linker.cpp revision 3c005d60194aadd92584258118c06782c9deab11
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, int dlflags, 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 if ((dlflags & RTLD_NOLOAD) != 0) { 714 return NULL; 715 } 716 717 // Read the ELF header and load the segments. 718 if (!elf_reader.Load(extinfo)) { 719 return NULL; 720 } 721 722 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 723 if (si == NULL) { 724 return NULL; 725 } 726 si->base = elf_reader.load_start(); 727 si->size = elf_reader.load_size(); 728 si->load_bias = elf_reader.load_bias(); 729 si->phnum = elf_reader.phdr_count(); 730 si->phdr = elf_reader.loaded_phdr(); 731 732 // At this point we know that whatever is loaded @ base is a valid ELF 733 // shared library whose segments are properly mapped in. 734 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 735 reinterpret_cast<void*>(si->base), si->size, si->name); 736 737 if (!soinfo_link_image(si, extinfo)) { 738 soinfo_free(si); 739 return NULL; 740 } 741 742 return si; 743} 744 745static soinfo *find_loaded_library_by_name(const char* name) { 746 const char* search_name = SEARCH_NAME(name); 747 for (soinfo* si = solist; si != NULL; si = si->next) { 748 if (!strcmp(search_name, si->name)) { 749 return si; 750 } 751 } 752 return NULL; 753} 754 755static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 756 if (name == NULL) { 757 return somain; 758 } 759 760 soinfo* si = find_loaded_library_by_name(name); 761 762 // Library might still be loaded, the accurate detection 763 // of this fact is done by load_library 764 if (si == NULL) { 765 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 766 si = load_library(name, dlflags, extinfo); 767 } 768 769 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 770 DL_ERR("recursive link to \"%s\"", si->name); 771 return NULL; 772 } 773 774 return si; 775} 776 777static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 778 soinfo* si = find_library_internal(name, dlflags, extinfo); 779 if (si != NULL) { 780 si->ref_count++; 781 } 782 return si; 783} 784 785static void soinfo_unload(soinfo* si) { 786 if (si->ref_count == 1) { 787 TRACE("unloading '%s'", si->name); 788 si->CallDestructors(); 789 790 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 791 si->get_children().for_each([&] (soinfo* child) { 792 TRACE("%s needs to unload %s", si->name, child->name); 793 soinfo_unload(child); 794 }); 795 } else { 796 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 797 if (d->d_tag == DT_NEEDED) { 798 const char* library_name = si->strtab + d->d_un.d_val; 799 TRACE("%s needs to unload %s", si->name, library_name); 800 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 801 if (needed != NULL) { 802 soinfo_unload(needed); 803 } else { 804 // Not found: for example if symlink was deleted between dlopen and dlclose 805 // Since we cannot really handle errors at this point - print and continue. 806 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 807 } 808 } 809 } 810 } 811 812 notify_gdb_of_unload(si); 813 si->ref_count = 0; 814 soinfo_free(si); 815 } else { 816 si->ref_count--; 817 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 818 } 819} 820 821void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 822 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 823} 824 825void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 826 if (!get_AT_SECURE()) { 827 parse_LD_LIBRARY_PATH(ld_library_path); 828 } 829} 830 831soinfo* do_dlopen(const char* name, int flags, soinfo* caller, const android_dlextinfo* extinfo) { 832 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 833 DL_ERR("invalid flags to dlopen: %x", flags); 834 return NULL; 835 } 836 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 837 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 838 return NULL; 839 } 840 protect_data(PROT_READ | PROT_WRITE); 841 soinfo* si = find_library(name, flags, extinfo); 842 if (si != NULL) { 843 si->CallConstructors(); 844 } 845 protect_data(PROT_READ); 846 return si; 847} 848 849void do_dlclose(soinfo* si) { 850 protect_data(PROT_READ | PROT_WRITE); 851 soinfo_unload(si); 852 protect_data(PROT_READ); 853} 854 855#if defined(USE_RELA) 856static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 857 ElfW(Sym)* s; 858 soinfo* lsi; 859 860 for (size_t idx = 0; idx < count; ++idx, ++rela) { 861 unsigned type = ELFW(R_TYPE)(rela->r_info); 862 unsigned sym = ELFW(R_SYM)(rela->r_info); 863 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 864 ElfW(Addr) sym_addr = 0; 865 const char* sym_name = NULL; 866 867 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 868 if (type == 0) { // R_*_NONE 869 continue; 870 } 871 if (sym != 0) { 872 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 873 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 874 if (s == NULL) { 875 // We only allow an undefined symbol if this is a weak reference... 876 s = &si->symtab[sym]; 877 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 878 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 879 return -1; 880 } 881 882 /* IHI0044C AAELF 4.5.1.1: 883 884 Libraries are not searched to resolve weak references. 885 It is not an error for a weak reference to remain unsatisfied. 886 887 During linking, the value of an undefined weak reference is: 888 - Zero if the relocation type is absolute 889 - The address of the place if the relocation is pc-relative 890 - The address of nominal base address if the relocation 891 type is base-relative. 892 */ 893 894 switch (type) { 895#if defined(__aarch64__) 896 case R_AARCH64_JUMP_SLOT: 897 case R_AARCH64_GLOB_DAT: 898 case R_AARCH64_ABS64: 899 case R_AARCH64_ABS32: 900 case R_AARCH64_ABS16: 901 case R_AARCH64_RELATIVE: 902 /* 903 * The sym_addr was initialized to be zero above, or the relocation 904 * code below does not care about value of sym_addr. 905 * No need to do anything. 906 */ 907 break; 908#elif defined(__x86_64__) 909 case R_X86_64_JUMP_SLOT: 910 case R_X86_64_GLOB_DAT: 911 case R_X86_64_32: 912 case R_X86_64_64: 913 case R_X86_64_RELATIVE: 914 // No need to do anything. 915 break; 916 case R_X86_64_PC32: 917 sym_addr = reloc; 918 break; 919#endif 920 default: 921 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 922 return -1; 923 } 924 } else { 925 // We got a definition. 926 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 927 } 928 count_relocation(kRelocSymbol); 929 } else { 930 s = NULL; 931 } 932 933 switch (type) { 934#if defined(__aarch64__) 935 case R_AARCH64_JUMP_SLOT: 936 count_relocation(kRelocAbsolute); 937 MARK(rela->r_offset); 938 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 939 reloc, (sym_addr + rela->r_addend), sym_name); 940 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 941 break; 942 case R_AARCH64_GLOB_DAT: 943 count_relocation(kRelocAbsolute); 944 MARK(rela->r_offset); 945 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 946 reloc, (sym_addr + rela->r_addend), sym_name); 947 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 948 break; 949 case R_AARCH64_ABS64: 950 count_relocation(kRelocAbsolute); 951 MARK(rela->r_offset); 952 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 953 reloc, (sym_addr + rela->r_addend), sym_name); 954 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 955 break; 956 case R_AARCH64_ABS32: 957 count_relocation(kRelocAbsolute); 958 MARK(rela->r_offset); 959 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 960 reloc, (sym_addr + rela->r_addend), sym_name); 961 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 962 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 963 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 964 } else { 965 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 966 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 967 static_cast<ElfW(Addr)>(INT32_MIN), 968 static_cast<ElfW(Addr)>(UINT32_MAX)); 969 return -1; 970 } 971 break; 972 case R_AARCH64_ABS16: 973 count_relocation(kRelocAbsolute); 974 MARK(rela->r_offset); 975 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 976 reloc, (sym_addr + rela->r_addend), sym_name); 977 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 978 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 979 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 980 } else { 981 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 982 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 983 static_cast<ElfW(Addr)>(INT16_MIN), 984 static_cast<ElfW(Addr)>(UINT16_MAX)); 985 return -1; 986 } 987 break; 988 case R_AARCH64_PREL64: 989 count_relocation(kRelocRelative); 990 MARK(rela->r_offset); 991 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 992 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 993 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 994 break; 995 case R_AARCH64_PREL32: 996 count_relocation(kRelocRelative); 997 MARK(rela->r_offset); 998 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 999 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1000 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1001 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1002 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1003 } else { 1004 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1005 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1006 static_cast<ElfW(Addr)>(INT32_MIN), 1007 static_cast<ElfW(Addr)>(UINT32_MAX)); 1008 return -1; 1009 } 1010 break; 1011 case R_AARCH64_PREL16: 1012 count_relocation(kRelocRelative); 1013 MARK(rela->r_offset); 1014 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1015 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1016 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1017 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1018 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1019 } else { 1020 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1021 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1022 static_cast<ElfW(Addr)>(INT16_MIN), 1023 static_cast<ElfW(Addr)>(UINT16_MAX)); 1024 return -1; 1025 } 1026 break; 1027 1028 case R_AARCH64_RELATIVE: 1029 count_relocation(kRelocRelative); 1030 MARK(rela->r_offset); 1031 if (sym) { 1032 DL_ERR("odd RELATIVE form..."); 1033 return -1; 1034 } 1035 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1036 reloc, (si->base + rela->r_addend)); 1037 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1038 break; 1039 1040 case R_AARCH64_COPY: 1041 /* 1042 * ET_EXEC is not supported so this should not happen. 1043 * 1044 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1045 * 1046 * Section 4.7.1.10 "Dynamic relocations" 1047 * R_AARCH64_COPY may only appear in executable objects where e_type is 1048 * set to ET_EXEC. 1049 */ 1050 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1051 return -1; 1052 case R_AARCH64_TLS_TPREL64: 1053 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1054 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1055 break; 1056 case R_AARCH64_TLS_DTPREL32: 1057 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1058 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1059 break; 1060#elif defined(__x86_64__) 1061 case R_X86_64_JUMP_SLOT: 1062 count_relocation(kRelocAbsolute); 1063 MARK(rela->r_offset); 1064 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1065 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1066 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1067 break; 1068 case R_X86_64_GLOB_DAT: 1069 count_relocation(kRelocAbsolute); 1070 MARK(rela->r_offset); 1071 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1072 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1073 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1074 break; 1075 case R_X86_64_RELATIVE: 1076 count_relocation(kRelocRelative); 1077 MARK(rela->r_offset); 1078 if (sym) { 1079 DL_ERR("odd RELATIVE form..."); 1080 return -1; 1081 } 1082 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1083 static_cast<size_t>(si->base)); 1084 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1085 break; 1086 case R_X86_64_32: 1087 count_relocation(kRelocRelative); 1088 MARK(rela->r_offset); 1089 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1090 static_cast<size_t>(sym_addr), sym_name); 1091 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1092 break; 1093 case R_X86_64_64: 1094 count_relocation(kRelocRelative); 1095 MARK(rela->r_offset); 1096 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1097 static_cast<size_t>(sym_addr), sym_name); 1098 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1099 break; 1100 case R_X86_64_PC32: 1101 count_relocation(kRelocRelative); 1102 MARK(rela->r_offset); 1103 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1104 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1105 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1106 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1107 break; 1108#endif 1109 1110 default: 1111 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1112 return -1; 1113 } 1114 } 1115 return 0; 1116} 1117 1118#else // REL, not RELA. 1119 1120static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1121 ElfW(Sym)* s; 1122 soinfo* lsi; 1123 1124 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1125 unsigned type = ELFW(R_TYPE)(rel->r_info); 1126 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1127 unsigned sym = ELFW(R_SYM)(rel->r_info); 1128 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1129 ElfW(Addr) sym_addr = 0; 1130 const char* sym_name = NULL; 1131 1132 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1133 if (type == 0) { // R_*_NONE 1134 continue; 1135 } 1136 if (sym != 0) { 1137 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1138 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1139 if (s == NULL) { 1140 // We only allow an undefined symbol if this is a weak reference... 1141 s = &si->symtab[sym]; 1142 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1143 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1144 return -1; 1145 } 1146 1147 /* IHI0044C AAELF 4.5.1.1: 1148 1149 Libraries are not searched to resolve weak references. 1150 It is not an error for a weak reference to remain 1151 unsatisfied. 1152 1153 During linking, the value of an undefined weak reference is: 1154 - Zero if the relocation type is absolute 1155 - The address of the place if the relocation is pc-relative 1156 - The address of nominal base address if the relocation 1157 type is base-relative. 1158 */ 1159 1160 switch (type) { 1161#if defined(__arm__) 1162 case R_ARM_JUMP_SLOT: 1163 case R_ARM_GLOB_DAT: 1164 case R_ARM_ABS32: 1165 case R_ARM_RELATIVE: /* Don't care. */ 1166 // sym_addr was initialized to be zero above or relocation 1167 // code below does not care about value of sym_addr. 1168 // No need to do anything. 1169 break; 1170#elif defined(__i386__) 1171 case R_386_JMP_SLOT: 1172 case R_386_GLOB_DAT: 1173 case R_386_32: 1174 case R_386_RELATIVE: /* Don't care. */ 1175 // sym_addr was initialized to be zero above or relocation 1176 // code below does not care about value of sym_addr. 1177 // No need to do anything. 1178 break; 1179 case R_386_PC32: 1180 sym_addr = reloc; 1181 break; 1182#endif 1183 1184#if defined(__arm__) 1185 case R_ARM_COPY: 1186 // Fall through. Can't really copy if weak symbol is not found at run-time. 1187#endif 1188 default: 1189 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1190 return -1; 1191 } 1192 } else { 1193 // We got a definition. 1194 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1195 } 1196 count_relocation(kRelocSymbol); 1197 } else { 1198 s = NULL; 1199 } 1200 1201 switch (type) { 1202#if defined(__arm__) 1203 case R_ARM_JUMP_SLOT: 1204 count_relocation(kRelocAbsolute); 1205 MARK(rel->r_offset); 1206 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1207 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1208 break; 1209 case R_ARM_GLOB_DAT: 1210 count_relocation(kRelocAbsolute); 1211 MARK(rel->r_offset); 1212 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1213 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1214 break; 1215 case R_ARM_ABS32: 1216 count_relocation(kRelocAbsolute); 1217 MARK(rel->r_offset); 1218 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1219 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1220 break; 1221 case R_ARM_REL32: 1222 count_relocation(kRelocRelative); 1223 MARK(rel->r_offset); 1224 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1225 reloc, sym_addr, rel->r_offset, sym_name); 1226 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1227 break; 1228 case R_ARM_COPY: 1229 /* 1230 * ET_EXEC is not supported so this should not happen. 1231 * 1232 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1233 * 1234 * Section 4.7.1.10 "Dynamic relocations" 1235 * R_ARM_COPY may only appear in executable objects where e_type is 1236 * set to ET_EXEC. 1237 */ 1238 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1239 return -1; 1240#elif defined(__i386__) 1241 case R_386_JMP_SLOT: 1242 count_relocation(kRelocAbsolute); 1243 MARK(rel->r_offset); 1244 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1245 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1246 break; 1247 case R_386_GLOB_DAT: 1248 count_relocation(kRelocAbsolute); 1249 MARK(rel->r_offset); 1250 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1251 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1252 break; 1253 case R_386_32: 1254 count_relocation(kRelocRelative); 1255 MARK(rel->r_offset); 1256 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1257 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1258 break; 1259 case R_386_PC32: 1260 count_relocation(kRelocRelative); 1261 MARK(rel->r_offset); 1262 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1263 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1264 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1265 break; 1266#elif defined(__mips__) 1267 case R_MIPS_REL32: 1268#if defined(__LP64__) 1269 // MIPS Elf64_Rel entries contain compound relocations 1270 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1271 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1272 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1273 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1274 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1275 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1276 return -1; 1277 } 1278#endif 1279 count_relocation(kRelocAbsolute); 1280 MARK(rel->r_offset); 1281 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1282 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1283 if (s) { 1284 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1285 } else { 1286 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1287 } 1288 break; 1289#endif 1290 1291#if defined(__arm__) 1292 case R_ARM_RELATIVE: 1293#elif defined(__i386__) 1294 case R_386_RELATIVE: 1295#endif 1296 count_relocation(kRelocRelative); 1297 MARK(rel->r_offset); 1298 if (sym) { 1299 DL_ERR("odd RELATIVE form..."); 1300 return -1; 1301 } 1302 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1303 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1304 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1305 break; 1306 1307 default: 1308 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1309 return -1; 1310 } 1311 } 1312 return 0; 1313} 1314#endif 1315 1316#if defined(__mips__) 1317static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1318 ElfW(Addr)** got = si->plt_got; 1319 if (got == NULL) { 1320 return true; 1321 } 1322 unsigned local_gotno = si->mips_local_gotno; 1323 unsigned gotsym = si->mips_gotsym; 1324 unsigned symtabno = si->mips_symtabno; 1325 ElfW(Sym)* symtab = si->symtab; 1326 1327 // got[0] is the address of the lazy resolver function. 1328 // got[1] may be used for a GNU extension. 1329 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1330 // FIXME: maybe this should be in a separate routine? 1331 if ((si->flags & FLAG_LINKER) == 0) { 1332 size_t g = 0; 1333 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1334 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1335 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1336 } 1337 // Relocate the local GOT entries. 1338 for (; g < local_gotno; g++) { 1339 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1340 } 1341 } 1342 1343 // Now for the global GOT entries... 1344 ElfW(Sym)* sym = symtab + gotsym; 1345 got = si->plt_got + local_gotno; 1346 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1347 // This is an undefined reference... try to locate it. 1348 const char* sym_name = si->strtab + sym->st_name; 1349 soinfo* lsi; 1350 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1351 if (s == NULL) { 1352 // We only allow an undefined symbol if this is a weak reference. 1353 s = &symtab[g]; 1354 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1355 DL_ERR("cannot locate \"%s\"...", sym_name); 1356 return false; 1357 } 1358 *got = 0; 1359 } else { 1360 // FIXME: is this sufficient? 1361 // For reference see NetBSD link loader 1362 // 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 1363 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1364 } 1365 } 1366 return true; 1367} 1368#endif 1369 1370void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1371 if (functions == NULL) { 1372 return; 1373 } 1374 1375 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1376 1377 int begin = reverse ? (count - 1) : 0; 1378 int end = reverse ? -1 : count; 1379 int step = reverse ? -1 : 1; 1380 1381 for (int i = begin; i != end; i += step) { 1382 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1383 CallFunction("function", functions[i]); 1384 } 1385 1386 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1387} 1388 1389void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1390 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1391 return; 1392 } 1393 1394 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1395 function(); 1396 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1397 1398 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1399 // are still writable. This happens with our debug malloc (see http://b/7941716). 1400 protect_data(PROT_READ | PROT_WRITE); 1401} 1402 1403void soinfo::CallPreInitConstructors() { 1404 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1405 // but ignored in a shared library. 1406 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1407} 1408 1409void soinfo::CallConstructors() { 1410 if (constructors_called) { 1411 return; 1412 } 1413 1414 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1415 // protect against recursive constructor calls. One simple example of constructor recursion 1416 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1417 // 1. The program depends on libc, so libc's constructor is called here. 1418 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1419 // 3. dlopen() calls the constructors on the newly created 1420 // soinfo for libc_malloc_debug_leak.so. 1421 // 4. The debug .so depends on libc, so CallConstructors is 1422 // called again with the libc soinfo. If it doesn't trigger the early- 1423 // out above, the libc constructor will be called again (recursively!). 1424 constructors_called = true; 1425 1426 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1427 // The GNU dynamic linker silently ignores these, but we warn the developer. 1428 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1429 name, preinit_array_count); 1430 } 1431 1432 get_children().for_each([] (soinfo* si) { 1433 si->CallConstructors(); 1434 }); 1435 1436 TRACE("\"%s\": calling constructors", name); 1437 1438 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1439 CallFunction("DT_INIT", init_func); 1440 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1441} 1442 1443void soinfo::CallDestructors() { 1444 TRACE("\"%s\": calling destructors", name); 1445 1446 // DT_FINI_ARRAY must be parsed in reverse order. 1447 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1448 1449 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1450 CallFunction("DT_FINI", fini_func); 1451 1452 // This is needed on second call to dlopen 1453 // after library has been unloaded with RTLD_NODELETE 1454 constructors_called = false; 1455} 1456 1457void soinfo::add_child(soinfo* child) { 1458 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1459 return; 1460 } 1461 1462 this->children.push_front(child); 1463 child->parents.push_front(this); 1464} 1465 1466void soinfo::remove_all_links() { 1467 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1468 return; 1469 } 1470 1471 // 1. Untie connected soinfos from 'this'. 1472 children.for_each([&] (soinfo* child) { 1473 child->parents.remove_if([&] (const soinfo* parent) { 1474 return parent == this; 1475 }); 1476 }); 1477 1478 parents.for_each([&] (soinfo* parent) { 1479 parent->children.for_each([&] (const soinfo* child) { 1480 return child == this; 1481 }); 1482 }); 1483 1484 // 2. Once everything untied - clear local lists. 1485 parents.clear(); 1486 children.clear(); 1487} 1488 1489void soinfo::set_st_dev(dev_t dev) { 1490 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1491 return; 1492 } 1493 1494 st_dev = dev; 1495} 1496 1497void soinfo::set_st_ino(ino_t ino) { 1498 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1499 return; 1500 } 1501 1502 st_ino = ino; 1503} 1504 1505dev_t soinfo::get_st_dev() { 1506 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1507 return 0; 1508 } 1509 1510 return st_dev; 1511}; 1512 1513ino_t soinfo::get_st_ino() { 1514 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1515 return 0; 1516 } 1517 1518 return st_ino; 1519} 1520 1521// This is a return on get_children() in case 1522// 'this->flags' does not have FLAG_NEW_SOINFO set. 1523static soinfo::soinfo_list_t g_empty_list; 1524 1525soinfo::soinfo_list_t& soinfo::get_children() { 1526 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1527 return g_empty_list; 1528 } 1529 1530 return this->children; 1531} 1532 1533/* Force any of the closed stdin, stdout and stderr to be associated with 1534 /dev/null. */ 1535static int nullify_closed_stdio() { 1536 int dev_null, i, status; 1537 int return_value = 0; 1538 1539 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1540 if (dev_null < 0) { 1541 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1542 return -1; 1543 } 1544 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1545 1546 /* If any of the stdio file descriptors is valid and not associated 1547 with /dev/null, dup /dev/null to it. */ 1548 for (i = 0; i < 3; i++) { 1549 /* If it is /dev/null already, we are done. */ 1550 if (i == dev_null) { 1551 continue; 1552 } 1553 1554 TRACE("[ Nullifying stdio file descriptor %d]", i); 1555 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1556 1557 /* If file is opened, we are good. */ 1558 if (status != -1) { 1559 continue; 1560 } 1561 1562 /* The only error we allow is that the file descriptor does not 1563 exist, in which case we dup /dev/null to it. */ 1564 if (errno != EBADF) { 1565 DL_ERR("fcntl failed: %s", strerror(errno)); 1566 return_value = -1; 1567 continue; 1568 } 1569 1570 /* Try dupping /dev/null to this stdio file descriptor and 1571 repeat if there is a signal. Note that any errors in closing 1572 the stdio descriptor are lost. */ 1573 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1574 if (status < 0) { 1575 DL_ERR("dup2 failed: %s", strerror(errno)); 1576 return_value = -1; 1577 continue; 1578 } 1579 } 1580 1581 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1582 if (dev_null > 2) { 1583 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1584 status = TEMP_FAILURE_RETRY(close(dev_null)); 1585 if (status == -1) { 1586 DL_ERR("close failed: %s", strerror(errno)); 1587 return_value = -1; 1588 } 1589 } 1590 1591 return return_value; 1592} 1593 1594static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1595 /* "base" might wrap around UINT32_MAX. */ 1596 ElfW(Addr) base = si->load_bias; 1597 const ElfW(Phdr)* phdr = si->phdr; 1598 int phnum = si->phnum; 1599 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1600 1601 /* We can't debug anything until the linker is relocated */ 1602 if (!relocating_linker) { 1603 INFO("[ linking %s ]", si->name); 1604 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1605 } 1606 1607 /* Extract dynamic section */ 1608 size_t dynamic_count; 1609 ElfW(Word) dynamic_flags; 1610 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1611 &dynamic_count, &dynamic_flags); 1612 if (si->dynamic == NULL) { 1613 if (!relocating_linker) { 1614 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1615 } 1616 return false; 1617 } else { 1618 if (!relocating_linker) { 1619 DEBUG("dynamic = %p", si->dynamic); 1620 } 1621 } 1622 1623#if defined(__arm__) 1624 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1625 &si->ARM_exidx, &si->ARM_exidx_count); 1626#endif 1627 1628 // Extract useful information from dynamic section. 1629 uint32_t needed_count = 0; 1630 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1631 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1632 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1633 switch (d->d_tag) { 1634 case DT_HASH: 1635 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1636 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1637 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1638 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1639 break; 1640 case DT_STRTAB: 1641 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1642 break; 1643 case DT_SYMTAB: 1644 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1645 break; 1646#if !defined(__LP64__) 1647 case DT_PLTREL: 1648 if (d->d_un.d_val != DT_REL) { 1649 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1650 return false; 1651 } 1652 break; 1653#endif 1654 case DT_JMPREL: 1655#if defined(USE_RELA) 1656 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1657#else 1658 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1659#endif 1660 break; 1661 case DT_PLTRELSZ: 1662#if defined(USE_RELA) 1663 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1664#else 1665 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1666#endif 1667 break; 1668#if defined(__mips__) 1669 case DT_PLTGOT: 1670 // Used by mips and mips64. 1671 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1672 break; 1673#endif 1674 case DT_DEBUG: 1675 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1676 // if the dynamic table is writable 1677// FIXME: not working currently for N64 1678// The flags for the LOAD and DYNAMIC program headers do not agree. 1679// The LOAD section containng the dynamic table has been mapped as 1680// read-only, but the DYNAMIC header claims it is writable. 1681#if !(defined(__mips__) && defined(__LP64__)) 1682 if ((dynamic_flags & PF_W) != 0) { 1683 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1684 } 1685 break; 1686#endif 1687#if defined(USE_RELA) 1688 case DT_RELA: 1689 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1690 break; 1691 case DT_RELASZ: 1692 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1693 break; 1694 case DT_REL: 1695 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1696 return false; 1697 case DT_RELSZ: 1698 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1699 return false; 1700#else 1701 case DT_REL: 1702 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1703 break; 1704 case DT_RELSZ: 1705 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1706 break; 1707 case DT_RELA: 1708 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1709 return false; 1710#endif 1711 case DT_INIT: 1712 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1713 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1714 break; 1715 case DT_FINI: 1716 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1717 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1718 break; 1719 case DT_INIT_ARRAY: 1720 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1721 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1722 break; 1723 case DT_INIT_ARRAYSZ: 1724 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1725 break; 1726 case DT_FINI_ARRAY: 1727 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1728 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1729 break; 1730 case DT_FINI_ARRAYSZ: 1731 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1732 break; 1733 case DT_PREINIT_ARRAY: 1734 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1735 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1736 break; 1737 case DT_PREINIT_ARRAYSZ: 1738 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1739 break; 1740 case DT_TEXTREL: 1741#if defined(__LP64__) 1742 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1743 return false; 1744#else 1745 si->has_text_relocations = true; 1746 break; 1747#endif 1748 case DT_SYMBOLIC: 1749 si->has_DT_SYMBOLIC = true; 1750 break; 1751 case DT_NEEDED: 1752 ++needed_count; 1753 break; 1754 case DT_FLAGS: 1755 if (d->d_un.d_val & DF_TEXTREL) { 1756#if defined(__LP64__) 1757 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1758 return false; 1759#else 1760 si->has_text_relocations = true; 1761#endif 1762 } 1763 if (d->d_un.d_val & DF_SYMBOLIC) { 1764 si->has_DT_SYMBOLIC = true; 1765 } 1766 break; 1767#if defined(__mips__) 1768 case DT_STRSZ: 1769 case DT_SYMENT: 1770 case DT_RELENT: 1771 break; 1772 case DT_MIPS_RLD_MAP: 1773 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1774 { 1775 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1776 *dp = &_r_debug; 1777 } 1778 break; 1779 case DT_MIPS_RLD_VERSION: 1780 case DT_MIPS_FLAGS: 1781 case DT_MIPS_BASE_ADDRESS: 1782 case DT_MIPS_UNREFEXTNO: 1783 break; 1784 1785 case DT_MIPS_SYMTABNO: 1786 si->mips_symtabno = d->d_un.d_val; 1787 break; 1788 1789 case DT_MIPS_LOCAL_GOTNO: 1790 si->mips_local_gotno = d->d_un.d_val; 1791 break; 1792 1793 case DT_MIPS_GOTSYM: 1794 si->mips_gotsym = d->d_un.d_val; 1795 break; 1796#endif 1797 1798 default: 1799 DEBUG("Unused DT entry: type %p arg %p", 1800 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1801 break; 1802 } 1803 } 1804 1805 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1806 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1807 1808 // Sanity checks. 1809 if (relocating_linker && needed_count != 0) { 1810 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1811 return false; 1812 } 1813 if (si->nbucket == 0) { 1814 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1815 return false; 1816 } 1817 if (si->strtab == 0) { 1818 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1819 return false; 1820 } 1821 if (si->symtab == 0) { 1822 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1823 return false; 1824 } 1825 1826 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1827 if (si->flags & FLAG_EXE) { 1828 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1829 size_t preload_count = 0; 1830 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1831 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1832 if (lsi != NULL) { 1833 g_ld_preloads[preload_count++] = lsi; 1834 } else { 1835 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1836 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1837 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1838 } 1839 } 1840 } 1841 1842 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1843 soinfo** pneeded = needed; 1844 1845 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1846 if (d->d_tag == DT_NEEDED) { 1847 const char* library_name = si->strtab + d->d_un.d_val; 1848 DEBUG("%s needs %s", si->name, library_name); 1849 soinfo* lsi = find_library(library_name, 0, NULL); 1850 if (lsi == NULL) { 1851 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1852 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1853 library_name, si->name, tmp_err_buf); 1854 return false; 1855 } 1856 1857 si->add_child(lsi); 1858 *pneeded++ = lsi; 1859 } 1860 } 1861 *pneeded = NULL; 1862 1863#if !defined(__LP64__) 1864 if (si->has_text_relocations) { 1865 // Make segments writable to allow text relocations to work properly. We will later call 1866 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1867#if !defined(__i386__) // The platform itself has too many text relocations on x86. 1868 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1869 "security hardening. Please fix.", si->name); 1870#endif 1871 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1872 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1873 si->name, strerror(errno)); 1874 return false; 1875 } 1876 } 1877#endif 1878 1879#if defined(USE_RELA) 1880 if (si->plt_rela != NULL) { 1881 DEBUG("[ relocating %s plt ]\n", si->name); 1882 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1883 return false; 1884 } 1885 } 1886 if (si->rela != NULL) { 1887 DEBUG("[ relocating %s ]\n", si->name); 1888 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1889 return false; 1890 } 1891 } 1892#else 1893 if (si->plt_rel != NULL) { 1894 DEBUG("[ relocating %s plt ]", si->name); 1895 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1896 return false; 1897 } 1898 } 1899 if (si->rel != NULL) { 1900 DEBUG("[ relocating %s ]", si->name); 1901 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1902 return false; 1903 } 1904 } 1905#endif 1906 1907#if defined(__mips__) 1908 if (!mips_relocate_got(si, needed)) { 1909 return false; 1910 } 1911#endif 1912 1913 si->flags |= FLAG_LINKED; 1914 DEBUG("[ finished linking %s ]", si->name); 1915 1916#if !defined(__LP64__) 1917 if (si->has_text_relocations) { 1918 // All relocations are done, we can protect our segments back to read-only. 1919 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1920 DL_ERR("can't protect segments for \"%s\": %s", 1921 si->name, strerror(errno)); 1922 return false; 1923 } 1924 } 1925#endif 1926 1927 /* We can also turn on GNU RELRO protection */ 1928 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1929 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1930 si->name, strerror(errno)); 1931 return false; 1932 } 1933 1934 /* Handle serializing/sharing the RELRO segment */ 1935 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1936 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1937 extinfo->relro_fd) < 0) { 1938 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1939 si->name, strerror(errno)); 1940 return false; 1941 } 1942 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1943 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1944 extinfo->relro_fd) < 0) { 1945 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1946 si->name, strerror(errno)); 1947 return false; 1948 } 1949 } 1950 1951 notify_gdb_of_load(si); 1952 return true; 1953} 1954 1955/* 1956 * This function add vdso to internal dso list. 1957 * It helps to stack unwinding through signal handlers. 1958 * Also, it makes bionic more like glibc. 1959 */ 1960static void add_vdso(KernelArgumentBlock& args __unused) { 1961#if defined(AT_SYSINFO_EHDR) 1962 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1963 if (ehdr_vdso == NULL) { 1964 return; 1965 } 1966 1967 soinfo* si = soinfo_alloc("[vdso]", NULL); 1968 1969 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1970 si->phnum = ehdr_vdso->e_phnum; 1971 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1972 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1973 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1974 1975 soinfo_link_image(si, NULL); 1976#endif 1977} 1978 1979/* 1980 * This is linker soinfo for GDB. See details below. 1981 */ 1982static soinfo linker_soinfo_for_gdb; 1983 1984/* gdb expects the linker to be in the debug shared object list. 1985 * Without this, gdb has trouble locating the linker's ".text" 1986 * and ".plt" sections. Gdb could also potentially use this to 1987 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1988 * Don't use soinfo_alloc(), because the linker shouldn't 1989 * be on the soinfo list. 1990 */ 1991static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 1992#if defined(__LP64__) 1993 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 1994#else 1995 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 1996#endif 1997 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 1998 linker_soinfo_for_gdb.base = linker_base; 1999 2000 /* 2001 * Set the dynamic field in the link map otherwise gdb will complain with 2002 * the following: 2003 * warning: .dynamic section for "/system/bin/linker" is not at the 2004 * expected address (wrong library or version mismatch?) 2005 */ 2006 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2007 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2008 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2009 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2010 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2011} 2012 2013/* 2014 * This code is called after the linker has linked itself and 2015 * fixed it's own GOT. It is safe to make references to externs 2016 * and other non-local data at this point. 2017 */ 2018static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2019 /* NOTE: we store the args pointer on a special location 2020 * of the temporary TLS area in order to pass it to 2021 * the C Library's runtime initializer. 2022 * 2023 * The initializer must clear the slot and reset the TLS 2024 * to point to a different location to ensure that no other 2025 * shared library constructor can access it. 2026 */ 2027 __libc_init_tls(args); 2028 2029#if TIMING 2030 struct timeval t0, t1; 2031 gettimeofday(&t0, 0); 2032#endif 2033 2034 // Initialize environment functions, and get to the ELF aux vectors table. 2035 linker_env_init(args); 2036 2037 // If this is a setuid/setgid program, close the security hole described in 2038 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2039 if (get_AT_SECURE()) { 2040 nullify_closed_stdio(); 2041 } 2042 2043 debuggerd_init(); 2044 2045 // Get a few environment variables. 2046 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2047 if (LD_DEBUG != NULL) { 2048 g_ld_debug_verbosity = atoi(LD_DEBUG); 2049 } 2050 2051 // Normally, these are cleaned by linker_env_init, but the test 2052 // doesn't cost us anything. 2053 const char* ldpath_env = NULL; 2054 const char* ldpreload_env = NULL; 2055 if (!get_AT_SECURE()) { 2056 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2057 ldpreload_env = linker_env_get("LD_PRELOAD"); 2058 } 2059 2060 // Linker does not call constructors for its own 2061 // global variables so we need to initialize 2062 // the allocators explicitly. 2063 g_soinfo_allocator.init(); 2064 g_soinfo_links_allocator.init(); 2065 2066 INFO("[ android linker & debugger ]"); 2067 2068 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2069 if (si == NULL) { 2070 exit(EXIT_FAILURE); 2071 } 2072 2073 /* bootstrap the link map, the main exe always needs to be first */ 2074 si->flags |= FLAG_EXE; 2075 link_map* map = &(si->link_map_head); 2076 2077 map->l_addr = 0; 2078 map->l_name = args.argv[0]; 2079 map->l_prev = NULL; 2080 map->l_next = NULL; 2081 2082 _r_debug.r_map = map; 2083 r_debug_tail = map; 2084 2085 init_linker_info_for_gdb(linker_base); 2086 2087 // Extract information passed from the kernel. 2088 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2089 si->phnum = args.getauxval(AT_PHNUM); 2090 si->entry = args.getauxval(AT_ENTRY); 2091 2092 /* Compute the value of si->base. We can't rely on the fact that 2093 * the first entry is the PHDR because this will not be true 2094 * for certain executables (e.g. some in the NDK unit test suite) 2095 */ 2096 si->base = 0; 2097 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2098 si->load_bias = 0; 2099 for (size_t i = 0; i < si->phnum; ++i) { 2100 if (si->phdr[i].p_type == PT_PHDR) { 2101 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2102 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2103 break; 2104 } 2105 } 2106 si->dynamic = NULL; 2107 si->ref_count = 1; 2108 2109 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2110 if (elf_hdr->e_type != ET_DYN) { 2111 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2112 exit(EXIT_FAILURE); 2113 } 2114 2115 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2116 parse_LD_LIBRARY_PATH(ldpath_env); 2117 parse_LD_PRELOAD(ldpreload_env); 2118 2119 somain = si; 2120 2121 if (!soinfo_link_image(si, NULL)) { 2122 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2123 exit(EXIT_FAILURE); 2124 } 2125 2126 add_vdso(args); 2127 2128 si->CallPreInitConstructors(); 2129 2130 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2131 g_ld_preloads[i]->CallConstructors(); 2132 } 2133 2134 /* After the link_image, the si->load_bias is initialized. 2135 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2136 * We need to update this value for so exe here. So Unwind_Backtrace 2137 * for some arch like x86 could work correctly within so exe. 2138 */ 2139 map->l_addr = si->load_bias; 2140 si->CallConstructors(); 2141 2142#if TIMING 2143 gettimeofday(&t1, NULL); 2144 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2145 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2146 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2147#endif 2148#if STATS 2149 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2150 linker_stats.count[kRelocAbsolute], 2151 linker_stats.count[kRelocRelative], 2152 linker_stats.count[kRelocCopy], 2153 linker_stats.count[kRelocSymbol]); 2154#endif 2155#if COUNT_PAGES 2156 { 2157 unsigned n; 2158 unsigned i; 2159 unsigned count = 0; 2160 for (n = 0; n < 4096; n++) { 2161 if (bitmask[n]) { 2162 unsigned x = bitmask[n]; 2163#if defined(__LP64__) 2164 for (i = 0; i < 32; i++) { 2165#else 2166 for (i = 0; i < 8; i++) { 2167#endif 2168 if (x & 1) { 2169 count++; 2170 } 2171 x >>= 1; 2172 } 2173 } 2174 } 2175 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2176 } 2177#endif 2178 2179#if TIMING || STATS || COUNT_PAGES 2180 fflush(stdout); 2181#endif 2182 2183 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2184 return si->entry; 2185} 2186 2187/* Compute the load-bias of an existing executable. This shall only 2188 * be used to compute the load bias of an executable or shared library 2189 * that was loaded by the kernel itself. 2190 * 2191 * Input: 2192 * elf -> address of ELF header, assumed to be at the start of the file. 2193 * Return: 2194 * load bias, i.e. add the value of any p_vaddr in the file to get 2195 * the corresponding address in memory. 2196 */ 2197static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2198 ElfW(Addr) offset = elf->e_phoff; 2199 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2200 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2201 2202 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2203 if (phdr->p_type == PT_LOAD) { 2204 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2205 } 2206 } 2207 return 0; 2208} 2209 2210/* 2211 * This is the entry point for the linker, called from begin.S. This 2212 * method is responsible for fixing the linker's own relocations, and 2213 * then calling __linker_init_post_relocation(). 2214 * 2215 * Because this method is called before the linker has fixed it's own 2216 * relocations, any attempt to reference an extern variable, extern 2217 * function, or other GOT reference will generate a segfault. 2218 */ 2219extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2220 // Initialize static variables. 2221 solist = get_libdl_info(); 2222 sonext = get_libdl_info(); 2223 2224 KernelArgumentBlock args(raw_args); 2225 2226 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2227 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2228 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2229 2230 soinfo linker_so; 2231 memset(&linker_so, 0, sizeof(soinfo)); 2232 2233 strcpy(linker_so.name, "[dynamic linker]"); 2234 linker_so.base = linker_addr; 2235 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2236 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2237 linker_so.dynamic = NULL; 2238 linker_so.phdr = phdr; 2239 linker_so.phnum = elf_hdr->e_phnum; 2240 linker_so.flags |= FLAG_LINKER; 2241 2242 if (!soinfo_link_image(&linker_so, NULL)) { 2243 // It would be nice to print an error message, but if the linker 2244 // can't link itself, there's no guarantee that we'll be able to 2245 // call write() (because it involves a GOT reference). We may as 2246 // well try though... 2247 const char* msg = "CANNOT LINK EXECUTABLE: "; 2248 write(2, msg, strlen(msg)); 2249 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2250 write(2, "\n", 1); 2251 _exit(EXIT_FAILURE); 2252 } 2253 2254 // We have successfully fixed our own relocations. It's safe to run 2255 // the main part of the linker now. 2256 args.abort_message_ptr = &g_abort_message; 2257 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2258 2259 protect_data(PROT_READ); 2260 2261 // Return the address that the calling assembly stub should jump to. 2262 return start_address; 2263} 2264