linker.cpp revision 172955a4e30b88ce8239a7ef426b4e8903e9923c
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/mman.h> 38#include <sys/stat.h> 39#include <unistd.h> 40 41// Private C library headers. 42#include "private/bionic_tls.h" 43#include "private/KernelArgumentBlock.h" 44#include "private/ScopedPthreadMutexLocker.h" 45#include "private/ScopedFd.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 68#if defined(__LP64__) 69#define SEARCH_NAME(x) x 70#else 71// Nvidia drivers are relying on the bug: 72// http://code.google.com/p/android/issues/detail?id=6670 73// so we continue to use base-name lookup for lp32 74static const char* get_base_name(const char* name) { 75 const char* bname = strrchr(name, '/'); 76 return bname ? bname + 1 : name; 77} 78#define SEARCH_NAME(x) get_base_name(x) 79#endif 80 81static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 82static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 83 84static LinkerAllocator<soinfo> g_soinfo_allocator; 85static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator; 86 87static soinfo* solist; 88static soinfo* sonext; 89static soinfo* somain; /* main process, always the one after libdl_info */ 90 91static const char* const kDefaultLdPaths[] = { 92#if defined(__LP64__) 93 "/vendor/lib64", 94 "/system/lib64", 95#else 96 "/vendor/lib", 97 "/system/lib", 98#endif 99 NULL 100}; 101 102#define LDPATH_BUFSIZE (LDPATH_MAX*64) 103#define LDPATH_MAX 8 104 105#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 106#define LDPRELOAD_MAX 8 107 108static char g_ld_library_paths_buffer[LDPATH_BUFSIZE]; 109static const char* g_ld_library_paths[LDPATH_MAX + 1]; 110 111static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE]; 112static const char* g_ld_preload_names[LDPRELOAD_MAX + 1]; 113 114static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1]; 115 116__LIBC_HIDDEN__ int g_ld_debug_verbosity; 117 118__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd. 119 120enum RelocationKind { 121 kRelocAbsolute = 0, 122 kRelocRelative, 123 kRelocCopy, 124 kRelocSymbol, 125 kRelocMax 126}; 127 128#if STATS 129struct linker_stats_t { 130 int count[kRelocMax]; 131}; 132 133static linker_stats_t linker_stats; 134 135static void count_relocation(RelocationKind kind) { 136 ++linker_stats.count[kind]; 137} 138#else 139static void count_relocation(RelocationKind) { 140} 141#endif 142 143#if COUNT_PAGES 144static unsigned bitmask[4096]; 145#if defined(__LP64__) 146#define MARK(offset) \ 147 do { \ 148 if ((((offset) >> 12) >> 5) < 4096) \ 149 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 150 } while (0) 151#else 152#define MARK(offset) \ 153 do { \ 154 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 155 } while (0) 156#endif 157#else 158#define MARK(x) do {} while (0) 159#endif 160 161// You shouldn't try to call memory-allocating functions in the dynamic linker. 162// Guard against the most obvious ones. 163#define DISALLOW_ALLOCATION(return_type, name, ...) \ 164 return_type name __VA_ARGS__ \ 165 { \ 166 __libc_fatal("ERROR: " #name " called from the dynamic linker!\n"); \ 167 } 168DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 169DISALLOW_ALLOCATION(void, free, (void* u __unused)); 170DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 171DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 172 173static char tmp_err_buf[768]; 174static char __linker_dl_err_buf[768]; 175 176char* linker_get_error_buffer() { 177 return &__linker_dl_err_buf[0]; 178} 179 180size_t linker_get_error_buffer_size() { 181 return sizeof(__linker_dl_err_buf); 182} 183 184/* 185 * This function is an empty stub where GDB locates a breakpoint to get notified 186 * about linker activity. 187 */ 188extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 189 190static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 191static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 192static link_map* r_debug_tail = 0; 193 194static void insert_soinfo_into_debug_map(soinfo* info) { 195 // Copy the necessary fields into the debug structure. 196 link_map* map = &(info->link_map_head); 197 map->l_addr = info->load_bias; 198 map->l_name = reinterpret_cast<char*>(info->name); 199 map->l_ld = info->dynamic; 200 201 /* Stick the new library at the end of the list. 202 * gdb tends to care more about libc than it does 203 * about leaf libraries, and ordering it this way 204 * reduces the back-and-forth over the wire. 205 */ 206 if (r_debug_tail) { 207 r_debug_tail->l_next = map; 208 map->l_prev = r_debug_tail; 209 map->l_next = 0; 210 } else { 211 _r_debug.r_map = map; 212 map->l_prev = 0; 213 map->l_next = 0; 214 } 215 r_debug_tail = map; 216} 217 218static void remove_soinfo_from_debug_map(soinfo* info) { 219 link_map* map = &(info->link_map_head); 220 221 if (r_debug_tail == map) { 222 r_debug_tail = map->l_prev; 223 } 224 225 if (map->l_prev) { 226 map->l_prev->l_next = map->l_next; 227 } 228 if (map->l_next) { 229 map->l_next->l_prev = map->l_prev; 230 } 231} 232 233static void notify_gdb_of_load(soinfo* info) { 234 if (info->flags & FLAG_EXE) { 235 // GDB already knows about the main executable 236 return; 237 } 238 239 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 240 241 _r_debug.r_state = r_debug::RT_ADD; 242 rtld_db_dlactivity(); 243 244 insert_soinfo_into_debug_map(info); 245 246 _r_debug.r_state = r_debug::RT_CONSISTENT; 247 rtld_db_dlactivity(); 248} 249 250static void notify_gdb_of_unload(soinfo* info) { 251 if (info->flags & FLAG_EXE) { 252 // GDB already knows about the main executable 253 return; 254 } 255 256 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 257 258 _r_debug.r_state = r_debug::RT_DELETE; 259 rtld_db_dlactivity(); 260 261 remove_soinfo_from_debug_map(info); 262 263 _r_debug.r_state = r_debug::RT_CONSISTENT; 264 rtld_db_dlactivity(); 265} 266 267void notify_gdb_of_libraries() { 268 _r_debug.r_state = r_debug::RT_ADD; 269 rtld_db_dlactivity(); 270 _r_debug.r_state = r_debug::RT_CONSISTENT; 271 rtld_db_dlactivity(); 272} 273 274LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 275 return g_soinfo_links_allocator.alloc(); 276} 277 278void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 279 g_soinfo_links_allocator.free(entry); 280} 281 282static void protect_data(int protection) { 283 g_soinfo_allocator.protect_all(protection); 284 g_soinfo_links_allocator.protect_all(protection); 285} 286 287static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 288 if (strlen(name) >= SOINFO_NAME_LEN) { 289 DL_ERR("library name \"%s\" too long", name); 290 return NULL; 291 } 292 293 soinfo* si = g_soinfo_allocator.alloc(); 294 295 // Initialize the new element. 296 memset(si, 0, sizeof(soinfo)); 297 strlcpy(si->name, name, sizeof(si->name)); 298 si->flags = FLAG_NEW_SOINFO; 299 300 if (file_stat != NULL) { 301 si->set_st_dev(file_stat->st_dev); 302 si->set_st_ino(file_stat->st_ino); 303 } 304 305 sonext->next = si; 306 sonext = si; 307 308 TRACE("name %s: allocated soinfo @ %p", name, si); 309 return si; 310} 311 312static void soinfo_free(soinfo* si) { 313 if (si == NULL) { 314 return; 315 } 316 317 if (si->base != 0 && si->size != 0) { 318 munmap(reinterpret_cast<void*>(si->base), si->size); 319 } 320 321 soinfo *prev = NULL, *trav; 322 323 TRACE("name %s: freeing soinfo @ %p", si->name, si); 324 325 for (trav = solist; trav != NULL; trav = trav->next) { 326 if (trav == si) 327 break; 328 prev = trav; 329 } 330 if (trav == NULL) { 331 /* si was not in solist */ 332 DL_ERR("name \"%s\" is not in solist!", si->name); 333 return; 334 } 335 336 // clear links to/from si 337 si->remove_all_links(); 338 339 /* prev will never be NULL, because the first entry in solist is 340 always the static libdl_info. 341 */ 342 prev->next = si->next; 343 if (si == sonext) { 344 sonext = prev; 345 } 346 347 g_soinfo_allocator.free(si); 348} 349 350 351static void parse_path(const char* path, const char* delimiters, 352 const char** array, char* buf, size_t buf_size, size_t max_count) { 353 if (path == NULL) { 354 return; 355 } 356 357 size_t len = strlcpy(buf, path, buf_size); 358 359 size_t i = 0; 360 char* buf_p = buf; 361 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 362 if (*array[i] != '\0') { 363 ++i; 364 } 365 } 366 367 // Forget the last path if we had to truncate; this occurs if the 2nd to 368 // last char isn't '\0' (i.e. wasn't originally a delimiter). 369 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 370 array[i - 1] = NULL; 371 } else { 372 array[i] = NULL; 373 } 374} 375 376static void parse_LD_LIBRARY_PATH(const char* path) { 377 parse_path(path, ":", g_ld_library_paths, 378 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 379} 380 381static void parse_LD_PRELOAD(const char* path) { 382 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 383 parse_path(path, " :", g_ld_preload_names, 384 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 385} 386 387#if defined(__arm__) 388 389/* For a given PC, find the .so that it belongs to. 390 * Returns the base address of the .ARM.exidx section 391 * for that .so, and the number of 8-byte entries 392 * in that section (via *pcount). 393 * 394 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 395 * 396 * This function is exposed via dlfcn.cpp and libdl.so. 397 */ 398_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 399 unsigned addr = (unsigned)pc; 400 401 for (soinfo* si = solist; si != 0; si = si->next) { 402 if ((addr >= si->base) && (addr < (si->base + si->size))) { 403 *pcount = si->ARM_exidx_count; 404 return (_Unwind_Ptr)si->ARM_exidx; 405 } 406 } 407 *pcount = 0; 408 return NULL; 409} 410 411#endif 412 413/* Here, we only have to provide a callback to iterate across all the 414 * loaded libraries. gcc_eh does the rest. */ 415int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 416 int rv = 0; 417 for (soinfo* si = solist; si != NULL; si = si->next) { 418 dl_phdr_info dl_info; 419 dl_info.dlpi_addr = si->link_map_head.l_addr; 420 dl_info.dlpi_name = si->link_map_head.l_name; 421 dl_info.dlpi_phdr = si->phdr; 422 dl_info.dlpi_phnum = si->phnum; 423 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 424 if (rv != 0) { 425 break; 426 } 427 } 428 return rv; 429} 430 431static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 432 ElfW(Sym)* symtab = si->symtab; 433 const char* strtab = si->strtab; 434 435 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 436 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 437 438 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 439 ElfW(Sym)* s = symtab + n; 440 if (strcmp(strtab + s->st_name, name)) continue; 441 442 /* only concern ourselves with global and weak symbol definitions */ 443 switch (ELF_ST_BIND(s->st_info)) { 444 case STB_GLOBAL: 445 case STB_WEAK: 446 if (s->st_shndx == SHN_UNDEF) { 447 continue; 448 } 449 450 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 451 name, si->name, reinterpret_cast<void*>(s->st_value), 452 static_cast<size_t>(s->st_size)); 453 return s; 454 case STB_LOCAL: 455 continue; 456 default: 457 __libc_fatal("ERROR: Unexpected ST_BIND value: %d for '%s' in '%s'", 458 ELF_ST_BIND(s->st_info), name, si->name); 459 } 460 } 461 462 TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd", 463 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 464 465 466 return NULL; 467} 468 469static unsigned elfhash(const char* _name) { 470 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 471 unsigned h = 0, g; 472 473 while (*name) { 474 h = (h << 4) + *name++; 475 g = h & 0xf0000000; 476 h ^= g; 477 h ^= g >> 24; 478 } 479 return h; 480} 481 482static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 483 unsigned elf_hash = elfhash(name); 484 ElfW(Sym)* s = NULL; 485 486 if (si != NULL && somain != NULL) { 487 /* 488 * Local scope is executable scope. Just start looking into it right away 489 * for the shortcut. 490 */ 491 492 if (si == somain) { 493 s = soinfo_elf_lookup(si, elf_hash, name); 494 if (s != NULL) { 495 *lsi = si; 496 goto done; 497 } 498 } else { 499 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 500 501 /* 502 * If this object was built with symbolic relocations disabled, the 503 * first place to look to resolve external references is the main 504 * executable. 505 */ 506 507 if (!si->has_DT_SYMBOLIC) { 508 DEBUG("%s: looking up %s in executable %s", 509 si->name, name, somain->name); 510 s = soinfo_elf_lookup(somain, elf_hash, name); 511 if (s != NULL) { 512 *lsi = somain; 513 goto done; 514 } 515 } 516 517 /* Look for symbols in the local scope (the object who is 518 * searching). This happens with C++ templates on x86 for some 519 * reason. 520 * 521 * Notes on weak symbols: 522 * The ELF specs are ambiguous about treatment of weak definitions in 523 * dynamic linking. Some systems return the first definition found 524 * and some the first non-weak definition. This is system dependent. 525 * Here we return the first definition found for simplicity. */ 526 527 s = soinfo_elf_lookup(si, elf_hash, name); 528 if (s != NULL) { 529 *lsi = si; 530 goto done; 531 } 532 533 /* 534 * If this object was built with -Bsymbolic and symbol is not found 535 * in the local scope, try to find the symbol in the main executable. 536 */ 537 538 if (si->has_DT_SYMBOLIC) { 539 DEBUG("%s: looking up %s in executable %s after local scope", 540 si->name, name, somain->name); 541 s = soinfo_elf_lookup(somain, elf_hash, name); 542 if (s != NULL) { 543 *lsi = somain; 544 goto done; 545 } 546 } 547 } 548 } 549 550 /* Next, look for it in the preloads list */ 551 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 552 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name); 553 if (s != NULL) { 554 *lsi = g_ld_preloads[i]; 555 goto done; 556 } 557 } 558 559 for (int i = 0; needed[i] != NULL; i++) { 560 DEBUG("%s: looking up %s in %s", 561 si->name, name, needed[i]->name); 562 s = soinfo_elf_lookup(needed[i], elf_hash, name); 563 if (s != NULL) { 564 *lsi = needed[i]; 565 goto done; 566 } 567 } 568 569done: 570 if (s != NULL) { 571 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 572 "found in %s, base = %p, load bias = %p", 573 si->name, name, reinterpret_cast<void*>(s->st_value), 574 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 575 reinterpret_cast<void*>((*lsi)->load_bias)); 576 return s; 577 } 578 579 return NULL; 580} 581 582// Another soinfo list allocator to use in dlsym. We don't reuse 583// SoinfoListAllocator because it is write-protected most of the time. 584static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_list_allocator_rw; 585class SoinfoListAllocatorRW { 586 public: 587 static LinkedListEntry<soinfo>* alloc() { 588 return g_soinfo_list_allocator_rw.alloc(); 589 } 590 591 static void free(LinkedListEntry<soinfo>* ptr) { 592 g_soinfo_list_allocator_rw.free(ptr); 593 } 594}; 595 596// This is used by dlsym(3). It performs symbol lookup only within the 597// specified soinfo object and its dependencies in breadth first order. 598ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) { 599 LinkedList<soinfo, SoinfoListAllocatorRW> visit_list; 600 LinkedList<soinfo, SoinfoListAllocatorRW> visited; 601 visit_list.push_back(si); 602 soinfo* current_soinfo; 603 while ((current_soinfo = visit_list.pop_front()) != nullptr) { 604 if (visited.contains(current_soinfo)) { 605 continue; 606 } 607 608 ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name); 609 610 if (result != nullptr) { 611 *found = current_soinfo; 612 visit_list.clear(); 613 visited.clear(); 614 return result; 615 } 616 visited.push_back(current_soinfo); 617 618 current_soinfo->get_children().for_each([&](soinfo* child) { 619 visit_list.push_back(child); 620 }); 621 } 622 623 visit_list.clear(); 624 visited.clear(); 625 return nullptr; 626} 627 628/* This is used by dlsym(3) to performs a global symbol lookup. If the 629 start value is null (for RTLD_DEFAULT), the search starts at the 630 beginning of the global solist. Otherwise the search starts at the 631 specified soinfo (for RTLD_NEXT). 632 */ 633ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 634 unsigned elf_hash = elfhash(name); 635 636 if (start == NULL) { 637 start = solist; 638 } 639 640 ElfW(Sym)* s = NULL; 641 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 642 s = soinfo_elf_lookup(si, elf_hash, name); 643 if (s != NULL) { 644 *found = si; 645 break; 646 } 647 } 648 649 if (s != NULL) { 650 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 651 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 652 } 653 654 return s; 655} 656 657soinfo* find_containing_library(const void* p) { 658 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 659 for (soinfo* si = solist; si != NULL; si = si->next) { 660 if (address >= si->base && address - si->base < si->size) { 661 return si; 662 } 663 } 664 return NULL; 665} 666 667ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 668 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 669 670 // Search the library's symbol table for any defined symbol which 671 // contains this address. 672 for (size_t i = 0; i < si->nchain; ++i) { 673 ElfW(Sym)* sym = &si->symtab[i]; 674 if (sym->st_shndx != SHN_UNDEF && 675 soaddr >= sym->st_value && 676 soaddr < sym->st_value + sym->st_size) { 677 return sym; 678 } 679 } 680 681 return NULL; 682} 683 684static int open_library_on_path(const char* name, const char* const paths[]) { 685 char buf[512]; 686 for (size_t i = 0; paths[i] != NULL; ++i) { 687 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 688 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 689 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 690 continue; 691 } 692 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 693 if (fd != -1) { 694 return fd; 695 } 696 } 697 return -1; 698} 699 700static int open_library(const char* name) { 701 TRACE("[ opening %s ]", name); 702 703 // If the name contains a slash, we should attempt to open it directly and not search the paths. 704 if (strchr(name, '/') != NULL) { 705 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 706 if (fd != -1) { 707 return fd; 708 } 709 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 710#if defined(__LP64__) 711 return -1; 712#endif 713 } 714 715 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 716 int fd = open_library_on_path(name, g_ld_library_paths); 717 if (fd == -1) { 718 fd = open_library_on_path(name, kDefaultLdPaths); 719 } 720 return fd; 721} 722 723static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 724 int fd = -1; 725 ScopedFd file_guard(-1); 726 727 if (extinfo != NULL && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) { 728 fd = extinfo->library_fd; 729 } else { 730 // Open the file. 731 fd = open_library(name); 732 if (fd == -1) { 733 DL_ERR("library \"%s\" not found", name); 734 return NULL; 735 } 736 737 file_guard.reset(fd); 738 } 739 740 ElfReader elf_reader(name, fd); 741 742 struct stat file_stat; 743 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 744 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 745 return NULL; 746 } 747 748 // Check for symlink and other situations where 749 // file can have different names. 750 for (soinfo* si = solist; si != NULL; si = si->next) { 751 if (si->get_st_dev() != 0 && 752 si->get_st_ino() != 0 && 753 si->get_st_dev() == file_stat.st_dev && 754 si->get_st_ino() == file_stat.st_ino) { 755 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 756 return si; 757 } 758 } 759 760 if ((dlflags & RTLD_NOLOAD) != 0) { 761 return NULL; 762 } 763 764 // Read the ELF header and load the segments. 765 if (!elf_reader.Load(extinfo)) { 766 return NULL; 767 } 768 769 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 770 if (si == NULL) { 771 return NULL; 772 } 773 si->base = elf_reader.load_start(); 774 si->size = elf_reader.load_size(); 775 si->load_bias = elf_reader.load_bias(); 776 si->phnum = elf_reader.phdr_count(); 777 si->phdr = elf_reader.loaded_phdr(); 778 779 // At this point we know that whatever is loaded @ base is a valid ELF 780 // shared library whose segments are properly mapped in. 781 TRACE("[ load_library base=%p size=%zu name='%s' ]", 782 reinterpret_cast<void*>(si->base), si->size, si->name); 783 784 if (!soinfo_link_image(si, extinfo)) { 785 soinfo_free(si); 786 return NULL; 787 } 788 789 return si; 790} 791 792static soinfo *find_loaded_library_by_name(const char* name) { 793 const char* search_name = SEARCH_NAME(name); 794 for (soinfo* si = solist; si != NULL; si = si->next) { 795 if (!strcmp(search_name, si->name)) { 796 return si; 797 } 798 } 799 return NULL; 800} 801 802static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 803 if (name == NULL) { 804 return somain; 805 } 806 807 soinfo* si = find_loaded_library_by_name(name); 808 809 // Library might still be loaded, the accurate detection 810 // of this fact is done by load_library 811 if (si == NULL) { 812 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 813 si = load_library(name, dlflags, extinfo); 814 } 815 816 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 817 DL_ERR("recursive link to \"%s\"", si->name); 818 return NULL; 819 } 820 821 return si; 822} 823 824static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 825 soinfo* si = find_library_internal(name, dlflags, extinfo); 826 if (si != NULL) { 827 si->ref_count++; 828 } 829 return si; 830} 831 832static void soinfo_unload(soinfo* si) { 833 if (si->ref_count == 1) { 834 TRACE("unloading '%s'", si->name); 835 si->CallDestructors(); 836 837 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 838 si->get_children().for_each([&] (soinfo* child) { 839 TRACE("%s needs to unload %s", si->name, child->name); 840 soinfo_unload(child); 841 }); 842 } else { 843 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 844 if (d->d_tag == DT_NEEDED) { 845 const char* library_name = si->strtab + d->d_un.d_val; 846 TRACE("%s needs to unload %s", si->name, library_name); 847 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 848 if (needed != NULL) { 849 soinfo_unload(needed); 850 } else { 851 // Not found: for example if symlink was deleted between dlopen and dlclose 852 // Since we cannot really handle errors at this point - print and continue. 853 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 854 } 855 } 856 } 857 } 858 859 notify_gdb_of_unload(si); 860 si->ref_count = 0; 861 soinfo_free(si); 862 } else { 863 si->ref_count--; 864 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 865 } 866} 867 868void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 869 // Use basic string manipulation calls to avoid snprintf. 870 // snprintf indirectly calls pthread_getspecific to get the size of a buffer. 871 // When debug malloc is enabled, this call returns 0. This in turn causes 872 // snprintf to do nothing, which causes libraries to fail to load. 873 // See b/17302493 for further details. 874 // Once the above bug is fixed, this code can be modified to use 875 // snprintf again. 876 size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2; 877 if (buffer_size < required_len) { 878 __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu", 879 buffer_size, required_len); 880 } 881 char* end = stpcpy(buffer, kDefaultLdPaths[0]); 882 *end = ':'; 883 strcpy(end + 1, kDefaultLdPaths[1]); 884} 885 886void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 887 if (!get_AT_SECURE()) { 888 parse_LD_LIBRARY_PATH(ld_library_path); 889 } 890} 891 892soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 893 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 894 DL_ERR("invalid flags to dlopen: %x", flags); 895 return NULL; 896 } 897 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 898 DL_ERR("invalid extended flags to android_dlopen_ext: %" PRIx64, extinfo->flags); 899 return NULL; 900 } 901 protect_data(PROT_READ | PROT_WRITE); 902 soinfo* si = find_library(name, flags, extinfo); 903 if (si != NULL) { 904 si->CallConstructors(); 905 } 906 protect_data(PROT_READ); 907 return si; 908} 909 910void do_dlclose(soinfo* si) { 911 protect_data(PROT_READ | PROT_WRITE); 912 soinfo_unload(si); 913 protect_data(PROT_READ); 914} 915 916#if defined(USE_RELA) 917static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 918 ElfW(Sym)* s; 919 soinfo* lsi; 920 921 for (size_t idx = 0; idx < count; ++idx, ++rela) { 922 unsigned type = ELFW(R_TYPE)(rela->r_info); 923 unsigned sym = ELFW(R_SYM)(rela->r_info); 924 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 925 ElfW(Addr) sym_addr = 0; 926 const char* sym_name = NULL; 927 928 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 929 if (type == 0) { // R_*_NONE 930 continue; 931 } 932 if (sym != 0) { 933 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 934 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 935 if (s == NULL) { 936 // We only allow an undefined symbol if this is a weak reference... 937 s = &si->symtab[sym]; 938 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 939 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 940 return -1; 941 } 942 943 /* IHI0044C AAELF 4.5.1.1: 944 945 Libraries are not searched to resolve weak references. 946 It is not an error for a weak reference to remain unsatisfied. 947 948 During linking, the value of an undefined weak reference is: 949 - Zero if the relocation type is absolute 950 - The address of the place if the relocation is pc-relative 951 - The address of nominal base address if the relocation 952 type is base-relative. 953 */ 954 955 switch (type) { 956#if defined(__aarch64__) 957 case R_AARCH64_JUMP_SLOT: 958 case R_AARCH64_GLOB_DAT: 959 case R_AARCH64_ABS64: 960 case R_AARCH64_ABS32: 961 case R_AARCH64_ABS16: 962 case R_AARCH64_RELATIVE: 963 /* 964 * The sym_addr was initialized to be zero above, or the relocation 965 * code below does not care about value of sym_addr. 966 * No need to do anything. 967 */ 968 break; 969#elif defined(__x86_64__) 970 case R_X86_64_JUMP_SLOT: 971 case R_X86_64_GLOB_DAT: 972 case R_X86_64_32: 973 case R_X86_64_64: 974 case R_X86_64_RELATIVE: 975 // No need to do anything. 976 break; 977 case R_X86_64_PC32: 978 sym_addr = reloc; 979 break; 980#endif 981 default: 982 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 983 return -1; 984 } 985 } else { 986 // We got a definition. 987 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 988 } 989 count_relocation(kRelocSymbol); 990 } else { 991 s = NULL; 992 } 993 994 switch (type) { 995#if defined(__aarch64__) 996 case R_AARCH64_JUMP_SLOT: 997 count_relocation(kRelocAbsolute); 998 MARK(rela->r_offset); 999 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 1000 reloc, (sym_addr + rela->r_addend), sym_name); 1001 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 1002 break; 1003 case R_AARCH64_GLOB_DAT: 1004 count_relocation(kRelocAbsolute); 1005 MARK(rela->r_offset); 1006 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 1007 reloc, (sym_addr + rela->r_addend), sym_name); 1008 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 1009 break; 1010 case R_AARCH64_ABS64: 1011 count_relocation(kRelocAbsolute); 1012 MARK(rela->r_offset); 1013 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 1014 reloc, (sym_addr + rela->r_addend), sym_name); 1015 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1016 break; 1017 case R_AARCH64_ABS32: 1018 count_relocation(kRelocAbsolute); 1019 MARK(rela->r_offset); 1020 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 1021 reloc, (sym_addr + rela->r_addend), sym_name); 1022 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 1023 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1024 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1025 } else { 1026 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1027 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1028 static_cast<ElfW(Addr)>(INT32_MIN), 1029 static_cast<ElfW(Addr)>(UINT32_MAX)); 1030 return -1; 1031 } 1032 break; 1033 case R_AARCH64_ABS16: 1034 count_relocation(kRelocAbsolute); 1035 MARK(rela->r_offset); 1036 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 1037 reloc, (sym_addr + rela->r_addend), sym_name); 1038 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 1039 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1040 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1041 } else { 1042 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1043 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1044 static_cast<ElfW(Addr)>(INT16_MIN), 1045 static_cast<ElfW(Addr)>(UINT16_MAX)); 1046 return -1; 1047 } 1048 break; 1049 case R_AARCH64_PREL64: 1050 count_relocation(kRelocRelative); 1051 MARK(rela->r_offset); 1052 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 1053 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1054 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 1055 break; 1056 case R_AARCH64_PREL32: 1057 count_relocation(kRelocRelative); 1058 MARK(rela->r_offset); 1059 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 1060 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1061 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1062 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1063 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1064 } else { 1065 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1066 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1067 static_cast<ElfW(Addr)>(INT32_MIN), 1068 static_cast<ElfW(Addr)>(UINT32_MAX)); 1069 return -1; 1070 } 1071 break; 1072 case R_AARCH64_PREL16: 1073 count_relocation(kRelocRelative); 1074 MARK(rela->r_offset); 1075 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1076 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1077 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1078 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1079 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1080 } else { 1081 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1082 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1083 static_cast<ElfW(Addr)>(INT16_MIN), 1084 static_cast<ElfW(Addr)>(UINT16_MAX)); 1085 return -1; 1086 } 1087 break; 1088 1089 case R_AARCH64_RELATIVE: 1090 count_relocation(kRelocRelative); 1091 MARK(rela->r_offset); 1092 if (sym) { 1093 DL_ERR("odd RELATIVE form..."); 1094 return -1; 1095 } 1096 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1097 reloc, (si->base + rela->r_addend)); 1098 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1099 break; 1100 1101 case R_AARCH64_COPY: 1102 /* 1103 * ET_EXEC is not supported so this should not happen. 1104 * 1105 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1106 * 1107 * Section 4.7.1.10 "Dynamic relocations" 1108 * R_AARCH64_COPY may only appear in executable objects where e_type is 1109 * set to ET_EXEC. 1110 */ 1111 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1112 return -1; 1113 case R_AARCH64_TLS_TPREL64: 1114 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1115 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1116 break; 1117 case R_AARCH64_TLS_DTPREL32: 1118 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1119 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1120 break; 1121#elif defined(__x86_64__) 1122 case R_X86_64_JUMP_SLOT: 1123 count_relocation(kRelocAbsolute); 1124 MARK(rela->r_offset); 1125 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1126 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1127 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1128 break; 1129 case R_X86_64_GLOB_DAT: 1130 count_relocation(kRelocAbsolute); 1131 MARK(rela->r_offset); 1132 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1133 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1134 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1135 break; 1136 case R_X86_64_RELATIVE: 1137 count_relocation(kRelocRelative); 1138 MARK(rela->r_offset); 1139 if (sym) { 1140 DL_ERR("odd RELATIVE form..."); 1141 return -1; 1142 } 1143 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1144 static_cast<size_t>(si->base)); 1145 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1146 break; 1147 case R_X86_64_32: 1148 count_relocation(kRelocRelative); 1149 MARK(rela->r_offset); 1150 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1151 static_cast<size_t>(sym_addr), sym_name); 1152 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1153 break; 1154 case R_X86_64_64: 1155 count_relocation(kRelocRelative); 1156 MARK(rela->r_offset); 1157 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1158 static_cast<size_t>(sym_addr), sym_name); 1159 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1160 break; 1161 case R_X86_64_PC32: 1162 count_relocation(kRelocRelative); 1163 MARK(rela->r_offset); 1164 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1165 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1166 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1167 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1168 break; 1169#endif 1170 1171 default: 1172 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1173 return -1; 1174 } 1175 } 1176 return 0; 1177} 1178 1179#else // REL, not RELA. 1180 1181static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1182 ElfW(Sym)* s; 1183 soinfo* lsi; 1184 1185 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1186 unsigned type = ELFW(R_TYPE)(rel->r_info); 1187 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1188 unsigned sym = ELFW(R_SYM)(rel->r_info); 1189 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1190 ElfW(Addr) sym_addr = 0; 1191 const char* sym_name = NULL; 1192 1193 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1194 if (type == 0) { // R_*_NONE 1195 continue; 1196 } 1197 if (sym != 0) { 1198 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1199 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1200 if (s == NULL) { 1201 // We only allow an undefined symbol if this is a weak reference... 1202 s = &si->symtab[sym]; 1203 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1204 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1205 return -1; 1206 } 1207 1208 /* IHI0044C AAELF 4.5.1.1: 1209 1210 Libraries are not searched to resolve weak references. 1211 It is not an error for a weak reference to remain 1212 unsatisfied. 1213 1214 During linking, the value of an undefined weak reference is: 1215 - Zero if the relocation type is absolute 1216 - The address of the place if the relocation is pc-relative 1217 - The address of nominal base address if the relocation 1218 type is base-relative. 1219 */ 1220 1221 switch (type) { 1222#if defined(__arm__) 1223 case R_ARM_JUMP_SLOT: 1224 case R_ARM_GLOB_DAT: 1225 case R_ARM_ABS32: 1226 case R_ARM_RELATIVE: /* Don't care. */ 1227 // sym_addr was initialized to be zero above or relocation 1228 // code below does not care about value of sym_addr. 1229 // No need to do anything. 1230 break; 1231#elif defined(__i386__) 1232 case R_386_JMP_SLOT: 1233 case R_386_GLOB_DAT: 1234 case R_386_32: 1235 case R_386_RELATIVE: /* Don't care. */ 1236 // sym_addr was initialized to be zero above or relocation 1237 // code below does not care about value of sym_addr. 1238 // No need to do anything. 1239 break; 1240 case R_386_PC32: 1241 sym_addr = reloc; 1242 break; 1243#endif 1244 1245#if defined(__arm__) 1246 case R_ARM_COPY: 1247 // Fall through. Can't really copy if weak symbol is not found at run-time. 1248#endif 1249 default: 1250 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1251 return -1; 1252 } 1253 } else { 1254 // We got a definition. 1255 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1256 } 1257 count_relocation(kRelocSymbol); 1258 } else { 1259 s = NULL; 1260 } 1261 1262 switch (type) { 1263#if defined(__arm__) 1264 case R_ARM_JUMP_SLOT: 1265 count_relocation(kRelocAbsolute); 1266 MARK(rel->r_offset); 1267 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1268 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1269 break; 1270 case R_ARM_GLOB_DAT: 1271 count_relocation(kRelocAbsolute); 1272 MARK(rel->r_offset); 1273 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1274 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1275 break; 1276 case R_ARM_ABS32: 1277 count_relocation(kRelocAbsolute); 1278 MARK(rel->r_offset); 1279 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1280 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1281 break; 1282 case R_ARM_REL32: 1283 count_relocation(kRelocRelative); 1284 MARK(rel->r_offset); 1285 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1286 reloc, sym_addr, rel->r_offset, sym_name); 1287 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1288 break; 1289 case R_ARM_COPY: 1290 /* 1291 * ET_EXEC is not supported so this should not happen. 1292 * 1293 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1294 * 1295 * Section 4.7.1.10 "Dynamic relocations" 1296 * R_ARM_COPY may only appear in executable objects where e_type is 1297 * set to ET_EXEC. 1298 */ 1299 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1300 return -1; 1301#elif defined(__i386__) 1302 case R_386_JMP_SLOT: 1303 count_relocation(kRelocAbsolute); 1304 MARK(rel->r_offset); 1305 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1306 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1307 break; 1308 case R_386_GLOB_DAT: 1309 count_relocation(kRelocAbsolute); 1310 MARK(rel->r_offset); 1311 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1312 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1313 break; 1314 case R_386_32: 1315 count_relocation(kRelocRelative); 1316 MARK(rel->r_offset); 1317 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1318 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1319 break; 1320 case R_386_PC32: 1321 count_relocation(kRelocRelative); 1322 MARK(rel->r_offset); 1323 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1324 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1325 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1326 break; 1327#elif defined(__mips__) 1328 case R_MIPS_REL32: 1329#if defined(__LP64__) 1330 // MIPS Elf64_Rel entries contain compound relocations 1331 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1332 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1333 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1334 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1335 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1336 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1337 return -1; 1338 } 1339#endif 1340 count_relocation(kRelocAbsolute); 1341 MARK(rel->r_offset); 1342 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1343 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1344 if (s) { 1345 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1346 } else { 1347 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1348 } 1349 break; 1350#endif 1351 1352#if defined(__arm__) 1353 case R_ARM_RELATIVE: 1354#elif defined(__i386__) 1355 case R_386_RELATIVE: 1356#endif 1357 count_relocation(kRelocRelative); 1358 MARK(rel->r_offset); 1359 if (sym) { 1360 DL_ERR("odd RELATIVE form..."); 1361 return -1; 1362 } 1363 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1364 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1365 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1366 break; 1367 1368 default: 1369 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1370 return -1; 1371 } 1372 } 1373 return 0; 1374} 1375#endif 1376 1377#if defined(__mips__) 1378static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1379 ElfW(Addr)** got = si->plt_got; 1380 if (got == NULL) { 1381 return true; 1382 } 1383 unsigned local_gotno = si->mips_local_gotno; 1384 unsigned gotsym = si->mips_gotsym; 1385 unsigned symtabno = si->mips_symtabno; 1386 ElfW(Sym)* symtab = si->symtab; 1387 1388 // got[0] is the address of the lazy resolver function. 1389 // got[1] may be used for a GNU extension. 1390 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1391 // FIXME: maybe this should be in a separate routine? 1392 if ((si->flags & FLAG_LINKER) == 0) { 1393 size_t g = 0; 1394 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1395 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1396 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1397 } 1398 // Relocate the local GOT entries. 1399 for (; g < local_gotno; g++) { 1400 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1401 } 1402 } 1403 1404 // Now for the global GOT entries... 1405 ElfW(Sym)* sym = symtab + gotsym; 1406 got = si->plt_got + local_gotno; 1407 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1408 // This is an undefined reference... try to locate it. 1409 const char* sym_name = si->strtab + sym->st_name; 1410 soinfo* lsi; 1411 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1412 if (s == NULL) { 1413 // We only allow an undefined symbol if this is a weak reference. 1414 s = &symtab[g]; 1415 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1416 DL_ERR("cannot locate \"%s\"...", sym_name); 1417 return false; 1418 } 1419 *got = 0; 1420 } else { 1421 // FIXME: is this sufficient? 1422 // For reference see NetBSD link loader 1423 // 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 1424 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1425 } 1426 } 1427 return true; 1428} 1429#endif 1430 1431void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1432 if (functions == NULL) { 1433 return; 1434 } 1435 1436 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1437 1438 int begin = reverse ? (count - 1) : 0; 1439 int end = reverse ? -1 : count; 1440 int step = reverse ? -1 : 1; 1441 1442 for (int i = begin; i != end; i += step) { 1443 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1444 CallFunction("function", functions[i]); 1445 } 1446 1447 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1448} 1449 1450void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1451 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1452 return; 1453 } 1454 1455 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1456 function(); 1457 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1458 1459 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1460 // are still writable. This happens with our debug malloc (see http://b/7941716). 1461 protect_data(PROT_READ | PROT_WRITE); 1462} 1463 1464void soinfo::CallPreInitConstructors() { 1465 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1466 // but ignored in a shared library. 1467 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1468} 1469 1470void soinfo::CallConstructors() { 1471 if (constructors_called) { 1472 return; 1473 } 1474 1475 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1476 // protect against recursive constructor calls. One simple example of constructor recursion 1477 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1478 // 1. The program depends on libc, so libc's constructor is called here. 1479 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1480 // 3. dlopen() calls the constructors on the newly created 1481 // soinfo for libc_malloc_debug_leak.so. 1482 // 4. The debug .so depends on libc, so CallConstructors is 1483 // called again with the libc soinfo. If it doesn't trigger the early- 1484 // out above, the libc constructor will be called again (recursively!). 1485 constructors_called = true; 1486 1487 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1488 // The GNU dynamic linker silently ignores these, but we warn the developer. 1489 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1490 name, preinit_array_count); 1491 } 1492 1493 get_children().for_each([] (soinfo* si) { 1494 si->CallConstructors(); 1495 }); 1496 1497 TRACE("\"%s\": calling constructors", name); 1498 1499 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1500 CallFunction("DT_INIT", init_func); 1501 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1502} 1503 1504void soinfo::CallDestructors() { 1505 TRACE("\"%s\": calling destructors", name); 1506 1507 // DT_FINI_ARRAY must be parsed in reverse order. 1508 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1509 1510 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1511 CallFunction("DT_FINI", fini_func); 1512 1513 // This is needed on second call to dlopen 1514 // after library has been unloaded with RTLD_NODELETE 1515 constructors_called = false; 1516} 1517 1518void soinfo::add_child(soinfo* child) { 1519 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1520 return; 1521 } 1522 1523 this->children.push_front(child); 1524 child->parents.push_front(this); 1525} 1526 1527void soinfo::remove_all_links() { 1528 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1529 return; 1530 } 1531 1532 // 1. Untie connected soinfos from 'this'. 1533 children.for_each([&] (soinfo* child) { 1534 child->parents.remove_if([&] (const soinfo* parent) { 1535 return parent == this; 1536 }); 1537 }); 1538 1539 parents.for_each([&] (soinfo* parent) { 1540 parent->children.for_each([&] (const soinfo* child) { 1541 return child == this; 1542 }); 1543 }); 1544 1545 // 2. Once everything untied - clear local lists. 1546 parents.clear(); 1547 children.clear(); 1548} 1549 1550void soinfo::set_st_dev(dev_t dev) { 1551 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1552 return; 1553 } 1554 1555 st_dev = dev; 1556} 1557 1558void soinfo::set_st_ino(ino_t ino) { 1559 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1560 return; 1561 } 1562 1563 st_ino = ino; 1564} 1565 1566dev_t soinfo::get_st_dev() { 1567 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1568 return 0; 1569 } 1570 1571 return st_dev; 1572}; 1573 1574ino_t soinfo::get_st_ino() { 1575 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1576 return 0; 1577 } 1578 1579 return st_ino; 1580} 1581 1582// This is a return on get_children() in case 1583// 'this->flags' does not have FLAG_NEW_SOINFO set. 1584static soinfo::soinfo_list_t g_empty_list; 1585 1586soinfo::soinfo_list_t& soinfo::get_children() { 1587 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1588 return g_empty_list; 1589 } 1590 1591 return this->children; 1592} 1593 1594/* Force any of the closed stdin, stdout and stderr to be associated with 1595 /dev/null. */ 1596static int nullify_closed_stdio() { 1597 int dev_null, i, status; 1598 int return_value = 0; 1599 1600 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1601 if (dev_null < 0) { 1602 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1603 return -1; 1604 } 1605 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1606 1607 /* If any of the stdio file descriptors is valid and not associated 1608 with /dev/null, dup /dev/null to it. */ 1609 for (i = 0; i < 3; i++) { 1610 /* If it is /dev/null already, we are done. */ 1611 if (i == dev_null) { 1612 continue; 1613 } 1614 1615 TRACE("[ Nullifying stdio file descriptor %d]", i); 1616 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1617 1618 /* If file is opened, we are good. */ 1619 if (status != -1) { 1620 continue; 1621 } 1622 1623 /* The only error we allow is that the file descriptor does not 1624 exist, in which case we dup /dev/null to it. */ 1625 if (errno != EBADF) { 1626 DL_ERR("fcntl failed: %s", strerror(errno)); 1627 return_value = -1; 1628 continue; 1629 } 1630 1631 /* Try dupping /dev/null to this stdio file descriptor and 1632 repeat if there is a signal. Note that any errors in closing 1633 the stdio descriptor are lost. */ 1634 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1635 if (status < 0) { 1636 DL_ERR("dup2 failed: %s", strerror(errno)); 1637 return_value = -1; 1638 continue; 1639 } 1640 } 1641 1642 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1643 if (dev_null > 2) { 1644 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1645 status = TEMP_FAILURE_RETRY(close(dev_null)); 1646 if (status == -1) { 1647 DL_ERR("close failed: %s", strerror(errno)); 1648 return_value = -1; 1649 } 1650 } 1651 1652 return return_value; 1653} 1654 1655static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1656 /* "base" might wrap around UINT32_MAX. */ 1657 ElfW(Addr) base = si->load_bias; 1658 const ElfW(Phdr)* phdr = si->phdr; 1659 int phnum = si->phnum; 1660 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1661 1662 /* We can't debug anything until the linker is relocated */ 1663 if (!relocating_linker) { 1664 INFO("[ linking %s ]", si->name); 1665 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1666 } 1667 1668 /* Extract dynamic section */ 1669 size_t dynamic_count; 1670 ElfW(Word) dynamic_flags; 1671 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1672 &dynamic_count, &dynamic_flags); 1673 if (si->dynamic == NULL) { 1674 if (!relocating_linker) { 1675 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1676 } 1677 return false; 1678 } else { 1679 if (!relocating_linker) { 1680 DEBUG("dynamic = %p", si->dynamic); 1681 } 1682 } 1683 1684#if defined(__arm__) 1685 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1686 &si->ARM_exidx, &si->ARM_exidx_count); 1687#endif 1688 1689 // Extract useful information from dynamic section. 1690 uint32_t needed_count = 0; 1691 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1692 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1693 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1694 switch (d->d_tag) { 1695 case DT_HASH: 1696 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1697 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1698 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1699 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1700 break; 1701 case DT_STRTAB: 1702 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1703 break; 1704 case DT_SYMTAB: 1705 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1706 break; 1707#if !defined(__LP64__) 1708 case DT_PLTREL: 1709 if (d->d_un.d_val != DT_REL) { 1710 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1711 return false; 1712 } 1713 break; 1714#endif 1715 case DT_JMPREL: 1716#if defined(USE_RELA) 1717 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1718#else 1719 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1720#endif 1721 break; 1722 case DT_PLTRELSZ: 1723#if defined(USE_RELA) 1724 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1725#else 1726 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1727#endif 1728 break; 1729#if defined(__mips__) 1730 case DT_PLTGOT: 1731 // Used by mips and mips64. 1732 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1733 break; 1734#endif 1735 case DT_DEBUG: 1736 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1737 // if the dynamic table is writable 1738// FIXME: not working currently for N64 1739// The flags for the LOAD and DYNAMIC program headers do not agree. 1740// The LOAD section containng the dynamic table has been mapped as 1741// read-only, but the DYNAMIC header claims it is writable. 1742#if !(defined(__mips__) && defined(__LP64__)) 1743 if ((dynamic_flags & PF_W) != 0) { 1744 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1745 } 1746 break; 1747#endif 1748#if defined(USE_RELA) 1749 case DT_RELA: 1750 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1751 break; 1752 case DT_RELASZ: 1753 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1754 break; 1755 case DT_REL: 1756 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1757 return false; 1758 case DT_RELSZ: 1759 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1760 return false; 1761#else 1762 case DT_REL: 1763 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1764 break; 1765 case DT_RELSZ: 1766 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1767 break; 1768 case DT_RELA: 1769 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1770 return false; 1771#endif 1772 case DT_INIT: 1773 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1774 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1775 break; 1776 case DT_FINI: 1777 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1778 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1779 break; 1780 case DT_INIT_ARRAY: 1781 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1782 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1783 break; 1784 case DT_INIT_ARRAYSZ: 1785 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1786 break; 1787 case DT_FINI_ARRAY: 1788 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1789 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1790 break; 1791 case DT_FINI_ARRAYSZ: 1792 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1793 break; 1794 case DT_PREINIT_ARRAY: 1795 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1796 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1797 break; 1798 case DT_PREINIT_ARRAYSZ: 1799 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1800 break; 1801 case DT_TEXTREL: 1802#if defined(__LP64__) 1803 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1804 return false; 1805#else 1806 si->has_text_relocations = true; 1807 break; 1808#endif 1809 case DT_SYMBOLIC: 1810 si->has_DT_SYMBOLIC = true; 1811 break; 1812 case DT_NEEDED: 1813 ++needed_count; 1814 break; 1815 case DT_FLAGS: 1816 if (d->d_un.d_val & DF_TEXTREL) { 1817#if defined(__LP64__) 1818 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1819 return false; 1820#else 1821 si->has_text_relocations = true; 1822#endif 1823 } 1824 if (d->d_un.d_val & DF_SYMBOLIC) { 1825 si->has_DT_SYMBOLIC = true; 1826 } 1827 break; 1828#if defined(__mips__) 1829 case DT_STRSZ: 1830 case DT_SYMENT: 1831 case DT_RELENT: 1832 break; 1833 case DT_MIPS_RLD_MAP: 1834 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1835 { 1836 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1837 *dp = &_r_debug; 1838 } 1839 break; 1840 case DT_MIPS_RLD_VERSION: 1841 case DT_MIPS_FLAGS: 1842 case DT_MIPS_BASE_ADDRESS: 1843 case DT_MIPS_UNREFEXTNO: 1844 break; 1845 1846 case DT_MIPS_SYMTABNO: 1847 si->mips_symtabno = d->d_un.d_val; 1848 break; 1849 1850 case DT_MIPS_LOCAL_GOTNO: 1851 si->mips_local_gotno = d->d_un.d_val; 1852 break; 1853 1854 case DT_MIPS_GOTSYM: 1855 si->mips_gotsym = d->d_un.d_val; 1856 break; 1857#endif 1858 1859 default: 1860 DEBUG("Unused DT entry: type %p arg %p", 1861 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1862 break; 1863 } 1864 } 1865 1866 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1867 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1868 1869 // Sanity checks. 1870 if (relocating_linker && needed_count != 0) { 1871 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1872 return false; 1873 } 1874 if (si->nbucket == 0) { 1875 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1876 return false; 1877 } 1878 if (si->strtab == 0) { 1879 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1880 return false; 1881 } 1882 if (si->symtab == 0) { 1883 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1884 return false; 1885 } 1886 1887 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1888 if (si->flags & FLAG_EXE) { 1889 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1890 size_t preload_count = 0; 1891 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1892 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1893 if (lsi != NULL) { 1894 g_ld_preloads[preload_count++] = lsi; 1895 } else { 1896 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1897 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1898 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1899 } 1900 } 1901 } 1902 1903 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1904 soinfo** pneeded = needed; 1905 1906 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1907 if (d->d_tag == DT_NEEDED) { 1908 const char* library_name = si->strtab + d->d_un.d_val; 1909 DEBUG("%s needs %s", si->name, library_name); 1910 soinfo* lsi = find_library(library_name, 0, NULL); 1911 if (lsi == NULL) { 1912 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1913 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1914 library_name, si->name, tmp_err_buf); 1915 return false; 1916 } 1917 1918 si->add_child(lsi); 1919 *pneeded++ = lsi; 1920 } 1921 } 1922 *pneeded = NULL; 1923 1924#if !defined(__LP64__) 1925 if (si->has_text_relocations) { 1926 // Make segments writable to allow text relocations to work properly. We will later call 1927 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1928 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1929 "security hardening. Please fix.", si->name); 1930 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1931 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1932 si->name, strerror(errno)); 1933 return false; 1934 } 1935 } 1936#endif 1937 1938#if defined(USE_RELA) 1939 if (si->plt_rela != NULL) { 1940 DEBUG("[ relocating %s plt ]\n", si->name); 1941 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1942 return false; 1943 } 1944 } 1945 if (si->rela != NULL) { 1946 DEBUG("[ relocating %s ]\n", si->name); 1947 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1948 return false; 1949 } 1950 } 1951#else 1952 if (si->plt_rel != NULL) { 1953 DEBUG("[ relocating %s plt ]", si->name); 1954 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1955 return false; 1956 } 1957 } 1958 if (si->rel != NULL) { 1959 DEBUG("[ relocating %s ]", si->name); 1960 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1961 return false; 1962 } 1963 } 1964#endif 1965 1966#if defined(__mips__) 1967 if (!mips_relocate_got(si, needed)) { 1968 return false; 1969 } 1970#endif 1971 1972 si->flags |= FLAG_LINKED; 1973 DEBUG("[ finished linking %s ]", si->name); 1974 1975#if !defined(__LP64__) 1976 if (si->has_text_relocations) { 1977 // All relocations are done, we can protect our segments back to read-only. 1978 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1979 DL_ERR("can't protect segments for \"%s\": %s", 1980 si->name, strerror(errno)); 1981 return false; 1982 } 1983 } 1984#endif 1985 1986 /* We can also turn on GNU RELRO protection */ 1987 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1988 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1989 si->name, strerror(errno)); 1990 return false; 1991 } 1992 1993 /* Handle serializing/sharing the RELRO segment */ 1994 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1995 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1996 extinfo->relro_fd) < 0) { 1997 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1998 si->name, strerror(errno)); 1999 return false; 2000 } 2001 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 2002 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 2003 extinfo->relro_fd) < 0) { 2004 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 2005 si->name, strerror(errno)); 2006 return false; 2007 } 2008 } 2009 2010 notify_gdb_of_load(si); 2011 return true; 2012} 2013 2014/* 2015 * This function add vdso to internal dso list. 2016 * It helps to stack unwinding through signal handlers. 2017 * Also, it makes bionic more like glibc. 2018 */ 2019static void add_vdso(KernelArgumentBlock& args __unused) { 2020#if defined(AT_SYSINFO_EHDR) 2021 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 2022 if (ehdr_vdso == NULL) { 2023 return; 2024 } 2025 2026 soinfo* si = soinfo_alloc("[vdso]", NULL); 2027 2028 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 2029 si->phnum = ehdr_vdso->e_phnum; 2030 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 2031 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2032 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 2033 2034 soinfo_link_image(si, NULL); 2035#endif 2036} 2037 2038/* 2039 * This is linker soinfo for GDB. See details below. 2040 */ 2041static soinfo linker_soinfo_for_gdb; 2042 2043/* gdb expects the linker to be in the debug shared object list. 2044 * Without this, gdb has trouble locating the linker's ".text" 2045 * and ".plt" sections. Gdb could also potentially use this to 2046 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2047 * Don't use soinfo_alloc(), because the linker shouldn't 2048 * be on the soinfo list. 2049 */ 2050static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 2051#if defined(__LP64__) 2052 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 2053#else 2054 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 2055#endif 2056 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 2057 linker_soinfo_for_gdb.base = linker_base; 2058 2059 /* 2060 * Set the dynamic field in the link map otherwise gdb will complain with 2061 * the following: 2062 * warning: .dynamic section for "/system/bin/linker" is not at the 2063 * expected address (wrong library or version mismatch?) 2064 */ 2065 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2066 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2067 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2068 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2069 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2070} 2071 2072/* 2073 * This code is called after the linker has linked itself and 2074 * fixed it's own GOT. It is safe to make references to externs 2075 * and other non-local data at this point. 2076 */ 2077static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2078 /* NOTE: we store the args pointer on a special location 2079 * of the temporary TLS area in order to pass it to 2080 * the C Library's runtime initializer. 2081 * 2082 * The initializer must clear the slot and reset the TLS 2083 * to point to a different location to ensure that no other 2084 * shared library constructor can access it. 2085 */ 2086 __libc_init_tls(args); 2087 2088#if TIMING 2089 struct timeval t0, t1; 2090 gettimeofday(&t0, 0); 2091#endif 2092 2093 // Initialize environment functions, and get to the ELF aux vectors table. 2094 linker_env_init(args); 2095 2096 // If this is a setuid/setgid program, close the security hole described in 2097 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2098 if (get_AT_SECURE()) { 2099 nullify_closed_stdio(); 2100 } 2101 2102 debuggerd_init(); 2103 2104 // Get a few environment variables. 2105 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2106 if (LD_DEBUG != NULL) { 2107 g_ld_debug_verbosity = atoi(LD_DEBUG); 2108 } 2109 2110 // Normally, these are cleaned by linker_env_init, but the test 2111 // doesn't cost us anything. 2112 const char* ldpath_env = NULL; 2113 const char* ldpreload_env = NULL; 2114 if (!get_AT_SECURE()) { 2115 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2116 ldpreload_env = linker_env_get("LD_PRELOAD"); 2117 } 2118 2119 INFO("[ android linker & debugger ]"); 2120 2121 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2122 if (si == NULL) { 2123 exit(EXIT_FAILURE); 2124 } 2125 2126 /* bootstrap the link map, the main exe always needs to be first */ 2127 si->flags |= FLAG_EXE; 2128 link_map* map = &(si->link_map_head); 2129 2130 map->l_addr = 0; 2131 map->l_name = args.argv[0]; 2132 map->l_prev = NULL; 2133 map->l_next = NULL; 2134 2135 _r_debug.r_map = map; 2136 r_debug_tail = map; 2137 2138 init_linker_info_for_gdb(linker_base); 2139 2140 // Extract information passed from the kernel. 2141 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2142 si->phnum = args.getauxval(AT_PHNUM); 2143 si->entry = args.getauxval(AT_ENTRY); 2144 2145 /* Compute the value of si->base. We can't rely on the fact that 2146 * the first entry is the PHDR because this will not be true 2147 * for certain executables (e.g. some in the NDK unit test suite) 2148 */ 2149 si->base = 0; 2150 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2151 si->load_bias = 0; 2152 for (size_t i = 0; i < si->phnum; ++i) { 2153 if (si->phdr[i].p_type == PT_PHDR) { 2154 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2155 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2156 break; 2157 } 2158 } 2159 si->dynamic = NULL; 2160 si->ref_count = 1; 2161 2162 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2163 if (elf_hdr->e_type != ET_DYN) { 2164 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2165 exit(EXIT_FAILURE); 2166 } 2167 2168 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2169 parse_LD_LIBRARY_PATH(ldpath_env); 2170 parse_LD_PRELOAD(ldpreload_env); 2171 2172 somain = si; 2173 2174 if (!soinfo_link_image(si, NULL)) { 2175 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2176 exit(EXIT_FAILURE); 2177 } 2178 2179 add_vdso(args); 2180 2181 si->CallPreInitConstructors(); 2182 2183 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2184 g_ld_preloads[i]->CallConstructors(); 2185 } 2186 2187 /* After the link_image, the si->load_bias is initialized. 2188 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2189 * We need to update this value for so exe here. So Unwind_Backtrace 2190 * for some arch like x86 could work correctly within so exe. 2191 */ 2192 map->l_addr = si->load_bias; 2193 si->CallConstructors(); 2194 2195#if TIMING 2196 gettimeofday(&t1, NULL); 2197 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2198 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2199 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2200#endif 2201#if STATS 2202 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2203 linker_stats.count[kRelocAbsolute], 2204 linker_stats.count[kRelocRelative], 2205 linker_stats.count[kRelocCopy], 2206 linker_stats.count[kRelocSymbol]); 2207#endif 2208#if COUNT_PAGES 2209 { 2210 unsigned n; 2211 unsigned i; 2212 unsigned count = 0; 2213 for (n = 0; n < 4096; n++) { 2214 if (bitmask[n]) { 2215 unsigned x = bitmask[n]; 2216#if defined(__LP64__) 2217 for (i = 0; i < 32; i++) { 2218#else 2219 for (i = 0; i < 8; i++) { 2220#endif 2221 if (x & 1) { 2222 count++; 2223 } 2224 x >>= 1; 2225 } 2226 } 2227 } 2228 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2229 } 2230#endif 2231 2232#if TIMING || STATS || COUNT_PAGES 2233 fflush(stdout); 2234#endif 2235 2236 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2237 return si->entry; 2238} 2239 2240/* Compute the load-bias of an existing executable. This shall only 2241 * be used to compute the load bias of an executable or shared library 2242 * that was loaded by the kernel itself. 2243 * 2244 * Input: 2245 * elf -> address of ELF header, assumed to be at the start of the file. 2246 * Return: 2247 * load bias, i.e. add the value of any p_vaddr in the file to get 2248 * the corresponding address in memory. 2249 */ 2250static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2251 ElfW(Addr) offset = elf->e_phoff; 2252 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2253 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2254 2255 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2256 if (phdr->p_type == PT_LOAD) { 2257 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2258 } 2259 } 2260 return 0; 2261} 2262 2263extern "C" void _start(); 2264 2265/* 2266 * This is the entry point for the linker, called from begin.S. This 2267 * method is responsible for fixing the linker's own relocations, and 2268 * then calling __linker_init_post_relocation(). 2269 * 2270 * Because this method is called before the linker has fixed it's own 2271 * relocations, any attempt to reference an extern variable, extern 2272 * function, or other GOT reference will generate a segfault. 2273 */ 2274extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2275 // Initialize static variables. 2276 solist = get_libdl_info(); 2277 sonext = get_libdl_info(); 2278 2279 KernelArgumentBlock args(raw_args); 2280 2281 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2282 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY); 2283 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2284 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2285 2286 soinfo linker_so; 2287 memset(&linker_so, 0, sizeof(soinfo)); 2288 2289 // If the linker is not acting as PT_INTERP entry_point is equal to 2290 // _start. Which means that the linker is running as an executable and 2291 // already linked by PT_INTERP. 2292 // 2293 // This happens when user tries to run 'adb shell /system/bin/linker' 2294 // see also https://code.google.com/p/android/issues/detail?id=63174 2295 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) { 2296 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]); 2297 } 2298 2299 strcpy(linker_so.name, "[dynamic linker]"); 2300 linker_so.base = linker_addr; 2301 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2302 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2303 linker_so.dynamic = NULL; 2304 linker_so.phdr = phdr; 2305 linker_so.phnum = elf_hdr->e_phnum; 2306 linker_so.flags |= FLAG_LINKER; 2307 2308 if (!soinfo_link_image(&linker_so, NULL)) { 2309 // It would be nice to print an error message, but if the linker 2310 // can't link itself, there's no guarantee that we'll be able to 2311 // call write() (because it involves a GOT reference). We may as 2312 // well try though... 2313 const char* msg = "CANNOT LINK EXECUTABLE: "; 2314 write(2, msg, strlen(msg)); 2315 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2316 write(2, "\n", 1); 2317 _exit(EXIT_FAILURE); 2318 } 2319 2320 // Initialize the linker's own global variables 2321 linker_so.CallConstructors(); 2322 2323 // We have successfully fixed our own relocations. It's safe to run 2324 // the main part of the linker now. 2325 args.abort_message_ptr = &g_abort_message; 2326 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2327 2328 protect_data(PROT_READ); 2329 2330 // Return the address that the calling assembly stub should jump to. 2331 return start_address; 2332} 2333