 // MIPS Elf64_Rel entries contain compound relocations 1249 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1250 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1251 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1252 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1253 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1254 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1255 return -1; 1256 } 1257#endif 1258 count_relocation(kRelocAbsolute); 1259 MARK(rel->r_offset); 1260 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1261 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1262 if (s) { 1263 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1264 } else { 1265 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1266 } 1267 break; 1268#endif 1269 1270#if defined(__arm__) 1271 case R_ARM_RELATIVE: 1272#elif defined(__i386__) 1273 case R_386_RELATIVE: 1274#endif 1275 count_relocation(kRelocRelative); 1276 MARK(rel->r_offset); 1277 if (sym) { 1278 DL_ERR("odd RELATIVE form..."); 1279 return -1; 1280 } 1281 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1282 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1283 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1284 break; 1285 1286 default: 1287 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1288 return -1; 1289 } 1290 } 1291 return 0; 1292} 1293#endif 1294 1295#if defined(__mips__) 1296static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1297 ElfW(Addr)** got = si->plt_got; 1298 if (got == NULL) { 1299 return true; 1300 } 1301 unsigned local_gotno = si->mips_local_gotno; 1302 unsigned gotsym = si->mips_gotsym; 1303 unsigned symtabno = si->mips_symtabno; 1304 ElfW(Sym)* symtab = si->symtab; 1305 1306 // got[0] is the address of the lazy resolver function. 1307 // got[1] may be used for a GNU extension. 1308 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1309 // FIXME: maybe this should be in a separate routine? 1310 if ((si->flags & FLAG_LINKER) == 0) { 1311 size_t g = 0; 1312 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1313 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1314 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1315 } 1316 // Relocate the local GOT entries. 1317 for (; g < local_gotno; g++) { 1318 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1319 } 1320 } 1321 1322 // Now for the global GOT entries... 1323 ElfW(Sym)* sym = symtab + gotsym; 1324 got = si->plt_got + local_gotno; 1325 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1326 // This is an undefined reference... try to locate it. 1327 const char* sym_name = si->strtab + sym->st_name; 1328 soinfo* lsi; 1329 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1330 if (s == NULL) { 1331 // We only allow an undefined symbol if this is a weak reference. 1332 s = &symtab[g]; 1333 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1334 DL_ERR("cannot locate \"%s\"...", sym_name); 1335 return false; 1336 } 1337 *got = 0; 1338 } else { 1339 // FIXME: is this sufficient? 1340 // For reference see NetBSD link loader 1341 // 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 1342 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1343 } 1344 } 1345 return true; 1346} 1347#endif 1348 1349void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1350 if (functions == NULL) { 1351 return; 1352 } 1353 1354 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1355 1356 int begin = reverse ? (count - 1) : 0; 1357 int end = reverse ? -1 : count; 1358 int step = reverse ? -1 : 1; 1359 1360 for (int i = begin; i != end; i += step) { 1361 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1362 CallFunction("function", functions[i]); 1363 } 1364 1365 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1366} 1367 1368void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1369 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1370 return; 1371 } 1372 1373 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1374 function(); 1375 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1376 1377 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1378 // are still writable. This happens with our debug malloc (see http://b/7941716). 1379 protect_data(PROT_READ | PROT_WRITE); 1380} 1381 1382void soinfo::CallPreInitConstructors() { 1383 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1384 // but ignored in a shared library. 1385 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1386} 1387 1388void soinfo::CallConstructors() { 1389 if (constructors_called) { 1390 return; 1391 } 1392 1393 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1394 // protect against recursive constructor calls. One simple example of constructor recursion 1395 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1396 // 1. The program depends on libc, so libc's constructor is called here. 1397 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1398 // 3. dlopen() calls the constructors on the newly created 1399 // soinfo for libc_malloc_debug_leak.so. 1400 // 4. The debug .so depends on libc, so CallConstructors is 1401 // called again with the libc soinfo. If it doesn't trigger the early- 1402 // out above, the libc constructor will be called again (recursively!). 1403 constructors_called = true; 1404 1405 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1406 // The GNU dynamic linker silently ignores these, but we warn the developer. 1407 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1408 name, preinit_array_count); 1409 } 1410 1411 get_children().for_each([] (soinfo* si) { 1412 si->CallConstructors(); 1413 }); 1414 1415 TRACE("\"%s\": calling constructors", name); 1416 1417 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1418 CallFunction("DT_INIT", init_func); 1419 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1420} 1421 1422void soinfo::CallDestructors() { 1423 TRACE("\"%s\": calling destructors", name); 1424 1425 // DT_FINI_ARRAY must be parsed in reverse order. 1426 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1427 1428 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1429 CallFunction("DT_FINI", fini_func); 1430} 1431 1432void soinfo::add_child(soinfo* child) { 1433 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1434 return; 1435 } 1436 1437 this->children.push_front(child); 1438 child->parents.push_front(this); 1439} 1440 1441void soinfo::remove_all_links() { 1442 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1443 return; 1444 } 1445 1446 // 1. Untie connected soinfos from 'this'. 1447 children.for_each([&] (soinfo* child) { 1448 child->parents.remove_if([&] (const soinfo* parent) { 1449 return parent == this; 1450 }); 1451 }); 1452 1453 parents.for_each([&] (soinfo* parent) { 1454 parent->children.for_each([&] (const soinfo* child) { 1455 return child == this; 1456 }); 1457 }); 1458 1459 // 2. Once everything untied - clear local lists. 1460 parents.clear(); 1461 children.clear(); 1462} 1463 1464void soinfo::set_st_dev(dev_t dev) { 1465 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1466 return; 1467 } 1468 1469 st_dev = dev; 1470} 1471 1472void soinfo::set_st_ino(ino_t ino) { 1473 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1474 return; 1475 } 1476 1477 st_ino = ino; 1478} 1479 1480dev_t soinfo::get_st_dev() { 1481 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1482 return 0; 1483 } 1484 1485 return st_dev; 1486}; 1487 1488ino_t soinfo::get_st_ino() { 1489 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1490 return 0; 1491 } 1492 1493 return st_ino; 1494} 1495 1496// This is a return on get_children() in case 1497// 'this->flags' does not have FLAG_NEW_SOINFO set. 1498static soinfo::soinfo_list_t g_empty_list; 1499 1500soinfo::soinfo_list_t& soinfo::get_children() { 1501 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1502 return g_empty_list; 1503 } 1504 1505 return this->children; 1506} 1507 1508/* Force any of the closed stdin, stdout and stderr to be associated with 1509 /dev/null. */ 1510static int nullify_closed_stdio() { 1511 int dev_null, i, status; 1512 int return_value = 0; 1513 1514 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1515 if (dev_null < 0) { 1516 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1517 return -1; 1518 } 1519 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1520 1521 /* If any of the stdio file descriptors is valid and not associated 1522 with /dev/null, dup /dev/null to it. */ 1523 for (i = 0; i < 3; i++) { 1524 /* If it is /dev/null already, we are done. */ 1525 if (i == dev_null) { 1526 continue; 1527 } 1528 1529 TRACE("[ Nullifying stdio file descriptor %d]", i); 1530 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1531 1532 /* If file is opened, we are good. */ 1533 if (status != -1) { 1534 continue; 1535 } 1536 1537 /* The only error we allow is that the file descriptor does not 1538 exist, in which case we dup /dev/null to it. */ 1539 if (errno != EBADF) { 1540 DL_ERR("fcntl failed: %s", strerror(errno)); 1541 return_value = -1; 1542 continue; 1543 } 1544 1545 /* Try dupping /dev/null to this stdio file descriptor and 1546 repeat if there is a signal. Note that any errors in closing 1547 the stdio descriptor are lost. */ 1548 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1549 if (status < 0) { 1550 DL_ERR("dup2 failed: %s", strerror(errno)); 1551 return_value = -1; 1552 continue; 1553 } 1554 } 1555 1556 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1557 if (dev_null > 2) { 1558 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1559 status = TEMP_FAILURE_RETRY(close(dev_null)); 1560 if (status == -1) { 1561 DL_ERR("close failed: %s", strerror(errno)); 1562 return_value = -1; 1563 } 1564 } 1565 1566 return return_value; 1567} 1568 1569static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1570 /* "base" might wrap around UINT32_MAX. */ 1571 ElfW(Addr) base = si->load_bias; 1572 const ElfW(Phdr)* phdr = si->phdr; 1573 int phnum = si->phnum; 1574 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1575 1576 /* We can't debug anything until the linker is relocated */ 1577 if (!relocating_linker) { 1578 INFO("[ linking %s ]", si->name); 1579 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1580 } 1581 1582 /* Extract dynamic section */ 1583 size_t dynamic_count; 1584 ElfW(Word) dynamic_flags; 1585 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1586 &dynamic_count, &dynamic_flags); 1587 if (si->dynamic == NULL) { 1588 if (!relocating_linker) { 1589 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1590 } 1591 return false; 1592 } else { 1593 if (!relocating_linker) { 1594 DEBUG("dynamic = %p", si->dynamic); 1595 } 1596 } 1597 1598#if defined(__arm__) 1599 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1600 &si->ARM_exidx, &si->ARM_exidx_count); 1601#endif 1602 1603 // Extract useful information from dynamic section. 1604 uint32_t needed_count = 0; 1605 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1606 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1607 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1608 switch (d->d_tag) { 1609 case DT_HASH: 1610 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1611 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1612 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1613 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1614 break; 1615 case DT_STRTAB: 1616 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1617 break; 1618 case DT_SYMTAB: 1619 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1620 break; 1621#if !defined(__LP64__) 1622 case DT_PLTREL: 1623 if (d->d_un.d_val != DT_REL) { 1624 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1625 return false; 1626 } 1627 break; 1628#endif 1629 case DT_JMPREL: 1630#if defined(USE_RELA) 1631 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1632#else 1633 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1634#endif 1635 break; 1636 case DT_PLTRELSZ: 1637#if defined(USE_RELA) 1638 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1639#else 1640 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1641#endif 1642 break; 1643#if defined(__mips__) 1644 case DT_PLTGOT: 1645 // Used by mips and mips64. 1646 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1647 break; 1648#endif 1649 case DT_DEBUG: 1650 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1651 // if the dynamic table is writable 1652// FIXME: not working currently for N64 1653// The flags for the LOAD and DYNAMIC program headers do not agree. 1654// The LOAD section containng the dynamic table has been mapped as 1655// read-only, but the DYNAMIC header claims it is writable. 1656#if !(defined(__mips__) && defined(__LP64__)) 1657 if ((dynamic_flags & PF_W) != 0) { 1658 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1659 } 1660 break; 1661#endif 1662#if defined(USE_RELA) 1663 case DT_RELA: 1664 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1665 break; 1666 case DT_RELASZ: 1667 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1668 break; 1669 case DT_REL: 1670 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1671 return false; 1672 case DT_RELSZ: 1673 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1674 return false; 1675#else 1676 case DT_REL: 1677 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1678 break; 1679 case DT_RELSZ: 1680 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1681 break; 1682 case DT_RELA: 1683 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1684 return false; 1685#endif 1686 case DT_INIT: 1687 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1688 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1689 break; 1690 case DT_FINI: 1691 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1692 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1693 break; 1694 case DT_INIT_ARRAY: 1695 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1696 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1697 break; 1698 case DT_INIT_ARRAYSZ: 1699 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1700 break; 1701 case DT_FINI_ARRAY: 1702 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1703 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1704 break; 1705 case DT_FINI_ARRAYSZ: 1706 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1707 break; 1708 case DT_PREINIT_ARRAY: 1709 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1710 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1711 break; 1712 case DT_PREINIT_ARRAYSZ: 1713 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1714 break; 1715 case DT_TEXTREL: 1716#if defined(__LP64__) 1717 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1718 return false; 1719#else 1720 si->has_text_relocations = true; 1721 break; 1722#endif 1723 case DT_SYMBOLIC: 1724 si->has_DT_SYMBOLIC = true; 1725 break; 1726 case DT_NEEDED: 1727 ++needed_count; 1728 break; 1729 case DT_FLAGS: 1730 if (d->d_un.d_val & DF_TEXTREL) { 1731#if defined(__LP64__) 1732 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1733 return false; 1734#else 1735 si->has_text_relocations = true; 1736#endif 1737 } 1738 if (d->d_un.d_val & DF_SYMBOLIC) { 1739 si->has_DT_SYMBOLIC = true; 1740 } 1741 break; 1742#if defined(__mips__) 1743 case DT_STRSZ: 1744 case DT_SYMENT: 1745 case DT_RELENT: 1746 break; 1747 case DT_MIPS_RLD_MAP: 1748 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1749 { 1750 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1751 *dp = &_r_debug; 1752 } 1753 break; 1754 case DT_MIPS_RLD_VERSION: 1755 case DT_MIPS_FLAGS: 1756 case DT_MIPS_BASE_ADDRESS: 1757 case DT_MIPS_UNREFEXTNO: 1758 break; 1759 1760 case DT_MIPS_SYMTABNO: 1761 si->mips_symtabno = d->d_un.d_val; 1762 break; 1763 1764 case DT_MIPS_LOCAL_GOTNO: 1765 si->mips_local_gotno = d->d_un.d_val; 1766 break; 1767 1768 case DT_MIPS_GOTSYM: 1769 si->mips_gotsym = d->d_un.d_val; 1770 break; 1771#endif 1772 1773 default: 1774 DEBUG("Unused DT entry: type %p arg %p", 1775 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1776 break; 1777 } 1778 } 1779 1780 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1781 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1782 1783 // Sanity checks. 1784 if (relocating_linker && needed_count != 0) { 1785 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1786 return false; 1787 } 1788 if (si->nbucket == 0) { 1789 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1790 return false; 1791 } 1792 if (si->strtab == 0) { 1793 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1794 return false; 1795 } 1796 if (si->symtab == 0) { 1797 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1798 return false; 1799 } 1800 1801 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1802 if (si->flags & FLAG_EXE) { 1803 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1804 size_t preload_count = 0; 1805 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1806 soinfo* lsi = find_library(g_ld_preload_names[i], NULL); 1807 if (lsi != NULL) { 1808 g_ld_preloads[preload_count++] = lsi; 1809 } else { 1810 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1811 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1812 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1813 } 1814 } 1815 } 1816 1817 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1818 soinfo** pneeded = needed; 1819 1820 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1821 if (d->d_tag == DT_NEEDED) { 1822 const char* library_name = si->strtab + d->d_un.d_val; 1823 DEBUG("%s needs %s", si->name, library_name); 1824 soinfo* lsi = find_library(library_name, NULL); 1825 if (lsi == NULL) { 1826 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1827 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1828 library_name, si->name, tmp_err_buf); 1829 return false; 1830 } 1831 1832 si->add_child(lsi); 1833 *pneeded++ = lsi; 1834 } 1835 } 1836 *pneeded = NULL; 1837 1838#if !defined(__LP64__) 1839 if (si->has_text_relocations) { 1840 // Make segments writable to allow text relocations to work properly. We will later call 1841 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1842#if !defined(__i386__) // The platform itself has too many text relocations on x86. 1843 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1844 "security hardening. Please fix.", si->name); 1845#endif 1846 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1847 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1848 si->name, strerror(errno)); 1849 return false; 1850 } 1851 } 1852#endif 1853 1854#if defined(USE_RELA) 1855 if (si->plt_rela != NULL) { 1856 DEBUG("[ relocating %s plt ]\n", si->name); 1857 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1858 return false; 1859 } 1860 } 1861 if (si->rela != NULL) { 1862 DEBUG("[ relocating %s ]\n", si->name); 1863 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1864 return false; 1865 } 1866 } 1867#else 1868 if (si->plt_rel != NULL) { 1869 DEBUG("[ relocating %s plt ]", si->name); 1870 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1871 return false; 1872 } 1873 } 1874 if (si->rel != NULL) { 1875 DEBUG("[ relocating %s ]", si->name); 1876 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1877 return false; 1878 } 1879 } 1880#endif 1881 1882#if defined(__mips__) 1883 if (!mips_relocate_got(si, needed)) { 1884 return false; 1885 } 1886#endif 1887 1888 si->flags |= FLAG_LINKED; 1889 DEBUG("[ finished linking %s ]", si->name); 1890 1891#if !defined(__LP64__) 1892 if (si->has_text_relocations) { 1893 // All relocations are done, we can protect our segments back to read-only. 1894 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1895 DL_ERR("can't protect segments for \"%s\": %s", 1896 si->name, strerror(errno)); 1897 return false; 1898 } 1899 } 1900#endif 1901 1902 /* We can also turn on GNU RELRO protection */ 1903 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1904 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1905 si->name, strerror(errno)); 1906 return false; 1907 } 1908 1909 /* Handle serializing/sharing the RELRO segment */ 1910 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1911 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1912 extinfo->relro_fd) < 0) { 1913 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1914 si->name, strerror(errno)); 1915 return false; 1916 } 1917 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1918 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1919 extinfo->relro_fd) < 0) { 1920 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1921 si->name, strerror(errno)); 1922 return false; 1923 } 1924 } 1925 1926 notify_gdb_of_load(si); 1927 return true; 1928} 1929 1930/* 1931 * This function add vdso to internal dso list. 1932 * It helps to stack unwinding through signal handlers. 1933 * Also, it makes bionic more like glibc. 1934 */ 1935static void add_vdso(KernelArgumentBlock& args __unused) { 1936#if defined(AT_SYSINFO_EHDR) 1937 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1938 if (ehdr_vdso == NULL) { 1939 return; 1940 } 1941 1942 soinfo* si = soinfo_alloc("[vdso]", NULL); 1943 1944 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1945 si->phnum = ehdr_vdso->e_phnum; 1946 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1947 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1948 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1949 1950 soinfo_link_image(si, NULL); 1951#endif 1952} 1953 1954/* 1955 * This is linker soinfo for GDB. See details below. 1956 */ 1957static soinfo linker_soinfo_for_gdb; 1958 1959/* gdb expects the linker to be in the debug shared object list. 1960 * Without this, gdb has trouble locating the linker's ".text" 1961 * and ".plt" sections. Gdb could also potentially use this to 1962 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1963 * Don't use soinfo_alloc(), because the linker shouldn't 1964 * be on the soinfo list. 1965 */ 1966static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 1967#if defined(__LP64__) 1968 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 1969#else 1970 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 1971#endif 1972 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 1973 linker_soinfo_for_gdb.base = linker_base; 1974 1975 /* 1976 * Set the dynamic field in the link map otherwise gdb will complain with 1977 * the following: 1978 * warning: .dynamic section for "/system/bin/linker" is not at the 1979 * expected address (wrong library or version mismatch?) 1980 */ 1981 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 1982 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 1983 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 1984 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 1985 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 1986} 1987 1988/* 1989 * This code is called after the linker has linked itself and 1990 * fixed it's own GOT. It is safe to make references to externs 1991 * and other non-local data at this point. 1992 */ 1993static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 1994 /* NOTE: we store the args pointer on a special location 1995 * of the temporary TLS area in order to pass it to 1996 * the C Library's runtime initializer. 1997 * 1998 * The initializer must clear the slot and reset the TLS 1999 * to point to a different location to ensure that no other 2000 * shared library constructor can access it. 2001 */ 2002 __libc_init_tls(args); 2003 2004#if TIMING 2005 struct timeval t0, t1; 2006 gettimeofday(&t0, 0); 2007#endif 2008 2009 // Initialize environment functions, and get to the ELF aux vectors table. 2010 linker_env_init(args); 2011 2012 // If this is a setuid/setgid program, close the security hole described in 2013 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2014 if (get_AT_SECURE()) { 2015 nullify_closed_stdio(); 2016 } 2017 2018 debuggerd_init(); 2019 2020 // Get a few environment variables. 2021 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2022 if (LD_DEBUG != NULL) { 2023 g_ld_debug_verbosity = atoi(LD_DEBUG); 2024 } 2025 2026 // Normally, these are cleaned by linker_env_init, but the test 2027 // doesn't cost us anything. 2028 const char* ldpath_env = NULL; 2029 const char* ldpreload_env = NULL; 2030 if (!get_AT_SECURE()) { 2031 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2032 ldpreload_env = linker_env_get("LD_PRELOAD"); 2033 } 2034 2035 // Linker does not call constructors for its own 2036 // global variables so we need to initialize 2037 // the allocators explicitly. 2038 g_soinfo_allocator.init(); 2039 g_soinfo_links_allocator.init(); 2040 2041 INFO("[ android linker & debugger ]"); 2042 2043 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2044 if (si == NULL) { 2045 exit(EXIT_FAILURE); 2046 } 2047 2048 /* bootstrap the link map, the main exe always needs to be first */ 2049 si->flags |= FLAG_EXE; 2050 link_map* map = &(si->link_map_head); 2051 2052 map->l_addr = 0; 2053 map->l_name = args.argv[0]; 2054 map->l_prev = NULL; 2055 map->l_next = NULL; 2056 2057 _r_debug.r_map = map; 2058 r_debug_tail = map; 2059 2060 init_linker_info_for_gdb(linker_base); 2061 2062 // Extract information passed from the kernel. 2063 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2064 si->phnum = args.getauxval(AT_PHNUM); 2065 si->entry = args.getauxval(AT_ENTRY); 2066 2067 /* Compute the value of si->base. We can't rely on the fact that 2068 * the first entry is the PHDR because this will not be true 2069 * for certain executables (e.g. some in the NDK unit test suite) 2070 */ 2071 si->base = 0; 2072 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2073 si->load_bias = 0; 2074 for (size_t i = 0; i < si->phnum; ++i) { 2075 if (si->phdr[i].p_type == PT_PHDR) { 2076 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2077 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2078 break; 2079 } 2080 } 2081 si->dynamic = NULL; 2082 si->ref_count = 1; 2083 2084 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2085 if (elf_hdr->e_type != ET_DYN) { 2086 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2087 exit(EXIT_FAILURE); 2088 } 2089 2090 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2091 parse_LD_LIBRARY_PATH(ldpath_env); 2092 parse_LD_PRELOAD(ldpreload_env); 2093 2094 somain = si; 2095 2096 if (!soinfo_link_image(si, NULL)) { 2097 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2098 exit(EXIT_FAILURE); 2099 } 2100 2101 add_vdso(args); 2102 2103 si->CallPreInitConstructors(); 2104 2105 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2106 g_ld_preloads[i]->CallConstructors(); 2107 } 2108 2109 /* After the link_image, the si->load_bias is initialized. 2110 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2111 * We need to update this value for so exe here. So Unwind_Backtrace 2112 * for some arch like x86 could work correctly within so exe. 2113 */ 2114 map->l_addr = si->load_bias; 2115 si->CallConstructors(); 2116 2117#if TIMING 2118 gettimeofday(&t1, NULL); 2119 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2120 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2121 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2122#endif 2123#if STATS 2124 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2125 linker_stats.count[kRelocAbsolute], 2126 linker_stats.count[kRelocRelative], 2127 linker_stats.count[kRelocCopy], 2128 linker_stats.count[kRelocSymbol]); 2129#endif 2130#if COUNT_PAGES 2131 { 2132 unsigned n; 2133 unsigned i; 2134 unsigned count = 0; 2135 for (n = 0; n < 4096; n++) { 2136 if (bitmask[n]) { 2137 unsigned x = bitmask[n]; 2138#if defined(__LP64__) 2139 for (i = 0; i < 32; i++) { 2140#else 2141 for (i = 0; i < 8; i++) { 2142#endif 2143 if (x & 1) { 2144 count++; 2145 } 2146 x >>= 1; 2147 } 2148 } 2149 } 2150 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2151 } 2152#endif 2153 2154#if TIMING || STATS || COUNT_PAGES 2155 fflush(stdout); 2156#endif 2157 2158 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2159 return si->entry; 2160} 2161 2162/* Compute the load-bias of an existing executable. This shall only 2163 * be used to compute the load bias of an executable or shared library 2164 * that was loaded by the kernel itself. 2165 * 2166 * Input: 2167 * elf -> address of ELF header, assumed to be at the start of the file. 2168 * Return: 2169 * load bias, i.e. add the value of any p_vaddr in the file to get 2170 * the corresponding address in memory. 2171 */ 2172static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2173 ElfW(Addr) offset = elf->e_phoff; 2174 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2175 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2176 2177 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2178 if (phdr->p_type == PT_LOAD) { 2179 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2180 } 2181 } 2182 return 0; 2183} 2184 2185/* 2186 * This is the entry point for the linker, called from begin.S. This 2187 * method is responsible for fixing the linker's own relocations, and 2188 * then calling __linker_init_post_relocation(). 2189 * 2190 * Because this method is called before the linker has fixed it's own 2191 * relocations, any attempt to reference an extern variable, extern 2192 * function, or other GOT reference will generate a segfault. 2193 */ 2194extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2195 // Initialize static variables. 2196 solist = get_libdl_info(); 2197 sonext = get_libdl_info(); 2198 2199 KernelArgumentBlock args(raw_args); 2200 2201 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2202 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2203 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2204 2205 soinfo linker_so; 2206 memset(&linker_so, 0, sizeof(soinfo)); 2207 2208 strcpy(linker_so.name, "[dynamic linker]"); 2209 linker_so.base = linker_addr; 2210 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2211 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2212 linker_so.dynamic = NULL; 2213 linker_so.phdr = phdr; 2214 linker_so.phnum = elf_hdr->e_phnum; 2215 linker_so.flags |= FLAG_LINKER; 2216 2217 if (!soinfo_link_image(&linker_so, NULL)) { 2218 // It would be nice to print an error message, but if the linker 2219 // can't link itself, there's no guarantee that we'll be able to 2220 // call write() (because it involves a GOT reference). We may as 2221 // well try though... 2222 const char* msg = "CANNOT LINK EXECUTABLE: "; 2223 write(2, msg, strlen(msg)); 2224 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2225 write(2, "\n", 1); 2226 _exit(EXIT_FAILURE); 2227 } 2228 2229 // We have successfully fixed our own relocations. It's safe to run 2230 // the main part of the linker now. 2231 args.abort_message_ptr = &g_abort_message; 2232 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2233 2234 protect_data(PROT_READ); 2235 2236 // Return the address that the calling assembly stub should jump to. 2237 return start_address; 2238} 2239