linker.cpp revision 422106a24d620af4be58e8d92a2e9b7b6167b72d
1/* 2 * Copyright (C) 2008, 2009 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <dlfcn.h> 30#include <errno.h> 31#include <fcntl.h> 32#include <inttypes.h> 33#include <pthread.h> 34#include <stdio.h> 35#include <stdlib.h> 36#include <string.h> 37#include <sys/mman.h> 38#include <sys/stat.h> 39#include <unistd.h> 40 41// Private C library headers. 42#include "private/bionic_tls.h" 43#include "private/KernelArgumentBlock.h" 44#include "private/ScopedPthreadMutexLocker.h" 45#include "private/ScopedFd.h" 46 47#include "linker.h" 48#include "linker_debug.h" 49#include "linker_environ.h" 50#include "linker_phdr.h" 51#include "linker_allocator.h" 52 53/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< 54 * 55 * Do NOT use malloc() and friends or pthread_*() code here. 56 * Don't use printf() either; it's caused mysterious memory 57 * corruption in the past. 58 * The linker runs before we bring up libc and it's easiest 59 * to make sure it does not depend on any complex libc features 60 * 61 * open issues / todo: 62 * 63 * - cleaner error reporting 64 * - after linking, set as much stuff as possible to READONLY 65 * and NOEXEC 66 */ 67 68#if defined(__LP64__) 69#define SEARCH_NAME(x) x 70#else 71// Nvidia drivers are relying on the bug: 72// http://code.google.com/p/android/issues/detail?id=6670 73// so we continue to use base-name lookup for lp32 74static const char* get_base_name(const char* name) { 75 const char* bname = strrchr(name, '/'); 76 return bname ? bname + 1 : name; 77} 78#define SEARCH_NAME(x) get_base_name(x) 79#endif 80 81static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 82static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 83 84static LinkerAllocator<soinfo> g_soinfo_allocator; 85static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator; 86 87static soinfo* solist; 88static soinfo* sonext; 89static soinfo* somain; /* main process, always the one after libdl_info */ 90 91static const char* const kDefaultLdPaths[] = { 92#if defined(__LP64__) 93 "/vendor/lib64", 94 "/system/lib64", 95#else 96 "/vendor/lib", 97 "/system/lib", 98#endif 99 NULL 100}; 101 102#define LDPATH_BUFSIZE (LDPATH_MAX*64) 103#define LDPATH_MAX 8 104 105#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 106#define LDPRELOAD_MAX 8 107 108static char g_ld_library_paths_buffer[LDPATH_BUFSIZE]; 109static const char* g_ld_library_paths[LDPATH_MAX + 1]; 110 111static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE]; 112static const char* g_ld_preload_names[LDPRELOAD_MAX + 1]; 113 114static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1]; 115 116__LIBC_HIDDEN__ int g_ld_debug_verbosity; 117 118__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd. 119 120enum RelocationKind { 121 kRelocAbsolute = 0, 122 kRelocRelative, 123 kRelocCopy, 124 kRelocSymbol, 125 kRelocMax 126}; 127 128enum class SymbolLookupScope { 129 kAllowLocal, 130 kExcludeLocal, 131}; 132 133#if STATS 134struct linker_stats_t { 135 int count[kRelocMax]; 136}; 137 138static linker_stats_t linker_stats; 139 140static void count_relocation(RelocationKind kind) { 141 ++linker_stats.count[kind]; 142} 143#else 144static void count_relocation(RelocationKind) { 145} 146#endif 147 148#if COUNT_PAGES 149static unsigned bitmask[4096]; 150#if defined(__LP64__) 151#define MARK(offset) \ 152 do { \ 153 if ((((offset) >> 12) >> 5) < 4096) \ 154 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 155 } while (0) 156#else 157#define MARK(offset) \ 158 do { \ 159 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 160 } while (0) 161#endif 162#else 163#define MARK(x) do {} while (0) 164#endif 165 166// You shouldn't try to call memory-allocating functions in the dynamic linker. 167// Guard against the most obvious ones. 168#define DISALLOW_ALLOCATION(return_type, name, ...) \ 169 return_type name __VA_ARGS__ \ 170 { \ 171 __libc_fatal("ERROR: " #name " called from the dynamic linker!\n"); \ 172 } 173DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 174DISALLOW_ALLOCATION(void, free, (void* u __unused)); 175DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 176DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 177 178static char tmp_err_buf[768]; 179static char __linker_dl_err_buf[768]; 180 181char* linker_get_error_buffer() { 182 return &__linker_dl_err_buf[0]; 183} 184 185size_t linker_get_error_buffer_size() { 186 return sizeof(__linker_dl_err_buf); 187} 188 189/* 190 * This function is an empty stub where GDB locates a breakpoint to get notified 191 * about linker activity. 192 */ 193extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 194 195static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 196static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 197static link_map* r_debug_tail = 0; 198 199static void insert_soinfo_into_debug_map(soinfo* info) { 200 // Copy the necessary fields into the debug structure. 201 link_map* map = &(info->link_map_head); 202 map->l_addr = info->load_bias; 203 map->l_name = reinterpret_cast<char*>(info->name); 204 map->l_ld = info->dynamic; 205 206 /* Stick the new library at the end of the list. 207 * gdb tends to care more about libc than it does 208 * about leaf libraries, and ordering it this way 209 * reduces the back-and-forth over the wire. 210 */ 211 if (r_debug_tail) { 212 r_debug_tail->l_next = map; 213 map->l_prev = r_debug_tail; 214 map->l_next = 0; 215 } else { 216 _r_debug.r_map = map; 217 map->l_prev = 0; 218 map->l_next = 0; 219 } 220 r_debug_tail = map; 221} 222 223static void remove_soinfo_from_debug_map(soinfo* info) { 224 link_map* map = &(info->link_map_head); 225 226 if (r_debug_tail == map) { 227 r_debug_tail = map->l_prev; 228 } 229 230 if (map->l_prev) { 231 map->l_prev->l_next = map->l_next; 232 } 233 if (map->l_next) { 234 map->l_next->l_prev = map->l_prev; 235 } 236} 237 238static void notify_gdb_of_load(soinfo* info) { 239 if (info->flags & FLAG_EXE) { 240 // GDB already knows about the main executable 241 return; 242 } 243 244 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 245 246 _r_debug.r_state = r_debug::RT_ADD; 247 rtld_db_dlactivity(); 248 249 insert_soinfo_into_debug_map(info); 250 251 _r_debug.r_state = r_debug::RT_CONSISTENT; 252 rtld_db_dlactivity(); 253} 254 255static void notify_gdb_of_unload(soinfo* info) { 256 if (info->flags & FLAG_EXE) { 257 // GDB already knows about the main executable 258 return; 259 } 260 261 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 262 263 _r_debug.r_state = r_debug::RT_DELETE; 264 rtld_db_dlactivity(); 265 266 remove_soinfo_from_debug_map(info); 267 268 _r_debug.r_state = r_debug::RT_CONSISTENT; 269 rtld_db_dlactivity(); 270} 271 272void notify_gdb_of_libraries() { 273 _r_debug.r_state = r_debug::RT_ADD; 274 rtld_db_dlactivity(); 275 _r_debug.r_state = r_debug::RT_CONSISTENT; 276 rtld_db_dlactivity(); 277} 278 279LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 280 return g_soinfo_links_allocator.alloc(); 281} 282 283void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 284 g_soinfo_links_allocator.free(entry); 285} 286 287static void protect_data(int protection) { 288 g_soinfo_allocator.protect_all(protection); 289 g_soinfo_links_allocator.protect_all(protection); 290} 291 292static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 293 if (strlen(name) >= SOINFO_NAME_LEN) { 294 DL_ERR("library name \"%s\" too long", name); 295 return NULL; 296 } 297 298 soinfo* si = g_soinfo_allocator.alloc(); 299 300 // Initialize the new element. 301 memset(si, 0, sizeof(soinfo)); 302 strlcpy(si->name, name, sizeof(si->name)); 303 si->flags = FLAG_NEW_SOINFO; 304 305 if (file_stat != NULL) { 306 si->set_st_dev(file_stat->st_dev); 307 si->set_st_ino(file_stat->st_ino); 308 } 309 310 sonext->next = si; 311 sonext = si; 312 313 TRACE("name %s: allocated soinfo @ %p", name, si); 314 return si; 315} 316 317static void soinfo_free(soinfo* si) { 318 if (si == NULL) { 319 return; 320 } 321 322 if (si->base != 0 && si->size != 0) { 323 munmap(reinterpret_cast<void*>(si->base), si->size); 324 } 325 326 soinfo *prev = NULL, *trav; 327 328 TRACE("name %s: freeing soinfo @ %p", si->name, si); 329 330 for (trav = solist; trav != NULL; trav = trav->next) { 331 if (trav == si) 332 break; 333 prev = trav; 334 } 335 if (trav == NULL) { 336 /* si was not in solist */ 337 DL_ERR("name \"%s\" is not in solist!", si->name); 338 return; 339 } 340 341 // clear links to/from si 342 si->remove_all_links(); 343 344 /* prev will never be NULL, because the first entry in solist is 345 always the static libdl_info. 346 */ 347 prev->next = si->next; 348 if (si == sonext) { 349 sonext = prev; 350 } 351 352 g_soinfo_allocator.free(si); 353} 354 355 356static void parse_path(const char* path, const char* delimiters, 357 const char** array, char* buf, size_t buf_size, size_t max_count) { 358 if (path == NULL) { 359 return; 360 } 361 362 size_t len = strlcpy(buf, path, buf_size); 363 364 size_t i = 0; 365 char* buf_p = buf; 366 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 367 if (*array[i] != '\0') { 368 ++i; 369 } 370 } 371 372 // Forget the last path if we had to truncate; this occurs if the 2nd to 373 // last char isn't '\0' (i.e. wasn't originally a delimiter). 374 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 375 array[i - 1] = NULL; 376 } else { 377 array[i] = NULL; 378 } 379} 380 381static void parse_LD_LIBRARY_PATH(const char* path) { 382 parse_path(path, ":", g_ld_library_paths, 383 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 384} 385 386static void parse_LD_PRELOAD(const char* path) { 387 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 388 parse_path(path, " :", g_ld_preload_names, 389 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 390} 391 392#if defined(__arm__) 393 394/* For a given PC, find the .so that it belongs to. 395 * Returns the base address of the .ARM.exidx section 396 * for that .so, and the number of 8-byte entries 397 * in that section (via *pcount). 398 * 399 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 400 * 401 * This function is exposed via dlfcn.cpp and libdl.so. 402 */ 403_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 404 unsigned addr = (unsigned)pc; 405 406 for (soinfo* si = solist; si != 0; si = si->next) { 407 if ((addr >= si->base) && (addr < (si->base + si->size))) { 408 *pcount = si->ARM_exidx_count; 409 return (_Unwind_Ptr)si->ARM_exidx; 410 } 411 } 412 *pcount = 0; 413 return NULL; 414} 415 416#endif 417 418/* Here, we only have to provide a callback to iterate across all the 419 * loaded libraries. gcc_eh does the rest. */ 420int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 421 int rv = 0; 422 for (soinfo* si = solist; si != NULL; si = si->next) { 423 dl_phdr_info dl_info; 424 dl_info.dlpi_addr = si->link_map_head.l_addr; 425 dl_info.dlpi_name = si->link_map_head.l_name; 426 dl_info.dlpi_phdr = si->phdr; 427 dl_info.dlpi_phnum = si->phnum; 428 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 429 if (rv != 0) { 430 break; 431 } 432 } 433 return rv; 434} 435 436static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name, const SymbolLookupScope& lookup_scope) { 437 ElfW(Sym)* symtab = si->symtab; 438 const char* strtab = si->strtab; 439 440 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 441 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 442 443 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 444 ElfW(Sym)* s = symtab + n; 445 if (strcmp(strtab + s->st_name, name)) continue; 446 447 switch (ELF_ST_BIND(s->st_info)) { 448 case STB_GLOBAL: 449 case STB_WEAK: 450 if (s->st_shndx == SHN_UNDEF) { 451 continue; 452 } 453 454 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 455 name, si->name, reinterpret_cast<void*>(s->st_value), 456 static_cast<size_t>(s->st_size)); 457 return s; 458 case STB_LOCAL: 459 if (lookup_scope != SymbolLookupScope::kAllowLocal) { 460 continue; 461 } 462 TRACE_TYPE(LOOKUP, "FOUND LOCAL %s in %s (%p) %zd", 463 name, si->name, reinterpret_cast<void*>(s->st_value), 464 static_cast<size_t>(s->st_size)); 465 return s; 466 default: 467 __libc_fatal("ERROR: Unexpected ST_BIND value: %d for '%s' in '%s'", 468 ELF_ST_BIND(s->st_info), name, si->name); 469 } 470 } 471 472 TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd", 473 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 474 475 476 return NULL; 477} 478 479static unsigned elfhash(const char* _name) { 480 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 481 unsigned h = 0, g; 482 483 while (*name) { 484 h = (h << 4) + *name++; 485 g = h & 0xf0000000; 486 h ^= g; 487 h ^= g >> 24; 488 } 489 return h; 490} 491 492static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 493 unsigned elf_hash = elfhash(name); 494 ElfW(Sym)* s = NULL; 495 496 if (si != NULL && somain != NULL) { 497 /* 498 * Local scope is executable scope. Just start looking into it right away 499 * for the shortcut. 500 */ 501 502 if (si == somain) { 503 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 504 if (s != NULL) { 505 *lsi = si; 506 goto done; 507 } 508 } else { 509 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 510 511 /* 512 * If this object was built with symbolic relocations disabled, the 513 * first place to look to resolve external references is the main 514 * executable. 515 */ 516 517 if (!si->has_DT_SYMBOLIC) { 518 DEBUG("%s: looking up %s in executable %s", 519 si->name, name, somain->name); 520 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 521 if (s != NULL) { 522 *lsi = somain; 523 goto done; 524 } 525 } 526 527 /* Look for symbols in the local scope (the object who is 528 * searching). This happens with C++ templates on x86 for some 529 * reason. 530 * 531 * Notes on weak symbols: 532 * The ELF specs are ambiguous about treatment of weak definitions in 533 * dynamic linking. Some systems return the first definition found 534 * and some the first non-weak definition. This is system dependent. 535 * Here we return the first definition found for simplicity. */ 536 537 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 538 if (s != NULL) { 539 *lsi = si; 540 goto done; 541 } 542 543 /* 544 * If this object was built with -Bsymbolic and symbol is not found 545 * in the local scope, try to find the symbol in the main executable. 546 */ 547 548 if (si->has_DT_SYMBOLIC) { 549 DEBUG("%s: looking up %s in executable %s after local scope", 550 si->name, name, somain->name); 551 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 552 if (s != NULL) { 553 *lsi = somain; 554 goto done; 555 } 556 } 557 } 558 } 559 560 /* Next, look for it in the preloads list */ 561 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 562 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 563 if (s != NULL) { 564 *lsi = g_ld_preloads[i]; 565 goto done; 566 } 567 } 568 569 for (int i = 0; needed[i] != NULL; i++) { 570 DEBUG("%s: looking up %s in %s", 571 si->name, name, needed[i]->name); 572 s = soinfo_elf_lookup(needed[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 573 if (s != NULL) { 574 *lsi = needed[i]; 575 goto done; 576 } 577 } 578 579done: 580 if (s != NULL) { 581 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 582 "found in %s, base = %p, load bias = %p", 583 si->name, name, reinterpret_cast<void*>(s->st_value), 584 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 585 reinterpret_cast<void*>((*lsi)->load_bias)); 586 return s; 587 } 588 589 return NULL; 590} 591 592// Another soinfo list allocator to use in dlsym. We don't reuse 593// SoinfoListAllocator because it is write-protected most of the time. 594static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_list_allocator_rw; 595class SoinfoListAllocatorRW { 596 public: 597 static LinkedListEntry<soinfo>* alloc() { 598 return g_soinfo_list_allocator_rw.alloc(); 599 } 600 601 static void free(LinkedListEntry<soinfo>* ptr) { 602 g_soinfo_list_allocator_rw.free(ptr); 603 } 604}; 605 606// This is used by dlsym(3). It performs symbol lookup only within the 607// specified soinfo object and its dependencies in breadth first order. 608ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name, soinfo* caller) { 609 LinkedList<soinfo, SoinfoListAllocatorRW> visit_list; 610 visit_list.push_back(si); 611 soinfo* current_soinfo; 612 while ((current_soinfo = visit_list.pop_front()) != nullptr) { 613 ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name, 614 caller == current_soinfo ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 615 616 if (result != nullptr) { 617 *found = current_soinfo; 618 visit_list.clear(); 619 return result; 620 } 621 622 current_soinfo->get_children().for_each([&](soinfo* child) { 623 visit_list.push_back(child); 624 }); 625 } 626 627 visit_list.clear(); 628 return nullptr; 629} 630 631/* This is used by dlsym(3) to performs a global symbol lookup. If the 632 start value is null (for RTLD_DEFAULT), the search starts at the 633 beginning of the global solist. Otherwise the search starts at the 634 specified soinfo (for RTLD_NEXT). 635 */ 636ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start, soinfo* caller) { 637 unsigned elf_hash = elfhash(name); 638 639 if (start == NULL) { 640 start = solist; 641 } 642 643 ElfW(Sym)* s = NULL; 644 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 645 s = soinfo_elf_lookup(si, elf_hash, name, 646 caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 647 if (s != NULL) { 648 *found = si; 649 break; 650 } 651 } 652 653 if (s != NULL) { 654 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 655 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 656 } 657 658 return s; 659} 660 661soinfo* find_containing_library(const void* p) { 662 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 663 for (soinfo* si = solist; si != NULL; si = si->next) { 664 if (address >= si->base && address - si->base < si->size) { 665 return si; 666 } 667 } 668 return NULL; 669} 670 671ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 672 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 673 674 // Search the library's symbol table for any defined symbol which 675 // contains this address. 676 for (size_t i = 0; i < si->nchain; ++i) { 677 ElfW(Sym)* sym = &si->symtab[i]; 678 if (sym->st_shndx != SHN_UNDEF && 679 soaddr >= sym->st_value && 680 soaddr < sym->st_value + sym->st_size) { 681 return sym; 682 } 683 } 684 685 return NULL; 686} 687 688static int open_library_on_path(const char* name, const char* const paths[]) { 689 char buf[512]; 690 for (size_t i = 0; paths[i] != NULL; ++i) { 691 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 692 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 693 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 694 continue; 695 } 696 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 697 if (fd != -1) { 698 return fd; 699 } 700 } 701 return -1; 702} 703 704static int open_library(const char* name) { 705 TRACE("[ opening %s ]", name); 706 707 // If the name contains a slash, we should attempt to open it directly and not search the paths. 708 if (strchr(name, '/') != NULL) { 709 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 710 if (fd != -1) { 711 return fd; 712 } 713 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 714#if defined(__LP64__) 715 return -1; 716#endif 717 } 718 719 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 720 int fd = open_library_on_path(name, g_ld_library_paths); 721 if (fd == -1) { 722 fd = open_library_on_path(name, kDefaultLdPaths); 723 } 724 return fd; 725} 726 727static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 728 int fd = -1; 729 ScopedFd file_guard(-1); 730 731 if (extinfo != NULL && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) { 732 fd = extinfo->library_fd; 733 } else { 734 // Open the file. 735 fd = open_library(name); 736 if (fd == -1) { 737 DL_ERR("library \"%s\" not found", name); 738 return NULL; 739 } 740 741 file_guard.reset(fd); 742 } 743 744 ElfReader elf_reader(name, fd); 745 746 struct stat file_stat; 747 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 748 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 749 return NULL; 750 } 751 752 // Check for symlink and other situations where 753 // file can have different names. 754 for (soinfo* si = solist; si != NULL; si = si->next) { 755 if (si->get_st_dev() != 0 && 756 si->get_st_ino() != 0 && 757 si->get_st_dev() == file_stat.st_dev && 758 si->get_st_ino() == file_stat.st_ino) { 759 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 760 return si; 761 } 762 } 763 764 if ((dlflags & RTLD_NOLOAD) != 0) { 765 return NULL; 766 } 767 768 // Read the ELF header and load the segments. 769 if (!elf_reader.Load(extinfo)) { 770 return NULL; 771 } 772 773 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 774 if (si == NULL) { 775 return NULL; 776 } 777 si->base = elf_reader.load_start(); 778 si->size = elf_reader.load_size(); 779 si->load_bias = elf_reader.load_bias(); 780 si->phnum = elf_reader.phdr_count(); 781 si->phdr = elf_reader.loaded_phdr(); 782 783 // At this point we know that whatever is loaded @ base is a valid ELF 784 // shared library whose segments are properly mapped in. 785 TRACE("[ load_library base=%p size=%zu name='%s' ]", 786 reinterpret_cast<void*>(si->base), si->size, si->name); 787 788 if (!soinfo_link_image(si, extinfo)) { 789 soinfo_free(si); 790 return NULL; 791 } 792 793 return si; 794} 795 796static soinfo *find_loaded_library_by_name(const char* name) { 797 const char* search_name = SEARCH_NAME(name); 798 for (soinfo* si = solist; si != NULL; si = si->next) { 799 if (!strcmp(search_name, si->name)) { 800 return si; 801 } 802 } 803 return NULL; 804} 805 806static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 807 if (name == NULL) { 808 return somain; 809 } 810 811 soinfo* si = find_loaded_library_by_name(name); 812 813 // Library might still be loaded, the accurate detection 814 // of this fact is done by load_library 815 if (si == NULL) { 816 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 817 si = load_library(name, dlflags, extinfo); 818 } 819 820 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 821 DL_ERR("recursive link to \"%s\"", si->name); 822 return NULL; 823 } 824 825 return si; 826} 827 828static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 829 soinfo* si = find_library_internal(name, dlflags, extinfo); 830 if (si != NULL) { 831 si->ref_count++; 832 } 833 return si; 834} 835 836static void soinfo_unload(soinfo* si) { 837 if (si->ref_count == 1) { 838 TRACE("unloading '%s'", si->name); 839 si->CallDestructors(); 840 841 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 842 si->get_children().for_each([&] (soinfo* child) { 843 TRACE("%s needs to unload %s", si->name, child->name); 844 soinfo_unload(child); 845 }); 846 } else { 847 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 848 if (d->d_tag == DT_NEEDED) { 849 const char* library_name = si->strtab + d->d_un.d_val; 850 TRACE("%s needs to unload %s", si->name, library_name); 851 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 852 if (needed != NULL) { 853 soinfo_unload(needed); 854 } else { 855 // Not found: for example if symlink was deleted between dlopen and dlclose 856 // Since we cannot really handle errors at this point - print and continue. 857 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 858 } 859 } 860 } 861 } 862 863 notify_gdb_of_unload(si); 864 si->ref_count = 0; 865 soinfo_free(si); 866 } else { 867 si->ref_count--; 868 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 869 } 870} 871 872void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 873 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 874} 875 876void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 877 if (!get_AT_SECURE()) { 878 parse_LD_LIBRARY_PATH(ld_library_path); 879 } 880} 881 882soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 883 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 884 DL_ERR("invalid flags to dlopen: %x", flags); 885 return NULL; 886 } 887 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 888 DL_ERR("invalid extended flags to android_dlopen_ext: %" PRIx64, extinfo->flags); 889 return NULL; 890 } 891 protect_data(PROT_READ | PROT_WRITE); 892 soinfo* si = find_library(name, flags, extinfo); 893 if (si != NULL) { 894 si->CallConstructors(); 895 } 896 protect_data(PROT_READ); 897 return si; 898} 899 900void do_dlclose(soinfo* si) { 901 protect_data(PROT_READ | PROT_WRITE); 902 soinfo_unload(si); 903 protect_data(PROT_READ); 904} 905 906#if defined(USE_RELA) 907static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 908 ElfW(Sym)* s; 909 soinfo* lsi; 910 911 for (size_t idx = 0; idx < count; ++idx, ++rela) { 912 unsigned type = ELFW(R_TYPE)(rela->r_info); 913 unsigned sym = ELFW(R_SYM)(rela->r_info); 914 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 915 ElfW(Addr) sym_addr = 0; 916 const char* sym_name = NULL; 917 918 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 919 if (type == 0) { // R_*_NONE 920 continue; 921 } 922 if (sym != 0) { 923 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 924 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 925 if (s == NULL) { 926 // We only allow an undefined symbol if this is a weak reference... 927 s = &si->symtab[sym]; 928 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 929 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 930 return -1; 931 } 932 933 /* IHI0044C AAELF 4.5.1.1: 934 935 Libraries are not searched to resolve weak references. 936 It is not an error for a weak reference to remain unsatisfied. 937 938 During linking, the value of an undefined weak reference is: 939 - Zero if the relocation type is absolute 940 - The address of the place if the relocation is pc-relative 941 - The address of nominal base address if the relocation 942 type is base-relative. 943 */ 944 945 switch (type) { 946#if defined(__aarch64__) 947 case R_AARCH64_JUMP_SLOT: 948 case R_AARCH64_GLOB_DAT: 949 case R_AARCH64_ABS64: 950 case R_AARCH64_ABS32: 951 case R_AARCH64_ABS16: 952 case R_AARCH64_RELATIVE: 953 /* 954 * The sym_addr was initialized to be zero above, or the relocation 955 * code below does not care about value of sym_addr. 956 * No need to do anything. 957 */ 958 break; 959#elif defined(__x86_64__) 960 case R_X86_64_JUMP_SLOT: 961 case R_X86_64_GLOB_DAT: 962 case R_X86_64_32: 963 case R_X86_64_64: 964 case R_X86_64_RELATIVE: 965 // No need to do anything. 966 break; 967 case R_X86_64_PC32: 968 sym_addr = reloc; 969 break; 970#endif 971 default: 972 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 973 return -1; 974 } 975 } else { 976 // We got a definition. 977 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 978 } 979 count_relocation(kRelocSymbol); 980 } else { 981 s = NULL; 982 } 983 984 switch (type) { 985#if defined(__aarch64__) 986 case R_AARCH64_JUMP_SLOT: 987 count_relocation(kRelocAbsolute); 988 MARK(rela->r_offset); 989 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 990 reloc, (sym_addr + rela->r_addend), sym_name); 991 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 992 break; 993 case R_AARCH64_GLOB_DAT: 994 count_relocation(kRelocAbsolute); 995 MARK(rela->r_offset); 996 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 997 reloc, (sym_addr + rela->r_addend), sym_name); 998 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 999 break; 1000 case R_AARCH64_ABS64: 1001 count_relocation(kRelocAbsolute); 1002 MARK(rela->r_offset); 1003 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 1004 reloc, (sym_addr + rela->r_addend), sym_name); 1005 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1006 break; 1007 case R_AARCH64_ABS32: 1008 count_relocation(kRelocAbsolute); 1009 MARK(rela->r_offset); 1010 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 1011 reloc, (sym_addr + rela->r_addend), sym_name); 1012 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 1013 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1014 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1015 } else { 1016 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1017 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1018 static_cast<ElfW(Addr)>(INT32_MIN), 1019 static_cast<ElfW(Addr)>(UINT32_MAX)); 1020 return -1; 1021 } 1022 break; 1023 case R_AARCH64_ABS16: 1024 count_relocation(kRelocAbsolute); 1025 MARK(rela->r_offset); 1026 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 1027 reloc, (sym_addr + rela->r_addend), sym_name); 1028 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 1029 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1030 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1031 } else { 1032 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1033 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1034 static_cast<ElfW(Addr)>(INT16_MIN), 1035 static_cast<ElfW(Addr)>(UINT16_MAX)); 1036 return -1; 1037 } 1038 break; 1039 case R_AARCH64_PREL64: 1040 count_relocation(kRelocRelative); 1041 MARK(rela->r_offset); 1042 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 1043 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1044 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 1045 break; 1046 case R_AARCH64_PREL32: 1047 count_relocation(kRelocRelative); 1048 MARK(rela->r_offset); 1049 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 1050 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1051 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1052 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1053 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1054 } else { 1055 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1056 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1057 static_cast<ElfW(Addr)>(INT32_MIN), 1058 static_cast<ElfW(Addr)>(UINT32_MAX)); 1059 return -1; 1060 } 1061 break; 1062 case R_AARCH64_PREL16: 1063 count_relocation(kRelocRelative); 1064 MARK(rela->r_offset); 1065 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1066 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1067 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1068 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1069 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1070 } else { 1071 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1072 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1073 static_cast<ElfW(Addr)>(INT16_MIN), 1074 static_cast<ElfW(Addr)>(UINT16_MAX)); 1075 return -1; 1076 } 1077 break; 1078 1079 case R_AARCH64_RELATIVE: 1080 count_relocation(kRelocRelative); 1081 MARK(rela->r_offset); 1082 if (sym) { 1083 DL_ERR("odd RELATIVE form..."); 1084 return -1; 1085 } 1086 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1087 reloc, (si->base + rela->r_addend)); 1088 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1089 break; 1090 1091 case R_AARCH64_COPY: 1092 /* 1093 * ET_EXEC is not supported so this should not happen. 1094 * 1095 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1096 * 1097 * Section 4.7.1.10 "Dynamic relocations" 1098 * R_AARCH64_COPY may only appear in executable objects where e_type is 1099 * set to ET_EXEC. 1100 */ 1101 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name); 1102 return -1; 1103 case R_AARCH64_TLS_TPREL64: 1104 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1105 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1106 break; 1107 case R_AARCH64_TLS_DTPREL32: 1108 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1109 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1110 break; 1111#elif defined(__x86_64__) 1112 case R_X86_64_JUMP_SLOT: 1113 count_relocation(kRelocAbsolute); 1114 MARK(rela->r_offset); 1115 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1116 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1117 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1118 break; 1119 case R_X86_64_GLOB_DAT: 1120 count_relocation(kRelocAbsolute); 1121 MARK(rela->r_offset); 1122 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1123 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1124 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1125 break; 1126 case R_X86_64_RELATIVE: 1127 count_relocation(kRelocRelative); 1128 MARK(rela->r_offset); 1129 if (sym) { 1130 DL_ERR("odd RELATIVE form..."); 1131 return -1; 1132 } 1133 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1134 static_cast<size_t>(si->base)); 1135 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1136 break; 1137 case R_X86_64_32: 1138 count_relocation(kRelocRelative); 1139 MARK(rela->r_offset); 1140 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1141 static_cast<size_t>(sym_addr), sym_name); 1142 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1143 break; 1144 case R_X86_64_64: 1145 count_relocation(kRelocRelative); 1146 MARK(rela->r_offset); 1147 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1148 static_cast<size_t>(sym_addr), sym_name); 1149 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1150 break; 1151 case R_X86_64_PC32: 1152 count_relocation(kRelocRelative); 1153 MARK(rela->r_offset); 1154 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1155 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1156 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1157 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1158 break; 1159#endif 1160 1161 default: 1162 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1163 return -1; 1164 } 1165 } 1166 return 0; 1167} 1168 1169#else // REL, not RELA. 1170 1171static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1172 ElfW(Sym)* s; 1173 soinfo* lsi; 1174 1175 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1176 unsigned type = ELFW(R_TYPE)(rel->r_info); 1177 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1178 unsigned sym = ELFW(R_SYM)(rel->r_info); 1179 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1180 ElfW(Addr) sym_addr = 0; 1181 const char* sym_name = NULL; 1182 1183 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1184 if (type == 0) { // R_*_NONE 1185 continue; 1186 } 1187 if (sym != 0) { 1188 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1189 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1190 if (s == NULL) { 1191 // We only allow an undefined symbol if this is a weak reference... 1192 s = &si->symtab[sym]; 1193 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1194 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1195 return -1; 1196 } 1197 1198 /* IHI0044C AAELF 4.5.1.1: 1199 1200 Libraries are not searched to resolve weak references. 1201 It is not an error for a weak reference to remain 1202 unsatisfied. 1203 1204 During linking, the value of an undefined weak reference is: 1205 - Zero if the relocation type is absolute 1206 - The address of the place if the relocation is pc-relative 1207 - The address of nominal base address if the relocation 1208 type is base-relative. 1209 */ 1210 1211 switch (type) { 1212#if defined(__arm__) 1213 case R_ARM_JUMP_SLOT: 1214 case R_ARM_GLOB_DAT: 1215 case R_ARM_ABS32: 1216 case R_ARM_RELATIVE: /* Don't care. */ 1217 // sym_addr was initialized to be zero above or relocation 1218 // code below does not care about value of sym_addr. 1219 // No need to do anything. 1220 break; 1221#elif defined(__i386__) 1222 case R_386_JMP_SLOT: 1223 case R_386_GLOB_DAT: 1224 case R_386_32: 1225 case R_386_RELATIVE: /* Don't care. */ 1226 // sym_addr was initialized to be zero above or relocation 1227 // code below does not care about value of sym_addr. 1228 // No need to do anything. 1229 break; 1230 case R_386_PC32: 1231 sym_addr = reloc; 1232 break; 1233#endif 1234 1235#if defined(__arm__) 1236 case R_ARM_COPY: 1237 // Fall through. Can't really copy if weak symbol is not found at run-time. 1238#endif 1239 default: 1240 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1241 return -1; 1242 } 1243 } else { 1244 // We got a definition. 1245 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1246 } 1247 count_relocation(kRelocSymbol); 1248 } else { 1249 s = NULL; 1250 } 1251 1252 switch (type) { 1253#if defined(__arm__) 1254 case R_ARM_JUMP_SLOT: 1255 count_relocation(kRelocAbsolute); 1256 MARK(rel->r_offset); 1257 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1258 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1259 break; 1260 case R_ARM_GLOB_DAT: 1261 count_relocation(kRelocAbsolute); 1262 MARK(rel->r_offset); 1263 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1264 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1265 break; 1266 case R_ARM_ABS32: 1267 count_relocation(kRelocAbsolute); 1268 MARK(rel->r_offset); 1269 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1270 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1271 break; 1272 case R_ARM_REL32: 1273 count_relocation(kRelocRelative); 1274 MARK(rel->r_offset); 1275 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1276 reloc, sym_addr, rel->r_offset, sym_name); 1277 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1278 break; 1279 case R_ARM_COPY: 1280 /* 1281 * ET_EXEC is not supported so this should not happen. 1282 * 1283 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1284 * 1285 * Section 4.7.1.10 "Dynamic relocations" 1286 * R_ARM_COPY may only appear in executable objects where e_type is 1287 * set to ET_EXEC. 1288 */ 1289 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name); 1290 return -1; 1291#elif defined(__i386__) 1292 case R_386_JMP_SLOT: 1293 count_relocation(kRelocAbsolute); 1294 MARK(rel->r_offset); 1295 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1296 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1297 break; 1298 case R_386_GLOB_DAT: 1299 count_relocation(kRelocAbsolute); 1300 MARK(rel->r_offset); 1301 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1302 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1303 break; 1304 case R_386_32: 1305 count_relocation(kRelocRelative); 1306 MARK(rel->r_offset); 1307 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1308 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1309 break; 1310 case R_386_PC32: 1311 count_relocation(kRelocRelative); 1312 MARK(rel->r_offset); 1313 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1314 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1315 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1316 break; 1317#elif defined(__mips__) 1318 case R_MIPS_REL32: 1319#if defined(__LP64__) 1320 // MIPS Elf64_Rel entries contain compound relocations 1321 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1322 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1323 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1324 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1325 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1326 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1327 return -1; 1328 } 1329#endif 1330 count_relocation(kRelocAbsolute); 1331 MARK(rel->r_offset); 1332 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1333 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1334 if (s) { 1335 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1336 } else { 1337 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1338 } 1339 break; 1340#endif 1341 1342#if defined(__arm__) 1343 case R_ARM_RELATIVE: 1344#elif defined(__i386__) 1345 case R_386_RELATIVE: 1346#endif 1347 count_relocation(kRelocRelative); 1348 MARK(rel->r_offset); 1349 if (sym) { 1350 DL_ERR("odd RELATIVE form..."); 1351 return -1; 1352 } 1353 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1354 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1355 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1356 break; 1357 1358 default: 1359 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1360 return -1; 1361 } 1362 } 1363 return 0; 1364} 1365#endif 1366 1367#if defined(__mips__) 1368static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1369 ElfW(Addr)** got = si->plt_got; 1370 if (got == NULL) { 1371 return true; 1372 } 1373 unsigned local_gotno = si->mips_local_gotno; 1374 unsigned gotsym = si->mips_gotsym; 1375 unsigned symtabno = si->mips_symtabno; 1376 ElfW(Sym)* symtab = si->symtab; 1377 1378 // got[0] is the address of the lazy resolver function. 1379 // got[1] may be used for a GNU extension. 1380 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1381 // FIXME: maybe this should be in a separate routine? 1382 if ((si->flags & FLAG_LINKER) == 0) { 1383 size_t g = 0; 1384 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1385 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1386 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1387 } 1388 // Relocate the local GOT entries. 1389 for (; g < local_gotno; g++) { 1390 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1391 } 1392 } 1393 1394 // Now for the global GOT entries... 1395 ElfW(Sym)* sym = symtab + gotsym; 1396 got = si->plt_got + local_gotno; 1397 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1398 // This is an undefined reference... try to locate it. 1399 const char* sym_name = si->strtab + sym->st_name; 1400 soinfo* lsi; 1401 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1402 if (s == NULL) { 1403 // We only allow an undefined symbol if this is a weak reference. 1404 s = &symtab[g]; 1405 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1406 DL_ERR("cannot locate \"%s\"...", sym_name); 1407 return false; 1408 } 1409 *got = 0; 1410 } else { 1411 // FIXME: is this sufficient? 1412 // For reference see NetBSD link loader 1413 // 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 1414 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1415 } 1416 } 1417 return true; 1418} 1419#endif 1420 1421void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1422 if (functions == NULL) { 1423 return; 1424 } 1425 1426 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1427 1428 int begin = reverse ? (count - 1) : 0; 1429 int end = reverse ? -1 : count; 1430 int step = reverse ? -1 : 1; 1431 1432 for (int i = begin; i != end; i += step) { 1433 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1434 CallFunction("function", functions[i]); 1435 } 1436 1437 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1438} 1439 1440void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1441 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1442 return; 1443 } 1444 1445 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1446 function(); 1447 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1448 1449 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1450 // are still writable. This happens with our debug malloc (see http://b/7941716). 1451 protect_data(PROT_READ | PROT_WRITE); 1452} 1453 1454void soinfo::CallPreInitConstructors() { 1455 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1456 // but ignored in a shared library. 1457 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1458} 1459 1460void soinfo::CallConstructors() { 1461 if (constructors_called) { 1462 return; 1463 } 1464 1465 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1466 // protect against recursive constructor calls. One simple example of constructor recursion 1467 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1468 // 1. The program depends on libc, so libc's constructor is called here. 1469 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1470 // 3. dlopen() calls the constructors on the newly created 1471 // soinfo for libc_malloc_debug_leak.so. 1472 // 4. The debug .so depends on libc, so CallConstructors is 1473 // called again with the libc soinfo. If it doesn't trigger the early- 1474 // out above, the libc constructor will be called again (recursively!). 1475 constructors_called = true; 1476 1477 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1478 // The GNU dynamic linker silently ignores these, but we warn the developer. 1479 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1480 name, preinit_array_count); 1481 } 1482 1483 get_children().for_each([] (soinfo* si) { 1484 si->CallConstructors(); 1485 }); 1486 1487 TRACE("\"%s\": calling constructors", name); 1488 1489 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1490 CallFunction("DT_INIT", init_func); 1491 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1492} 1493 1494void soinfo::CallDestructors() { 1495 TRACE("\"%s\": calling destructors", name); 1496 1497 // DT_FINI_ARRAY must be parsed in reverse order. 1498 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1499 1500 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1501 CallFunction("DT_FINI", fini_func); 1502 1503 // This is needed on second call to dlopen 1504 // after library has been unloaded with RTLD_NODELETE 1505 constructors_called = false; 1506} 1507 1508void soinfo::add_child(soinfo* child) { 1509 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1510 return; 1511 } 1512 1513 this->children.push_front(child); 1514 child->parents.push_front(this); 1515} 1516 1517void soinfo::remove_all_links() { 1518 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1519 return; 1520 } 1521 1522 // 1. Untie connected soinfos from 'this'. 1523 children.for_each([&] (soinfo* child) { 1524 child->parents.remove_if([&] (const soinfo* parent) { 1525 return parent == this; 1526 }); 1527 }); 1528 1529 parents.for_each([&] (soinfo* parent) { 1530 parent->children.for_each([&] (const soinfo* child) { 1531 return child == this; 1532 }); 1533 }); 1534 1535 // 2. Once everything untied - clear local lists. 1536 parents.clear(); 1537 children.clear(); 1538} 1539 1540void soinfo::set_st_dev(dev_t dev) { 1541 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1542 return; 1543 } 1544 1545 st_dev = dev; 1546} 1547 1548void soinfo::set_st_ino(ino_t ino) { 1549 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1550 return; 1551 } 1552 1553 st_ino = ino; 1554} 1555 1556dev_t soinfo::get_st_dev() { 1557 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1558 return 0; 1559 } 1560 1561 return st_dev; 1562}; 1563 1564ino_t soinfo::get_st_ino() { 1565 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1566 return 0; 1567 } 1568 1569 return st_ino; 1570} 1571 1572// This is a return on get_children() in case 1573// 'this->flags' does not have FLAG_NEW_SOINFO set. 1574static soinfo::soinfo_list_t g_empty_list; 1575 1576soinfo::soinfo_list_t& soinfo::get_children() { 1577 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1578 return g_empty_list; 1579 } 1580 1581 return this->children; 1582} 1583 1584/* Force any of the closed stdin, stdout and stderr to be associated with 1585 /dev/null. */ 1586static int nullify_closed_stdio() { 1587 int dev_null, i, status; 1588 int return_value = 0; 1589 1590 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1591 if (dev_null < 0) { 1592 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1593 return -1; 1594 } 1595 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1596 1597 /* If any of the stdio file descriptors is valid and not associated 1598 with /dev/null, dup /dev/null to it. */ 1599 for (i = 0; i < 3; i++) { 1600 /* If it is /dev/null already, we are done. */ 1601 if (i == dev_null) { 1602 continue; 1603 } 1604 1605 TRACE("[ Nullifying stdio file descriptor %d]", i); 1606 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1607 1608 /* If file is opened, we are good. */ 1609 if (status != -1) { 1610 continue; 1611 } 1612 1613 /* The only error we allow is that the file descriptor does not 1614 exist, in which case we dup /dev/null to it. */ 1615 if (errno != EBADF) { 1616 DL_ERR("fcntl failed: %s", strerror(errno)); 1617 return_value = -1; 1618 continue; 1619 } 1620 1621 /* Try dupping /dev/null to this stdio file descriptor and 1622 repeat if there is a signal. Note that any errors in closing 1623 the stdio descriptor are lost. */ 1624 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1625 if (status < 0) { 1626 DL_ERR("dup2 failed: %s", strerror(errno)); 1627 return_value = -1; 1628 continue; 1629 } 1630 } 1631 1632 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1633 if (dev_null > 2) { 1634 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1635 status = TEMP_FAILURE_RETRY(close(dev_null)); 1636 if (status == -1) { 1637 DL_ERR("close failed: %s", strerror(errno)); 1638 return_value = -1; 1639 } 1640 } 1641 1642 return return_value; 1643} 1644 1645static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1646 /* "base" might wrap around UINT32_MAX. */ 1647 ElfW(Addr) base = si->load_bias; 1648 const ElfW(Phdr)* phdr = si->phdr; 1649 int phnum = si->phnum; 1650 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1651 1652 /* We can't debug anything until the linker is relocated */ 1653 if (!relocating_linker) { 1654 INFO("[ linking %s ]", si->name); 1655 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1656 } 1657 1658 /* Extract dynamic section */ 1659 size_t dynamic_count; 1660 ElfW(Word) dynamic_flags; 1661 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1662 &dynamic_count, &dynamic_flags); 1663 if (si->dynamic == NULL) { 1664 if (!relocating_linker) { 1665 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1666 } 1667 return false; 1668 } else { 1669 if (!relocating_linker) { 1670 DEBUG("dynamic = %p", si->dynamic); 1671 } 1672 } 1673 1674#if defined(__arm__) 1675 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1676 &si->ARM_exidx, &si->ARM_exidx_count); 1677#endif 1678 1679 // Extract useful information from dynamic section. 1680 uint32_t needed_count = 0; 1681 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1682 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1683 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1684 switch (d->d_tag) { 1685 case DT_HASH: 1686 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1687 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1688 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1689 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1690 break; 1691 case DT_STRTAB: 1692 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1693 break; 1694 case DT_SYMTAB: 1695 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1696 break; 1697#if !defined(__LP64__) 1698 case DT_PLTREL: 1699 if (d->d_un.d_val != DT_REL) { 1700 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1701 return false; 1702 } 1703 break; 1704#endif 1705 case DT_JMPREL: 1706#if defined(USE_RELA) 1707 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1708#else 1709 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1710#endif 1711 break; 1712 case DT_PLTRELSZ: 1713#if defined(USE_RELA) 1714 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1715#else 1716 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1717#endif 1718 break; 1719#if defined(__mips__) 1720 case DT_PLTGOT: 1721 // Used by mips and mips64. 1722 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1723 break; 1724#endif 1725 case DT_DEBUG: 1726 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1727 // if the dynamic table is writable 1728// FIXME: not working currently for N64 1729// The flags for the LOAD and DYNAMIC program headers do not agree. 1730// The LOAD section containng the dynamic table has been mapped as 1731// read-only, but the DYNAMIC header claims it is writable. 1732#if !(defined(__mips__) && defined(__LP64__)) 1733 if ((dynamic_flags & PF_W) != 0) { 1734 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1735 } 1736 break; 1737#endif 1738#if defined(USE_RELA) 1739 case DT_RELA: 1740 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1741 break; 1742 case DT_RELASZ: 1743 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1744 break; 1745 case DT_REL: 1746 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1747 return false; 1748 case DT_RELSZ: 1749 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1750 return false; 1751#else 1752 case DT_REL: 1753 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1754 break; 1755 case DT_RELSZ: 1756 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1757 break; 1758 case DT_RELA: 1759 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1760 return false; 1761#endif 1762 case DT_INIT: 1763 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1764 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1765 break; 1766 case DT_FINI: 1767 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1768 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1769 break; 1770 case DT_INIT_ARRAY: 1771 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1772 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1773 break; 1774 case DT_INIT_ARRAYSZ: 1775 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1776 break; 1777 case DT_FINI_ARRAY: 1778 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1779 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1780 break; 1781 case DT_FINI_ARRAYSZ: 1782 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1783 break; 1784 case DT_PREINIT_ARRAY: 1785 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1786 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1787 break; 1788 case DT_PREINIT_ARRAYSZ: 1789 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1790 break; 1791 case DT_TEXTREL: 1792#if defined(__LP64__) 1793 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1794 return false; 1795#else 1796 si->has_text_relocations = true; 1797 break; 1798#endif 1799 case DT_SYMBOLIC: 1800 si->has_DT_SYMBOLIC = true; 1801 break; 1802 case DT_NEEDED: 1803 ++needed_count; 1804 break; 1805 case DT_FLAGS: 1806 if (d->d_un.d_val & DF_TEXTREL) { 1807#if defined(__LP64__) 1808 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1809 return false; 1810#else 1811 si->has_text_relocations = true; 1812#endif 1813 } 1814 if (d->d_un.d_val & DF_SYMBOLIC) { 1815 si->has_DT_SYMBOLIC = true; 1816 } 1817 break; 1818#if defined(__mips__) 1819 case DT_STRSZ: 1820 case DT_SYMENT: 1821 case DT_RELENT: 1822 break; 1823 case DT_MIPS_RLD_MAP: 1824 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1825 { 1826 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1827 *dp = &_r_debug; 1828 } 1829 break; 1830 case DT_MIPS_RLD_VERSION: 1831 case DT_MIPS_FLAGS: 1832 case DT_MIPS_BASE_ADDRESS: 1833 case DT_MIPS_UNREFEXTNO: 1834 break; 1835 1836 case DT_MIPS_SYMTABNO: 1837 si->mips_symtabno = d->d_un.d_val; 1838 break; 1839 1840 case DT_MIPS_LOCAL_GOTNO: 1841 si->mips_local_gotno = d->d_un.d_val; 1842 break; 1843 1844 case DT_MIPS_GOTSYM: 1845 si->mips_gotsym = d->d_un.d_val; 1846 break; 1847#endif 1848 1849 default: 1850 DEBUG("Unused DT entry: type %p arg %p", 1851 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1852 break; 1853 } 1854 } 1855 1856 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1857 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1858 1859 // Sanity checks. 1860 if (relocating_linker && needed_count != 0) { 1861 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1862 return false; 1863 } 1864 if (si->nbucket == 0) { 1865 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1866 return false; 1867 } 1868 if (si->strtab == 0) { 1869 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1870 return false; 1871 } 1872 if (si->symtab == 0) { 1873 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1874 return false; 1875 } 1876 1877 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1878 if (si->flags & FLAG_EXE) { 1879 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1880 size_t preload_count = 0; 1881 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1882 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1883 if (lsi != NULL) { 1884 g_ld_preloads[preload_count++] = lsi; 1885 } else { 1886 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1887 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1888 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1889 } 1890 } 1891 } 1892 1893 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1894 soinfo** pneeded = needed; 1895 1896 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1897 if (d->d_tag == DT_NEEDED) { 1898 const char* library_name = si->strtab + d->d_un.d_val; 1899 DEBUG("%s needs %s", si->name, library_name); 1900 soinfo* lsi = find_library(library_name, 0, NULL); 1901 if (lsi == NULL) { 1902 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1903 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1904 library_name, si->name, tmp_err_buf); 1905 return false; 1906 } 1907 1908 si->add_child(lsi); 1909 *pneeded++ = lsi; 1910 } 1911 } 1912 *pneeded = NULL; 1913 1914#if !defined(__LP64__) 1915 if (si->has_text_relocations) { 1916 // Make segments writable to allow text relocations to work properly. We will later call 1917 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1918 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1919 "security hardening. Please fix.", si->name); 1920 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1921 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1922 si->name, strerror(errno)); 1923 return false; 1924 } 1925 } 1926#endif 1927 1928#if defined(USE_RELA) 1929 if (si->plt_rela != NULL) { 1930 DEBUG("[ relocating %s plt ]\n", si->name); 1931 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1932 return false; 1933 } 1934 } 1935 if (si->rela != NULL) { 1936 DEBUG("[ relocating %s ]\n", si->name); 1937 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1938 return false; 1939 } 1940 } 1941#else 1942 if (si->plt_rel != NULL) { 1943 DEBUG("[ relocating %s plt ]", si->name); 1944 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1945 return false; 1946 } 1947 } 1948 if (si->rel != NULL) { 1949 DEBUG("[ relocating %s ]", si->name); 1950 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1951 return false; 1952 } 1953 } 1954#endif 1955 1956#if defined(__mips__) 1957 if (!mips_relocate_got(si, needed)) { 1958 return false; 1959 } 1960#endif 1961 1962 si->flags |= FLAG_LINKED; 1963 DEBUG("[ finished linking %s ]", si->name); 1964 1965#if !defined(__LP64__) 1966 if (si->has_text_relocations) { 1967 // All relocations are done, we can protect our segments back to read-only. 1968 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1969 DL_ERR("can't protect segments for \"%s\": %s", 1970 si->name, strerror(errno)); 1971 return false; 1972 } 1973 } 1974#endif 1975 1976 /* We can also turn on GNU RELRO protection */ 1977 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1978 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1979 si->name, strerror(errno)); 1980 return false; 1981 } 1982 1983 /* Handle serializing/sharing the RELRO segment */ 1984 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1985 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1986 extinfo->relro_fd) < 0) { 1987 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1988 si->name, strerror(errno)); 1989 return false; 1990 } 1991 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1992 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1993 extinfo->relro_fd) < 0) { 1994 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1995 si->name, strerror(errno)); 1996 return false; 1997 } 1998 } 1999 2000 notify_gdb_of_load(si); 2001 return true; 2002} 2003 2004/* 2005 * This function add vdso to internal dso list. 2006 * It helps to stack unwinding through signal handlers. 2007 * Also, it makes bionic more like glibc. 2008 */ 2009static void add_vdso(KernelArgumentBlock& args __unused) { 2010#if defined(AT_SYSINFO_EHDR) 2011 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 2012 if (ehdr_vdso == NULL) { 2013 return; 2014 } 2015 2016 soinfo* si = soinfo_alloc("[vdso]", NULL); 2017 2018 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 2019 si->phnum = ehdr_vdso->e_phnum; 2020 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 2021 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2022 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 2023 2024 soinfo_link_image(si, NULL); 2025#endif 2026} 2027 2028/* 2029 * This is linker soinfo for GDB. See details below. 2030 */ 2031static soinfo linker_soinfo_for_gdb; 2032 2033/* gdb expects the linker to be in the debug shared object list. 2034 * Without this, gdb has trouble locating the linker's ".text" 2035 * and ".plt" sections. Gdb could also potentially use this to 2036 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2037 * Don't use soinfo_alloc(), because the linker shouldn't 2038 * be on the soinfo list. 2039 */ 2040static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 2041#if defined(__LP64__) 2042 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 2043#else 2044 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 2045#endif 2046 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 2047 linker_soinfo_for_gdb.base = linker_base; 2048 2049 /* 2050 * Set the dynamic field in the link map otherwise gdb will complain with 2051 * the following: 2052 * warning: .dynamic section for "/system/bin/linker" is not at the 2053 * expected address (wrong library or version mismatch?) 2054 */ 2055 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2056 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2057 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2058 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2059 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2060} 2061 2062/* 2063 * This code is called after the linker has linked itself and 2064 * fixed it's own GOT. It is safe to make references to externs 2065 * and other non-local data at this point. 2066 */ 2067static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2068 /* NOTE: we store the args pointer on a special location 2069 * of the temporary TLS area in order to pass it to 2070 * the C Library's runtime initializer. 2071 * 2072 * The initializer must clear the slot and reset the TLS 2073 * to point to a different location to ensure that no other 2074 * shared library constructor can access it. 2075 */ 2076 __libc_init_tls(args); 2077 2078#if TIMING 2079 struct timeval t0, t1; 2080 gettimeofday(&t0, 0); 2081#endif 2082 2083 // Initialize environment functions, and get to the ELF aux vectors table. 2084 linker_env_init(args); 2085 2086 // If this is a setuid/setgid program, close the security hole described in 2087 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2088 if (get_AT_SECURE()) { 2089 nullify_closed_stdio(); 2090 } 2091 2092 debuggerd_init(); 2093 2094 // Get a few environment variables. 2095 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2096 if (LD_DEBUG != NULL) { 2097 g_ld_debug_verbosity = atoi(LD_DEBUG); 2098 } 2099 2100 // Normally, these are cleaned by linker_env_init, but the test 2101 // doesn't cost us anything. 2102 const char* ldpath_env = NULL; 2103 const char* ldpreload_env = NULL; 2104 if (!get_AT_SECURE()) { 2105 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2106 ldpreload_env = linker_env_get("LD_PRELOAD"); 2107 } 2108 2109 INFO("[ android linker & debugger ]"); 2110 2111 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2112 if (si == NULL) { 2113 exit(EXIT_FAILURE); 2114 } 2115 2116 /* bootstrap the link map, the main exe always needs to be first */ 2117 si->flags |= FLAG_EXE; 2118 link_map* map = &(si->link_map_head); 2119 2120 map->l_addr = 0; 2121 map->l_name = args.argv[0]; 2122 map->l_prev = NULL; 2123 map->l_next = NULL; 2124 2125 _r_debug.r_map = map; 2126 r_debug_tail = map; 2127 2128 init_linker_info_for_gdb(linker_base); 2129 2130 // Extract information passed from the kernel. 2131 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2132 si->phnum = args.getauxval(AT_PHNUM); 2133 si->entry = args.getauxval(AT_ENTRY); 2134 2135 /* Compute the value of si->base. We can't rely on the fact that 2136 * the first entry is the PHDR because this will not be true 2137 * for certain executables (e.g. some in the NDK unit test suite) 2138 */ 2139 si->base = 0; 2140 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2141 si->load_bias = 0; 2142 for (size_t i = 0; i < si->phnum; ++i) { 2143 if (si->phdr[i].p_type == PT_PHDR) { 2144 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2145 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2146 break; 2147 } 2148 } 2149 si->dynamic = NULL; 2150 si->ref_count = 1; 2151 2152 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2153 if (elf_hdr->e_type != ET_DYN) { 2154 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2155 exit(EXIT_FAILURE); 2156 } 2157 2158 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2159 parse_LD_LIBRARY_PATH(ldpath_env); 2160 parse_LD_PRELOAD(ldpreload_env); 2161 2162 somain = si; 2163 2164 if (!soinfo_link_image(si, NULL)) { 2165 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2166 exit(EXIT_FAILURE); 2167 } 2168 2169 add_vdso(args); 2170 2171 si->CallPreInitConstructors(); 2172 2173 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2174 g_ld_preloads[i]->CallConstructors(); 2175 } 2176 2177 /* After the link_image, the si->load_bias is initialized. 2178 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2179 * We need to update this value for so exe here. So Unwind_Backtrace 2180 * for some arch like x86 could work correctly within so exe. 2181 */ 2182 map->l_addr = si->load_bias; 2183 si->CallConstructors(); 2184 2185#if TIMING 2186 gettimeofday(&t1, NULL); 2187 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2188 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2189 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2190#endif 2191#if STATS 2192 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2193 linker_stats.count[kRelocAbsolute], 2194 linker_stats.count[kRelocRelative], 2195 linker_stats.count[kRelocCopy], 2196 linker_stats.count[kRelocSymbol]); 2197#endif 2198#if COUNT_PAGES 2199 { 2200 unsigned n; 2201 unsigned i; 2202 unsigned count = 0; 2203 for (n = 0; n < 4096; n++) { 2204 if (bitmask[n]) { 2205 unsigned x = bitmask[n]; 2206#if defined(__LP64__) 2207 for (i = 0; i < 32; i++) { 2208#else 2209 for (i = 0; i < 8; i++) { 2210#endif 2211 if (x & 1) { 2212 count++; 2213 } 2214 x >>= 1; 2215 } 2216 } 2217 } 2218 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2219 } 2220#endif 2221 2222#if TIMING || STATS || COUNT_PAGES 2223 fflush(stdout); 2224#endif 2225 2226 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2227 return si->entry; 2228} 2229 2230/* Compute the load-bias of an existing executable. This shall only 2231 * be used to compute the load bias of an executable or shared library 2232 * that was loaded by the kernel itself. 2233 * 2234 * Input: 2235 * elf -> address of ELF header, assumed to be at the start of the file. 2236 * Return: 2237 * load bias, i.e. add the value of any p_vaddr in the file to get 2238 * the corresponding address in memory. 2239 */ 2240static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2241 ElfW(Addr) offset = elf->e_phoff; 2242 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2243 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2244 2245 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2246 if (phdr->p_type == PT_LOAD) { 2247 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2248 } 2249 } 2250 return 0; 2251} 2252 2253extern "C" void _start(); 2254 2255/* 2256 * This is the entry point for the linker, called from begin.S. This 2257 * method is responsible for fixing the linker's own relocations, and 2258 * then calling __linker_init_post_relocation(). 2259 * 2260 * Because this method is called before the linker has fixed it's own 2261 * relocations, any attempt to reference an extern variable, extern 2262 * function, or other GOT reference will generate a segfault. 2263 */ 2264extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2265 // Initialize static variables. 2266 solist = get_libdl_info(); 2267 sonext = get_libdl_info(); 2268 2269 KernelArgumentBlock args(raw_args); 2270 2271 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2272 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY); 2273 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2274 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2275 2276 soinfo linker_so; 2277 memset(&linker_so, 0, sizeof(soinfo)); 2278 2279 // If the linker is not acting as PT_INTERP entry_point is equal to 2280 // _start. Which means that the linker is running as an executable and 2281 // already linked by PT_INTERP. 2282 // 2283 // This happens when user tries to run 'adb shell /system/bin/linker' 2284 // see also https://code.google.com/p/android/issues/detail?id=63174 2285 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) { 2286 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]); 2287 } 2288 2289 strcpy(linker_so.name, "[dynamic linker]"); 2290 linker_so.base = linker_addr; 2291 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2292 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2293 linker_so.dynamic = NULL; 2294 linker_so.phdr = phdr; 2295 linker_so.phnum = elf_hdr->e_phnum; 2296 linker_so.flags |= FLAG_LINKER; 2297 2298 if (!soinfo_link_image(&linker_so, NULL)) { 2299 // It would be nice to print an error message, but if the linker 2300 // can't link itself, there's no guarantee that we'll be able to 2301 // call write() (because it involves a GOT reference). We may as 2302 // well try though... 2303 const char* msg = "CANNOT LINK EXECUTABLE: "; 2304 write(2, msg, strlen(msg)); 2305 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2306 write(2, "\n", 1); 2307 _exit(EXIT_FAILURE); 2308 } 2309 2310 // Initialize the linker's own global variables 2311 linker_so.CallConstructors(); 2312 2313 // We have successfully fixed our own relocations. It's safe to run 2314 // the main part of the linker now. 2315 args.abort_message_ptr = &g_abort_message; 2316 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2317 2318 protect_data(PROT_READ); 2319 2320 // Return the address that the calling assembly stub should jump to. 2321 return start_address; 2322} 2323