linker.cpp revision 489e498434f53269c44e3c13039eb630e86e1fd9
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 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 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 167 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 168 write(2, msg, strlen(msg)); \ 169 abort(); \ 170 } 171DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 172DISALLOW_ALLOCATION(void, free, (void* u __unused)); 173DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 174DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 175 176static char tmp_err_buf[768]; 177static char __linker_dl_err_buf[768]; 178 179char* linker_get_error_buffer() { 180 return &__linker_dl_err_buf[0]; 181} 182 183size_t linker_get_error_buffer_size() { 184 return sizeof(__linker_dl_err_buf); 185} 186 187/* 188 * This function is an empty stub where GDB locates a breakpoint to get notified 189 * about linker activity. 190 */ 191extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 192 193static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 194static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 195static link_map* r_debug_tail = 0; 196 197static void insert_soinfo_into_debug_map(soinfo* info) { 198 // Copy the necessary fields into the debug structure. 199 link_map* map = &(info->link_map_head); 200 map->l_addr = info->load_bias; 201 map->l_name = reinterpret_cast<char*>(info->name); 202 map->l_ld = info->dynamic; 203 204 /* Stick the new library at the end of the list. 205 * gdb tends to care more about libc than it does 206 * about leaf libraries, and ordering it this way 207 * reduces the back-and-forth over the wire. 208 */ 209 if (r_debug_tail) { 210 r_debug_tail->l_next = map; 211 map->l_prev = r_debug_tail; 212 map->l_next = 0; 213 } else { 214 _r_debug.r_map = map; 215 map->l_prev = 0; 216 map->l_next = 0; 217 } 218 r_debug_tail = map; 219} 220 221static void remove_soinfo_from_debug_map(soinfo* info) { 222 link_map* map = &(info->link_map_head); 223 224 if (r_debug_tail == map) { 225 r_debug_tail = map->l_prev; 226 } 227 228 if (map->l_prev) { 229 map->l_prev->l_next = map->l_next; 230 } 231 if (map->l_next) { 232 map->l_next->l_prev = map->l_prev; 233 } 234} 235 236static void notify_gdb_of_load(soinfo* info) { 237 if (info->flags & FLAG_EXE) { 238 // GDB already knows about the main executable 239 return; 240 } 241 242 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 243 244 _r_debug.r_state = r_debug::RT_ADD; 245 rtld_db_dlactivity(); 246 247 insert_soinfo_into_debug_map(info); 248 249 _r_debug.r_state = r_debug::RT_CONSISTENT; 250 rtld_db_dlactivity(); 251} 252 253static void notify_gdb_of_unload(soinfo* info) { 254 if (info->flags & FLAG_EXE) { 255 // GDB already knows about the main executable 256 return; 257 } 258 259 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 260 261 _r_debug.r_state = r_debug::RT_DELETE; 262 rtld_db_dlactivity(); 263 264 remove_soinfo_from_debug_map(info); 265 266 _r_debug.r_state = r_debug::RT_CONSISTENT; 267 rtld_db_dlactivity(); 268} 269 270void notify_gdb_of_libraries() { 271 _r_debug.r_state = r_debug::RT_ADD; 272 rtld_db_dlactivity(); 273 _r_debug.r_state = r_debug::RT_CONSISTENT; 274 rtld_db_dlactivity(); 275} 276 277LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 278 return g_soinfo_links_allocator.alloc(); 279} 280 281void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 282 g_soinfo_links_allocator.free(entry); 283} 284 285static void protect_data(int protection) { 286 g_soinfo_allocator.protect_all(protection); 287 g_soinfo_links_allocator.protect_all(protection); 288} 289 290static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 291 if (strlen(name) >= SOINFO_NAME_LEN) { 292 DL_ERR("library name \"%s\" too long", name); 293 return NULL; 294 } 295 296 soinfo* si = g_soinfo_allocator.alloc(); 297 298 // Initialize the new element. 299 memset(si, 0, sizeof(soinfo)); 300 strlcpy(si->name, name, sizeof(si->name)); 301 si->flags = FLAG_NEW_SOINFO; 302 303 if (file_stat != NULL) { 304 si->set_st_dev(file_stat->st_dev); 305 si->set_st_ino(file_stat->st_ino); 306 } 307 308 sonext->next = si; 309 sonext = si; 310 311 TRACE("name %s: allocated soinfo @ %p", name, si); 312 return si; 313} 314 315static void soinfo_free(soinfo* si) { 316 if (si == NULL) { 317 return; 318 } 319 320 if (si->base != 0 && si->size != 0) { 321 munmap(reinterpret_cast<void*>(si->base), si->size); 322 } 323 324 soinfo *prev = NULL, *trav; 325 326 TRACE("name %s: freeing soinfo @ %p", si->name, si); 327 328 for (trav = solist; trav != NULL; trav = trav->next) { 329 if (trav == si) 330 break; 331 prev = trav; 332 } 333 if (trav == NULL) { 334 /* si was not in solist */ 335 DL_ERR("name \"%s\" is not in solist!", si->name); 336 return; 337 } 338 339 // clear links to/from si 340 si->remove_all_links(); 341 342 /* prev will never be NULL, because the first entry in solist is 343 always the static libdl_info. 344 */ 345 prev->next = si->next; 346 if (si == sonext) { 347 sonext = prev; 348 } 349 350 g_soinfo_allocator.free(si); 351} 352 353 354static void parse_path(const char* path, const char* delimiters, 355 const char** array, char* buf, size_t buf_size, size_t max_count) { 356 if (path == NULL) { 357 return; 358 } 359 360 size_t len = strlcpy(buf, path, buf_size); 361 362 size_t i = 0; 363 char* buf_p = buf; 364 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 365 if (*array[i] != '\0') { 366 ++i; 367 } 368 } 369 370 // Forget the last path if we had to truncate; this occurs if the 2nd to 371 // last char isn't '\0' (i.e. wasn't originally a delimiter). 372 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 373 array[i - 1] = NULL; 374 } else { 375 array[i] = NULL; 376 } 377} 378 379static void parse_LD_LIBRARY_PATH(const char* path) { 380 parse_path(path, ":", g_ld_library_paths, 381 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 382} 383 384static void parse_LD_PRELOAD(const char* path) { 385 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 386 parse_path(path, " :", g_ld_preload_names, 387 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 388} 389 390#if defined(__arm__) 391 392/* For a given PC, find the .so that it belongs to. 393 * Returns the base address of the .ARM.exidx section 394 * for that .so, and the number of 8-byte entries 395 * in that section (via *pcount). 396 * 397 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 398 * 399 * This function is exposed via dlfcn.cpp and libdl.so. 400 */ 401_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 402 unsigned addr = (unsigned)pc; 403 404 for (soinfo* si = solist; si != 0; si = si->next) { 405 if ((addr >= si->base) && (addr < (si->base + si->size))) { 406 *pcount = si->ARM_exidx_count; 407 return (_Unwind_Ptr)si->ARM_exidx; 408 } 409 } 410 *pcount = 0; 411 return NULL; 412} 413 414#endif 415 416/* Here, we only have to provide a callback to iterate across all the 417 * loaded libraries. gcc_eh does the rest. */ 418int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 419 int rv = 0; 420 for (soinfo* si = solist; si != NULL; si = si->next) { 421 dl_phdr_info dl_info; 422 dl_info.dlpi_addr = si->link_map_head.l_addr; 423 dl_info.dlpi_name = si->link_map_head.l_name; 424 dl_info.dlpi_phdr = si->phdr; 425 dl_info.dlpi_phnum = si->phnum; 426 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 427 if (rv != 0) { 428 break; 429 } 430 } 431 return rv; 432} 433 434static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 435 ElfW(Sym)* symtab = si->symtab; 436 const char* strtab = si->strtab; 437 438 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 439 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 440 441 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 442 ElfW(Sym)* s = symtab + n; 443 if (strcmp(strtab + s->st_name, name)) continue; 444 445 /* only concern ourselves with global and weak symbol definitions */ 446 switch (ELF_ST_BIND(s->st_info)) { 447 case STB_GLOBAL: 448 case STB_WEAK: 449 if (s->st_shndx == SHN_UNDEF) { 450 continue; 451 } 452 453 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 454 name, si->name, reinterpret_cast<void*>(s->st_value), 455 static_cast<size_t>(s->st_size)); 456 return s; 457 } 458 } 459 460 return NULL; 461} 462 463static unsigned elfhash(const char* _name) { 464 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 465 unsigned h = 0, g; 466 467 while (*name) { 468 h = (h << 4) + *name++; 469 g = h & 0xf0000000; 470 h ^= g; 471 h ^= g >> 24; 472 } 473 return h; 474} 475 476static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 477 unsigned elf_hash = elfhash(name); 478 ElfW(Sym)* s = NULL; 479 480 if (si != NULL && somain != NULL) { 481 /* 482 * Local scope is executable scope. Just start looking into it right away 483 * for the shortcut. 484 */ 485 486 if (si == somain) { 487 s = soinfo_elf_lookup(si, elf_hash, name); 488 if (s != NULL) { 489 *lsi = si; 490 goto done; 491 } 492 } else { 493 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 494 495 /* 496 * If this object was built with symbolic relocations disabled, the 497 * first place to look to resolve external references is the main 498 * executable. 499 */ 500 501 if (!si->has_DT_SYMBOLIC) { 502 DEBUG("%s: looking up %s in executable %s", 503 si->name, name, somain->name); 504 s = soinfo_elf_lookup(somain, elf_hash, name); 505 if (s != NULL) { 506 *lsi = somain; 507 goto done; 508 } 509 } 510 511 /* Look for symbols in the local scope (the object who is 512 * searching). This happens with C++ templates on x86 for some 513 * reason. 514 * 515 * Notes on weak symbols: 516 * The ELF specs are ambiguous about treatment of weak definitions in 517 * dynamic linking. Some systems return the first definition found 518 * and some the first non-weak definition. This is system dependent. 519 * Here we return the first definition found for simplicity. */ 520 521 s = soinfo_elf_lookup(si, elf_hash, name); 522 if (s != NULL) { 523 *lsi = si; 524 goto done; 525 } 526 527 /* 528 * If this object was built with -Bsymbolic and symbol is not found 529 * in the local scope, try to find the symbol in the main executable. 530 */ 531 532 if (si->has_DT_SYMBOLIC) { 533 DEBUG("%s: looking up %s in executable %s after local scope", 534 si->name, name, somain->name); 535 s = soinfo_elf_lookup(somain, elf_hash, name); 536 if (s != NULL) { 537 *lsi = somain; 538 goto done; 539 } 540 } 541 } 542 } 543 544 /* Next, look for it in the preloads list */ 545 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 546 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name); 547 if (s != NULL) { 548 *lsi = g_ld_preloads[i]; 549 goto done; 550 } 551 } 552 553 for (int i = 0; needed[i] != NULL; i++) { 554 DEBUG("%s: looking up %s in %s", 555 si->name, name, needed[i]->name); 556 s = soinfo_elf_lookup(needed[i], elf_hash, name); 557 if (s != NULL) { 558 *lsi = needed[i]; 559 goto done; 560 } 561 } 562 563done: 564 if (s != NULL) { 565 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 566 "found in %s, base = %p, load bias = %p", 567 si->name, name, reinterpret_cast<void*>(s->st_value), 568 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 569 reinterpret_cast<void*>((*lsi)->load_bias)); 570 return s; 571 } 572 573 return NULL; 574} 575 576/* This is used by dlsym(3). It performs symbol lookup only within the 577 specified soinfo object and not in any of its dependencies. 578 579 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 580 that it should do a breadth first search through the dependency 581 tree. This agrees with the ELF spec (aka System V Application 582 Binary Interface) where in Chapter 5 it discuss resolving "Shared 583 Object Dependencies" in breadth first search order. 584 */ 585ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) { 586 return soinfo_elf_lookup(si, elfhash(name), name); 587} 588 589/* This is used by dlsym(3) to performs a global symbol lookup. If the 590 start value is null (for RTLD_DEFAULT), the search starts at the 591 beginning of the global solist. Otherwise the search starts at the 592 specified soinfo (for RTLD_NEXT). 593 */ 594ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 595 unsigned elf_hash = elfhash(name); 596 597 if (start == NULL) { 598 start = solist; 599 } 600 601 ElfW(Sym)* s = NULL; 602 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 603 s = soinfo_elf_lookup(si, elf_hash, name); 604 if (s != NULL) { 605 *found = si; 606 break; 607 } 608 } 609 610 if (s != NULL) { 611 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 612 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 613 } 614 615 return s; 616} 617 618soinfo* find_containing_library(const void* p) { 619 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 620 for (soinfo* si = solist; si != NULL; si = si->next) { 621 if (address >= si->base && address - si->base < si->size) { 622 return si; 623 } 624 } 625 return NULL; 626} 627 628ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 629 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 630 631 // Search the library's symbol table for any defined symbol which 632 // contains this address. 633 for (size_t i = 0; i < si->nchain; ++i) { 634 ElfW(Sym)* sym = &si->symtab[i]; 635 if (sym->st_shndx != SHN_UNDEF && 636 soaddr >= sym->st_value && 637 soaddr < sym->st_value + sym->st_size) { 638 return sym; 639 } 640 } 641 642 return NULL; 643} 644 645static int open_library_on_path(const char* name, const char* const paths[]) { 646 char buf[512]; 647 for (size_t i = 0; paths[i] != NULL; ++i) { 648 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 649 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 650 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 651 continue; 652 } 653 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 654 if (fd != -1) { 655 return fd; 656 } 657 } 658 return -1; 659} 660 661static int open_library(const char* name) { 662 TRACE("[ opening %s ]", name); 663 664 // If the name contains a slash, we should attempt to open it directly and not search the paths. 665 if (strchr(name, '/') != NULL) { 666 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 667 if (fd != -1) { 668 return fd; 669 } 670 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 671#if defined(__LP64__) 672 // TODO: uncomment this after bug b/7465467 is fixed. 673 // return -1; 674#endif 675 } 676 677 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 678 int fd = open_library_on_path(name, g_ld_library_paths); 679 if (fd == -1) { 680 fd = open_library_on_path(name, kDefaultLdPaths); 681 } 682 return fd; 683} 684 685static soinfo* load_library(const char* name, const android_dlextinfo* extinfo) { 686 // Open the file. 687 int fd = open_library(name); 688 if (fd == -1) { 689 DL_ERR("library \"%s\" not found", name); 690 return NULL; 691 } 692 693 ElfReader elf_reader(name, fd); 694 695 struct stat file_stat; 696 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 697 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 698 return NULL; 699 } 700 701 // Check for symlink and other situations where 702 // file can have different names. 703 for (soinfo* si = solist; si != NULL; si = si->next) { 704 if (si->get_st_dev() != 0 && 705 si->get_st_ino() != 0 && 706 si->get_st_dev() == file_stat.st_dev && 707 si->get_st_ino() == file_stat.st_ino) { 708 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 709 return si; 710 } 711 } 712 713 // Read the ELF header and load the segments. 714 if (!elf_reader.Load(extinfo)) { 715 return NULL; 716 } 717 718 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 719 if (si == NULL) { 720 return NULL; 721 } 722 si->base = elf_reader.load_start(); 723 si->size = elf_reader.load_size(); 724 si->load_bias = elf_reader.load_bias(); 725 si->phnum = elf_reader.phdr_count(); 726 si->phdr = elf_reader.loaded_phdr(); 727 728 // At this point we know that whatever is loaded @ base is a valid ELF 729 // shared library whose segments are properly mapped in. 730 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 731 reinterpret_cast<void*>(si->base), si->size, si->name); 732 733 if (!soinfo_link_image(si, extinfo)) { 734 soinfo_free(si); 735 return NULL; 736 } 737 738 return si; 739} 740 741static soinfo *find_loaded_library_by_name(const char* name) { 742 const char* search_name = SEARCH_NAME(name); 743 for (soinfo* si = solist; si != NULL; si = si->next) { 744 if (!strcmp(search_name, si->name)) { 745 return si; 746 } 747 } 748 return NULL; 749} 750 751static soinfo* find_library_internal(const char* name, const android_dlextinfo* extinfo) { 752 if (name == NULL) { 753 return somain; 754 } 755 756 soinfo* si = find_loaded_library_by_name(name); 757 if (si != NULL) { 758 if (si->flags & FLAG_LINKED) { 759 return si; 760 } 761 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 762 return NULL; 763 } 764 765 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 766 return load_library(name, extinfo); 767} 768 769static soinfo* find_library(const char* name, const android_dlextinfo* extinfo) { 770 soinfo* si = find_library_internal(name, extinfo); 771 if (si != NULL) { 772 si->ref_count++; 773 } 774 return si; 775} 776 777static int soinfo_unload(soinfo* si) { 778 if (si->ref_count == 1) { 779 TRACE("unloading '%s'", si->name); 780 si->CallDestructors(); 781 782 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 783 si->get_children().for_each([&] (soinfo* child) { 784 TRACE("%s needs to unload %s", si->name, child->name); 785 soinfo_unload(child); 786 }); 787 } else { 788 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 789 if (d->d_tag == DT_NEEDED) { 790 const char* library_name = si->strtab + d->d_un.d_val; 791 TRACE("%s needs to unload %s", si->name, library_name); 792 soinfo_unload(find_loaded_library_by_name(library_name)); 793 } 794 } 795 } 796 797 notify_gdb_of_unload(si); 798 si->ref_count = 0; 799 soinfo_free(si); 800 } else { 801 si->ref_count--; 802 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 803 } 804 return 0; 805} 806 807void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 808 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 809} 810 811void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 812 if (!get_AT_SECURE()) { 813 parse_LD_LIBRARY_PATH(ld_library_path); 814 } 815} 816 817soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 818 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 819 DL_ERR("invalid flags to dlopen: %x", flags); 820 return NULL; 821 } 822 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 823 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 824 return NULL; 825 } 826 protect_data(PROT_READ | PROT_WRITE); 827 soinfo* si = find_library(name, extinfo); 828 if (si != NULL) { 829 si->CallConstructors(); 830 somain->add_child(si); 831 } 832 protect_data(PROT_READ); 833 return si; 834} 835 836int do_dlclose(soinfo* si) { 837 protect_data(PROT_READ | PROT_WRITE); 838 int result = soinfo_unload(si); 839 protect_data(PROT_READ); 840 return result; 841} 842 843#if defined(USE_RELA) 844static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 845 ElfW(Sym)* s; 846 soinfo* lsi; 847 848 for (size_t idx = 0; idx < count; ++idx, ++rela) { 849 unsigned type = ELFW(R_TYPE)(rela->r_info); 850 unsigned sym = ELFW(R_SYM)(rela->r_info); 851 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 852 ElfW(Addr) sym_addr = 0; 853 const char* sym_name = NULL; 854 855 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 856 if (type == 0) { // R_*_NONE 857 continue; 858 } 859 if (sym != 0) { 860 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 861 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 862 if (s == NULL) { 863 // We only allow an undefined symbol if this is a weak reference... 864 s = &si->symtab[sym]; 865 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 866 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 867 return -1; 868 } 869 870 /* IHI0044C AAELF 4.5.1.1: 871 872 Libraries are not searched to resolve weak references. 873 It is not an error for a weak reference to remain unsatisfied. 874 875 During linking, the value of an undefined weak reference is: 876 - Zero if the relocation type is absolute 877 - The address of the place if the relocation is pc-relative 878 - The address of nominal base address if the relocation 879 type is base-relative. 880 */ 881 882 switch (type) { 883#if defined(__aarch64__) 884 case R_AARCH64_JUMP_SLOT: 885 case R_AARCH64_GLOB_DAT: 886 case R_AARCH64_ABS64: 887 case R_AARCH64_ABS32: 888 case R_AARCH64_ABS16: 889 case R_AARCH64_RELATIVE: 890 /* 891 * The sym_addr was initialized to be zero above, or the relocation 892 * code below does not care about value of sym_addr. 893 * No need to do anything. 894 */ 895 break; 896#elif defined(__x86_64__) 897 case R_X86_64_JUMP_SLOT: 898 case R_X86_64_GLOB_DAT: 899 case R_X86_64_32: 900 case R_X86_64_RELATIVE: 901 // No need to do anything. 902 break; 903 case R_X86_64_PC32: 904 sym_addr = reloc; 905 break; 906#endif 907 default: 908 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 909 return -1; 910 } 911 } else { 912 // We got a definition. 913 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 914 } 915 count_relocation(kRelocSymbol); 916 } else { 917 s = NULL; 918 } 919 920 switch (type) { 921#if defined(__aarch64__) 922 case R_AARCH64_JUMP_SLOT: 923 count_relocation(kRelocAbsolute); 924 MARK(rela->r_offset); 925 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 926 reloc, (sym_addr + rela->r_addend), sym_name); 927 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 928 break; 929 case R_AARCH64_GLOB_DAT: 930 count_relocation(kRelocAbsolute); 931 MARK(rela->r_offset); 932 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 933 reloc, (sym_addr + rela->r_addend), sym_name); 934 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 935 break; 936 case R_AARCH64_ABS64: 937 count_relocation(kRelocAbsolute); 938 MARK(rela->r_offset); 939 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 940 reloc, (sym_addr + rela->r_addend), sym_name); 941 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 942 break; 943 case R_AARCH64_ABS32: 944 count_relocation(kRelocAbsolute); 945 MARK(rela->r_offset); 946 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 947 reloc, (sym_addr + rela->r_addend), sym_name); 948 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 949 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 950 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 951 } else { 952 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 953 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 954 static_cast<ElfW(Addr)>(INT32_MIN), 955 static_cast<ElfW(Addr)>(UINT32_MAX)); 956 return -1; 957 } 958 break; 959 case R_AARCH64_ABS16: 960 count_relocation(kRelocAbsolute); 961 MARK(rela->r_offset); 962 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 963 reloc, (sym_addr + rela->r_addend), sym_name); 964 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 965 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 966 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 967 } else { 968 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 969 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 970 static_cast<ElfW(Addr)>(INT16_MIN), 971 static_cast<ElfW(Addr)>(UINT16_MAX)); 972 return -1; 973 } 974 break; 975 case R_AARCH64_PREL64: 976 count_relocation(kRelocRelative); 977 MARK(rela->r_offset); 978 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 979 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 980 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 981 break; 982 case R_AARCH64_PREL32: 983 count_relocation(kRelocRelative); 984 MARK(rela->r_offset); 985 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 986 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 987 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 988 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 989 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 990 } else { 991 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 992 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 993 static_cast<ElfW(Addr)>(INT32_MIN), 994 static_cast<ElfW(Addr)>(UINT32_MAX)); 995 return -1; 996 } 997 break; 998 case R_AARCH64_PREL16: 999 count_relocation(kRelocRelative); 1000 MARK(rela->r_offset); 1001 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1002 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1003 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1004 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1005 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1006 } else { 1007 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1008 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1009 static_cast<ElfW(Addr)>(INT16_MIN), 1010 static_cast<ElfW(Addr)>(UINT16_MAX)); 1011 return -1; 1012 } 1013 break; 1014 1015 case R_AARCH64_RELATIVE: 1016 count_relocation(kRelocRelative); 1017 MARK(rela->r_offset); 1018 if (sym) { 1019 DL_ERR("odd RELATIVE form..."); 1020 return -1; 1021 } 1022 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1023 reloc, (si->base + rela->r_addend)); 1024 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1025 break; 1026 1027 case R_AARCH64_COPY: 1028 /* 1029 * ET_EXEC is not supported so this should not happen. 1030 * 1031 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1032 * 1033 * Section 4.7.1.10 "Dynamic relocations" 1034 * R_AARCH64_COPY may only appear in executable objects where e_type is 1035 * set to ET_EXEC. 1036 */ 1037 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1038 return -1; 1039 case R_AARCH64_TLS_TPREL64: 1040 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1041 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1042 break; 1043 case R_AARCH64_TLS_DTPREL32: 1044 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1045 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1046 break; 1047#elif defined(__x86_64__) 1048 case R_X86_64_JUMP_SLOT: 1049 count_relocation(kRelocAbsolute); 1050 MARK(rela->r_offset); 1051 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1052 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1053 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1054 break; 1055 case R_X86_64_GLOB_DAT: 1056 count_relocation(kRelocAbsolute); 1057 MARK(rela->r_offset); 1058 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1059 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1060 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1061 break; 1062 case R_X86_64_RELATIVE: 1063 count_relocation(kRelocRelative); 1064 MARK(rela->r_offset); 1065 if (sym) { 1066 DL_ERR("odd RELATIVE form..."); 1067 return -1; 1068 } 1069 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1070 static_cast<size_t>(si->base)); 1071 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1072 break; 1073 case R_X86_64_32: 1074 count_relocation(kRelocRelative); 1075 MARK(rela->r_offset); 1076 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1077 static_cast<size_t>(sym_addr), sym_name); 1078 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1079 break; 1080 case R_X86_64_64: 1081 count_relocation(kRelocRelative); 1082 MARK(rela->r_offset); 1083 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1084 static_cast<size_t>(sym_addr), sym_name); 1085 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1086 break; 1087 case R_X86_64_PC32: 1088 count_relocation(kRelocRelative); 1089 MARK(rela->r_offset); 1090 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1091 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1092 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1093 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1094 break; 1095#endif 1096 1097 default: 1098 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1099 return -1; 1100 } 1101 } 1102 return 0; 1103} 1104 1105#else // REL, not RELA. 1106 1107static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1108 ElfW(Sym)* s; 1109 soinfo* lsi; 1110 1111 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1112 unsigned type = ELFW(R_TYPE)(rel->r_info); 1113 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1114 unsigned sym = ELFW(R_SYM)(rel->r_info); 1115 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1116 ElfW(Addr) sym_addr = 0; 1117 const char* sym_name = NULL; 1118 1119 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1120 if (type == 0) { // R_*_NONE 1121 continue; 1122 } 1123 if (sym != 0) { 1124 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1125 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1126 if (s == NULL) { 1127 // We only allow an undefined symbol if this is a weak reference... 1128 s = &si->symtab[sym]; 1129 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1130 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1131 return -1; 1132 } 1133 1134 /* IHI0044C AAELF 4.5.1.1: 1135 1136 Libraries are not searched to resolve weak references. 1137 It is not an error for a weak reference to remain 1138 unsatisfied. 1139 1140 During linking, the value of an undefined weak reference is: 1141 - Zero if the relocation type is absolute 1142 - The address of the place if the relocation is pc-relative 1143 - The address of nominal base address if the relocation 1144 type is base-relative. 1145 */ 1146 1147 switch (type) { 1148#if defined(__arm__) 1149 case R_ARM_JUMP_SLOT: 1150 case R_ARM_GLOB_DAT: 1151 case R_ARM_ABS32: 1152 case R_ARM_RELATIVE: /* Don't care. */ 1153 // sym_addr was initialized to be zero above or relocation 1154 // code below does not care about value of sym_addr. 1155 // No need to do anything. 1156 break; 1157#elif defined(__i386__) 1158 case R_386_JMP_SLOT: 1159 case R_386_GLOB_DAT: 1160 case R_386_32: 1161 case R_386_RELATIVE: /* Don't care. */ 1162 // sym_addr was initialized to be zero above or relocation 1163 // code below does not care about value of sym_addr. 1164 // No need to do anything. 1165 break; 1166 case R_386_PC32: 1167 sym_addr = reloc; 1168 break; 1169#endif 1170 1171#if defined(__arm__) 1172 case R_ARM_COPY: 1173 // Fall through. Can't really copy if weak symbol is not found at run-time. 1174#endif 1175 default: 1176 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1177 return -1; 1178 } 1179 } else { 1180 // We got a definition. 1181 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1182 } 1183 count_relocation(kRelocSymbol); 1184 } else { 1185 s = NULL; 1186 } 1187 1188 switch (type) { 1189#if defined(__arm__) 1190 case R_ARM_JUMP_SLOT: 1191 count_relocation(kRelocAbsolute); 1192 MARK(rel->r_offset); 1193 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1194 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1195 break; 1196 case R_ARM_GLOB_DAT: 1197 count_relocation(kRelocAbsolute); 1198 MARK(rel->r_offset); 1199 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1200 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1201 break; 1202 case R_ARM_ABS32: 1203 count_relocation(kRelocAbsolute); 1204 MARK(rel->r_offset); 1205 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1206 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1207 break; 1208 case R_ARM_REL32: 1209 count_relocation(kRelocRelative); 1210 MARK(rel->r_offset); 1211 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1212 reloc, sym_addr, rel->r_offset, sym_name); 1213 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1214 break; 1215 case R_ARM_COPY: 1216 /* 1217 * ET_EXEC is not supported so this should not happen. 1218 * 1219 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1220 * 1221 * Section 4.7.1.10 "Dynamic relocations" 1222 * R_ARM_COPY may only appear in executable objects where e_type is 1223 * set to ET_EXEC. 1224 */ 1225 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1226 return -1; 1227#elif defined(__i386__) 1228 case R_386_JMP_SLOT: 1229 count_relocation(kRelocAbsolute); 1230 MARK(rel->r_offset); 1231 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1232 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1233 break; 1234 case R_386_GLOB_DAT: 1235 count_relocation(kRelocAbsolute); 1236 MARK(rel->r_offset); 1237 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1238 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1239 break; 1240 case R_386_32: 1241 count_relocation(kRelocRelative); 1242 MARK(rel->r_offset); 1243 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1244 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1245 break; 1246 case R_386_PC32: 1247 count_relocation(kRelocRelative); 1248 MARK(rel->r_offset); 1249 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1250 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1251 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1252 break; 1253#elif defined(__mips__) 1254 case R_MIPS_REL32: 1255#if defined(__LP64__) 1256 // MIPS Elf64_Rel entries contain compound relocations 1257 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1258 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1259 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1260 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1261 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1262 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1263 return -1; 1264 } 1265#endif 1266 count_relocation(kRelocAbsolute); 1267 MARK(rel->r_offset); 1268 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1269 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1270 if (s) { 1271 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1272 } else { 1273 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1274 } 1275 break; 1276#endif 1277 1278#if defined(__arm__) 1279 case R_ARM_RELATIVE: 1280#elif defined(__i386__) 1281 case R_386_RELATIVE: 1282#endif 1283 count_relocation(kRelocRelative); 1284 MARK(rel->r_offset); 1285 if (sym) { 1286 DL_ERR("odd RELATIVE form..."); 1287 return -1; 1288 } 1289 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1290 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1291 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1292 break; 1293 1294 default: 1295 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1296 return -1; 1297 } 1298 } 1299 return 0; 1300} 1301#endif 1302 1303#if defined(__mips__) 1304static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1305 ElfW(Addr)** got = si->plt_got; 1306 if (got == NULL) { 1307 return true; 1308 } 1309 unsigned local_gotno = si->mips_local_gotno; 1310 unsigned gotsym = si->mips_gotsym; 1311 unsigned symtabno = si->mips_symtabno; 1312 ElfW(Sym)* symtab = si->symtab; 1313 1314 // got[0] is the address of the lazy resolver function. 1315 // got[1] may be used for a GNU extension. 1316 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1317 // FIXME: maybe this should be in a separate routine? 1318 if ((si->flags & FLAG_LINKER) == 0) { 1319 size_t g = 0; 1320 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1321 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1322 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1323 } 1324 // Relocate the local GOT entries. 1325 for (; g < local_gotno; g++) { 1326 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1327 } 1328 } 1329 1330 // Now for the global GOT entries... 1331 ElfW(Sym)* sym = symtab + gotsym; 1332 got = si->plt_got + local_gotno; 1333 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1334 // This is an undefined reference... try to locate it. 1335 const char* sym_name = si->strtab + sym->st_name; 1336 soinfo* lsi; 1337 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1338 if (s == NULL) { 1339 // We only allow an undefined symbol if this is a weak reference. 1340 s = &symtab[g]; 1341 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1342 DL_ERR("cannot locate \"%s\"...", sym_name); 1343 return false; 1344 } 1345 *got = 0; 1346 } else { 1347 // FIXME: is this sufficient? 1348 // For reference see NetBSD link loader 1349 // 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 1350 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1351 } 1352 } 1353 return true; 1354} 1355#endif 1356 1357void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1358 if (functions == NULL) { 1359 return; 1360 } 1361 1362 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1363 1364 int begin = reverse ? (count - 1) : 0; 1365 int end = reverse ? -1 : count; 1366 int step = reverse ? -1 : 1; 1367 1368 for (int i = begin; i != end; i += step) { 1369 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1370 CallFunction("function", functions[i]); 1371 } 1372 1373 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1374} 1375 1376void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1377 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1378 return; 1379 } 1380 1381 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1382 function(); 1383 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1384 1385 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1386 // are still writable. This happens with our debug malloc (see http://b/7941716). 1387 protect_data(PROT_READ | PROT_WRITE); 1388} 1389 1390void soinfo::CallPreInitConstructors() { 1391 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1392 // but ignored in a shared library. 1393 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1394} 1395 1396void soinfo::CallConstructors() { 1397 if (constructors_called) { 1398 return; 1399 } 1400 1401 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1402 // protect against recursive constructor calls. One simple example of constructor recursion 1403 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1404 // 1. The program depends on libc, so libc's constructor is called here. 1405 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1406 // 3. dlopen() calls the constructors on the newly created 1407 // soinfo for libc_malloc_debug_leak.so. 1408 // 4. The debug .so depends on libc, so CallConstructors is 1409 // called again with the libc soinfo. If it doesn't trigger the early- 1410 // out above, the libc constructor will be called again (recursively!). 1411 constructors_called = true; 1412 1413 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1414 // The GNU dynamic linker silently ignores these, but we warn the developer. 1415 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1416 name, preinit_array_count); 1417 } 1418 1419 get_children().for_each([] (soinfo* si) { 1420 si->CallConstructors(); 1421 }); 1422 1423 TRACE("\"%s\": calling constructors", name); 1424 1425 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1426 CallFunction("DT_INIT", init_func); 1427 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1428} 1429 1430void soinfo::CallDestructors() { 1431 TRACE("\"%s\": calling destructors", name); 1432 1433 // DT_FINI_ARRAY must be parsed in reverse order. 1434 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1435 1436 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1437 CallFunction("DT_FINI", fini_func); 1438} 1439 1440void soinfo::add_child(soinfo* child) { 1441 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1442 return; 1443 } 1444 1445 this->children.push_front(child); 1446 child->parents.push_front(this); 1447} 1448 1449void soinfo::remove_all_links() { 1450 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1451 return; 1452 } 1453 1454 // 1. Untie connected soinfos from 'this'. 1455 children.for_each([&] (soinfo* child) { 1456 child->parents.remove_if([&] (const soinfo* parent) { 1457 return parent == this; 1458 }); 1459 }); 1460 1461 parents.for_each([&] (soinfo* parent) { 1462 parent->children.for_each([&] (const soinfo* child) { 1463 return child == this; 1464 }); 1465 }); 1466 1467 // 2. Once everything untied - clear local lists. 1468 parents.clear(); 1469 children.clear(); 1470} 1471 1472void soinfo::set_st_dev(dev_t dev) { 1473 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1474 return; 1475 } 1476 1477 st_dev = dev; 1478} 1479 1480void soinfo::set_st_ino(ino_t ino) { 1481 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1482 return; 1483 } 1484 1485 st_ino = ino; 1486} 1487 1488dev_t soinfo::get_st_dev() { 1489 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1490 return 0; 1491 } 1492 1493 return st_dev; 1494}; 1495 1496ino_t soinfo::get_st_ino() { 1497 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1498 return 0; 1499 } 1500 1501 return st_ino; 1502} 1503 1504// This is a return on get_children() in case 1505// 'this->flags' does not have FLAG_NEW_SOINFO set. 1506static soinfo::soinfo_list_t g_empty_list; 1507 1508soinfo::soinfo_list_t& soinfo::get_children() { 1509 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1510 return g_empty_list; 1511 } 1512 1513 return this->children; 1514} 1515 1516/* Force any of the closed stdin, stdout and stderr to be associated with 1517 /dev/null. */ 1518static int nullify_closed_stdio() { 1519 int dev_null, i, status; 1520 int return_value = 0; 1521 1522 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1523 if (dev_null < 0) { 1524 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1525 return -1; 1526 } 1527 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1528 1529 /* If any of the stdio file descriptors is valid and not associated 1530 with /dev/null, dup /dev/null to it. */ 1531 for (i = 0; i < 3; i++) { 1532 /* If it is /dev/null already, we are done. */ 1533 if (i == dev_null) { 1534 continue; 1535 } 1536 1537 TRACE("[ Nullifying stdio file descriptor %d]", i); 1538 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1539 1540 /* If file is opened, we are good. */ 1541 if (status != -1) { 1542 continue; 1543 } 1544 1545 /* The only error we allow is that the file descriptor does not 1546 exist, in which case we dup /dev/null to it. */ 1547 if (errno != EBADF) { 1548 DL_ERR("fcntl failed: %s", strerror(errno)); 1549 return_value = -1; 1550 continue; 1551 } 1552 1553 /* Try dupping /dev/null to this stdio file descriptor and 1554 repeat if there is a signal. Note that any errors in closing 1555 the stdio descriptor are lost. */ 1556 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1557 if (status < 0) { 1558 DL_ERR("dup2 failed: %s", strerror(errno)); 1559 return_value = -1; 1560 continue; 1561 } 1562 } 1563 1564 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1565 if (dev_null > 2) { 1566 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1567 status = TEMP_FAILURE_RETRY(close(dev_null)); 1568 if (status == -1) { 1569 DL_ERR("close failed: %s", strerror(errno)); 1570 return_value = -1; 1571 } 1572 } 1573 1574 return return_value; 1575} 1576 1577static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1578 /* "base" might wrap around UINT32_MAX. */ 1579 ElfW(Addr) base = si->load_bias; 1580 const ElfW(Phdr)* phdr = si->phdr; 1581 int phnum = si->phnum; 1582 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1583 1584 /* We can't debug anything until the linker is relocated */ 1585 if (!relocating_linker) { 1586 INFO("[ linking %s ]", si->name); 1587 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1588 } 1589 1590 /* Extract dynamic section */ 1591 size_t dynamic_count; 1592 ElfW(Word) dynamic_flags; 1593 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1594 &dynamic_count, &dynamic_flags); 1595 if (si->dynamic == NULL) { 1596 if (!relocating_linker) { 1597 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1598 } 1599 return false; 1600 } else { 1601 if (!relocating_linker) { 1602 DEBUG("dynamic = %p", si->dynamic); 1603 } 1604 } 1605 1606#if defined(__arm__) 1607 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1608 &si->ARM_exidx, &si->ARM_exidx_count); 1609#endif 1610 1611 // Extract useful information from dynamic section. 1612 uint32_t needed_count = 0; 1613 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1614 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1615 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1616 switch (d->d_tag) { 1617 case DT_HASH: 1618 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1619 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1620 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1621 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1622 break; 1623 case DT_STRTAB: 1624 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1625 break; 1626 case DT_SYMTAB: 1627 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1628 break; 1629#if !defined(__LP64__) 1630 case DT_PLTREL: 1631 if (d->d_un.d_val != DT_REL) { 1632 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1633 return false; 1634 } 1635 break; 1636#endif 1637 case DT_JMPREL: 1638#if defined(USE_RELA) 1639 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1640#else 1641 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1642#endif 1643 break; 1644 case DT_PLTRELSZ: 1645#if defined(USE_RELA) 1646 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1647#else 1648 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1649#endif 1650 break; 1651#if defined(__mips__) 1652 case DT_PLTGOT: 1653 // Used by mips and mips64. 1654 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1655 break; 1656#endif 1657 case DT_DEBUG: 1658 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1659 // if the dynamic table is writable 1660// FIXME: not working currently for N64 1661// The flags for the LOAD and DYNAMIC program headers do not agree. 1662// The LOAD section containng the dynamic table has been mapped as 1663// read-only, but the DYNAMIC header claims it is writable. 1664#if !(defined(__mips__) && defined(__LP64__)) 1665 if ((dynamic_flags & PF_W) != 0) { 1666 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1667 } 1668 break; 1669#endif 1670#if defined(USE_RELA) 1671 case DT_RELA: 1672 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1673 break; 1674 case DT_RELASZ: 1675 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1676 break; 1677 case DT_REL: 1678 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1679 return false; 1680 case DT_RELSZ: 1681 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1682 return false; 1683#else 1684 case DT_REL: 1685 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1686 break; 1687 case DT_RELSZ: 1688 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1689 break; 1690 case DT_RELA: 1691 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1692 return false; 1693#endif 1694 case DT_INIT: 1695 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1696 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1697 break; 1698 case DT_FINI: 1699 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1700 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1701 break; 1702 case DT_INIT_ARRAY: 1703 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1704 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1705 break; 1706 case DT_INIT_ARRAYSZ: 1707 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1708 break; 1709 case DT_FINI_ARRAY: 1710 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1711 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1712 break; 1713 case DT_FINI_ARRAYSZ: 1714 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1715 break; 1716 case DT_PREINIT_ARRAY: 1717 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1718 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1719 break; 1720 case DT_PREINIT_ARRAYSZ: 1721 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1722 break; 1723 case DT_TEXTREL: 1724#if defined(__LP64__) 1725 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1726 return false; 1727#else 1728 si->has_text_relocations = true; 1729 break; 1730#endif 1731 case DT_SYMBOLIC: 1732 si->has_DT_SYMBOLIC = true; 1733 break; 1734 case DT_NEEDED: 1735 ++needed_count; 1736 break; 1737 case DT_FLAGS: 1738 if (d->d_un.d_val & DF_TEXTREL) { 1739#if defined(__LP64__) 1740 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1741 return false; 1742#else 1743 si->has_text_relocations = true; 1744#endif 1745 } 1746 if (d->d_un.d_val & DF_SYMBOLIC) { 1747 si->has_DT_SYMBOLIC = true; 1748 } 1749 break; 1750#if defined(__mips__) 1751 case DT_STRSZ: 1752 case DT_SYMENT: 1753 case DT_RELENT: 1754 break; 1755 case DT_MIPS_RLD_MAP: 1756 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1757 { 1758 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1759 *dp = &_r_debug; 1760 } 1761 break; 1762 case DT_MIPS_RLD_VERSION: 1763 case DT_MIPS_FLAGS: 1764 case DT_MIPS_BASE_ADDRESS: 1765 case DT_MIPS_UNREFEXTNO: 1766 break; 1767 1768 case DT_MIPS_SYMTABNO: 1769 si->mips_symtabno = d->d_un.d_val; 1770 break; 1771 1772 case DT_MIPS_LOCAL_GOTNO: 1773 si->mips_local_gotno = d->d_un.d_val; 1774 break; 1775 1776 case DT_MIPS_GOTSYM: 1777 si->mips_gotsym = d->d_un.d_val; 1778 break; 1779#endif 1780 1781 default: 1782 DEBUG("Unused DT entry: type %p arg %p", 1783 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1784 break; 1785 } 1786 } 1787 1788 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1789 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1790 1791 // Sanity checks. 1792 if (relocating_linker && needed_count != 0) { 1793 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1794 return false; 1795 } 1796 if (si->nbucket == 0) { 1797 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1798 return false; 1799 } 1800 if (si->strtab == 0) { 1801 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1802 return false; 1803 } 1804 if (si->symtab == 0) { 1805 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1806 return false; 1807 } 1808 1809 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1810 if (si->flags & FLAG_EXE) { 1811 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1812 size_t preload_count = 0; 1813 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1814 soinfo* lsi = find_library(g_ld_preload_names[i], NULL); 1815 if (lsi != NULL) { 1816 g_ld_preloads[preload_count++] = lsi; 1817 } else { 1818 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1819 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1820 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1821 } 1822 } 1823 } 1824 1825 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1826 soinfo** pneeded = needed; 1827 1828 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1829 if (d->d_tag == DT_NEEDED) { 1830 const char* library_name = si->strtab + d->d_un.d_val; 1831 DEBUG("%s needs %s", si->name, library_name); 1832 soinfo* lsi = find_library(library_name, NULL); 1833 if (lsi == NULL) { 1834 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1835 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1836 library_name, si->name, tmp_err_buf); 1837 return false; 1838 } 1839 1840 si->add_child(lsi); 1841 *pneeded++ = lsi; 1842 } 1843 } 1844 *pneeded = NULL; 1845 1846#if !defined(__LP64__) 1847 if (si->has_text_relocations) { 1848 // Make segments writable to allow text relocations to work properly. We will later call 1849 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1850#if !defined(__i386__) // The platform itself has too many text relocations on x86. 1851 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1852 "security hardening. Please fix.", si->name); 1853#endif 1854 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1855 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1856 si->name, strerror(errno)); 1857 return false; 1858 } 1859 } 1860#endif 1861 1862#if defined(USE_RELA) 1863 if (si->plt_rela != NULL) { 1864 DEBUG("[ relocating %s plt ]\n", si->name); 1865 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1866 return false; 1867 } 1868 } 1869 if (si->rela != NULL) { 1870 DEBUG("[ relocating %s ]\n", si->name); 1871 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1872 return false; 1873 } 1874 } 1875#else 1876 if (si->plt_rel != NULL) { 1877 DEBUG("[ relocating %s plt ]", si->name); 1878 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1879 return false; 1880 } 1881 } 1882 if (si->rel != NULL) { 1883 DEBUG("[ relocating %s ]", si->name); 1884 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1885 return false; 1886 } 1887 } 1888#endif 1889 1890#if defined(__mips__) 1891 if (!mips_relocate_got(si, needed)) { 1892 return false; 1893 } 1894#endif 1895 1896 si->flags |= FLAG_LINKED; 1897 DEBUG("[ finished linking %s ]", si->name); 1898 1899#if !defined(__LP64__) 1900 if (si->has_text_relocations) { 1901 // All relocations are done, we can protect our segments back to read-only. 1902 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1903 DL_ERR("can't protect segments for \"%s\": %s", 1904 si->name, strerror(errno)); 1905 return false; 1906 } 1907 } 1908#endif 1909 1910 /* We can also turn on GNU RELRO protection */ 1911 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1912 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1913 si->name, strerror(errno)); 1914 return false; 1915 } 1916 1917 /* Handle serializing/sharing the RELRO segment */ 1918 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1919 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1920 extinfo->relro_fd) < 0) { 1921 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1922 si->name, strerror(errno)); 1923 return false; 1924 } 1925 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1926 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1927 extinfo->relro_fd) < 0) { 1928 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1929 si->name, strerror(errno)); 1930 return false; 1931 } 1932 } 1933 1934 notify_gdb_of_load(si); 1935 return true; 1936} 1937 1938/* 1939 * This function add vdso to internal dso list. 1940 * It helps to stack unwinding through signal handlers. 1941 * Also, it makes bionic more like glibc. 1942 */ 1943static void add_vdso(KernelArgumentBlock& args __unused) { 1944#if defined(AT_SYSINFO_EHDR) 1945 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1946 if (ehdr_vdso == NULL) { 1947 return; 1948 } 1949 1950 soinfo* si = soinfo_alloc("[vdso]", NULL); 1951 1952 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1953 si->phnum = ehdr_vdso->e_phnum; 1954 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1955 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1956 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1957 1958 soinfo_link_image(si, NULL); 1959#endif 1960} 1961 1962/* 1963 * This is linker soinfo for GDB. See details below. 1964 */ 1965static soinfo linker_soinfo_for_gdb; 1966 1967/* gdb expects the linker to be in the debug shared object list. 1968 * Without this, gdb has trouble locating the linker's ".text" 1969 * and ".plt" sections. Gdb could also potentially use this to 1970 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1971 * Don't use soinfo_alloc(), because the linker shouldn't 1972 * be on the soinfo list. 1973 */ 1974static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 1975#if defined(__LP64__) 1976 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 1977#else 1978 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 1979#endif 1980 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 1981 linker_soinfo_for_gdb.base = linker_base; 1982 1983 /* 1984 * Set the dynamic field in the link map otherwise gdb will complain with 1985 * the following: 1986 * warning: .dynamic section for "/system/bin/linker" is not at the 1987 * expected address (wrong library or version mismatch?) 1988 */ 1989 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 1990 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 1991 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 1992 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 1993 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 1994} 1995 1996/* 1997 * This code is called after the linker has linked itself and 1998 * fixed it's own GOT. It is safe to make references to externs 1999 * and other non-local data at this point. 2000 */ 2001static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2002 /* NOTE: we store the args pointer on a special location 2003 * of the temporary TLS area in order to pass it to 2004 * the C Library's runtime initializer. 2005 * 2006 * The initializer must clear the slot and reset the TLS 2007 * to point to a different location to ensure that no other 2008 * shared library constructor can access it. 2009 */ 2010 __libc_init_tls(args); 2011 2012#if TIMING 2013 struct timeval t0, t1; 2014 gettimeofday(&t0, 0); 2015#endif 2016 2017 // Initialize environment functions, and get to the ELF aux vectors table. 2018 linker_env_init(args); 2019 2020 // If this is a setuid/setgid program, close the security hole described in 2021 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2022 if (get_AT_SECURE()) { 2023 nullify_closed_stdio(); 2024 } 2025 2026 debuggerd_init(); 2027 2028 // Get a few environment variables. 2029 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2030 if (LD_DEBUG != NULL) { 2031 g_ld_debug_verbosity = atoi(LD_DEBUG); 2032 } 2033 2034 // Normally, these are cleaned by linker_env_init, but the test 2035 // doesn't cost us anything. 2036 const char* ldpath_env = NULL; 2037 const char* ldpreload_env = NULL; 2038 if (!get_AT_SECURE()) { 2039 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2040 ldpreload_env = linker_env_get("LD_PRELOAD"); 2041 } 2042 2043 // Linker does not call constructors for its own 2044 // global variables so we need to initialize 2045 // the allocators explicitly. 2046 g_soinfo_allocator.init(); 2047 g_soinfo_links_allocator.init(); 2048 2049 INFO("[ android linker & debugger ]"); 2050 2051 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2052 if (si == NULL) { 2053 exit(EXIT_FAILURE); 2054 } 2055 2056 /* bootstrap the link map, the main exe always needs to be first */ 2057 si->flags |= FLAG_EXE; 2058 link_map* map = &(si->link_map_head); 2059 2060 map->l_addr = 0; 2061 map->l_name = args.argv[0]; 2062 map->l_prev = NULL; 2063 map->l_next = NULL; 2064 2065 _r_debug.r_map = map; 2066 r_debug_tail = map; 2067 2068 init_linker_info_for_gdb(linker_base); 2069 2070 // Extract information passed from the kernel. 2071 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2072 si->phnum = args.getauxval(AT_PHNUM); 2073 si->entry = args.getauxval(AT_ENTRY); 2074 2075 /* Compute the value of si->base. We can't rely on the fact that 2076 * the first entry is the PHDR because this will not be true 2077 * for certain executables (e.g. some in the NDK unit test suite) 2078 */ 2079 si->base = 0; 2080 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2081 si->load_bias = 0; 2082 for (size_t i = 0; i < si->phnum; ++i) { 2083 if (si->phdr[i].p_type == PT_PHDR) { 2084 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2085 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2086 break; 2087 } 2088 } 2089 si->dynamic = NULL; 2090 si->ref_count = 1; 2091 2092 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2093 if (elf_hdr->e_type != ET_DYN) { 2094 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2095 exit(EXIT_FAILURE); 2096 } 2097 2098 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2099 parse_LD_LIBRARY_PATH(ldpath_env); 2100 parse_LD_PRELOAD(ldpreload_env); 2101 2102 somain = si; 2103 2104 if (!soinfo_link_image(si, NULL)) { 2105 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2106 exit(EXIT_FAILURE); 2107 } 2108 2109 add_vdso(args); 2110 2111 si->CallPreInitConstructors(); 2112 2113 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2114 g_ld_preloads[i]->CallConstructors(); 2115 } 2116 2117 /* After the link_image, the si->load_bias is initialized. 2118 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2119 * We need to update this value for so exe here. So Unwind_Backtrace 2120 * for some arch like x86 could work correctly within so exe. 2121 */ 2122 map->l_addr = si->load_bias; 2123 si->CallConstructors(); 2124 2125#if TIMING 2126 gettimeofday(&t1, NULL); 2127 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2128 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2129 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2130#endif 2131#if STATS 2132 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2133 linker_stats.count[kRelocAbsolute], 2134 linker_stats.count[kRelocRelative], 2135 linker_stats.count[kRelocCopy], 2136 linker_stats.count[kRelocSymbol]); 2137#endif 2138#if COUNT_PAGES 2139 { 2140 unsigned n; 2141 unsigned i; 2142 unsigned count = 0; 2143 for (n = 0; n < 4096; n++) { 2144 if (bitmask[n]) { 2145 unsigned x = bitmask[n]; 2146#if defined(__LP64__) 2147 for (i = 0; i < 32; i++) { 2148#else 2149 for (i = 0; i < 8; i++) { 2150#endif 2151 if (x & 1) { 2152 count++; 2153 } 2154 x >>= 1; 2155 } 2156 } 2157 } 2158 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2159 } 2160#endif 2161 2162#if TIMING || STATS || COUNT_PAGES 2163 fflush(stdout); 2164#endif 2165 2166 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2167 return si->entry; 2168} 2169 2170/* Compute the load-bias of an existing executable. This shall only 2171 * be used to compute the load bias of an executable or shared library 2172 * that was loaded by the kernel itself. 2173 * 2174 * Input: 2175 * elf -> address of ELF header, assumed to be at the start of the file. 2176 * Return: 2177 * load bias, i.e. add the value of any p_vaddr in the file to get 2178 * the corresponding address in memory. 2179 */ 2180static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2181 ElfW(Addr) offset = elf->e_phoff; 2182 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2183 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2184 2185 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2186 if (phdr->p_type == PT_LOAD) { 2187 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2188 } 2189 } 2190 return 0; 2191} 2192 2193/* 2194 * This is the entry point for the linker, called from begin.S. This 2195 * method is responsible for fixing the linker's own relocations, and 2196 * then calling __linker_init_post_relocation(). 2197 * 2198 * Because this method is called before the linker has fixed it's own 2199 * relocations, any attempt to reference an extern variable, extern 2200 * function, or other GOT reference will generate a segfault. 2201 */ 2202extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2203 // Initialize static variables. 2204 solist = get_libdl_info(); 2205 sonext = get_libdl_info(); 2206 2207 KernelArgumentBlock args(raw_args); 2208 2209 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2210 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2211 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2212 2213 soinfo linker_so; 2214 memset(&linker_so, 0, sizeof(soinfo)); 2215 2216 strcpy(linker_so.name, "[dynamic linker]"); 2217 linker_so.base = linker_addr; 2218 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2219 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2220 linker_so.dynamic = NULL; 2221 linker_so.phdr = phdr; 2222 linker_so.phnum = elf_hdr->e_phnum; 2223 linker_so.flags |= FLAG_LINKER; 2224 2225 if (!soinfo_link_image(&linker_so, NULL)) { 2226 // It would be nice to print an error message, but if the linker 2227 // can't link itself, there's no guarantee that we'll be able to 2228 // call write() (because it involves a GOT reference). We may as 2229 // well try though... 2230 const char* msg = "CANNOT LINK EXECUTABLE: "; 2231 write(2, msg, strlen(msg)); 2232 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2233 write(2, "\n", 1); 2234 _exit(EXIT_FAILURE); 2235 } 2236 2237 // We have successfully fixed our own relocations. It's safe to run 2238 // the main part of the linker now. 2239 args.abort_message_ptr = &g_abort_message; 2240 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2241 2242 protect_data(PROT_READ); 2243 2244 // Return the address that the calling assembly stub should jump to. 2245 return start_address; 2246} 2247