linker.cpp revision aa836f731016f7f1099d6a6ce47a35f1ec17dd4e
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 * - are we doing everything we should for ARM_COPY relocations? 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 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, 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 if ((si->flags & FLAG_EXE) == 0) { 1041 /* 1042 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1043 * 1044 * Section 4.7.1.10 "Dynamic relocations" 1045 * R_AARCH64_COPY may only appear in executable objects where e_type is 1046 * set to ET_EXEC. 1047 * 1048 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1049 * We should explicitly disallow ET_DYN executables from having 1050 * R_AARCH64_COPY relocations. 1051 */ 1052 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1053 return -1; 1054 } 1055 count_relocation(kRelocCopy); 1056 MARK(rela->r_offset); 1057 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1058 reloc, 1059 s->st_size, 1060 (sym_addr + rela->r_addend), 1061 sym_name); 1062 if (reloc == (sym_addr + rela->r_addend)) { 1063 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1064 1065 if (src == NULL) { 1066 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1067 return -1; 1068 } 1069 if (lsi->has_DT_SYMBOLIC) { 1070 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1071 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1072 return -1; 1073 } 1074 if (s->st_size < src->st_size) { 1075 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1076 si->name, s->st_size, src->st_size); 1077 return -1; 1078 } 1079 memcpy(reinterpret_cast<void*>(reloc), 1080 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1081 } else { 1082 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1083 return -1; 1084 } 1085 break; 1086 case R_AARCH64_TLS_TPREL64: 1087 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1088 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1089 break; 1090 case R_AARCH64_TLS_DTPREL32: 1091 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1092 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1093 break; 1094#elif defined(__x86_64__) 1095 case R_X86_64_JUMP_SLOT: 1096 count_relocation(kRelocAbsolute); 1097 MARK(rela->r_offset); 1098 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1099 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1100 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1101 break; 1102 case R_X86_64_GLOB_DAT: 1103 count_relocation(kRelocAbsolute); 1104 MARK(rela->r_offset); 1105 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1106 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1107 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1108 break; 1109 case R_X86_64_RELATIVE: 1110 count_relocation(kRelocRelative); 1111 MARK(rela->r_offset); 1112 if (sym) { 1113 DL_ERR("odd RELATIVE form..."); 1114 return -1; 1115 } 1116 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1117 static_cast<size_t>(si->base)); 1118 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1119 break; 1120 case R_X86_64_32: 1121 count_relocation(kRelocRelative); 1122 MARK(rela->r_offset); 1123 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1124 static_cast<size_t>(sym_addr), sym_name); 1125 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1126 break; 1127 case R_X86_64_64: 1128 count_relocation(kRelocRelative); 1129 MARK(rela->r_offset); 1130 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1131 static_cast<size_t>(sym_addr), sym_name); 1132 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1133 break; 1134 case R_X86_64_PC32: 1135 count_relocation(kRelocRelative); 1136 MARK(rela->r_offset); 1137 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1138 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1139 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1140 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1141 break; 1142#endif 1143 1144 default: 1145 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1146 return -1; 1147 } 1148 } 1149 return 0; 1150} 1151 1152#else // REL, not RELA. 1153 1154static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1155 ElfW(Sym)* s; 1156 soinfo* lsi; 1157 1158 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1159 unsigned type = ELFW(R_TYPE)(rel->r_info); 1160 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1161 unsigned sym = ELFW(R_SYM)(rel->r_info); 1162 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1163 ElfW(Addr) sym_addr = 0; 1164 const char* sym_name = NULL; 1165 1166 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1167 if (type == 0) { // R_*_NONE 1168 continue; 1169 } 1170 if (sym != 0) { 1171 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1172 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1173 if (s == NULL) { 1174 // We only allow an undefined symbol if this is a weak reference... 1175 s = &si->symtab[sym]; 1176 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1177 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1178 return -1; 1179 } 1180 1181 /* IHI0044C AAELF 4.5.1.1: 1182 1183 Libraries are not searched to resolve weak references. 1184 It is not an error for a weak reference to remain 1185 unsatisfied. 1186 1187 During linking, the value of an undefined weak reference is: 1188 - Zero if the relocation type is absolute 1189 - The address of the place if the relocation is pc-relative 1190 - The address of nominal base address if the relocation 1191 type is base-relative. 1192 */ 1193 1194 switch (type) { 1195#if defined(__arm__) 1196 case R_ARM_JUMP_SLOT: 1197 case R_ARM_GLOB_DAT: 1198 case R_ARM_ABS32: 1199 case R_ARM_RELATIVE: /* Don't care. */ 1200 // sym_addr was initialized to be zero above or relocation 1201 // code below does not care about value of sym_addr. 1202 // No need to do anything. 1203 break; 1204#elif defined(__i386__) 1205 case R_386_JMP_SLOT: 1206 case R_386_GLOB_DAT: 1207 case R_386_32: 1208 case R_386_RELATIVE: /* Don't care. */ 1209 // sym_addr was initialized to be zero above or relocation 1210 // code below does not care about value of sym_addr. 1211 // No need to do anything. 1212 break; 1213 case R_386_PC32: 1214 sym_addr = reloc; 1215 break; 1216#endif 1217 1218#if defined(__arm__) 1219 case R_ARM_COPY: 1220 // Fall through. Can't really copy if weak symbol is not found at run-time. 1221#endif 1222 default: 1223 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1224 return -1; 1225 } 1226 } else { 1227 // We got a definition. 1228 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1229 } 1230 count_relocation(kRelocSymbol); 1231 } else { 1232 s = NULL; 1233 } 1234 1235 switch (type) { 1236#if defined(__arm__) 1237 case R_ARM_JUMP_SLOT: 1238 count_relocation(kRelocAbsolute); 1239 MARK(rel->r_offset); 1240 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1241 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1242 break; 1243 case R_ARM_GLOB_DAT: 1244 count_relocation(kRelocAbsolute); 1245 MARK(rel->r_offset); 1246 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1247 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1248 break; 1249 case R_ARM_ABS32: 1250 count_relocation(kRelocAbsolute); 1251 MARK(rel->r_offset); 1252 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1253 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1254 break; 1255 case R_ARM_REL32: 1256 count_relocation(kRelocRelative); 1257 MARK(rel->r_offset); 1258 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1259 reloc, sym_addr, rel->r_offset, sym_name); 1260 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1261 break; 1262 case R_ARM_COPY: 1263 if ((si->flags & FLAG_EXE) == 0) { 1264 /* 1265 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1266 * 1267 * Section 4.7.1.10 "Dynamic relocations" 1268 * R_ARM_COPY may only appear in executable objects where e_type is 1269 * set to ET_EXEC. 1270 * 1271 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1272 * We should explicitly disallow ET_DYN executables from having 1273 * R_ARM_COPY relocations. 1274 */ 1275 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1276 return -1; 1277 } 1278 count_relocation(kRelocCopy); 1279 MARK(rel->r_offset); 1280 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1281 if (reloc == sym_addr) { 1282 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1283 1284 if (src == NULL) { 1285 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1286 return -1; 1287 } 1288 if (lsi->has_DT_SYMBOLIC) { 1289 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1290 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1291 return -1; 1292 } 1293 if (s->st_size < src->st_size) { 1294 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1295 si->name, s->st_size, src->st_size); 1296 return -1; 1297 } 1298 memcpy(reinterpret_cast<void*>(reloc), 1299 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1300 } else { 1301 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1302 return -1; 1303 } 1304 break; 1305#elif defined(__i386__) 1306 case R_386_JMP_SLOT: 1307 count_relocation(kRelocAbsolute); 1308 MARK(rel->r_offset); 1309 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1310 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1311 break; 1312 case R_386_GLOB_DAT: 1313 count_relocation(kRelocAbsolute); 1314 MARK(rel->r_offset); 1315 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1316 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1317 break; 1318 case R_386_32: 1319 count_relocation(kRelocRelative); 1320 MARK(rel->r_offset); 1321 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1322 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1323 break; 1324 case R_386_PC32: 1325 count_relocation(kRelocRelative); 1326 MARK(rel->r_offset); 1327 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1328 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1329 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1330 break; 1331#elif defined(__mips__) 1332 case R_MIPS_REL32: 1333#if defined(__LP64__) 1334 // MIPS Elf64_Rel entries contain compound relocations 1335 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1336 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1337 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1338 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1339 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1340 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1341 return -1; 1342 } 1343#endif 1344 count_relocation(kRelocAbsolute); 1345 MARK(rel->r_offset); 1346 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1347 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1348 if (s) { 1349 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1350 } else { 1351 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1352 } 1353 break; 1354#endif 1355 1356#if defined(__arm__) 1357 case R_ARM_RELATIVE: 1358#elif defined(__i386__) 1359 case R_386_RELATIVE: 1360#endif 1361 count_relocation(kRelocRelative); 1362 MARK(rel->r_offset); 1363 if (sym) { 1364 DL_ERR("odd RELATIVE form..."); 1365 return -1; 1366 } 1367 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1368 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1369 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1370 break; 1371 1372 default: 1373 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1374 return -1; 1375 } 1376 } 1377 return 0; 1378} 1379#endif 1380 1381#if defined(__mips__) 1382static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1383 ElfW(Addr)** got = si->plt_got; 1384 if (got == NULL) { 1385 return true; 1386 } 1387 unsigned local_gotno = si->mips_local_gotno; 1388 unsigned gotsym = si->mips_gotsym; 1389 unsigned symtabno = si->mips_symtabno; 1390 ElfW(Sym)* symtab = si->symtab; 1391 1392 // got[0] is the address of the lazy resolver function. 1393 // got[1] may be used for a GNU extension. 1394 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1395 // FIXME: maybe this should be in a separate routine? 1396 if ((si->flags & FLAG_LINKER) == 0) { 1397 size_t g = 0; 1398 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1399 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1400 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1401 } 1402 // Relocate the local GOT entries. 1403 for (; g < local_gotno; g++) { 1404 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1405 } 1406 } 1407 1408 // Now for the global GOT entries... 1409 ElfW(Sym)* sym = symtab + gotsym; 1410 got = si->plt_got + local_gotno; 1411 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1412 // This is an undefined reference... try to locate it. 1413 const char* sym_name = si->strtab + sym->st_name; 1414 soinfo* lsi; 1415 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1416 if (s == NULL) { 1417 // We only allow an undefined symbol if this is a weak reference. 1418 s = &symtab[g]; 1419 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1420 DL_ERR("cannot locate \"%s\"...", sym_name); 1421 return false; 1422 } 1423 *got = 0; 1424 } else { 1425 // FIXME: is this sufficient? 1426 // For reference see NetBSD link loader 1427 // 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 1428 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1429 } 1430 } 1431 return true; 1432} 1433#endif 1434 1435void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1436 if (functions == NULL) { 1437 return; 1438 } 1439 1440 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1441 1442 int begin = reverse ? (count - 1) : 0; 1443 int end = reverse ? -1 : count; 1444 int step = reverse ? -1 : 1; 1445 1446 for (int i = begin; i != end; i += step) { 1447 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1448 CallFunction("function", functions[i]); 1449 } 1450 1451 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1452} 1453 1454void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1455 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1456 return; 1457 } 1458 1459 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1460 function(); 1461 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1462 1463 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1464 // are still writable. This happens with our debug malloc (see http://b/7941716). 1465 protect_data(PROT_READ | PROT_WRITE); 1466} 1467 1468void soinfo::CallPreInitConstructors() { 1469 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1470 // but ignored in a shared library. 1471 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1472} 1473 1474void soinfo::CallConstructors() { 1475 if (constructors_called) { 1476 return; 1477 } 1478 1479 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1480 // protect against recursive constructor calls. One simple example of constructor recursion 1481 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1482 // 1. The program depends on libc, so libc's constructor is called here. 1483 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1484 // 3. dlopen() calls the constructors on the newly created 1485 // soinfo for libc_malloc_debug_leak.so. 1486 // 4. The debug .so depends on libc, so CallConstructors is 1487 // called again with the libc soinfo. If it doesn't trigger the early- 1488 // out above, the libc constructor will be called again (recursively!). 1489 constructors_called = true; 1490 1491 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1492 // The GNU dynamic linker silently ignores these, but we warn the developer. 1493 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1494 name, preinit_array_count); 1495 } 1496 1497 get_children().for_each([] (soinfo* si) { 1498 si->CallConstructors(); 1499 }); 1500 1501 TRACE("\"%s\": calling constructors", name); 1502 1503 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1504 CallFunction("DT_INIT", init_func); 1505 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1506} 1507 1508void soinfo::CallDestructors() { 1509 TRACE("\"%s\": calling destructors", name); 1510 1511 // DT_FINI_ARRAY must be parsed in reverse order. 1512 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1513 1514 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1515 CallFunction("DT_FINI", fini_func); 1516 1517 // This is needed on second call to dlopen 1518 // after library has been unloaded with RTLD_NODELETE 1519 constructors_called = false; 1520} 1521 1522void soinfo::add_child(soinfo* child) { 1523 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1524 return; 1525 } 1526 1527 this->children.push_front(child); 1528 child->parents.push_front(this); 1529} 1530 1531void soinfo::remove_all_links() { 1532 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1533 return; 1534 } 1535 1536 // 1. Untie connected soinfos from 'this'. 1537 children.for_each([&] (soinfo* child) { 1538 child->parents.remove_if([&] (const soinfo* parent) { 1539 return parent == this; 1540 }); 1541 }); 1542 1543 parents.for_each([&] (soinfo* parent) { 1544 parent->children.for_each([&] (const soinfo* child) { 1545 return child == this; 1546 }); 1547 }); 1548 1549 // 2. Once everything untied - clear local lists. 1550 parents.clear(); 1551 children.clear(); 1552} 1553 1554void soinfo::set_st_dev(dev_t dev) { 1555 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1556 return; 1557 } 1558 1559 st_dev = dev; 1560} 1561 1562void soinfo::set_st_ino(ino_t ino) { 1563 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1564 return; 1565 } 1566 1567 st_ino = ino; 1568} 1569 1570dev_t soinfo::get_st_dev() { 1571 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1572 return 0; 1573 } 1574 1575 return st_dev; 1576}; 1577 1578ino_t soinfo::get_st_ino() { 1579 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1580 return 0; 1581 } 1582 1583 return st_ino; 1584} 1585 1586// This is a return on get_children() in case 1587// 'this->flags' does not have FLAG_NEW_SOINFO set. 1588static soinfo::soinfo_list_t g_empty_list; 1589 1590soinfo::soinfo_list_t& soinfo::get_children() { 1591 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1592 return g_empty_list; 1593 } 1594 1595 return this->children; 1596} 1597 1598/* Force any of the closed stdin, stdout and stderr to be associated with 1599 /dev/null. */ 1600static int nullify_closed_stdio() { 1601 int dev_null, i, status; 1602 int return_value = 0; 1603 1604 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1605 if (dev_null < 0) { 1606 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1607 return -1; 1608 } 1609 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1610 1611 /* If any of the stdio file descriptors is valid and not associated 1612 with /dev/null, dup /dev/null to it. */ 1613 for (i = 0; i < 3; i++) { 1614 /* If it is /dev/null already, we are done. */ 1615 if (i == dev_null) { 1616 continue; 1617 } 1618 1619 TRACE("[ Nullifying stdio file descriptor %d]", i); 1620 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1621 1622 /* If file is opened, we are good. */ 1623 if (status != -1) { 1624 continue; 1625 } 1626 1627 /* The only error we allow is that the file descriptor does not 1628 exist, in which case we dup /dev/null to it. */ 1629 if (errno != EBADF) { 1630 DL_ERR("fcntl failed: %s", strerror(errno)); 1631 return_value = -1; 1632 continue; 1633 } 1634 1635 /* Try dupping /dev/null to this stdio file descriptor and 1636 repeat if there is a signal. Note that any errors in closing 1637 the stdio descriptor are lost. */ 1638 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1639 if (status < 0) { 1640 DL_ERR("dup2 failed: %s", strerror(errno)); 1641 return_value = -1; 1642 continue; 1643 } 1644 } 1645 1646 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1647 if (dev_null > 2) { 1648 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1649 status = TEMP_FAILURE_RETRY(close(dev_null)); 1650 if (status == -1) { 1651 DL_ERR("close failed: %s", strerror(errno)); 1652 return_value = -1; 1653 } 1654 } 1655 1656 return return_value; 1657} 1658 1659static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1660 /* "base" might wrap around UINT32_MAX. */ 1661 ElfW(Addr) base = si->load_bias; 1662 const ElfW(Phdr)* phdr = si->phdr; 1663 int phnum = si->phnum; 1664 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1665 1666 /* We can't debug anything until the linker is relocated */ 1667 if (!relocating_linker) { 1668 INFO("[ linking %s ]", si->name); 1669 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1670 } 1671 1672 /* Extract dynamic section */ 1673 size_t dynamic_count; 1674 ElfW(Word) dynamic_flags; 1675 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1676 &dynamic_count, &dynamic_flags); 1677 if (si->dynamic == NULL) { 1678 if (!relocating_linker) { 1679 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1680 } 1681 return false; 1682 } else { 1683 if (!relocating_linker) { 1684 DEBUG("dynamic = %p", si->dynamic); 1685 } 1686 } 1687 1688#if defined(__arm__) 1689 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1690 &si->ARM_exidx, &si->ARM_exidx_count); 1691#endif 1692 1693 // Extract useful information from dynamic section. 1694 uint32_t needed_count = 0; 1695 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1696 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1697 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1698 switch (d->d_tag) { 1699 case DT_HASH: 1700 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1701 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1702 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1703 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1704 break; 1705 case DT_STRTAB: 1706 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1707 break; 1708 case DT_SYMTAB: 1709 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1710 break; 1711#if !defined(__LP64__) 1712 case DT_PLTREL: 1713 if (d->d_un.d_val != DT_REL) { 1714 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1715 return false; 1716 } 1717 break; 1718#endif 1719 case DT_JMPREL: 1720#if defined(USE_RELA) 1721 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1722#else 1723 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1724#endif 1725 break; 1726 case DT_PLTRELSZ: 1727#if defined(USE_RELA) 1728 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1729#else 1730 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1731#endif 1732 break; 1733#if defined(__mips__) 1734 case DT_PLTGOT: 1735 // Used by mips and mips64. 1736 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1737 break; 1738#endif 1739 case DT_DEBUG: 1740 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1741 // if the dynamic table is writable 1742// FIXME: not working currently for N64 1743// The flags for the LOAD and DYNAMIC program headers do not agree. 1744// The LOAD section containng the dynamic table has been mapped as 1745// read-only, but the DYNAMIC header claims it is writable. 1746#if !(defined(__mips__) && defined(__LP64__)) 1747 if ((dynamic_flags & PF_W) != 0) { 1748 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1749 } 1750 break; 1751#endif 1752#if defined(USE_RELA) 1753 case DT_RELA: 1754 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1755 break; 1756 case DT_RELASZ: 1757 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1758 break; 1759 case DT_REL: 1760 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1761 return false; 1762 case DT_RELSZ: 1763 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1764 return false; 1765#else 1766 case DT_REL: 1767 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1768 break; 1769 case DT_RELSZ: 1770 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1771 break; 1772 case DT_RELA: 1773 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1774 return false; 1775#endif 1776 case DT_INIT: 1777 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1778 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1779 break; 1780 case DT_FINI: 1781 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1782 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1783 break; 1784 case DT_INIT_ARRAY: 1785 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1786 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1787 break; 1788 case DT_INIT_ARRAYSZ: 1789 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1790 break; 1791 case DT_FINI_ARRAY: 1792 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1793 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1794 break; 1795 case DT_FINI_ARRAYSZ: 1796 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1797 break; 1798 case DT_PREINIT_ARRAY: 1799 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1800 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1801 break; 1802 case DT_PREINIT_ARRAYSZ: 1803 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1804 break; 1805 case DT_TEXTREL: 1806#if defined(__LP64__) 1807 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1808 return false; 1809#else 1810 si->has_text_relocations = true; 1811 break; 1812#endif 1813 case DT_SYMBOLIC: 1814 si->has_DT_SYMBOLIC = true; 1815 break; 1816 case DT_NEEDED: 1817 ++needed_count; 1818 break; 1819 case DT_FLAGS: 1820 if (d->d_un.d_val & DF_TEXTREL) { 1821#if defined(__LP64__) 1822 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1823 return false; 1824#else 1825 si->has_text_relocations = true; 1826#endif 1827 } 1828 if (d->d_un.d_val & DF_SYMBOLIC) { 1829 si->has_DT_SYMBOLIC = true; 1830 } 1831 break; 1832#if defined(__mips__) 1833 case DT_STRSZ: 1834 case DT_SYMENT: 1835 case DT_RELENT: 1836 break; 1837 case DT_MIPS_RLD_MAP: 1838 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1839 { 1840 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1841 *dp = &_r_debug; 1842 } 1843 break; 1844 case DT_MIPS_RLD_VERSION: 1845 case DT_MIPS_FLAGS: 1846 case DT_MIPS_BASE_ADDRESS: 1847 case DT_MIPS_UNREFEXTNO: 1848 break; 1849 1850 case DT_MIPS_SYMTABNO: 1851 si->mips_symtabno = d->d_un.d_val; 1852 break; 1853 1854 case DT_MIPS_LOCAL_GOTNO: 1855 si->mips_local_gotno = d->d_un.d_val; 1856 break; 1857 1858 case DT_MIPS_GOTSYM: 1859 si->mips_gotsym = d->d_un.d_val; 1860 break; 1861#endif 1862 1863 default: 1864 DEBUG("Unused DT entry: type %p arg %p", 1865 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1866 break; 1867 } 1868 } 1869 1870 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1871 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1872 1873 // Sanity checks. 1874 if (relocating_linker && needed_count != 0) { 1875 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1876 return false; 1877 } 1878 if (si->nbucket == 0) { 1879 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1880 return false; 1881 } 1882 if (si->strtab == 0) { 1883 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1884 return false; 1885 } 1886 if (si->symtab == 0) { 1887 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1888 return false; 1889 } 1890 1891 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1892 if (si->flags & FLAG_EXE) { 1893 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1894 size_t preload_count = 0; 1895 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1896 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1897 if (lsi != NULL) { 1898 g_ld_preloads[preload_count++] = lsi; 1899 } else { 1900 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1901 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1902 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1903 } 1904 } 1905 } 1906 1907 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1908 soinfo** pneeded = needed; 1909 1910 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1911 if (d->d_tag == DT_NEEDED) { 1912 const char* library_name = si->strtab + d->d_un.d_val; 1913 DEBUG("%s needs %s", si->name, library_name); 1914 soinfo* lsi = find_library(library_name, 0, NULL); 1915 if (lsi == NULL) { 1916 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1917 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1918 library_name, si->name, tmp_err_buf); 1919 return false; 1920 } 1921 1922 si->add_child(lsi); 1923 *pneeded++ = lsi; 1924 } 1925 } 1926 *pneeded = NULL; 1927 1928#if !defined(__LP64__) 1929 if (si->has_text_relocations) { 1930 // Make segments writable to allow text relocations to work properly. We will later call 1931 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1932 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1933 "security hardening. Please fix.", si->name); 1934 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1935 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1936 si->name, strerror(errno)); 1937 return false; 1938 } 1939 } 1940#endif 1941 1942#if defined(USE_RELA) 1943 if (si->plt_rela != NULL) { 1944 DEBUG("[ relocating %s plt ]\n", si->name); 1945 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1946 return false; 1947 } 1948 } 1949 if (si->rela != NULL) { 1950 DEBUG("[ relocating %s ]\n", si->name); 1951 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1952 return false; 1953 } 1954 } 1955#else 1956 if (si->plt_rel != NULL) { 1957 DEBUG("[ relocating %s plt ]", si->name); 1958 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1959 return false; 1960 } 1961 } 1962 if (si->rel != NULL) { 1963 DEBUG("[ relocating %s ]", si->name); 1964 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1965 return false; 1966 } 1967 } 1968#endif 1969 1970#if defined(__mips__) 1971 if (!mips_relocate_got(si, needed)) { 1972 return false; 1973 } 1974#endif 1975 1976 si->flags |= FLAG_LINKED; 1977 DEBUG("[ finished linking %s ]", si->name); 1978 1979#if !defined(__LP64__) 1980 if (si->has_text_relocations) { 1981 // All relocations are done, we can protect our segments back to read-only. 1982 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1983 DL_ERR("can't protect segments for \"%s\": %s", 1984 si->name, strerror(errno)); 1985 return false; 1986 } 1987 } 1988#endif 1989 1990 /* We can also turn on GNU RELRO protection */ 1991 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1992 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1993 si->name, strerror(errno)); 1994 return false; 1995 } 1996 1997 /* Handle serializing/sharing the RELRO segment */ 1998 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1999 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 2000 extinfo->relro_fd) < 0) { 2001 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 2002 si->name, strerror(errno)); 2003 return false; 2004 } 2005 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 2006 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 2007 extinfo->relro_fd) < 0) { 2008 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 2009 si->name, strerror(errno)); 2010 return false; 2011 } 2012 } 2013 2014 notify_gdb_of_load(si); 2015 return true; 2016} 2017 2018/* 2019 * This function add vdso to internal dso list. 2020 * It helps to stack unwinding through signal handlers. 2021 * Also, it makes bionic more like glibc. 2022 */ 2023static void add_vdso(KernelArgumentBlock& args __unused) { 2024#if defined(AT_SYSINFO_EHDR) 2025 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 2026 if (ehdr_vdso == NULL) { 2027 return; 2028 } 2029 2030 soinfo* si = soinfo_alloc("[vdso]", NULL); 2031 2032 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 2033 si->phnum = ehdr_vdso->e_phnum; 2034 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 2035 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2036 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 2037 2038 soinfo_link_image(si, NULL); 2039#endif 2040} 2041 2042/* 2043 * This is linker soinfo for GDB. See details below. 2044 */ 2045static soinfo linker_soinfo_for_gdb; 2046 2047/* gdb expects the linker to be in the debug shared object list. 2048 * Without this, gdb has trouble locating the linker's ".text" 2049 * and ".plt" sections. Gdb could also potentially use this to 2050 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2051 * Don't use soinfo_alloc(), because the linker shouldn't 2052 * be on the soinfo list. 2053 */ 2054static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 2055#if defined(__LP64__) 2056 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 2057#else 2058 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 2059#endif 2060 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 2061 linker_soinfo_for_gdb.base = linker_base; 2062 2063 /* 2064 * Set the dynamic field in the link map otherwise gdb will complain with 2065 * the following: 2066 * warning: .dynamic section for "/system/bin/linker" is not at the 2067 * expected address (wrong library or version mismatch?) 2068 */ 2069 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2070 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2071 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2072 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2073 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2074} 2075 2076/* 2077 * This code is called after the linker has linked itself and 2078 * fixed it's own GOT. It is safe to make references to externs 2079 * and other non-local data at this point. 2080 */ 2081static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2082 /* NOTE: we store the args pointer on a special location 2083 * of the temporary TLS area in order to pass it to 2084 * the C Library's runtime initializer. 2085 * 2086 * The initializer must clear the slot and reset the TLS 2087 * to point to a different location to ensure that no other 2088 * shared library constructor can access it. 2089 */ 2090 __libc_init_tls(args); 2091 2092#if TIMING 2093 struct timeval t0, t1; 2094 gettimeofday(&t0, 0); 2095#endif 2096 2097 // Initialize environment functions, and get to the ELF aux vectors table. 2098 linker_env_init(args); 2099 2100 // If this is a setuid/setgid program, close the security hole described in 2101 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2102 if (get_AT_SECURE()) { 2103 nullify_closed_stdio(); 2104 } 2105 2106 debuggerd_init(); 2107 2108 // Get a few environment variables. 2109 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2110 if (LD_DEBUG != NULL) { 2111 g_ld_debug_verbosity = atoi(LD_DEBUG); 2112 } 2113 2114 // Normally, these are cleaned by linker_env_init, but the test 2115 // doesn't cost us anything. 2116 const char* ldpath_env = NULL; 2117 const char* ldpreload_env = NULL; 2118 if (!get_AT_SECURE()) { 2119 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2120 ldpreload_env = linker_env_get("LD_PRELOAD"); 2121 } 2122 2123 // Linker does not call constructors for its own 2124 // global variables so we need to initialize 2125 // the allocators explicitly. 2126 g_soinfo_allocator.init(); 2127 g_soinfo_links_allocator.init(); 2128 2129 INFO("[ android linker & debugger ]"); 2130 2131 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2132 if (si == NULL) { 2133 exit(EXIT_FAILURE); 2134 } 2135 2136 /* bootstrap the link map, the main exe always needs to be first */ 2137 si->flags |= FLAG_EXE; 2138 link_map* map = &(si->link_map_head); 2139 2140 map->l_addr = 0; 2141 map->l_name = args.argv[0]; 2142 map->l_prev = NULL; 2143 map->l_next = NULL; 2144 2145 _r_debug.r_map = map; 2146 r_debug_tail = map; 2147 2148 init_linker_info_for_gdb(linker_base); 2149 2150 // Extract information passed from the kernel. 2151 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2152 si->phnum = args.getauxval(AT_PHNUM); 2153 si->entry = args.getauxval(AT_ENTRY); 2154 2155 /* Compute the value of si->base. We can't rely on the fact that 2156 * the first entry is the PHDR because this will not be true 2157 * for certain executables (e.g. some in the NDK unit test suite) 2158 */ 2159 si->base = 0; 2160 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2161 si->load_bias = 0; 2162 for (size_t i = 0; i < si->phnum; ++i) { 2163 if (si->phdr[i].p_type == PT_PHDR) { 2164 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2165 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2166 break; 2167 } 2168 } 2169 si->dynamic = NULL; 2170 si->ref_count = 1; 2171 2172#if defined(__LP64__) 2173 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2174 if (elf_hdr->e_type != ET_DYN) { 2175 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2176 exit(EXIT_FAILURE); 2177 } 2178#endif 2179 2180 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2181 parse_LD_LIBRARY_PATH(ldpath_env); 2182 parse_LD_PRELOAD(ldpreload_env); 2183 2184 somain = si; 2185 2186 if (!soinfo_link_image(si, NULL)) { 2187 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2188 exit(EXIT_FAILURE); 2189 } 2190 2191 add_vdso(args); 2192 2193 si->CallPreInitConstructors(); 2194 2195 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2196 g_ld_preloads[i]->CallConstructors(); 2197 } 2198 2199 /* After the link_image, the si->load_bias is initialized. 2200 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2201 * We need to update this value for so exe here. So Unwind_Backtrace 2202 * for some arch like x86 could work correctly within so exe. 2203 */ 2204 map->l_addr = si->load_bias; 2205 si->CallConstructors(); 2206 2207#if TIMING 2208 gettimeofday(&t1, NULL); 2209 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2210 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2211 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2212#endif 2213#if STATS 2214 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2215 linker_stats.count[kRelocAbsolute], 2216 linker_stats.count[kRelocRelative], 2217 linker_stats.count[kRelocCopy], 2218 linker_stats.count[kRelocSymbol]); 2219#endif 2220#if COUNT_PAGES 2221 { 2222 unsigned n; 2223 unsigned i; 2224 unsigned count = 0; 2225 for (n = 0; n < 4096; n++) { 2226 if (bitmask[n]) { 2227 unsigned x = bitmask[n]; 2228#if defined(__LP64__) 2229 for (i = 0; i < 32; i++) { 2230#else 2231 for (i = 0; i < 8; i++) { 2232#endif 2233 if (x & 1) { 2234 count++; 2235 } 2236 x >>= 1; 2237 } 2238 } 2239 } 2240 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2241 } 2242#endif 2243 2244#if TIMING || STATS || COUNT_PAGES 2245 fflush(stdout); 2246#endif 2247 2248 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2249 return si->entry; 2250} 2251 2252/* Compute the load-bias of an existing executable. This shall only 2253 * be used to compute the load bias of an executable or shared library 2254 * that was loaded by the kernel itself. 2255 * 2256 * Input: 2257 * elf -> address of ELF header, assumed to be at the start of the file. 2258 * Return: 2259 * load bias, i.e. add the value of any p_vaddr in the file to get 2260 * the corresponding address in memory. 2261 */ 2262static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2263 ElfW(Addr) offset = elf->e_phoff; 2264 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2265 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2266 2267 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2268 if (phdr->p_type == PT_LOAD) { 2269 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2270 } 2271 } 2272 return 0; 2273} 2274 2275/* 2276 * This is the entry point for the linker, called from begin.S. This 2277 * method is responsible for fixing the linker's own relocations, and 2278 * then calling __linker_init_post_relocation(). 2279 * 2280 * Because this method is called before the linker has fixed it's own 2281 * relocations, any attempt to reference an extern variable, extern 2282 * function, or other GOT reference will generate a segfault. 2283 */ 2284extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2285 // Initialize static variables. 2286 solist = get_libdl_info(); 2287 sonext = get_libdl_info(); 2288 2289 KernelArgumentBlock args(raw_args); 2290 2291 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2292 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2293 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2294 2295 soinfo linker_so; 2296 memset(&linker_so, 0, sizeof(soinfo)); 2297 2298 strcpy(linker_so.name, "[dynamic linker]"); 2299 linker_so.base = linker_addr; 2300 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2301 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2302 linker_so.dynamic = NULL; 2303 linker_so.phdr = phdr; 2304 linker_so.phnum = elf_hdr->e_phnum; 2305 linker_so.flags |= FLAG_LINKER; 2306 2307 if (!soinfo_link_image(&linker_so, NULL)) { 2308 // It would be nice to print an error message, but if the linker 2309 // can't link itself, there's no guarantee that we'll be able to 2310 // call write() (because it involves a GOT reference). We may as 2311 // well try though... 2312 const char* msg = "CANNOT LINK EXECUTABLE: "; 2313 write(2, msg, strlen(msg)); 2314 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2315 write(2, "\n", 1); 2316 _exit(EXIT_FAILURE); 2317 } 2318 2319 // We have successfully fixed our own relocations. It's safe to run 2320 // the main part of the linker now. 2321 args.abort_message_ptr = &g_abort_message; 2322 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2323 2324 protect_data(PROT_READ); 2325 2326 // Return the address that the calling assembly stub should jump to. 2327 return start_address; 2328} 2329