linker.cpp revision d97e9f546ea195686a78e539315b273393609b9e
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 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 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 172 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 173 write(2, msg, strlen(msg)); \ 174 abort(); \ 175 } 176DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 177DISALLOW_ALLOCATION(void, free, (void* u __unused)); 178DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 179DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 180 181static char tmp_err_buf[768]; 182static char __linker_dl_err_buf[768]; 183 184char* linker_get_error_buffer() { 185 return &__linker_dl_err_buf[0]; 186} 187 188size_t linker_get_error_buffer_size() { 189 return sizeof(__linker_dl_err_buf); 190} 191 192/* 193 * This function is an empty stub where GDB locates a breakpoint to get notified 194 * about linker activity. 195 */ 196extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 197 198static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 199static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 200static link_map* r_debug_tail = 0; 201 202static void insert_soinfo_into_debug_map(soinfo* info) { 203 // Copy the necessary fields into the debug structure. 204 link_map* map = &(info->link_map_head); 205 map->l_addr = info->load_bias; 206 map->l_name = reinterpret_cast<char*>(info->name); 207 map->l_ld = info->dynamic; 208 209 /* Stick the new library at the end of the list. 210 * gdb tends to care more about libc than it does 211 * about leaf libraries, and ordering it this way 212 * reduces the back-and-forth over the wire. 213 */ 214 if (r_debug_tail) { 215 r_debug_tail->l_next = map; 216 map->l_prev = r_debug_tail; 217 map->l_next = 0; 218 } else { 219 _r_debug.r_map = map; 220 map->l_prev = 0; 221 map->l_next = 0; 222 } 223 r_debug_tail = map; 224} 225 226static void remove_soinfo_from_debug_map(soinfo* info) { 227 link_map* map = &(info->link_map_head); 228 229 if (r_debug_tail == map) { 230 r_debug_tail = map->l_prev; 231 } 232 233 if (map->l_prev) { 234 map->l_prev->l_next = map->l_next; 235 } 236 if (map->l_next) { 237 map->l_next->l_prev = map->l_prev; 238 } 239} 240 241static void notify_gdb_of_load(soinfo* info) { 242 if (info->flags & FLAG_EXE) { 243 // GDB already knows about the main executable 244 return; 245 } 246 247 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 248 249 _r_debug.r_state = r_debug::RT_ADD; 250 rtld_db_dlactivity(); 251 252 insert_soinfo_into_debug_map(info); 253 254 _r_debug.r_state = r_debug::RT_CONSISTENT; 255 rtld_db_dlactivity(); 256} 257 258static void notify_gdb_of_unload(soinfo* info) { 259 if (info->flags & FLAG_EXE) { 260 // GDB already knows about the main executable 261 return; 262 } 263 264 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 265 266 _r_debug.r_state = r_debug::RT_DELETE; 267 rtld_db_dlactivity(); 268 269 remove_soinfo_from_debug_map(info); 270 271 _r_debug.r_state = r_debug::RT_CONSISTENT; 272 rtld_db_dlactivity(); 273} 274 275void notify_gdb_of_libraries() { 276 _r_debug.r_state = r_debug::RT_ADD; 277 rtld_db_dlactivity(); 278 _r_debug.r_state = r_debug::RT_CONSISTENT; 279 rtld_db_dlactivity(); 280} 281 282LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 283 return g_soinfo_links_allocator.alloc(); 284} 285 286void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 287 g_soinfo_links_allocator.free(entry); 288} 289 290static void protect_data(int protection) { 291 g_soinfo_allocator.protect_all(protection); 292 g_soinfo_links_allocator.protect_all(protection); 293} 294 295static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 296 if (strlen(name) >= SOINFO_NAME_LEN) { 297 DL_ERR("library name \"%s\" too long", name); 298 return NULL; 299 } 300 301 soinfo* si = g_soinfo_allocator.alloc(); 302 303 // Initialize the new element. 304 memset(si, 0, sizeof(soinfo)); 305 strlcpy(si->name, name, sizeof(si->name)); 306 si->flags = FLAG_NEW_SOINFO; 307 308 if (file_stat != NULL) { 309 si->set_st_dev(file_stat->st_dev); 310 si->set_st_ino(file_stat->st_ino); 311 } 312 313 sonext->next = si; 314 sonext = si; 315 316 TRACE("name %s: allocated soinfo @ %p", name, si); 317 return si; 318} 319 320static void soinfo_free(soinfo* si) { 321 if (si == NULL) { 322 return; 323 } 324 325 if (si->base != 0 && si->size != 0) { 326 munmap(reinterpret_cast<void*>(si->base), si->size); 327 } 328 329 soinfo *prev = NULL, *trav; 330 331 TRACE("name %s: freeing soinfo @ %p", si->name, si); 332 333 for (trav = solist; trav != NULL; trav = trav->next) { 334 if (trav == si) 335 break; 336 prev = trav; 337 } 338 if (trav == NULL) { 339 /* si was not in solist */ 340 DL_ERR("name \"%s\" is not in solist!", si->name); 341 return; 342 } 343 344 // clear links to/from si 345 si->remove_all_links(); 346 347 /* prev will never be NULL, because the first entry in solist is 348 always the static libdl_info. 349 */ 350 prev->next = si->next; 351 if (si == sonext) { 352 sonext = prev; 353 } 354 355 g_soinfo_allocator.free(si); 356} 357 358 359static void parse_path(const char* path, const char* delimiters, 360 const char** array, char* buf, size_t buf_size, size_t max_count) { 361 if (path == NULL) { 362 return; 363 } 364 365 size_t len = strlcpy(buf, path, buf_size); 366 367 size_t i = 0; 368 char* buf_p = buf; 369 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 370 if (*array[i] != '\0') { 371 ++i; 372 } 373 } 374 375 // Forget the last path if we had to truncate; this occurs if the 2nd to 376 // last char isn't '\0' (i.e. wasn't originally a delimiter). 377 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 378 array[i - 1] = NULL; 379 } else { 380 array[i] = NULL; 381 } 382} 383 384static void parse_LD_LIBRARY_PATH(const char* path) { 385 parse_path(path, ":", g_ld_library_paths, 386 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 387} 388 389static void parse_LD_PRELOAD(const char* path) { 390 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 391 parse_path(path, " :", g_ld_preload_names, 392 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 393} 394 395#if defined(__arm__) 396 397/* For a given PC, find the .so that it belongs to. 398 * Returns the base address of the .ARM.exidx section 399 * for that .so, and the number of 8-byte entries 400 * in that section (via *pcount). 401 * 402 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 403 * 404 * This function is exposed via dlfcn.cpp and libdl.so. 405 */ 406_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 407 unsigned addr = (unsigned)pc; 408 409 for (soinfo* si = solist; si != 0; si = si->next) { 410 if ((addr >= si->base) && (addr < (si->base + si->size))) { 411 *pcount = si->ARM_exidx_count; 412 return (_Unwind_Ptr)si->ARM_exidx; 413 } 414 } 415 *pcount = 0; 416 return NULL; 417} 418 419#endif 420 421/* Here, we only have to provide a callback to iterate across all the 422 * loaded libraries. gcc_eh does the rest. */ 423int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 424 int rv = 0; 425 for (soinfo* si = solist; si != NULL; si = si->next) { 426 dl_phdr_info dl_info; 427 dl_info.dlpi_addr = si->link_map_head.l_addr; 428 dl_info.dlpi_name = si->link_map_head.l_name; 429 dl_info.dlpi_phdr = si->phdr; 430 dl_info.dlpi_phnum = si->phnum; 431 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 432 if (rv != 0) { 433 break; 434 } 435 } 436 return rv; 437} 438 439static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name, const SymbolLookupScope& lookup_scope) { 440 ElfW(Sym)* symtab = si->symtab; 441 const char* strtab = si->strtab; 442 443 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 444 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 445 446 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 447 ElfW(Sym)* s = symtab + n; 448 if (strcmp(strtab + s->st_name, name)) continue; 449 450 switch (ELF_ST_BIND(s->st_info)) { 451 case STB_GLOBAL: 452 case STB_WEAK: 453 if (s->st_shndx == SHN_UNDEF) { 454 continue; 455 } 456 457 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 458 name, si->name, reinterpret_cast<void*>(s->st_value), 459 static_cast<size_t>(s->st_size)); 460 return s; 461 case STB_LOCAL: 462 if (lookup_scope != SymbolLookupScope::kAllowLocal) { 463 continue; 464 } 465 TRACE_TYPE(LOOKUP, "FOUND LOCAL %s in %s (%p) %zd", 466 name, si->name, reinterpret_cast<void*>(s->st_value), 467 static_cast<size_t>(s->st_size)); 468 return s; 469 default: 470 const char* msg = "FATAL: Unexpected ST_BIND\n"; 471 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); 472 write(2, msg, strlen(msg)); 473 abort(); 474 } 475 } 476 477 return NULL; 478} 479 480static unsigned elfhash(const char* _name) { 481 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 482 unsigned h = 0, g; 483 484 while (*name) { 485 h = (h << 4) + *name++; 486 g = h & 0xf0000000; 487 h ^= g; 488 h ^= g >> 24; 489 } 490 return h; 491} 492 493static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 494 unsigned elf_hash = elfhash(name); 495 ElfW(Sym)* s = NULL; 496 497 if (si != NULL && somain != NULL) { 498 /* 499 * Local scope is executable scope. Just start looking into it right away 500 * for the shortcut. 501 */ 502 503 if (si == somain) { 504 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 505 if (s != NULL) { 506 *lsi = si; 507 goto done; 508 } 509 } else { 510 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 511 512 /* 513 * If this object was built with symbolic relocations disabled, the 514 * first place to look to resolve external references is the main 515 * executable. 516 */ 517 518 if (!si->has_DT_SYMBOLIC) { 519 DEBUG("%s: looking up %s in executable %s", 520 si->name, name, somain->name); 521 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 522 if (s != NULL) { 523 *lsi = somain; 524 goto done; 525 } 526 } 527 528 /* Look for symbols in the local scope (the object who is 529 * searching). This happens with C++ templates on x86 for some 530 * reason. 531 * 532 * Notes on weak symbols: 533 * The ELF specs are ambiguous about treatment of weak definitions in 534 * dynamic linking. Some systems return the first definition found 535 * and some the first non-weak definition. This is system dependent. 536 * Here we return the first definition found for simplicity. */ 537 538 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 539 if (s != NULL) { 540 *lsi = si; 541 goto done; 542 } 543 544 /* 545 * If this object was built with -Bsymbolic and symbol is not found 546 * in the local scope, try to find the symbol in the main executable. 547 */ 548 549 if (si->has_DT_SYMBOLIC) { 550 DEBUG("%s: looking up %s in executable %s after local scope", 551 si->name, name, somain->name); 552 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 553 if (s != NULL) { 554 *lsi = somain; 555 goto done; 556 } 557 } 558 } 559 } 560 561 /* Next, look for it in the preloads list */ 562 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 563 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 564 if (s != NULL) { 565 *lsi = g_ld_preloads[i]; 566 goto done; 567 } 568 } 569 570 for (int i = 0; needed[i] != NULL; i++) { 571 DEBUG("%s: looking up %s in %s", 572 si->name, name, needed[i]->name); 573 s = soinfo_elf_lookup(needed[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 574 if (s != NULL) { 575 *lsi = needed[i]; 576 goto done; 577 } 578 } 579 580done: 581 if (s != NULL) { 582 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 583 "found in %s, base = %p, load bias = %p", 584 si->name, name, reinterpret_cast<void*>(s->st_value), 585 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 586 reinterpret_cast<void*>((*lsi)->load_bias)); 587 return s; 588 } 589 590 return NULL; 591} 592 593/* This is used by dlsym(3). It performs symbol lookup only within the 594 specified soinfo object and not in any of its dependencies. 595 596 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 597 that it should do a breadth first search through the dependency 598 tree. This agrees with the ELF spec (aka System V Application 599 Binary Interface) where in Chapter 5 it discuss resolving "Shared 600 Object Dependencies" in breadth first search order. 601 */ 602ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name, soinfo* caller) { 603 return soinfo_elf_lookup(si, elfhash(name), name, 604 caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 605} 606 607/* This is used by dlsym(3) to performs a global symbol lookup. If the 608 start value is null (for RTLD_DEFAULT), the search starts at the 609 beginning of the global solist. Otherwise the search starts at the 610 specified soinfo (for RTLD_NEXT). 611 */ 612ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start, soinfo* caller) { 613 unsigned elf_hash = elfhash(name); 614 615 if (start == NULL) { 616 start = solist; 617 } 618 619 ElfW(Sym)* s = NULL; 620 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 621 s = soinfo_elf_lookup(si, elf_hash, name, 622 caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 623 if (s != NULL) { 624 *found = si; 625 break; 626 } 627 } 628 629 if (s != NULL) { 630 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 631 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 632 } 633 634 return s; 635} 636 637soinfo* find_containing_library(const void* p) { 638 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 639 for (soinfo* si = solist; si != NULL; si = si->next) { 640 if (address >= si->base && address - si->base < si->size) { 641 return si; 642 } 643 } 644 return NULL; 645} 646 647ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 648 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 649 650 // Search the library's symbol table for any defined symbol which 651 // contains this address. 652 for (size_t i = 0; i < si->nchain; ++i) { 653 ElfW(Sym)* sym = &si->symtab[i]; 654 if (sym->st_shndx != SHN_UNDEF && 655 soaddr >= sym->st_value && 656 soaddr < sym->st_value + sym->st_size) { 657 return sym; 658 } 659 } 660 661 return NULL; 662} 663 664static int open_library_on_path(const char* name, const char* const paths[]) { 665 char buf[512]; 666 for (size_t i = 0; paths[i] != NULL; ++i) { 667 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 668 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 669 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 670 continue; 671 } 672 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 673 if (fd != -1) { 674 return fd; 675 } 676 } 677 return -1; 678} 679 680static int open_library(const char* name) { 681 TRACE("[ opening %s ]", name); 682 683 // If the name contains a slash, we should attempt to open it directly and not search the paths. 684 if (strchr(name, '/') != NULL) { 685 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 686 if (fd != -1) { 687 return fd; 688 } 689 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 690#if defined(__LP64__) 691 return -1; 692#endif 693 } 694 695 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 696 int fd = open_library_on_path(name, g_ld_library_paths); 697 if (fd == -1) { 698 fd = open_library_on_path(name, kDefaultLdPaths); 699 } 700 return fd; 701} 702 703static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 704 // Open the file. 705 int fd = open_library(name); 706 if (fd == -1) { 707 DL_ERR("library \"%s\" not found", name); 708 return NULL; 709 } 710 711 ElfReader elf_reader(name, fd); 712 713 struct stat file_stat; 714 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 715 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 716 return NULL; 717 } 718 719 // Check for symlink and other situations where 720 // file can have different names. 721 for (soinfo* si = solist; si != NULL; si = si->next) { 722 if (si->get_st_dev() != 0 && 723 si->get_st_ino() != 0 && 724 si->get_st_dev() == file_stat.st_dev && 725 si->get_st_ino() == file_stat.st_ino) { 726 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 727 return si; 728 } 729 } 730 731 if ((dlflags & RTLD_NOLOAD) != 0) { 732 return NULL; 733 } 734 735 // Read the ELF header and load the segments. 736 if (!elf_reader.Load(extinfo)) { 737 return NULL; 738 } 739 740 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 741 if (si == NULL) { 742 return NULL; 743 } 744 si->base = elf_reader.load_start(); 745 si->size = elf_reader.load_size(); 746 si->load_bias = elf_reader.load_bias(); 747 si->phnum = elf_reader.phdr_count(); 748 si->phdr = elf_reader.loaded_phdr(); 749 750 // At this point we know that whatever is loaded @ base is a valid ELF 751 // shared library whose segments are properly mapped in. 752 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 753 reinterpret_cast<void*>(si->base), si->size, si->name); 754 755 if (!soinfo_link_image(si, extinfo)) { 756 soinfo_free(si); 757 return NULL; 758 } 759 760 return si; 761} 762 763static soinfo *find_loaded_library_by_name(const char* name) { 764 const char* search_name = SEARCH_NAME(name); 765 for (soinfo* si = solist; si != NULL; si = si->next) { 766 if (!strcmp(search_name, si->name)) { 767 return si; 768 } 769 } 770 return NULL; 771} 772 773static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 774 if (name == NULL) { 775 return somain; 776 } 777 778 soinfo* si = find_loaded_library_by_name(name); 779 780 // Library might still be loaded, the accurate detection 781 // of this fact is done by load_library 782 if (si == NULL) { 783 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 784 si = load_library(name, dlflags, extinfo); 785 } 786 787 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 788 DL_ERR("recursive link to \"%s\"", si->name); 789 return NULL; 790 } 791 792 return si; 793} 794 795static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 796 soinfo* si = find_library_internal(name, dlflags, extinfo); 797 if (si != NULL) { 798 si->ref_count++; 799 } 800 return si; 801} 802 803static void soinfo_unload(soinfo* si) { 804 if (si->ref_count == 1) { 805 TRACE("unloading '%s'", si->name); 806 si->CallDestructors(); 807 808 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 809 si->get_children().for_each([&] (soinfo* child) { 810 TRACE("%s needs to unload %s", si->name, child->name); 811 soinfo_unload(child); 812 }); 813 } else { 814 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 815 if (d->d_tag == DT_NEEDED) { 816 const char* library_name = si->strtab + d->d_un.d_val; 817 TRACE("%s needs to unload %s", si->name, library_name); 818 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 819 if (needed != NULL) { 820 soinfo_unload(needed); 821 } else { 822 // Not found: for example if symlink was deleted between dlopen and dlclose 823 // Since we cannot really handle errors at this point - print and continue. 824 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 825 } 826 } 827 } 828 } 829 830 notify_gdb_of_unload(si); 831 si->ref_count = 0; 832 soinfo_free(si); 833 } else { 834 si->ref_count--; 835 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 836 } 837} 838 839void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 840 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 841} 842 843void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 844 if (!get_AT_SECURE()) { 845 parse_LD_LIBRARY_PATH(ld_library_path); 846 } 847} 848 849soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 850 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 851 DL_ERR("invalid flags to dlopen: %x", flags); 852 return NULL; 853 } 854 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 855 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 856 return NULL; 857 } 858 protect_data(PROT_READ | PROT_WRITE); 859 soinfo* si = find_library(name, flags, extinfo); 860 if (si != NULL) { 861 si->CallConstructors(); 862 } 863 protect_data(PROT_READ); 864 return si; 865} 866 867void do_dlclose(soinfo* si) { 868 protect_data(PROT_READ | PROT_WRITE); 869 soinfo_unload(si); 870 protect_data(PROT_READ); 871} 872 873#if defined(USE_RELA) 874static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 875 ElfW(Sym)* s; 876 soinfo* lsi; 877 878 for (size_t idx = 0; idx < count; ++idx, ++rela) { 879 unsigned type = ELFW(R_TYPE)(rela->r_info); 880 unsigned sym = ELFW(R_SYM)(rela->r_info); 881 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 882 ElfW(Addr) sym_addr = 0; 883 const char* sym_name = NULL; 884 885 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 886 if (type == 0) { // R_*_NONE 887 continue; 888 } 889 if (sym != 0) { 890 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 891 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 892 if (s == NULL) { 893 // We only allow an undefined symbol if this is a weak reference... 894 s = &si->symtab[sym]; 895 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 896 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 897 return -1; 898 } 899 900 /* IHI0044C AAELF 4.5.1.1: 901 902 Libraries are not searched to resolve weak references. 903 It is not an error for a weak reference to remain unsatisfied. 904 905 During linking, the value of an undefined weak reference is: 906 - Zero if the relocation type is absolute 907 - The address of the place if the relocation is pc-relative 908 - The address of nominal base address if the relocation 909 type is base-relative. 910 */ 911 912 switch (type) { 913#if defined(__aarch64__) 914 case R_AARCH64_JUMP_SLOT: 915 case R_AARCH64_GLOB_DAT: 916 case R_AARCH64_ABS64: 917 case R_AARCH64_ABS32: 918 case R_AARCH64_ABS16: 919 case R_AARCH64_RELATIVE: 920 /* 921 * The sym_addr was initialized to be zero above, or the relocation 922 * code below does not care about value of sym_addr. 923 * No need to do anything. 924 */ 925 break; 926#elif defined(__x86_64__) 927 case R_X86_64_JUMP_SLOT: 928 case R_X86_64_GLOB_DAT: 929 case R_X86_64_32: 930 case R_X86_64_64: 931 case R_X86_64_RELATIVE: 932 // No need to do anything. 933 break; 934 case R_X86_64_PC32: 935 sym_addr = reloc; 936 break; 937#endif 938 default: 939 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 940 return -1; 941 } 942 } else { 943 // We got a definition. 944 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 945 } 946 count_relocation(kRelocSymbol); 947 } else { 948 s = NULL; 949 } 950 951 switch (type) { 952#if defined(__aarch64__) 953 case R_AARCH64_JUMP_SLOT: 954 count_relocation(kRelocAbsolute); 955 MARK(rela->r_offset); 956 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 957 reloc, (sym_addr + rela->r_addend), sym_name); 958 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 959 break; 960 case R_AARCH64_GLOB_DAT: 961 count_relocation(kRelocAbsolute); 962 MARK(rela->r_offset); 963 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 964 reloc, (sym_addr + rela->r_addend), sym_name); 965 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 966 break; 967 case R_AARCH64_ABS64: 968 count_relocation(kRelocAbsolute); 969 MARK(rela->r_offset); 970 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 971 reloc, (sym_addr + rela->r_addend), sym_name); 972 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 973 break; 974 case R_AARCH64_ABS32: 975 count_relocation(kRelocAbsolute); 976 MARK(rela->r_offset); 977 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 978 reloc, (sym_addr + rela->r_addend), sym_name); 979 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 980 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 981 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 982 } else { 983 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 984 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 985 static_cast<ElfW(Addr)>(INT32_MIN), 986 static_cast<ElfW(Addr)>(UINT32_MAX)); 987 return -1; 988 } 989 break; 990 case R_AARCH64_ABS16: 991 count_relocation(kRelocAbsolute); 992 MARK(rela->r_offset); 993 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 994 reloc, (sym_addr + rela->r_addend), sym_name); 995 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 996 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 997 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 998 } else { 999 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1000 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1001 static_cast<ElfW(Addr)>(INT16_MIN), 1002 static_cast<ElfW(Addr)>(UINT16_MAX)); 1003 return -1; 1004 } 1005 break; 1006 case R_AARCH64_PREL64: 1007 count_relocation(kRelocRelative); 1008 MARK(rela->r_offset); 1009 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 1010 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1011 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 1012 break; 1013 case R_AARCH64_PREL32: 1014 count_relocation(kRelocRelative); 1015 MARK(rela->r_offset); 1016 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 1017 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1018 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1019 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1020 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1021 } else { 1022 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1023 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1024 static_cast<ElfW(Addr)>(INT32_MIN), 1025 static_cast<ElfW(Addr)>(UINT32_MAX)); 1026 return -1; 1027 } 1028 break; 1029 case R_AARCH64_PREL16: 1030 count_relocation(kRelocRelative); 1031 MARK(rela->r_offset); 1032 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1033 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1034 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1035 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1036 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1037 } else { 1038 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1039 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1040 static_cast<ElfW(Addr)>(INT16_MIN), 1041 static_cast<ElfW(Addr)>(UINT16_MAX)); 1042 return -1; 1043 } 1044 break; 1045 1046 case R_AARCH64_RELATIVE: 1047 count_relocation(kRelocRelative); 1048 MARK(rela->r_offset); 1049 if (sym) { 1050 DL_ERR("odd RELATIVE form..."); 1051 return -1; 1052 } 1053 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1054 reloc, (si->base + rela->r_addend)); 1055 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1056 break; 1057 1058 case R_AARCH64_COPY: 1059 if ((si->flags & FLAG_EXE) == 0) { 1060 /* 1061 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1062 * 1063 * Section 4.7.1.10 "Dynamic relocations" 1064 * R_AARCH64_COPY may only appear in executable objects where e_type is 1065 * set to ET_EXEC. 1066 * 1067 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1068 * We should explicitly disallow ET_DYN executables from having 1069 * R_AARCH64_COPY relocations. 1070 */ 1071 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1072 return -1; 1073 } 1074 count_relocation(kRelocCopy); 1075 MARK(rela->r_offset); 1076 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1077 reloc, 1078 s->st_size, 1079 (sym_addr + rela->r_addend), 1080 sym_name); 1081 if (reloc == (sym_addr + rela->r_addend)) { 1082 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1083 1084 if (src == NULL) { 1085 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1086 return -1; 1087 } 1088 if (lsi->has_DT_SYMBOLIC) { 1089 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1090 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1091 return -1; 1092 } 1093 if (s->st_size < src->st_size) { 1094 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1095 si->name, s->st_size, src->st_size); 1096 return -1; 1097 } 1098 memcpy(reinterpret_cast<void*>(reloc), 1099 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1100 } else { 1101 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1102 return -1; 1103 } 1104 break; 1105 case R_AARCH64_TLS_TPREL64: 1106 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1107 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1108 break; 1109 case R_AARCH64_TLS_DTPREL32: 1110 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1111 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1112 break; 1113#elif defined(__x86_64__) 1114 case R_X86_64_JUMP_SLOT: 1115 count_relocation(kRelocAbsolute); 1116 MARK(rela->r_offset); 1117 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1118 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1119 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1120 break; 1121 case R_X86_64_GLOB_DAT: 1122 count_relocation(kRelocAbsolute); 1123 MARK(rela->r_offset); 1124 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1125 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1126 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1127 break; 1128 case R_X86_64_RELATIVE: 1129 count_relocation(kRelocRelative); 1130 MARK(rela->r_offset); 1131 if (sym) { 1132 DL_ERR("odd RELATIVE form..."); 1133 return -1; 1134 } 1135 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1136 static_cast<size_t>(si->base)); 1137 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1138 break; 1139 case R_X86_64_32: 1140 count_relocation(kRelocRelative); 1141 MARK(rela->r_offset); 1142 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1143 static_cast<size_t>(sym_addr), sym_name); 1144 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1145 break; 1146 case R_X86_64_64: 1147 count_relocation(kRelocRelative); 1148 MARK(rela->r_offset); 1149 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1150 static_cast<size_t>(sym_addr), sym_name); 1151 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1152 break; 1153 case R_X86_64_PC32: 1154 count_relocation(kRelocRelative); 1155 MARK(rela->r_offset); 1156 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1157 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1158 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1159 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1160 break; 1161#endif 1162 1163 default: 1164 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1165 return -1; 1166 } 1167 } 1168 return 0; 1169} 1170 1171#else // REL, not RELA. 1172 1173static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1174 ElfW(Sym)* s; 1175 soinfo* lsi; 1176 1177 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1178 unsigned type = ELFW(R_TYPE)(rel->r_info); 1179 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1180 unsigned sym = ELFW(R_SYM)(rel->r_info); 1181 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1182 ElfW(Addr) sym_addr = 0; 1183 const char* sym_name = NULL; 1184 1185 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1186 if (type == 0) { // R_*_NONE 1187 continue; 1188 } 1189 if (sym != 0) { 1190 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1191 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1192 if (s == NULL) { 1193 // We only allow an undefined symbol if this is a weak reference... 1194 s = &si->symtab[sym]; 1195 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1196 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1197 return -1; 1198 } 1199 1200 /* IHI0044C AAELF 4.5.1.1: 1201 1202 Libraries are not searched to resolve weak references. 1203 It is not an error for a weak reference to remain 1204 unsatisfied. 1205 1206 During linking, the value of an undefined weak reference is: 1207 - Zero if the relocation type is absolute 1208 - The address of the place if the relocation is pc-relative 1209 - The address of nominal base address if the relocation 1210 type is base-relative. 1211 */ 1212 1213 switch (type) { 1214#if defined(__arm__) 1215 case R_ARM_JUMP_SLOT: 1216 case R_ARM_GLOB_DAT: 1217 case R_ARM_ABS32: 1218 case R_ARM_RELATIVE: /* Don't care. */ 1219 // sym_addr was initialized to be zero above or relocation 1220 // code below does not care about value of sym_addr. 1221 // No need to do anything. 1222 break; 1223#elif defined(__i386__) 1224 case R_386_JMP_SLOT: 1225 case R_386_GLOB_DAT: 1226 case R_386_32: 1227 case R_386_RELATIVE: /* Don't care. */ 1228 // sym_addr was initialized to be zero above or relocation 1229 // code below does not care about value of sym_addr. 1230 // No need to do anything. 1231 break; 1232 case R_386_PC32: 1233 sym_addr = reloc; 1234 break; 1235#endif 1236 1237#if defined(__arm__) 1238 case R_ARM_COPY: 1239 // Fall through. Can't really copy if weak symbol is not found at run-time. 1240#endif 1241 default: 1242 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1243 return -1; 1244 } 1245 } else { 1246 // We got a definition. 1247 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1248 } 1249 count_relocation(kRelocSymbol); 1250 } else { 1251 s = NULL; 1252 } 1253 1254 switch (type) { 1255#if defined(__arm__) 1256 case R_ARM_JUMP_SLOT: 1257 count_relocation(kRelocAbsolute); 1258 MARK(rel->r_offset); 1259 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1260 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1261 break; 1262 case R_ARM_GLOB_DAT: 1263 count_relocation(kRelocAbsolute); 1264 MARK(rel->r_offset); 1265 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1266 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1267 break; 1268 case R_ARM_ABS32: 1269 count_relocation(kRelocAbsolute); 1270 MARK(rel->r_offset); 1271 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1272 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1273 break; 1274 case R_ARM_REL32: 1275 count_relocation(kRelocRelative); 1276 MARK(rel->r_offset); 1277 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1278 reloc, sym_addr, rel->r_offset, sym_name); 1279 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1280 break; 1281 case R_ARM_COPY: 1282 if ((si->flags & FLAG_EXE) == 0) { 1283 /* 1284 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1285 * 1286 * Section 4.7.1.10 "Dynamic relocations" 1287 * R_ARM_COPY may only appear in executable objects where e_type is 1288 * set to ET_EXEC. 1289 * 1290 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1291 * We should explicitly disallow ET_DYN executables from having 1292 * R_ARM_COPY relocations. 1293 */ 1294 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1295 return -1; 1296 } 1297 count_relocation(kRelocCopy); 1298 MARK(rel->r_offset); 1299 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1300 if (reloc == sym_addr) { 1301 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1302 1303 if (src == NULL) { 1304 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1305 return -1; 1306 } 1307 if (lsi->has_DT_SYMBOLIC) { 1308 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1309 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1310 return -1; 1311 } 1312 if (s->st_size < src->st_size) { 1313 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1314 si->name, s->st_size, src->st_size); 1315 return -1; 1316 } 1317 memcpy(reinterpret_cast<void*>(reloc), 1318 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1319 } else { 1320 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1321 return -1; 1322 } 1323 break; 1324#elif defined(__i386__) 1325 case R_386_JMP_SLOT: 1326 count_relocation(kRelocAbsolute); 1327 MARK(rel->r_offset); 1328 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1329 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1330 break; 1331 case R_386_GLOB_DAT: 1332 count_relocation(kRelocAbsolute); 1333 MARK(rel->r_offset); 1334 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1335 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1336 break; 1337 case R_386_32: 1338 count_relocation(kRelocRelative); 1339 MARK(rel->r_offset); 1340 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1341 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1342 break; 1343 case R_386_PC32: 1344 count_relocation(kRelocRelative); 1345 MARK(rel->r_offset); 1346 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1347 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1348 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1349 break; 1350#elif defined(__mips__) 1351 case R_MIPS_REL32: 1352#if defined(__LP64__) 1353 // MIPS Elf64_Rel entries contain compound relocations 1354 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1355 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1356 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1357 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1358 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1359 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1360 return -1; 1361 } 1362#endif 1363 count_relocation(kRelocAbsolute); 1364 MARK(rel->r_offset); 1365 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1366 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1367 if (s) { 1368 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1369 } else { 1370 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1371 } 1372 break; 1373#endif 1374 1375#if defined(__arm__) 1376 case R_ARM_RELATIVE: 1377#elif defined(__i386__) 1378 case R_386_RELATIVE: 1379#endif 1380 count_relocation(kRelocRelative); 1381 MARK(rel->r_offset); 1382 if (sym) { 1383 DL_ERR("odd RELATIVE form..."); 1384 return -1; 1385 } 1386 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1387 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1388 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1389 break; 1390 1391 default: 1392 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1393 return -1; 1394 } 1395 } 1396 return 0; 1397} 1398#endif 1399 1400#if defined(__mips__) 1401static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1402 ElfW(Addr)** got = si->plt_got; 1403 if (got == NULL) { 1404 return true; 1405 } 1406 unsigned local_gotno = si->mips_local_gotno; 1407 unsigned gotsym = si->mips_gotsym; 1408 unsigned symtabno = si->mips_symtabno; 1409 ElfW(Sym)* symtab = si->symtab; 1410 1411 // got[0] is the address of the lazy resolver function. 1412 // got[1] may be used for a GNU extension. 1413 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1414 // FIXME: maybe this should be in a separate routine? 1415 if ((si->flags & FLAG_LINKER) == 0) { 1416 size_t g = 0; 1417 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1418 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1419 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1420 } 1421 // Relocate the local GOT entries. 1422 for (; g < local_gotno; g++) { 1423 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1424 } 1425 } 1426 1427 // Now for the global GOT entries... 1428 ElfW(Sym)* sym = symtab + gotsym; 1429 got = si->plt_got + local_gotno; 1430 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1431 // This is an undefined reference... try to locate it. 1432 const char* sym_name = si->strtab + sym->st_name; 1433 soinfo* lsi; 1434 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1435 if (s == NULL) { 1436 // We only allow an undefined symbol if this is a weak reference. 1437 s = &symtab[g]; 1438 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1439 DL_ERR("cannot locate \"%s\"...", sym_name); 1440 return false; 1441 } 1442 *got = 0; 1443 } else { 1444 // FIXME: is this sufficient? 1445 // For reference see NetBSD link loader 1446 // 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 1447 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1448 } 1449 } 1450 return true; 1451} 1452#endif 1453 1454void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1455 if (functions == NULL) { 1456 return; 1457 } 1458 1459 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1460 1461 int begin = reverse ? (count - 1) : 0; 1462 int end = reverse ? -1 : count; 1463 int step = reverse ? -1 : 1; 1464 1465 for (int i = begin; i != end; i += step) { 1466 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1467 CallFunction("function", functions[i]); 1468 } 1469 1470 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1471} 1472 1473void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1474 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1475 return; 1476 } 1477 1478 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1479 function(); 1480 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1481 1482 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1483 // are still writable. This happens with our debug malloc (see http://b/7941716). 1484 protect_data(PROT_READ | PROT_WRITE); 1485} 1486 1487void soinfo::CallPreInitConstructors() { 1488 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1489 // but ignored in a shared library. 1490 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1491} 1492 1493void soinfo::CallConstructors() { 1494 if (constructors_called) { 1495 return; 1496 } 1497 1498 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1499 // protect against recursive constructor calls. One simple example of constructor recursion 1500 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1501 // 1. The program depends on libc, so libc's constructor is called here. 1502 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1503 // 3. dlopen() calls the constructors on the newly created 1504 // soinfo for libc_malloc_debug_leak.so. 1505 // 4. The debug .so depends on libc, so CallConstructors is 1506 // called again with the libc soinfo. If it doesn't trigger the early- 1507 // out above, the libc constructor will be called again (recursively!). 1508 constructors_called = true; 1509 1510 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1511 // The GNU dynamic linker silently ignores these, but we warn the developer. 1512 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1513 name, preinit_array_count); 1514 } 1515 1516 get_children().for_each([] (soinfo* si) { 1517 si->CallConstructors(); 1518 }); 1519 1520 TRACE("\"%s\": calling constructors", name); 1521 1522 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1523 CallFunction("DT_INIT", init_func); 1524 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1525} 1526 1527void soinfo::CallDestructors() { 1528 TRACE("\"%s\": calling destructors", name); 1529 1530 // DT_FINI_ARRAY must be parsed in reverse order. 1531 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1532 1533 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1534 CallFunction("DT_FINI", fini_func); 1535 1536 // This is needed on second call to dlopen 1537 // after library has been unloaded with RTLD_NODELETE 1538 constructors_called = false; 1539} 1540 1541void soinfo::add_child(soinfo* child) { 1542 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1543 return; 1544 } 1545 1546 this->children.push_front(child); 1547 child->parents.push_front(this); 1548} 1549 1550void soinfo::remove_all_links() { 1551 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1552 return; 1553 } 1554 1555 // 1. Untie connected soinfos from 'this'. 1556 children.for_each([&] (soinfo* child) { 1557 child->parents.remove_if([&] (const soinfo* parent) { 1558 return parent == this; 1559 }); 1560 }); 1561 1562 parents.for_each([&] (soinfo* parent) { 1563 parent->children.for_each([&] (const soinfo* child) { 1564 return child == this; 1565 }); 1566 }); 1567 1568 // 2. Once everything untied - clear local lists. 1569 parents.clear(); 1570 children.clear(); 1571} 1572 1573void soinfo::set_st_dev(dev_t dev) { 1574 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1575 return; 1576 } 1577 1578 st_dev = dev; 1579} 1580 1581void soinfo::set_st_ino(ino_t ino) { 1582 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1583 return; 1584 } 1585 1586 st_ino = ino; 1587} 1588 1589dev_t soinfo::get_st_dev() { 1590 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1591 return 0; 1592 } 1593 1594 return st_dev; 1595}; 1596 1597ino_t soinfo::get_st_ino() { 1598 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1599 return 0; 1600 } 1601 1602 return st_ino; 1603} 1604 1605// This is a return on get_children() in case 1606// 'this->flags' does not have FLAG_NEW_SOINFO set. 1607static soinfo::soinfo_list_t g_empty_list; 1608 1609soinfo::soinfo_list_t& soinfo::get_children() { 1610 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1611 return g_empty_list; 1612 } 1613 1614 return this->children; 1615} 1616 1617/* Force any of the closed stdin, stdout and stderr to be associated with 1618 /dev/null. */ 1619static int nullify_closed_stdio() { 1620 int dev_null, i, status; 1621 int return_value = 0; 1622 1623 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1624 if (dev_null < 0) { 1625 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1626 return -1; 1627 } 1628 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1629 1630 /* If any of the stdio file descriptors is valid and not associated 1631 with /dev/null, dup /dev/null to it. */ 1632 for (i = 0; i < 3; i++) { 1633 /* If it is /dev/null already, we are done. */ 1634 if (i == dev_null) { 1635 continue; 1636 } 1637 1638 TRACE("[ Nullifying stdio file descriptor %d]", i); 1639 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1640 1641 /* If file is opened, we are good. */ 1642 if (status != -1) { 1643 continue; 1644 } 1645 1646 /* The only error we allow is that the file descriptor does not 1647 exist, in which case we dup /dev/null to it. */ 1648 if (errno != EBADF) { 1649 DL_ERR("fcntl failed: %s", strerror(errno)); 1650 return_value = -1; 1651 continue; 1652 } 1653 1654 /* Try dupping /dev/null to this stdio file descriptor and 1655 repeat if there is a signal. Note that any errors in closing 1656 the stdio descriptor are lost. */ 1657 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1658 if (status < 0) { 1659 DL_ERR("dup2 failed: %s", strerror(errno)); 1660 return_value = -1; 1661 continue; 1662 } 1663 } 1664 1665 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1666 if (dev_null > 2) { 1667 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1668 status = TEMP_FAILURE_RETRY(close(dev_null)); 1669 if (status == -1) { 1670 DL_ERR("close failed: %s", strerror(errno)); 1671 return_value = -1; 1672 } 1673 } 1674 1675 return return_value; 1676} 1677 1678static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1679 /* "base" might wrap around UINT32_MAX. */ 1680 ElfW(Addr) base = si->load_bias; 1681 const ElfW(Phdr)* phdr = si->phdr; 1682 int phnum = si->phnum; 1683 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1684 1685 /* We can't debug anything until the linker is relocated */ 1686 if (!relocating_linker) { 1687 INFO("[ linking %s ]", si->name); 1688 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1689 } 1690 1691 /* Extract dynamic section */ 1692 size_t dynamic_count; 1693 ElfW(Word) dynamic_flags; 1694 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1695 &dynamic_count, &dynamic_flags); 1696 if (si->dynamic == NULL) { 1697 if (!relocating_linker) { 1698 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1699 } 1700 return false; 1701 } else { 1702 if (!relocating_linker) { 1703 DEBUG("dynamic = %p", si->dynamic); 1704 } 1705 } 1706 1707#if defined(__arm__) 1708 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1709 &si->ARM_exidx, &si->ARM_exidx_count); 1710#endif 1711 1712 // Extract useful information from dynamic section. 1713 uint32_t needed_count = 0; 1714 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1715 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1716 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1717 switch (d->d_tag) { 1718 case DT_HASH: 1719 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1720 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1721 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1722 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1723 break; 1724 case DT_STRTAB: 1725 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1726 break; 1727 case DT_SYMTAB: 1728 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1729 break; 1730#if !defined(__LP64__) 1731 case DT_PLTREL: 1732 if (d->d_un.d_val != DT_REL) { 1733 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1734 return false; 1735 } 1736 break; 1737#endif 1738 case DT_JMPREL: 1739#if defined(USE_RELA) 1740 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1741#else 1742 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1743#endif 1744 break; 1745 case DT_PLTRELSZ: 1746#if defined(USE_RELA) 1747 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1748#else 1749 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1750#endif 1751 break; 1752#if defined(__mips__) 1753 case DT_PLTGOT: 1754 // Used by mips and mips64. 1755 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1756 break; 1757#endif 1758 case DT_DEBUG: 1759 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1760 // if the dynamic table is writable 1761// FIXME: not working currently for N64 1762// The flags for the LOAD and DYNAMIC program headers do not agree. 1763// The LOAD section containng the dynamic table has been mapped as 1764// read-only, but the DYNAMIC header claims it is writable. 1765#if !(defined(__mips__) && defined(__LP64__)) 1766 if ((dynamic_flags & PF_W) != 0) { 1767 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1768 } 1769 break; 1770#endif 1771#if defined(USE_RELA) 1772 case DT_RELA: 1773 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1774 break; 1775 case DT_RELASZ: 1776 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1777 break; 1778 case DT_REL: 1779 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1780 return false; 1781 case DT_RELSZ: 1782 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1783 return false; 1784#else 1785 case DT_REL: 1786 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1787 break; 1788 case DT_RELSZ: 1789 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1790 break; 1791 case DT_RELA: 1792 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1793 return false; 1794#endif 1795 case DT_INIT: 1796 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1797 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1798 break; 1799 case DT_FINI: 1800 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1801 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1802 break; 1803 case DT_INIT_ARRAY: 1804 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1805 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1806 break; 1807 case DT_INIT_ARRAYSZ: 1808 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1809 break; 1810 case DT_FINI_ARRAY: 1811 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1812 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1813 break; 1814 case DT_FINI_ARRAYSZ: 1815 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1816 break; 1817 case DT_PREINIT_ARRAY: 1818 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1819 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1820 break; 1821 case DT_PREINIT_ARRAYSZ: 1822 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1823 break; 1824 case DT_TEXTREL: 1825#if defined(__LP64__) 1826 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1827 return false; 1828#else 1829 si->has_text_relocations = true; 1830 break; 1831#endif 1832 case DT_SYMBOLIC: 1833 si->has_DT_SYMBOLIC = true; 1834 break; 1835 case DT_NEEDED: 1836 ++needed_count; 1837 break; 1838 case DT_FLAGS: 1839 if (d->d_un.d_val & DF_TEXTREL) { 1840#if defined(__LP64__) 1841 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1842 return false; 1843#else 1844 si->has_text_relocations = true; 1845#endif 1846 } 1847 if (d->d_un.d_val & DF_SYMBOLIC) { 1848 si->has_DT_SYMBOLIC = true; 1849 } 1850 break; 1851#if defined(__mips__) 1852 case DT_STRSZ: 1853 case DT_SYMENT: 1854 case DT_RELENT: 1855 break; 1856 case DT_MIPS_RLD_MAP: 1857 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1858 { 1859 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1860 *dp = &_r_debug; 1861 } 1862 break; 1863 case DT_MIPS_RLD_VERSION: 1864 case DT_MIPS_FLAGS: 1865 case DT_MIPS_BASE_ADDRESS: 1866 case DT_MIPS_UNREFEXTNO: 1867 break; 1868 1869 case DT_MIPS_SYMTABNO: 1870 si->mips_symtabno = d->d_un.d_val; 1871 break; 1872 1873 case DT_MIPS_LOCAL_GOTNO: 1874 si->mips_local_gotno = d->d_un.d_val; 1875 break; 1876 1877 case DT_MIPS_GOTSYM: 1878 si->mips_gotsym = d->d_un.d_val; 1879 break; 1880#endif 1881 1882 default: 1883 DEBUG("Unused DT entry: type %p arg %p", 1884 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1885 break; 1886 } 1887 } 1888 1889 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1890 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1891 1892 // Sanity checks. 1893 if (relocating_linker && needed_count != 0) { 1894 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1895 return false; 1896 } 1897 if (si->nbucket == 0) { 1898 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1899 return false; 1900 } 1901 if (si->strtab == 0) { 1902 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1903 return false; 1904 } 1905 if (si->symtab == 0) { 1906 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1907 return false; 1908 } 1909 1910 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1911 if (si->flags & FLAG_EXE) { 1912 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1913 size_t preload_count = 0; 1914 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1915 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1916 if (lsi != NULL) { 1917 g_ld_preloads[preload_count++] = lsi; 1918 } else { 1919 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1920 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1921 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1922 } 1923 } 1924 } 1925 1926 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1927 soinfo** pneeded = needed; 1928 1929 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1930 if (d->d_tag == DT_NEEDED) { 1931 const char* library_name = si->strtab + d->d_un.d_val; 1932 DEBUG("%s needs %s", si->name, library_name); 1933 soinfo* lsi = find_library(library_name, 0, NULL); 1934 if (lsi == NULL) { 1935 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1936 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1937 library_name, si->name, tmp_err_buf); 1938 return false; 1939 } 1940 1941 si->add_child(lsi); 1942 *pneeded++ = lsi; 1943 } 1944 } 1945 *pneeded = NULL; 1946 1947#if !defined(__LP64__) 1948 if (si->has_text_relocations) { 1949 // Make segments writable to allow text relocations to work properly. We will later call 1950 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1951 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1952 "security hardening. Please fix.", si->name); 1953 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1954 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1955 si->name, strerror(errno)); 1956 return false; 1957 } 1958 } 1959#endif 1960 1961#if defined(USE_RELA) 1962 if (si->plt_rela != NULL) { 1963 DEBUG("[ relocating %s plt ]\n", si->name); 1964 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1965 return false; 1966 } 1967 } 1968 if (si->rela != NULL) { 1969 DEBUG("[ relocating %s ]\n", si->name); 1970 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1971 return false; 1972 } 1973 } 1974#else 1975 if (si->plt_rel != NULL) { 1976 DEBUG("[ relocating %s plt ]", si->name); 1977 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1978 return false; 1979 } 1980 } 1981 if (si->rel != NULL) { 1982 DEBUG("[ relocating %s ]", si->name); 1983 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1984 return false; 1985 } 1986 } 1987#endif 1988 1989#if defined(__mips__) 1990 if (!mips_relocate_got(si, needed)) { 1991 return false; 1992 } 1993#endif 1994 1995 si->flags |= FLAG_LINKED; 1996 DEBUG("[ finished linking %s ]", si->name); 1997 1998#if !defined(__LP64__) 1999 if (si->has_text_relocations) { 2000 // All relocations are done, we can protect our segments back to read-only. 2001 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 2002 DL_ERR("can't protect segments for \"%s\": %s", 2003 si->name, strerror(errno)); 2004 return false; 2005 } 2006 } 2007#endif 2008 2009 /* We can also turn on GNU RELRO protection */ 2010 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 2011 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 2012 si->name, strerror(errno)); 2013 return false; 2014 } 2015 2016 /* Handle serializing/sharing the RELRO segment */ 2017 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 2018 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 2019 extinfo->relro_fd) < 0) { 2020 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 2021 si->name, strerror(errno)); 2022 return false; 2023 } 2024 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 2025 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 2026 extinfo->relro_fd) < 0) { 2027 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 2028 si->name, strerror(errno)); 2029 return false; 2030 } 2031 } 2032 2033 notify_gdb_of_load(si); 2034 return true; 2035} 2036 2037/* 2038 * This function add vdso to internal dso list. 2039 * It helps to stack unwinding through signal handlers. 2040 * Also, it makes bionic more like glibc. 2041 */ 2042static void add_vdso(KernelArgumentBlock& args __unused) { 2043#if defined(AT_SYSINFO_EHDR) 2044 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 2045 if (ehdr_vdso == NULL) { 2046 return; 2047 } 2048 2049 soinfo* si = soinfo_alloc("[vdso]", NULL); 2050 2051 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 2052 si->phnum = ehdr_vdso->e_phnum; 2053 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 2054 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2055 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 2056 2057 soinfo_link_image(si, NULL); 2058#endif 2059} 2060 2061/* 2062 * This is linker soinfo for GDB. See details below. 2063 */ 2064static soinfo linker_soinfo_for_gdb; 2065 2066/* gdb expects the linker to be in the debug shared object list. 2067 * Without this, gdb has trouble locating the linker's ".text" 2068 * and ".plt" sections. Gdb could also potentially use this to 2069 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2070 * Don't use soinfo_alloc(), because the linker shouldn't 2071 * be on the soinfo list. 2072 */ 2073static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 2074#if defined(__LP64__) 2075 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 2076#else 2077 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 2078#endif 2079 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 2080 linker_soinfo_for_gdb.base = linker_base; 2081 2082 /* 2083 * Set the dynamic field in the link map otherwise gdb will complain with 2084 * the following: 2085 * warning: .dynamic section for "/system/bin/linker" is not at the 2086 * expected address (wrong library or version mismatch?) 2087 */ 2088 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2089 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2090 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2091 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2092 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2093} 2094 2095/* 2096 * This code is called after the linker has linked itself and 2097 * fixed it's own GOT. It is safe to make references to externs 2098 * and other non-local data at this point. 2099 */ 2100static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2101 /* NOTE: we store the args pointer on a special location 2102 * of the temporary TLS area in order to pass it to 2103 * the C Library's runtime initializer. 2104 * 2105 * The initializer must clear the slot and reset the TLS 2106 * to point to a different location to ensure that no other 2107 * shared library constructor can access it. 2108 */ 2109 __libc_init_tls(args); 2110 2111#if TIMING 2112 struct timeval t0, t1; 2113 gettimeofday(&t0, 0); 2114#endif 2115 2116 // Initialize environment functions, and get to the ELF aux vectors table. 2117 linker_env_init(args); 2118 2119 // If this is a setuid/setgid program, close the security hole described in 2120 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2121 if (get_AT_SECURE()) { 2122 nullify_closed_stdio(); 2123 } 2124 2125 debuggerd_init(); 2126 2127 // Get a few environment variables. 2128 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2129 if (LD_DEBUG != NULL) { 2130 g_ld_debug_verbosity = atoi(LD_DEBUG); 2131 } 2132 2133 // Normally, these are cleaned by linker_env_init, but the test 2134 // doesn't cost us anything. 2135 const char* ldpath_env = NULL; 2136 const char* ldpreload_env = NULL; 2137 if (!get_AT_SECURE()) { 2138 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2139 ldpreload_env = linker_env_get("LD_PRELOAD"); 2140 } 2141 2142 // Linker does not call constructors for its own 2143 // global variables so we need to initialize 2144 // the allocators explicitly. 2145 g_soinfo_allocator.init(); 2146 g_soinfo_links_allocator.init(); 2147 2148 INFO("[ android linker & debugger ]"); 2149 2150 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2151 if (si == NULL) { 2152 exit(EXIT_FAILURE); 2153 } 2154 2155 /* bootstrap the link map, the main exe always needs to be first */ 2156 si->flags |= FLAG_EXE; 2157 link_map* map = &(si->link_map_head); 2158 2159 map->l_addr = 0; 2160 map->l_name = args.argv[0]; 2161 map->l_prev = NULL; 2162 map->l_next = NULL; 2163 2164 _r_debug.r_map = map; 2165 r_debug_tail = map; 2166 2167 init_linker_info_for_gdb(linker_base); 2168 2169 // Extract information passed from the kernel. 2170 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2171 si->phnum = args.getauxval(AT_PHNUM); 2172 si->entry = args.getauxval(AT_ENTRY); 2173 2174 /* Compute the value of si->base. We can't rely on the fact that 2175 * the first entry is the PHDR because this will not be true 2176 * for certain executables (e.g. some in the NDK unit test suite) 2177 */ 2178 si->base = 0; 2179 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2180 si->load_bias = 0; 2181 for (size_t i = 0; i < si->phnum; ++i) { 2182 if (si->phdr[i].p_type == PT_PHDR) { 2183 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2184 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2185 break; 2186 } 2187 } 2188 si->dynamic = NULL; 2189 si->ref_count = 1; 2190 2191#if defined(__LP64__) 2192 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2193 if (elf_hdr->e_type != ET_DYN) { 2194 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2195 exit(EXIT_FAILURE); 2196 } 2197#endif 2198 2199 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2200 parse_LD_LIBRARY_PATH(ldpath_env); 2201 parse_LD_PRELOAD(ldpreload_env); 2202 2203 somain = si; 2204 2205 if (!soinfo_link_image(si, NULL)) { 2206 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2207 exit(EXIT_FAILURE); 2208 } 2209 2210 add_vdso(args); 2211 2212 si->CallPreInitConstructors(); 2213 2214 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2215 g_ld_preloads[i]->CallConstructors(); 2216 } 2217 2218 /* After the link_image, the si->load_bias is initialized. 2219 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2220 * We need to update this value for so exe here. So Unwind_Backtrace 2221 * for some arch like x86 could work correctly within so exe. 2222 */ 2223 map->l_addr = si->load_bias; 2224 si->CallConstructors(); 2225 2226#if TIMING 2227 gettimeofday(&t1, NULL); 2228 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2229 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2230 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2231#endif 2232#if STATS 2233 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2234 linker_stats.count[kRelocAbsolute], 2235 linker_stats.count[kRelocRelative], 2236 linker_stats.count[kRelocCopy], 2237 linker_stats.count[kRelocSymbol]); 2238#endif 2239#if COUNT_PAGES 2240 { 2241 unsigned n; 2242 unsigned i; 2243 unsigned count = 0; 2244 for (n = 0; n < 4096; n++) { 2245 if (bitmask[n]) { 2246 unsigned x = bitmask[n]; 2247#if defined(__LP64__) 2248 for (i = 0; i < 32; i++) { 2249#else 2250 for (i = 0; i < 8; i++) { 2251#endif 2252 if (x & 1) { 2253 count++; 2254 } 2255 x >>= 1; 2256 } 2257 } 2258 } 2259 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2260 } 2261#endif 2262 2263#if TIMING || STATS || COUNT_PAGES 2264 fflush(stdout); 2265#endif 2266 2267 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2268 return si->entry; 2269} 2270 2271/* Compute the load-bias of an existing executable. This shall only 2272 * be used to compute the load bias of an executable or shared library 2273 * that was loaded by the kernel itself. 2274 * 2275 * Input: 2276 * elf -> address of ELF header, assumed to be at the start of the file. 2277 * Return: 2278 * load bias, i.e. add the value of any p_vaddr in the file to get 2279 * the corresponding address in memory. 2280 */ 2281static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2282 ElfW(Addr) offset = elf->e_phoff; 2283 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2284 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2285 2286 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2287 if (phdr->p_type == PT_LOAD) { 2288 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2289 } 2290 } 2291 return 0; 2292} 2293 2294/* 2295 * This is the entry point for the linker, called from begin.S. This 2296 * method is responsible for fixing the linker's own relocations, and 2297 * then calling __linker_init_post_relocation(). 2298 * 2299 * Because this method is called before the linker has fixed it's own 2300 * relocations, any attempt to reference an extern variable, extern 2301 * function, or other GOT reference will generate a segfault. 2302 */ 2303extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2304 // Initialize static variables. 2305 solist = get_libdl_info(); 2306 sonext = get_libdl_info(); 2307 2308 KernelArgumentBlock args(raw_args); 2309 2310 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2311 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2312 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2313 2314 soinfo linker_so; 2315 memset(&linker_so, 0, sizeof(soinfo)); 2316 2317 strcpy(linker_so.name, "[dynamic linker]"); 2318 linker_so.base = linker_addr; 2319 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2320 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2321 linker_so.dynamic = NULL; 2322 linker_so.phdr = phdr; 2323 linker_so.phnum = elf_hdr->e_phnum; 2324 linker_so.flags |= FLAG_LINKER; 2325 2326 if (!soinfo_link_image(&linker_so, NULL)) { 2327 // It would be nice to print an error message, but if the linker 2328 // can't link itself, there's no guarantee that we'll be able to 2329 // call write() (because it involves a GOT reference). We may as 2330 // well try though... 2331 const char* msg = "CANNOT LINK EXECUTABLE: "; 2332 write(2, msg, strlen(msg)); 2333 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2334 write(2, "\n", 1); 2335 _exit(EXIT_FAILURE); 2336 } 2337 2338 // We have successfully fixed our own relocations. It's safe to run 2339 // the main part of the linker now. 2340 args.abort_message_ptr = &g_abort_message; 2341 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2342 2343 protect_data(PROT_READ); 2344 2345 // Return the address that the calling assembly stub should jump to. 2346 return start_address; 2347} 2348