linker.cpp revision d286796fce1e6fff407b719a53eb2afbeb96c327
1/* 2 * Copyright (C) 2008, 2009 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <dlfcn.h> 30#include <errno.h> 31#include <fcntl.h> 32#include <inttypes.h> 33#include <pthread.h> 34#include <stdio.h> 35#include <stdlib.h> 36#include <string.h> 37#include <sys/mman.h> 38#include <sys/stat.h> 39#include <unistd.h> 40 41// Private C library headers. 42#include "private/bionic_tls.h" 43#include "private/KernelArgumentBlock.h" 44#include "private/ScopedPthreadMutexLocker.h" 45 46#include "linker.h" 47#include "linker_debug.h" 48#include "linker_environ.h" 49#include "linker_phdr.h" 50#include "linker_allocator.h" 51 52/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< 53 * 54 * Do NOT use malloc() and friends or pthread_*() code here. 55 * Don't use printf() either; it's caused mysterious memory 56 * corruption in the past. 57 * The linker runs before we bring up libc and it's easiest 58 * to make sure it does not depend on any complex libc features 59 * 60 * open issues / todo: 61 * 62 * - cleaner error reporting 63 * - after linking, set as much stuff as possible to READONLY 64 * and NOEXEC 65 */ 66 67#if defined(__LP64__) 68#define SEARCH_NAME(x) x 69#else 70// Nvidia drivers are relying on the bug: 71// http://code.google.com/p/android/issues/detail?id=6670 72// so we continue to use base-name lookup for lp32 73static const char* get_base_name(const char* name) { 74 const char* bname = strrchr(name, '/'); 75 return bname ? bname + 1 : name; 76} 77#define SEARCH_NAME(x) get_base_name(x) 78#endif 79 80static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 81static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 82 83static LinkerAllocator<soinfo> g_soinfo_allocator; 84static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator; 85 86static soinfo* solist; 87static soinfo* sonext; 88static soinfo* somain; /* main process, always the one after libdl_info */ 89 90static const char* const kDefaultLdPaths[] = { 91#if defined(__LP64__) 92 "/vendor/lib64", 93 "/system/lib64", 94#else 95 "/vendor/lib", 96 "/system/lib", 97#endif 98 NULL 99}; 100 101#define LDPATH_BUFSIZE (LDPATH_MAX*64) 102#define LDPATH_MAX 8 103 104#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 105#define LDPRELOAD_MAX 8 106 107static char g_ld_library_paths_buffer[LDPATH_BUFSIZE]; 108static const char* g_ld_library_paths[LDPATH_MAX + 1]; 109 110static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE]; 111static const char* g_ld_preload_names[LDPRELOAD_MAX + 1]; 112 113static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1]; 114 115__LIBC_HIDDEN__ int g_ld_debug_verbosity; 116 117__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd. 118 119enum RelocationKind { 120 kRelocAbsolute = 0, 121 kRelocRelative, 122 kRelocCopy, 123 kRelocSymbol, 124 kRelocMax 125}; 126 127#if STATS 128struct linker_stats_t { 129 int count[kRelocMax]; 130}; 131 132static linker_stats_t linker_stats; 133 134static void count_relocation(RelocationKind kind) { 135 ++linker_stats.count[kind]; 136} 137#else 138static void count_relocation(RelocationKind) { 139} 140#endif 141 142#if COUNT_PAGES 143static unsigned bitmask[4096]; 144#if defined(__LP64__) 145#define MARK(offset) \ 146 do { \ 147 if ((((offset) >> 12) >> 5) < 4096) \ 148 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 149 } while (0) 150#else 151#define MARK(offset) \ 152 do { \ 153 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 154 } while (0) 155#endif 156#else 157#define MARK(x) do {} while (0) 158#endif 159 160// You shouldn't try to call memory-allocating functions in the dynamic linker. 161// Guard against the most obvious ones. 162#define DISALLOW_ALLOCATION(return_type, name, ...) \ 163 return_type name __VA_ARGS__ \ 164 { \ 165 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 166 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 167 write(2, msg, strlen(msg)); \ 168 abort(); \ 169 } 170DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 171DISALLOW_ALLOCATION(void, free, (void* u __unused)); 172DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 173DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 174 175static char tmp_err_buf[768]; 176static char __linker_dl_err_buf[768]; 177 178char* linker_get_error_buffer() { 179 return &__linker_dl_err_buf[0]; 180} 181 182size_t linker_get_error_buffer_size() { 183 return sizeof(__linker_dl_err_buf); 184} 185 186/* 187 * This function is an empty stub where GDB locates a breakpoint to get notified 188 * about linker activity. 189 */ 190extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 191 192static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 193static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 194static link_map* r_debug_tail = 0; 195 196static void insert_soinfo_into_debug_map(soinfo* info) { 197 // Copy the necessary fields into the debug structure. 198 link_map* map = &(info->link_map_head); 199 map->l_addr = info->load_bias; 200 map->l_name = reinterpret_cast<char*>(info->name); 201 map->l_ld = info->dynamic; 202 203 /* Stick the new library at the end of the list. 204 * gdb tends to care more about libc than it does 205 * about leaf libraries, and ordering it this way 206 * reduces the back-and-forth over the wire. 207 */ 208 if (r_debug_tail) { 209 r_debug_tail->l_next = map; 210 map->l_prev = r_debug_tail; 211 map->l_next = 0; 212 } else { 213 _r_debug.r_map = map; 214 map->l_prev = 0; 215 map->l_next = 0; 216 } 217 r_debug_tail = map; 218} 219 220static void remove_soinfo_from_debug_map(soinfo* info) { 221 link_map* map = &(info->link_map_head); 222 223 if (r_debug_tail == map) { 224 r_debug_tail = map->l_prev; 225 } 226 227 if (map->l_prev) { 228 map->l_prev->l_next = map->l_next; 229 } 230 if (map->l_next) { 231 map->l_next->l_prev = map->l_prev; 232 } 233} 234 235static void notify_gdb_of_load(soinfo* info) { 236 if (info->flags & FLAG_EXE) { 237 // GDB already knows about the main executable 238 return; 239 } 240 241 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 242 243 _r_debug.r_state = r_debug::RT_ADD; 244 rtld_db_dlactivity(); 245 246 insert_soinfo_into_debug_map(info); 247 248 _r_debug.r_state = r_debug::RT_CONSISTENT; 249 rtld_db_dlactivity(); 250} 251 252static void notify_gdb_of_unload(soinfo* info) { 253 if (info->flags & FLAG_EXE) { 254 // GDB already knows about the main executable 255 return; 256 } 257 258 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 259 260 _r_debug.r_state = r_debug::RT_DELETE; 261 rtld_db_dlactivity(); 262 263 remove_soinfo_from_debug_map(info); 264 265 _r_debug.r_state = r_debug::RT_CONSISTENT; 266 rtld_db_dlactivity(); 267} 268 269void notify_gdb_of_libraries() { 270 _r_debug.r_state = r_debug::RT_ADD; 271 rtld_db_dlactivity(); 272 _r_debug.r_state = r_debug::RT_CONSISTENT; 273 rtld_db_dlactivity(); 274} 275 276LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 277 return g_soinfo_links_allocator.alloc(); 278} 279 280void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 281 g_soinfo_links_allocator.free(entry); 282} 283 284static void protect_data(int protection) { 285 g_soinfo_allocator.protect_all(protection); 286 g_soinfo_links_allocator.protect_all(protection); 287} 288 289static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 290 if (strlen(name) >= SOINFO_NAME_LEN) { 291 DL_ERR("library name \"%s\" too long", name); 292 return NULL; 293 } 294 295 soinfo* si = g_soinfo_allocator.alloc(); 296 297 // Initialize the new element. 298 memset(si, 0, sizeof(soinfo)); 299 strlcpy(si->name, name, sizeof(si->name)); 300 si->flags = FLAG_NEW_SOINFO; 301 302 if (file_stat != NULL) { 303 si->set_st_dev(file_stat->st_dev); 304 si->set_st_ino(file_stat->st_ino); 305 } 306 307 sonext->next = si; 308 sonext = si; 309 310 TRACE("name %s: allocated soinfo @ %p", name, si); 311 return si; 312} 313 314static void soinfo_free(soinfo* si) { 315 if (si == NULL) { 316 return; 317 } 318 319 if (si->base != 0 && si->size != 0) { 320 munmap(reinterpret_cast<void*>(si->base), si->size); 321 } 322 323 soinfo *prev = NULL, *trav; 324 325 TRACE("name %s: freeing soinfo @ %p", si->name, si); 326 327 for (trav = solist; trav != NULL; trav = trav->next) { 328 if (trav == si) 329 break; 330 prev = trav; 331 } 332 if (trav == NULL) { 333 /* si was not in solist */ 334 DL_ERR("name \"%s\" is not in solist!", si->name); 335 return; 336 } 337 338 // clear links to/from si 339 si->remove_all_links(); 340 341 /* prev will never be NULL, because the first entry in solist is 342 always the static libdl_info. 343 */ 344 prev->next = si->next; 345 if (si == sonext) { 346 sonext = prev; 347 } 348 349 g_soinfo_allocator.free(si); 350} 351 352 353static void parse_path(const char* path, const char* delimiters, 354 const char** array, char* buf, size_t buf_size, size_t max_count) { 355 if (path == NULL) { 356 return; 357 } 358 359 size_t len = strlcpy(buf, path, buf_size); 360 361 size_t i = 0; 362 char* buf_p = buf; 363 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 364 if (*array[i] != '\0') { 365 ++i; 366 } 367 } 368 369 // Forget the last path if we had to truncate; this occurs if the 2nd to 370 // last char isn't '\0' (i.e. wasn't originally a delimiter). 371 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 372 array[i - 1] = NULL; 373 } else { 374 array[i] = NULL; 375 } 376} 377 378static void parse_LD_LIBRARY_PATH(const char* path) { 379 parse_path(path, ":", g_ld_library_paths, 380 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 381} 382 383static void parse_LD_PRELOAD(const char* path) { 384 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 385 parse_path(path, " :", g_ld_preload_names, 386 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 387} 388 389#if defined(__arm__) 390 391/* For a given PC, find the .so that it belongs to. 392 * Returns the base address of the .ARM.exidx section 393 * for that .so, and the number of 8-byte entries 394 * in that section (via *pcount). 395 * 396 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 397 * 398 * This function is exposed via dlfcn.cpp and libdl.so. 399 */ 400_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 401 unsigned addr = (unsigned)pc; 402 403 for (soinfo* si = solist; si != 0; si = si->next) { 404 if ((addr >= si->base) && (addr < (si->base + si->size))) { 405 *pcount = si->ARM_exidx_count; 406 return (_Unwind_Ptr)si->ARM_exidx; 407 } 408 } 409 *pcount = 0; 410 return NULL; 411} 412 413#endif 414 415/* Here, we only have to provide a callback to iterate across all the 416 * loaded libraries. gcc_eh does the rest. */ 417int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 418 int rv = 0; 419 for (soinfo* si = solist; si != NULL; si = si->next) { 420 dl_phdr_info dl_info; 421 dl_info.dlpi_addr = si->link_map_head.l_addr; 422 dl_info.dlpi_name = si->link_map_head.l_name; 423 dl_info.dlpi_phdr = si->phdr; 424 dl_info.dlpi_phnum = si->phnum; 425 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 426 if (rv != 0) { 427 break; 428 } 429 } 430 return rv; 431} 432 433static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 434 ElfW(Sym)* symtab = si->symtab; 435 const char* strtab = si->strtab; 436 437 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 438 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 439 440 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 441 ElfW(Sym)* s = symtab + n; 442 if (strcmp(strtab + s->st_name, name)) continue; 443 444 /* only concern ourselves with global and weak symbol definitions */ 445 switch (ELF_ST_BIND(s->st_info)) { 446 case STB_GLOBAL: 447 case STB_WEAK: 448 if (s->st_shndx == SHN_UNDEF) { 449 continue; 450 } 451 452 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 453 name, si->name, reinterpret_cast<void*>(s->st_value), 454 static_cast<size_t>(s->st_size)); 455 return s; 456 } 457 } 458 459 return NULL; 460} 461 462static unsigned elfhash(const char* _name) { 463 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 464 unsigned h = 0, g; 465 466 while (*name) { 467 h = (h << 4) + *name++; 468 g = h & 0xf0000000; 469 h ^= g; 470 h ^= g >> 24; 471 } 472 return h; 473} 474 475static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 476 unsigned elf_hash = elfhash(name); 477 ElfW(Sym)* s = NULL; 478 479 if (si != NULL && somain != NULL) { 480 /* 481 * Local scope is executable scope. Just start looking into it right away 482 * for the shortcut. 483 */ 484 485 if (si == somain) { 486 s = soinfo_elf_lookup(si, elf_hash, name); 487 if (s != NULL) { 488 *lsi = si; 489 goto done; 490 } 491 } else { 492 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 493 494 /* 495 * If this object was built with symbolic relocations disabled, the 496 * first place to look to resolve external references is the main 497 * executable. 498 */ 499 500 if (!si->has_DT_SYMBOLIC) { 501 DEBUG("%s: looking up %s in executable %s", 502 si->name, name, somain->name); 503 s = soinfo_elf_lookup(somain, elf_hash, name); 504 if (s != NULL) { 505 *lsi = somain; 506 goto done; 507 } 508 } 509 510 /* Look for symbols in the local scope (the object who is 511 * searching). This happens with C++ templates on x86 for some 512 * reason. 513 * 514 * Notes on weak symbols: 515 * The ELF specs are ambiguous about treatment of weak definitions in 516 * dynamic linking. Some systems return the first definition found 517 * and some the first non-weak definition. This is system dependent. 518 * Here we return the first definition found for simplicity. */ 519 520 s = soinfo_elf_lookup(si, elf_hash, name); 521 if (s != NULL) { 522 *lsi = si; 523 goto done; 524 } 525 526 /* 527 * If this object was built with -Bsymbolic and symbol is not found 528 * in the local scope, try to find the symbol in the main executable. 529 */ 530 531 if (si->has_DT_SYMBOLIC) { 532 DEBUG("%s: looking up %s in executable %s after local scope", 533 si->name, name, somain->name); 534 s = soinfo_elf_lookup(somain, elf_hash, name); 535 if (s != NULL) { 536 *lsi = somain; 537 goto done; 538 } 539 } 540 } 541 } 542 543 /* Next, look for it in the preloads list */ 544 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 545 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name); 546 if (s != NULL) { 547 *lsi = g_ld_preloads[i]; 548 goto done; 549 } 550 } 551 552 for (int i = 0; needed[i] != NULL; i++) { 553 DEBUG("%s: looking up %s in %s", 554 si->name, name, needed[i]->name); 555 s = soinfo_elf_lookup(needed[i], elf_hash, name); 556 if (s != NULL) { 557 *lsi = needed[i]; 558 goto done; 559 } 560 } 561 562done: 563 if (s != NULL) { 564 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 565 "found in %s, base = %p, load bias = %p", 566 si->name, name, reinterpret_cast<void*>(s->st_value), 567 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 568 reinterpret_cast<void*>((*lsi)->load_bias)); 569 return s; 570 } 571 572 return NULL; 573} 574 575/* This is used by dlsym(3). It performs symbol lookup only within the 576 specified soinfo object and not in any of its dependencies. 577 578 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 579 that it should do a breadth first search through the dependency 580 tree. This agrees with the ELF spec (aka System V Application 581 Binary Interface) where in Chapter 5 it discuss resolving "Shared 582 Object Dependencies" in breadth first search order. 583 */ 584ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) { 585 return soinfo_elf_lookup(si, elfhash(name), name); 586} 587 588/* This is used by dlsym(3) to performs a global symbol lookup. If the 589 start value is null (for RTLD_DEFAULT), the search starts at the 590 beginning of the global solist. Otherwise the search starts at the 591 specified soinfo (for RTLD_NEXT). 592 */ 593ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 594 unsigned elf_hash = elfhash(name); 595 596 if (start == NULL) { 597 start = solist; 598 } 599 600 ElfW(Sym)* s = NULL; 601 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 602 s = soinfo_elf_lookup(si, elf_hash, name); 603 if (s != NULL) { 604 *found = si; 605 break; 606 } 607 } 608 609 if (s != NULL) { 610 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 611 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 612 } 613 614 return s; 615} 616 617soinfo* find_containing_library(const void* p) { 618 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 619 for (soinfo* si = solist; si != NULL; si = si->next) { 620 if (address >= si->base && address - si->base < si->size) { 621 return si; 622 } 623 } 624 return NULL; 625} 626 627ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 628 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 629 630 // Search the library's symbol table for any defined symbol which 631 // contains this address. 632 for (size_t i = 0; i < si->nchain; ++i) { 633 ElfW(Sym)* sym = &si->symtab[i]; 634 if (sym->st_shndx != SHN_UNDEF && 635 soaddr >= sym->st_value && 636 soaddr < sym->st_value + sym->st_size) { 637 return sym; 638 } 639 } 640 641 return NULL; 642} 643 644static int open_library_on_path(const char* name, const char* const paths[]) { 645 char buf[512]; 646 for (size_t i = 0; paths[i] != NULL; ++i) { 647 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 648 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 649 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 650 continue; 651 } 652 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 653 if (fd != -1) { 654 return fd; 655 } 656 } 657 return -1; 658} 659 660static int open_library(const char* name) { 661 TRACE("[ opening %s ]", name); 662 663 // If the name contains a slash, we should attempt to open it directly and not search the paths. 664 if (strchr(name, '/') != NULL) { 665 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 666 if (fd != -1) { 667 return fd; 668 } 669 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 670#if defined(__LP64__) 671 // TODO: uncomment this after bug b/7465467 is fixed. 672 // return -1; 673#endif 674 } 675 676 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 677 int fd = open_library_on_path(name, g_ld_library_paths); 678 if (fd == -1) { 679 fd = open_library_on_path(name, kDefaultLdPaths); 680 } 681 return fd; 682} 683 684static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 685 // Open the file. 686 int fd = open_library(name); 687 if (fd == -1) { 688 DL_ERR("library \"%s\" not found", name); 689 return NULL; 690 } 691 692 ElfReader elf_reader(name, fd); 693 694 struct stat file_stat; 695 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 696 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 697 return NULL; 698 } 699 700 // Check for symlink and other situations where 701 // file can have different names. 702 for (soinfo* si = solist; si != NULL; si = si->next) { 703 if (si->get_st_dev() != 0 && 704 si->get_st_ino() != 0 && 705 si->get_st_dev() == file_stat.st_dev && 706 si->get_st_ino() == file_stat.st_ino) { 707 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 708 return si; 709 } 710 } 711 712 if ((dlflags & RTLD_NOLOAD) != 0) { 713 return NULL; 714 } 715 716 // Read the ELF header and load the segments. 717 if (!elf_reader.Load(extinfo)) { 718 return NULL; 719 } 720 721 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 722 if (si == NULL) { 723 return NULL; 724 } 725 si->base = elf_reader.load_start(); 726 si->size = elf_reader.load_size(); 727 si->load_bias = elf_reader.load_bias(); 728 si->phnum = elf_reader.phdr_count(); 729 si->phdr = elf_reader.loaded_phdr(); 730 731 // At this point we know that whatever is loaded @ base is a valid ELF 732 // shared library whose segments are properly mapped in. 733 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 734 reinterpret_cast<void*>(si->base), si->size, si->name); 735 736 if (!soinfo_link_image(si, extinfo)) { 737 soinfo_free(si); 738 return NULL; 739 } 740 741 return si; 742} 743 744static soinfo *find_loaded_library_by_name(const char* name) { 745 const char* search_name = SEARCH_NAME(name); 746 for (soinfo* si = solist; si != NULL; si = si->next) { 747 if (!strcmp(search_name, si->name)) { 748 return si; 749 } 750 } 751 return NULL; 752} 753 754static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 755 if (name == NULL) { 756 return somain; 757 } 758 759 soinfo* si = find_loaded_library_by_name(name); 760 761 // Library might still be loaded, the accurate detection 762 // of this fact is done by load_library 763 if (si == NULL) { 764 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 765 si = load_library(name, dlflags, extinfo); 766 } 767 768 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 769 DL_ERR("recursive link to \"%s\"", si->name); 770 return NULL; 771 } 772 773 return si; 774} 775 776static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 777 soinfo* si = find_library_internal(name, dlflags, extinfo); 778 if (si != NULL) { 779 si->ref_count++; 780 } 781 return si; 782} 783 784static void soinfo_unload(soinfo* si) { 785 if (si->ref_count == 1) { 786 TRACE("unloading '%s'", si->name); 787 si->CallDestructors(); 788 789 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 790 si->get_children().for_each([&] (soinfo* child) { 791 TRACE("%s needs to unload %s", si->name, child->name); 792 soinfo_unload(child); 793 }); 794 } else { 795 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 796 if (d->d_tag == DT_NEEDED) { 797 const char* library_name = si->strtab + d->d_un.d_val; 798 TRACE("%s needs to unload %s", si->name, library_name); 799 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 800 if (needed != NULL) { 801 soinfo_unload(needed); 802 } else { 803 // Not found: for example if symlink was deleted between dlopen and dlclose 804 // Since we cannot really handle errors at this point - print and continue. 805 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 806 } 807 } 808 } 809 } 810 811 notify_gdb_of_unload(si); 812 si->ref_count = 0; 813 soinfo_free(si); 814 } else { 815 si->ref_count--; 816 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 817 } 818} 819 820void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 821 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 822} 823 824void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 825 if (!get_AT_SECURE()) { 826 parse_LD_LIBRARY_PATH(ld_library_path); 827 } 828} 829 830soinfo* do_dlopen(const char* name, int flags, soinfo* /*caller*/, const android_dlextinfo* extinfo) { 831 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 832 DL_ERR("invalid flags to dlopen: %x", flags); 833 return NULL; 834 } 835 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 836 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 837 return NULL; 838 } 839 protect_data(PROT_READ | PROT_WRITE); 840 soinfo* si = find_library(name, flags, extinfo); 841 if (si != NULL) { 842 si->CallConstructors(); 843 } 844 protect_data(PROT_READ); 845 return si; 846} 847 848void do_dlclose(soinfo* si) { 849 protect_data(PROT_READ | PROT_WRITE); 850 soinfo_unload(si); 851 protect_data(PROT_READ); 852} 853 854#if defined(USE_RELA) 855static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 856 ElfW(Sym)* s; 857 soinfo* lsi; 858 859 for (size_t idx = 0; idx < count; ++idx, ++rela) { 860 unsigned type = ELFW(R_TYPE)(rela->r_info); 861 unsigned sym = ELFW(R_SYM)(rela->r_info); 862 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 863 ElfW(Addr) sym_addr = 0; 864 const char* sym_name = NULL; 865 866 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 867 if (type == 0) { // R_*_NONE 868 continue; 869 } 870 if (sym != 0) { 871 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 872 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 873 if (s == NULL) { 874 // We only allow an undefined symbol if this is a weak reference... 875 s = &si->symtab[sym]; 876 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 877 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 878 return -1; 879 } 880 881 /* IHI0044C AAELF 4.5.1.1: 882 883 Libraries are not searched to resolve weak references. 884 It is not an error for a weak reference to remain unsatisfied. 885 886 During linking, the value of an undefined weak reference is: 887 - Zero if the relocation type is absolute 888 - The address of the place if the relocation is pc-relative 889 - The address of nominal base address if the relocation 890 type is base-relative. 891 */ 892 893 switch (type) { 894#if defined(__aarch64__) 895 case R_AARCH64_JUMP_SLOT: 896 case R_AARCH64_GLOB_DAT: 897 case R_AARCH64_ABS64: 898 case R_AARCH64_ABS32: 899 case R_AARCH64_ABS16: 900 case R_AARCH64_RELATIVE: 901 /* 902 * The sym_addr was initialized to be zero above, or the relocation 903 * code below does not care about value of sym_addr. 904 * No need to do anything. 905 */ 906 break; 907#elif defined(__x86_64__) 908 case R_X86_64_JUMP_SLOT: 909 case R_X86_64_GLOB_DAT: 910 case R_X86_64_32: 911 case R_X86_64_64: 912 case R_X86_64_RELATIVE: 913 // No need to do anything. 914 break; 915 case R_X86_64_PC32: 916 sym_addr = reloc; 917 break; 918#endif 919 default: 920 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 921 return -1; 922 } 923 } else { 924 // We got a definition. 925 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 926 } 927 count_relocation(kRelocSymbol); 928 } else { 929 s = NULL; 930 } 931 932 switch (type) { 933#if defined(__aarch64__) 934 case R_AARCH64_JUMP_SLOT: 935 count_relocation(kRelocAbsolute); 936 MARK(rela->r_offset); 937 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 938 reloc, (sym_addr + rela->r_addend), sym_name); 939 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 940 break; 941 case R_AARCH64_GLOB_DAT: 942 count_relocation(kRelocAbsolute); 943 MARK(rela->r_offset); 944 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 945 reloc, (sym_addr + rela->r_addend), sym_name); 946 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 947 break; 948 case R_AARCH64_ABS64: 949 count_relocation(kRelocAbsolute); 950 MARK(rela->r_offset); 951 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 952 reloc, (sym_addr + rela->r_addend), sym_name); 953 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 954 break; 955 case R_AARCH64_ABS32: 956 count_relocation(kRelocAbsolute); 957 MARK(rela->r_offset); 958 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 959 reloc, (sym_addr + rela->r_addend), sym_name); 960 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 961 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 962 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 963 } else { 964 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 965 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 966 static_cast<ElfW(Addr)>(INT32_MIN), 967 static_cast<ElfW(Addr)>(UINT32_MAX)); 968 return -1; 969 } 970 break; 971 case R_AARCH64_ABS16: 972 count_relocation(kRelocAbsolute); 973 MARK(rela->r_offset); 974 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 975 reloc, (sym_addr + rela->r_addend), sym_name); 976 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 977 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 978 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 979 } else { 980 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 981 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 982 static_cast<ElfW(Addr)>(INT16_MIN), 983 static_cast<ElfW(Addr)>(UINT16_MAX)); 984 return -1; 985 } 986 break; 987 case R_AARCH64_PREL64: 988 count_relocation(kRelocRelative); 989 MARK(rela->r_offset); 990 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 991 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 992 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 993 break; 994 case R_AARCH64_PREL32: 995 count_relocation(kRelocRelative); 996 MARK(rela->r_offset); 997 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 998 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 999 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1000 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1001 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1002 } else { 1003 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1004 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1005 static_cast<ElfW(Addr)>(INT32_MIN), 1006 static_cast<ElfW(Addr)>(UINT32_MAX)); 1007 return -1; 1008 } 1009 break; 1010 case R_AARCH64_PREL16: 1011 count_relocation(kRelocRelative); 1012 MARK(rela->r_offset); 1013 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1014 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1015 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1016 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1017 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1018 } else { 1019 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1020 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1021 static_cast<ElfW(Addr)>(INT16_MIN), 1022 static_cast<ElfW(Addr)>(UINT16_MAX)); 1023 return -1; 1024 } 1025 break; 1026 1027 case R_AARCH64_RELATIVE: 1028 count_relocation(kRelocRelative); 1029 MARK(rela->r_offset); 1030 if (sym) { 1031 DL_ERR("odd RELATIVE form..."); 1032 return -1; 1033 } 1034 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1035 reloc, (si->base + rela->r_addend)); 1036 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1037 break; 1038 1039 case R_AARCH64_COPY: 1040 /* 1041 * ET_EXEC is not supported so this should not happen. 1042 * 1043 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1044 * 1045 * Section 4.7.1.10 "Dynamic relocations" 1046 * R_AARCH64_COPY may only appear in executable objects where e_type is 1047 * set to ET_EXEC. 1048 */ 1049 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1050 return -1; 1051 case R_AARCH64_TLS_TPREL64: 1052 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1053 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1054 break; 1055 case R_AARCH64_TLS_DTPREL32: 1056 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1057 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1058 break; 1059#elif defined(__x86_64__) 1060 case R_X86_64_JUMP_SLOT: 1061 count_relocation(kRelocAbsolute); 1062 MARK(rela->r_offset); 1063 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1064 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1065 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1066 break; 1067 case R_X86_64_GLOB_DAT: 1068 count_relocation(kRelocAbsolute); 1069 MARK(rela->r_offset); 1070 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1071 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1072 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1073 break; 1074 case R_X86_64_RELATIVE: 1075 count_relocation(kRelocRelative); 1076 MARK(rela->r_offset); 1077 if (sym) { 1078 DL_ERR("odd RELATIVE form..."); 1079 return -1; 1080 } 1081 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1082 static_cast<size_t>(si->base)); 1083 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1084 break; 1085 case R_X86_64_32: 1086 count_relocation(kRelocRelative); 1087 MARK(rela->r_offset); 1088 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1089 static_cast<size_t>(sym_addr), sym_name); 1090 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1091 break; 1092 case R_X86_64_64: 1093 count_relocation(kRelocRelative); 1094 MARK(rela->r_offset); 1095 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1096 static_cast<size_t>(sym_addr), sym_name); 1097 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1098 break; 1099 case R_X86_64_PC32: 1100 count_relocation(kRelocRelative); 1101 MARK(rela->r_offset); 1102 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1103 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1104 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1105 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1106 break; 1107#endif 1108 1109 default: 1110 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1111 return -1; 1112 } 1113 } 1114 return 0; 1115} 1116 1117#else // REL, not RELA. 1118 1119static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1120 ElfW(Sym)* s; 1121 soinfo* lsi; 1122 1123 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1124 unsigned type = ELFW(R_TYPE)(rel->r_info); 1125 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1126 unsigned sym = ELFW(R_SYM)(rel->r_info); 1127 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1128 ElfW(Addr) sym_addr = 0; 1129 const char* sym_name = NULL; 1130 1131 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1132 if (type == 0) { // R_*_NONE 1133 continue; 1134 } 1135 if (sym != 0) { 1136 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1137 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1138 if (s == NULL) { 1139 // We only allow an undefined symbol if this is a weak reference... 1140 s = &si->symtab[sym]; 1141 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1142 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1143 return -1; 1144 } 1145 1146 /* IHI0044C AAELF 4.5.1.1: 1147 1148 Libraries are not searched to resolve weak references. 1149 It is not an error for a weak reference to remain 1150 unsatisfied. 1151 1152 During linking, the value of an undefined weak reference is: 1153 - Zero if the relocation type is absolute 1154 - The address of the place if the relocation is pc-relative 1155 - The address of nominal base address if the relocation 1156 type is base-relative. 1157 */ 1158 1159 switch (type) { 1160#if defined(__arm__) 1161 case R_ARM_JUMP_SLOT: 1162 case R_ARM_GLOB_DAT: 1163 case R_ARM_ABS32: 1164 case R_ARM_RELATIVE: /* Don't care. */ 1165 // sym_addr was initialized to be zero above or relocation 1166 // code below does not care about value of sym_addr. 1167 // No need to do anything. 1168 break; 1169#elif defined(__i386__) 1170 case R_386_JMP_SLOT: 1171 case R_386_GLOB_DAT: 1172 case R_386_32: 1173 case R_386_RELATIVE: /* Don't care. */ 1174 // sym_addr was initialized to be zero above or relocation 1175 // code below does not care about value of sym_addr. 1176 // No need to do anything. 1177 break; 1178 case R_386_PC32: 1179 sym_addr = reloc; 1180 break; 1181#endif 1182 1183#if defined(__arm__) 1184 case R_ARM_COPY: 1185 // Fall through. Can't really copy if weak symbol is not found at run-time. 1186#endif 1187 default: 1188 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1189 return -1; 1190 } 1191 } else { 1192 // We got a definition. 1193 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1194 } 1195 count_relocation(kRelocSymbol); 1196 } else { 1197 s = NULL; 1198 } 1199 1200 switch (type) { 1201#if defined(__arm__) 1202 case R_ARM_JUMP_SLOT: 1203 count_relocation(kRelocAbsolute); 1204 MARK(rel->r_offset); 1205 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1206 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1207 break; 1208 case R_ARM_GLOB_DAT: 1209 count_relocation(kRelocAbsolute); 1210 MARK(rel->r_offset); 1211 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1212 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1213 break; 1214 case R_ARM_ABS32: 1215 count_relocation(kRelocAbsolute); 1216 MARK(rel->r_offset); 1217 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1218 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1219 break; 1220 case R_ARM_REL32: 1221 count_relocation(kRelocRelative); 1222 MARK(rel->r_offset); 1223 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1224 reloc, sym_addr, rel->r_offset, sym_name); 1225 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1226 break; 1227 case R_ARM_COPY: 1228 /* 1229 * ET_EXEC is not supported so this should not happen. 1230 * 1231 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1232 * 1233 * Section 4.7.1.10 "Dynamic relocations" 1234 * R_ARM_COPY may only appear in executable objects where e_type is 1235 * set to ET_EXEC. 1236 */ 1237 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1238 return -1; 1239#elif defined(__i386__) 1240 case R_386_JMP_SLOT: 1241 count_relocation(kRelocAbsolute); 1242 MARK(rel->r_offset); 1243 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1244 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1245 break; 1246 case R_386_GLOB_DAT: 1247 count_relocation(kRelocAbsolute); 1248 MARK(rel->r_offset); 1249 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1250 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1251 break; 1252 case R_386_32: 1253 count_relocation(kRelocRelative); 1254 MARK(rel->r_offset); 1255 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1256 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1257 break; 1258 case R_386_PC32: 1259 count_relocation(kRelocRelative); 1260 MARK(rel->r_offset); 1261 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1262 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1263 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1264 break; 1265#elif defined(__mips__) 1266 case R_MIPS_REL32: 1267#if defined(__LP64__) 1268 // MIPS Elf64_Rel entries contain compound relocations 1269 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1270 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1271 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1272 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1273 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1274 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1275 return -1; 1276 } 1277#endif 1278 count_relocation(kRelocAbsolute); 1279 MARK(rel->r_offset); 1280 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1281 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1282 if (s) { 1283 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1284 } else { 1285 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1286 } 1287 break; 1288#endif 1289 1290#if defined(__arm__) 1291 case R_ARM_RELATIVE: 1292#elif defined(__i386__) 1293 case R_386_RELATIVE: 1294#endif 1295 count_relocation(kRelocRelative); 1296 MARK(rel->r_offset); 1297 if (sym) { 1298 DL_ERR("odd RELATIVE form..."); 1299 return -1; 1300 } 1301 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1302 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1303 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1304 break; 1305 1306 default: 1307 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1308 return -1; 1309 } 1310 } 1311 return 0; 1312} 1313#endif 1314 1315#if defined(__mips__) 1316static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1317 ElfW(Addr)** got = si->plt_got; 1318 if (got == NULL) { 1319 return true; 1320 } 1321 unsigned local_gotno = si->mips_local_gotno; 1322 unsigned gotsym = si->mips_gotsym; 1323 unsigned symtabno = si->mips_symtabno; 1324 ElfW(Sym)* symtab = si->symtab; 1325 1326 // got[0] is the address of the lazy resolver function. 1327 // got[1] may be used for a GNU extension. 1328 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1329 // FIXME: maybe this should be in a separate routine? 1330 if ((si->flags & FLAG_LINKER) == 0) { 1331 size_t g = 0; 1332 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1333 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1334 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1335 } 1336 // Relocate the local GOT entries. 1337 for (; g < local_gotno; g++) { 1338 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1339 } 1340 } 1341 1342 // Now for the global GOT entries... 1343 ElfW(Sym)* sym = symtab + gotsym; 1344 got = si->plt_got + local_gotno; 1345 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1346 // This is an undefined reference... try to locate it. 1347 const char* sym_name = si->strtab + sym->st_name; 1348 soinfo* lsi; 1349 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1350 if (s == NULL) { 1351 // We only allow an undefined symbol if this is a weak reference. 1352 s = &symtab[g]; 1353 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1354 DL_ERR("cannot locate \"%s\"...", sym_name); 1355 return false; 1356 } 1357 *got = 0; 1358 } else { 1359 // FIXME: is this sufficient? 1360 // For reference see NetBSD link loader 1361 // 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 1362 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1363 } 1364 } 1365 return true; 1366} 1367#endif 1368 1369void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1370 if (functions == NULL) { 1371 return; 1372 } 1373 1374 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1375 1376 int begin = reverse ? (count - 1) : 0; 1377 int end = reverse ? -1 : count; 1378 int step = reverse ? -1 : 1; 1379 1380 for (int i = begin; i != end; i += step) { 1381 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1382 CallFunction("function", functions[i]); 1383 } 1384 1385 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1386} 1387 1388void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1389 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1390 return; 1391 } 1392 1393 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1394 function(); 1395 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1396 1397 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1398 // are still writable. This happens with our debug malloc (see http://b/7941716). 1399 protect_data(PROT_READ | PROT_WRITE); 1400} 1401 1402void soinfo::CallPreInitConstructors() { 1403 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1404 // but ignored in a shared library. 1405 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1406} 1407 1408void soinfo::CallConstructors() { 1409 if (constructors_called) { 1410 return; 1411 } 1412 1413 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1414 // protect against recursive constructor calls. One simple example of constructor recursion 1415 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1416 // 1. The program depends on libc, so libc's constructor is called here. 1417 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1418 // 3. dlopen() calls the constructors on the newly created 1419 // soinfo for libc_malloc_debug_leak.so. 1420 // 4. The debug .so depends on libc, so CallConstructors is 1421 // called again with the libc soinfo. If it doesn't trigger the early- 1422 // out above, the libc constructor will be called again (recursively!). 1423 constructors_called = true; 1424 1425 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1426 // The GNU dynamic linker silently ignores these, but we warn the developer. 1427 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1428 name, preinit_array_count); 1429 } 1430 1431 get_children().for_each([] (soinfo* si) { 1432 si->CallConstructors(); 1433 }); 1434 1435 TRACE("\"%s\": calling constructors", name); 1436 1437 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1438 CallFunction("DT_INIT", init_func); 1439 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1440} 1441 1442void soinfo::CallDestructors() { 1443 TRACE("\"%s\": calling destructors", name); 1444 1445 // DT_FINI_ARRAY must be parsed in reverse order. 1446 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1447 1448 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1449 CallFunction("DT_FINI", fini_func); 1450 1451 // This is needed on second call to dlopen 1452 // after library has been unloaded with RTLD_NODELETE 1453 constructors_called = false; 1454} 1455 1456void soinfo::add_child(soinfo* child) { 1457 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1458 return; 1459 } 1460 1461 this->children.push_front(child); 1462 child->parents.push_front(this); 1463} 1464 1465void soinfo::remove_all_links() { 1466 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1467 return; 1468 } 1469 1470 // 1. Untie connected soinfos from 'this'. 1471 children.for_each([&] (soinfo* child) { 1472 child->parents.remove_if([&] (const soinfo* parent) { 1473 return parent == this; 1474 }); 1475 }); 1476 1477 parents.for_each([&] (soinfo* parent) { 1478 parent->children.for_each([&] (const soinfo* child) { 1479 return child == this; 1480 }); 1481 }); 1482 1483 // 2. Once everything untied - clear local lists. 1484 parents.clear(); 1485 children.clear(); 1486} 1487 1488void soinfo::set_st_dev(dev_t dev) { 1489 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1490 return; 1491 } 1492 1493 st_dev = dev; 1494} 1495 1496void soinfo::set_st_ino(ino_t ino) { 1497 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1498 return; 1499 } 1500 1501 st_ino = ino; 1502} 1503 1504dev_t soinfo::get_st_dev() { 1505 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1506 return 0; 1507 } 1508 1509 return st_dev; 1510}; 1511 1512ino_t soinfo::get_st_ino() { 1513 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1514 return 0; 1515 } 1516 1517 return st_ino; 1518} 1519 1520// This is a return on get_children() in case 1521// 'this->flags' does not have FLAG_NEW_SOINFO set. 1522static soinfo::soinfo_list_t g_empty_list; 1523 1524soinfo::soinfo_list_t& soinfo::get_children() { 1525 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1526 return g_empty_list; 1527 } 1528 1529 return this->children; 1530} 1531 1532/* Force any of the closed stdin, stdout and stderr to be associated with 1533 /dev/null. */ 1534static int nullify_closed_stdio() { 1535 int dev_null, i, status; 1536 int return_value = 0; 1537 1538 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1539 if (dev_null < 0) { 1540 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1541 return -1; 1542 } 1543 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1544 1545 /* If any of the stdio file descriptors is valid and not associated 1546 with /dev/null, dup /dev/null to it. */ 1547 for (i = 0; i < 3; i++) { 1548 /* If it is /dev/null already, we are done. */ 1549 if (i == dev_null) { 1550 continue; 1551 } 1552 1553 TRACE("[ Nullifying stdio file descriptor %d]", i); 1554 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1555 1556 /* If file is opened, we are good. */ 1557 if (status != -1) { 1558 continue; 1559 } 1560 1561 /* The only error we allow is that the file descriptor does not 1562 exist, in which case we dup /dev/null to it. */ 1563 if (errno != EBADF) { 1564 DL_ERR("fcntl failed: %s", strerror(errno)); 1565 return_value = -1; 1566 continue; 1567 } 1568 1569 /* Try dupping /dev/null to this stdio file descriptor and 1570 repeat if there is a signal. Note that any errors in closing 1571 the stdio descriptor are lost. */ 1572 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1573 if (status < 0) { 1574 DL_ERR("dup2 failed: %s", strerror(errno)); 1575 return_value = -1; 1576 continue; 1577 } 1578 } 1579 1580 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1581 if (dev_null > 2) { 1582 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1583 status = TEMP_FAILURE_RETRY(close(dev_null)); 1584 if (status == -1) { 1585 DL_ERR("close failed: %s", strerror(errno)); 1586 return_value = -1; 1587 } 1588 } 1589 1590 return return_value; 1591} 1592 1593static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1594 /* "base" might wrap around UINT32_MAX. */ 1595 ElfW(Addr) base = si->load_bias; 1596 const ElfW(Phdr)* phdr = si->phdr; 1597 int phnum = si->phnum; 1598 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1599 1600 /* We can't debug anything until the linker is relocated */ 1601 if (!relocating_linker) { 1602 INFO("[ linking %s ]", si->name); 1603 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1604 } 1605 1606 /* Extract dynamic section */ 1607 size_t dynamic_count; 1608 ElfW(Word) dynamic_flags; 1609 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1610 &dynamic_count, &dynamic_flags); 1611 if (si->dynamic == NULL) { 1612 if (!relocating_linker) { 1613 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1614 } 1615 return false; 1616 } else { 1617 if (!relocating_linker) { 1618 DEBUG("dynamic = %p", si->dynamic); 1619 } 1620 } 1621 1622#if defined(__arm__) 1623 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1624 &si->ARM_exidx, &si->ARM_exidx_count); 1625#endif 1626 1627 // Extract useful information from dynamic section. 1628 uint32_t needed_count = 0; 1629 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1630 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1631 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1632 switch (d->d_tag) { 1633 case DT_HASH: 1634 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1635 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1636 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1637 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1638 break; 1639 case DT_STRTAB: 1640 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1641 break; 1642 case DT_SYMTAB: 1643 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1644 break; 1645#if !defined(__LP64__) 1646 case DT_PLTREL: 1647 if (d->d_un.d_val != DT_REL) { 1648 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1649 return false; 1650 } 1651 break; 1652#endif 1653 case DT_JMPREL: 1654#if defined(USE_RELA) 1655 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1656#else 1657 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1658#endif 1659 break; 1660 case DT_PLTRELSZ: 1661#if defined(USE_RELA) 1662 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1663#else 1664 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1665#endif 1666 break; 1667#if defined(__mips__) 1668 case DT_PLTGOT: 1669 // Used by mips and mips64. 1670 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1671 break; 1672#endif 1673 case DT_DEBUG: 1674 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1675 // if the dynamic table is writable 1676// FIXME: not working currently for N64 1677// The flags for the LOAD and DYNAMIC program headers do not agree. 1678// The LOAD section containng the dynamic table has been mapped as 1679// read-only, but the DYNAMIC header claims it is writable. 1680#if !(defined(__mips__) && defined(__LP64__)) 1681 if ((dynamic_flags & PF_W) != 0) { 1682 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1683 } 1684 break; 1685#endif 1686#if defined(USE_RELA) 1687 case DT_RELA: 1688 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1689 break; 1690 case DT_RELASZ: 1691 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1692 break; 1693 case DT_REL: 1694 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1695 return false; 1696 case DT_RELSZ: 1697 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1698 return false; 1699#else 1700 case DT_REL: 1701 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1702 break; 1703 case DT_RELSZ: 1704 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1705 break; 1706 case DT_RELA: 1707 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1708 return false; 1709#endif 1710 case DT_INIT: 1711 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1712 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1713 break; 1714 case DT_FINI: 1715 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1716 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1717 break; 1718 case DT_INIT_ARRAY: 1719 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1720 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1721 break; 1722 case DT_INIT_ARRAYSZ: 1723 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1724 break; 1725 case DT_FINI_ARRAY: 1726 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1727 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1728 break; 1729 case DT_FINI_ARRAYSZ: 1730 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1731 break; 1732 case DT_PREINIT_ARRAY: 1733 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1734 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1735 break; 1736 case DT_PREINIT_ARRAYSZ: 1737 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1738 break; 1739 case DT_TEXTREL: 1740#if defined(__LP64__) 1741 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1742 return false; 1743#else 1744 si->has_text_relocations = true; 1745 break; 1746#endif 1747 case DT_SYMBOLIC: 1748 si->has_DT_SYMBOLIC = true; 1749 break; 1750 case DT_NEEDED: 1751 ++needed_count; 1752 break; 1753 case DT_FLAGS: 1754 if (d->d_un.d_val & DF_TEXTREL) { 1755#if defined(__LP64__) 1756 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1757 return false; 1758#else 1759 si->has_text_relocations = true; 1760#endif 1761 } 1762 if (d->d_un.d_val & DF_SYMBOLIC) { 1763 si->has_DT_SYMBOLIC = true; 1764 } 1765 break; 1766#if defined(__mips__) 1767 case DT_STRSZ: 1768 case DT_SYMENT: 1769 case DT_RELENT: 1770 break; 1771 case DT_MIPS_RLD_MAP: 1772 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1773 { 1774 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1775 *dp = &_r_debug; 1776 } 1777 break; 1778 case DT_MIPS_RLD_VERSION: 1779 case DT_MIPS_FLAGS: 1780 case DT_MIPS_BASE_ADDRESS: 1781 case DT_MIPS_UNREFEXTNO: 1782 break; 1783 1784 case DT_MIPS_SYMTABNO: 1785 si->mips_symtabno = d->d_un.d_val; 1786 break; 1787 1788 case DT_MIPS_LOCAL_GOTNO: 1789 si->mips_local_gotno = d->d_un.d_val; 1790 break; 1791 1792 case DT_MIPS_GOTSYM: 1793 si->mips_gotsym = d->d_un.d_val; 1794 break; 1795#endif 1796 1797 default: 1798 DEBUG("Unused DT entry: type %p arg %p", 1799 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1800 break; 1801 } 1802 } 1803 1804 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1805 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1806 1807 // Sanity checks. 1808 if (relocating_linker && needed_count != 0) { 1809 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1810 return false; 1811 } 1812 if (si->nbucket == 0) { 1813 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1814 return false; 1815 } 1816 if (si->strtab == 0) { 1817 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1818 return false; 1819 } 1820 if (si->symtab == 0) { 1821 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1822 return false; 1823 } 1824 1825 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1826 if (si->flags & FLAG_EXE) { 1827 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1828 size_t preload_count = 0; 1829 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1830 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1831 if (lsi != NULL) { 1832 g_ld_preloads[preload_count++] = lsi; 1833 } else { 1834 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1835 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1836 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1837 } 1838 } 1839 } 1840 1841 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1842 soinfo** pneeded = needed; 1843 1844 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1845 if (d->d_tag == DT_NEEDED) { 1846 const char* library_name = si->strtab + d->d_un.d_val; 1847 DEBUG("%s needs %s", si->name, library_name); 1848 soinfo* lsi = find_library(library_name, 0, NULL); 1849 if (lsi == NULL) { 1850 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1851 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1852 library_name, si->name, tmp_err_buf); 1853 return false; 1854 } 1855 1856 si->add_child(lsi); 1857 *pneeded++ = lsi; 1858 } 1859 } 1860 *pneeded = NULL; 1861 1862#if !defined(__LP64__) 1863 if (si->has_text_relocations) { 1864 // Make segments writable to allow text relocations to work properly. We will later call 1865 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1866#if !defined(__i386__) // The platform itself has too many text relocations on x86. 1867 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1868 "security hardening. Please fix.", si->name); 1869#endif 1870 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1871 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1872 si->name, strerror(errno)); 1873 return false; 1874 } 1875 } 1876#endif 1877 1878#if defined(USE_RELA) 1879 if (si->plt_rela != NULL) { 1880 DEBUG("[ relocating %s plt ]\n", si->name); 1881 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1882 return false; 1883 } 1884 } 1885 if (si->rela != NULL) { 1886 DEBUG("[ relocating %s ]\n", si->name); 1887 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1888 return false; 1889 } 1890 } 1891#else 1892 if (si->plt_rel != NULL) { 1893 DEBUG("[ relocating %s plt ]", si->name); 1894 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1895 return false; 1896 } 1897 } 1898 if (si->rel != NULL) { 1899 DEBUG("[ relocating %s ]", si->name); 1900 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1901 return false; 1902 } 1903 } 1904#endif 1905 1906#if defined(__mips__) 1907 if (!mips_relocate_got(si, needed)) { 1908 return false; 1909 } 1910#endif 1911 1912 si->flags |= FLAG_LINKED; 1913 DEBUG("[ finished linking %s ]", si->name); 1914 1915#if !defined(__LP64__) 1916 if (si->has_text_relocations) { 1917 // All relocations are done, we can protect our segments back to read-only. 1918 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1919 DL_ERR("can't protect segments for \"%s\": %s", 1920 si->name, strerror(errno)); 1921 return false; 1922 } 1923 } 1924#endif 1925 1926 /* We can also turn on GNU RELRO protection */ 1927 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1928 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1929 si->name, strerror(errno)); 1930 return false; 1931 } 1932 1933 /* Handle serializing/sharing the RELRO segment */ 1934 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1935 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1936 extinfo->relro_fd) < 0) { 1937 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1938 si->name, strerror(errno)); 1939 return false; 1940 } 1941 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1942 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1943 extinfo->relro_fd) < 0) { 1944 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1945 si->name, strerror(errno)); 1946 return false; 1947 } 1948 } 1949 1950 notify_gdb_of_load(si); 1951 return true; 1952} 1953 1954/* 1955 * This function add vdso to internal dso list. 1956 * It helps to stack unwinding through signal handlers. 1957 * Also, it makes bionic more like glibc. 1958 */ 1959static void add_vdso(KernelArgumentBlock& args __unused) { 1960#if defined(AT_SYSINFO_EHDR) 1961 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1962 if (ehdr_vdso == NULL) { 1963 return; 1964 } 1965 1966 soinfo* si = soinfo_alloc("[vdso]", NULL); 1967 1968 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1969 si->phnum = ehdr_vdso->e_phnum; 1970 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1971 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1972 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1973 1974 soinfo_link_image(si, NULL); 1975#endif 1976} 1977 1978/* 1979 * This is linker soinfo for GDB. See details below. 1980 */ 1981static soinfo linker_soinfo_for_gdb; 1982 1983/* gdb expects the linker to be in the debug shared object list. 1984 * Without this, gdb has trouble locating the linker's ".text" 1985 * and ".plt" sections. Gdb could also potentially use this to 1986 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1987 * Don't use soinfo_alloc(), because the linker shouldn't 1988 * be on the soinfo list. 1989 */ 1990static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 1991#if defined(__LP64__) 1992 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 1993#else 1994 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 1995#endif 1996 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 1997 linker_soinfo_for_gdb.base = linker_base; 1998 1999 /* 2000 * Set the dynamic field in the link map otherwise gdb will complain with 2001 * the following: 2002 * warning: .dynamic section for "/system/bin/linker" is not at the 2003 * expected address (wrong library or version mismatch?) 2004 */ 2005 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2006 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2007 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2008 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2009 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2010} 2011 2012/* 2013 * This code is called after the linker has linked itself and 2014 * fixed it's own GOT. It is safe to make references to externs 2015 * and other non-local data at this point. 2016 */ 2017static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2018 /* NOTE: we store the args pointer on a special location 2019 * of the temporary TLS area in order to pass it to 2020 * the C Library's runtime initializer. 2021 * 2022 * The initializer must clear the slot and reset the TLS 2023 * to point to a different location to ensure that no other 2024 * shared library constructor can access it. 2025 */ 2026 __libc_init_tls(args); 2027 2028#if TIMING 2029 struct timeval t0, t1; 2030 gettimeofday(&t0, 0); 2031#endif 2032 2033 // Initialize environment functions, and get to the ELF aux vectors table. 2034 linker_env_init(args); 2035 2036 // If this is a setuid/setgid program, close the security hole described in 2037 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2038 if (get_AT_SECURE()) { 2039 nullify_closed_stdio(); 2040 } 2041 2042 debuggerd_init(); 2043 2044 // Get a few environment variables. 2045 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2046 if (LD_DEBUG != NULL) { 2047 g_ld_debug_verbosity = atoi(LD_DEBUG); 2048 } 2049 2050 // Normally, these are cleaned by linker_env_init, but the test 2051 // doesn't cost us anything. 2052 const char* ldpath_env = NULL; 2053 const char* ldpreload_env = NULL; 2054 if (!get_AT_SECURE()) { 2055 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2056 ldpreload_env = linker_env_get("LD_PRELOAD"); 2057 } 2058 2059 // Linker does not call constructors for its own 2060 // global variables so we need to initialize 2061 // the allocators explicitly. 2062 g_soinfo_allocator.init(); 2063 g_soinfo_links_allocator.init(); 2064 2065 INFO("[ android linker & debugger ]"); 2066 2067 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2068 if (si == NULL) { 2069 exit(EXIT_FAILURE); 2070 } 2071 2072 /* bootstrap the link map, the main exe always needs to be first */ 2073 si->flags |= FLAG_EXE; 2074 link_map* map = &(si->link_map_head); 2075 2076 map->l_addr = 0; 2077 map->l_name = args.argv[0]; 2078 map->l_prev = NULL; 2079 map->l_next = NULL; 2080 2081 _r_debug.r_map = map; 2082 r_debug_tail = map; 2083 2084 init_linker_info_for_gdb(linker_base); 2085 2086 // Extract information passed from the kernel. 2087 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2088 si->phnum = args.getauxval(AT_PHNUM); 2089 si->entry = args.getauxval(AT_ENTRY); 2090 2091 /* Compute the value of si->base. We can't rely on the fact that 2092 * the first entry is the PHDR because this will not be true 2093 * for certain executables (e.g. some in the NDK unit test suite) 2094 */ 2095 si->base = 0; 2096 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2097 si->load_bias = 0; 2098 for (size_t i = 0; i < si->phnum; ++i) { 2099 if (si->phdr[i].p_type == PT_PHDR) { 2100 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2101 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2102 break; 2103 } 2104 } 2105 si->dynamic = NULL; 2106 si->ref_count = 1; 2107 2108 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2109 if (elf_hdr->e_type != ET_DYN) { 2110 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2111 exit(EXIT_FAILURE); 2112 } 2113 2114 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2115 parse_LD_LIBRARY_PATH(ldpath_env); 2116 parse_LD_PRELOAD(ldpreload_env); 2117 2118 somain = si; 2119 2120 if (!soinfo_link_image(si, NULL)) { 2121 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2122 exit(EXIT_FAILURE); 2123 } 2124 2125 add_vdso(args); 2126 2127 si->CallPreInitConstructors(); 2128 2129 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2130 g_ld_preloads[i]->CallConstructors(); 2131 } 2132 2133 /* After the link_image, the si->load_bias is initialized. 2134 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2135 * We need to update this value for so exe here. So Unwind_Backtrace 2136 * for some arch like x86 could work correctly within so exe. 2137 */ 2138 map->l_addr = si->load_bias; 2139 si->CallConstructors(); 2140 2141#if TIMING 2142 gettimeofday(&t1, NULL); 2143 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2144 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2145 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2146#endif 2147#if STATS 2148 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2149 linker_stats.count[kRelocAbsolute], 2150 linker_stats.count[kRelocRelative], 2151 linker_stats.count[kRelocCopy], 2152 linker_stats.count[kRelocSymbol]); 2153#endif 2154#if COUNT_PAGES 2155 { 2156 unsigned n; 2157 unsigned i; 2158 unsigned count = 0; 2159 for (n = 0; n < 4096; n++) { 2160 if (bitmask[n]) { 2161 unsigned x = bitmask[n]; 2162#if defined(__LP64__) 2163 for (i = 0; i < 32; i++) { 2164#else 2165 for (i = 0; i < 8; i++) { 2166#endif 2167 if (x & 1) { 2168 count++; 2169 } 2170 x >>= 1; 2171 } 2172 } 2173 } 2174 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2175 } 2176#endif 2177 2178#if TIMING || STATS || COUNT_PAGES 2179 fflush(stdout); 2180#endif 2181 2182 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2183 return si->entry; 2184} 2185 2186/* Compute the load-bias of an existing executable. This shall only 2187 * be used to compute the load bias of an executable or shared library 2188 * that was loaded by the kernel itself. 2189 * 2190 * Input: 2191 * elf -> address of ELF header, assumed to be at the start of the file. 2192 * Return: 2193 * load bias, i.e. add the value of any p_vaddr in the file to get 2194 * the corresponding address in memory. 2195 */ 2196static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2197 ElfW(Addr) offset = elf->e_phoff; 2198 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2199 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2200 2201 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2202 if (phdr->p_type == PT_LOAD) { 2203 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2204 } 2205 } 2206 return 0; 2207} 2208 2209/* 2210 * This is the entry point for the linker, called from begin.S. This 2211 * method is responsible for fixing the linker's own relocations, and 2212 * then calling __linker_init_post_relocation(). 2213 * 2214 * Because this method is called before the linker has fixed it's own 2215 * relocations, any attempt to reference an extern variable, extern 2216 * function, or other GOT reference will generate a segfault. 2217 */ 2218extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2219 // Initialize static variables. 2220 solist = get_libdl_info(); 2221 sonext = get_libdl_info(); 2222 2223 KernelArgumentBlock args(raw_args); 2224 2225 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2226 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2227 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2228 2229 soinfo linker_so; 2230 memset(&linker_so, 0, sizeof(soinfo)); 2231 2232 strcpy(linker_so.name, "[dynamic linker]"); 2233 linker_so.base = linker_addr; 2234 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2235 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2236 linker_so.dynamic = NULL; 2237 linker_so.phdr = phdr; 2238 linker_so.phnum = elf_hdr->e_phnum; 2239 linker_so.flags |= FLAG_LINKER; 2240 2241 if (!soinfo_link_image(&linker_so, NULL)) { 2242 // It would be nice to print an error message, but if the linker 2243 // can't link itself, there's no guarantee that we'll be able to 2244 // call write() (because it involves a GOT reference). We may as 2245 // well try though... 2246 const char* msg = "CANNOT LINK EXECUTABLE: "; 2247 write(2, msg, strlen(msg)); 2248 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2249 write(2, "\n", 1); 2250 _exit(EXIT_FAILURE); 2251 } 2252 2253 // We have successfully fixed our own relocations. It's safe to run 2254 // the main part of the linker now. 2255 args.abort_message_ptr = &g_abort_message; 2256 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2257 2258 protect_data(PROT_READ); 2259 2260 // Return the address that the calling assembly stub should jump to. 2261 return start_address; 2262} 2263