linker.cpp revision 04dc91ae763adc403a14c88b4c46f77b3d2d71a3
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 * - are we doing everything we should for ARM_COPY relocations? 64 * - cleaner error reporting 65 * - after linking, set as much stuff as possible to READONLY 66 * and NOEXEC 67 */ 68 69#if defined(__LP64__) 70#define SEARCH_NAME(x) x 71#else 72// Nvidia drivers are relying on the bug: 73// http://code.google.com/p/android/issues/detail?id=6670 74// so we continue to use base-name lookup for lp32 75static const char* get_base_name(const char* name) { 76 const char* bname = strrchr(name, '/'); 77 return bname ? bname + 1 : name; 78} 79#define SEARCH_NAME(x) get_base_name(x) 80#endif 81 82static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 83static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 84 85static LinkerAllocator<soinfo> g_soinfo_allocator; 86static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator; 87 88static soinfo* solist; 89static soinfo* sonext; 90static soinfo* somain; /* main process, always the one after libdl_info */ 91 92static const char* const kDefaultLdPaths[] = { 93#if defined(__LP64__) 94 "/vendor/lib64", 95 "/system/lib64", 96#else 97 "/vendor/lib", 98 "/system/lib", 99#endif 100 NULL 101}; 102 103#define LDPATH_BUFSIZE (LDPATH_MAX*64) 104#define LDPATH_MAX 8 105 106#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 107#define LDPRELOAD_MAX 8 108 109static char g_ld_library_paths_buffer[LDPATH_BUFSIZE]; 110static const char* g_ld_library_paths[LDPATH_MAX + 1]; 111 112static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE]; 113static const char* g_ld_preload_names[LDPRELOAD_MAX + 1]; 114 115static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1]; 116 117__LIBC_HIDDEN__ int g_ld_debug_verbosity; 118 119__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd. 120 121enum RelocationKind { 122 kRelocAbsolute = 0, 123 kRelocRelative, 124 kRelocCopy, 125 kRelocSymbol, 126 kRelocMax 127}; 128 129enum class SymbolLookupScope { 130 kAllowLocal, 131 kExcludeLocal, 132}; 133 134#if STATS 135struct linker_stats_t { 136 int count[kRelocMax]; 137}; 138 139static linker_stats_t linker_stats; 140 141static void count_relocation(RelocationKind kind) { 142 ++linker_stats.count[kind]; 143} 144#else 145static void count_relocation(RelocationKind) { 146} 147#endif 148 149#if COUNT_PAGES 150static unsigned bitmask[4096]; 151#if defined(__LP64__) 152#define MARK(offset) \ 153 do { \ 154 if ((((offset) >> 12) >> 5) < 4096) \ 155 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 156 } while (0) 157#else 158#define MARK(offset) \ 159 do { \ 160 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 161 } while (0) 162#endif 163#else 164#define MARK(x) do {} while (0) 165#endif 166 167// You shouldn't try to call memory-allocating functions in the dynamic linker. 168// Guard against the most obvious ones. 169#define DISALLOW_ALLOCATION(return_type, name, ...) \ 170 return_type name __VA_ARGS__ \ 171 { \ 172 __libc_fatal("ERROR: " #name " called from the dynamic linker!\n"); \ 173 } 174DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 175DISALLOW_ALLOCATION(void, free, (void* u __unused)); 176DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 177DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 178 179static char tmp_err_buf[768]; 180static char __linker_dl_err_buf[768]; 181 182char* linker_get_error_buffer() { 183 return &__linker_dl_err_buf[0]; 184} 185 186size_t linker_get_error_buffer_size() { 187 return sizeof(__linker_dl_err_buf); 188} 189 190/* 191 * This function is an empty stub where GDB locates a breakpoint to get notified 192 * about linker activity. 193 */ 194extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 195 196static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER; 197static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 198static link_map* r_debug_tail = 0; 199 200static void insert_soinfo_into_debug_map(soinfo* info) { 201 // Copy the necessary fields into the debug structure. 202 link_map* map = &(info->link_map_head); 203 map->l_addr = info->load_bias; 204 map->l_name = reinterpret_cast<char*>(info->name); 205 map->l_ld = info->dynamic; 206 207 /* Stick the new library at the end of the list. 208 * gdb tends to care more about libc than it does 209 * about leaf libraries, and ordering it this way 210 * reduces the back-and-forth over the wire. 211 */ 212 if (r_debug_tail) { 213 r_debug_tail->l_next = map; 214 map->l_prev = r_debug_tail; 215 map->l_next = 0; 216 } else { 217 _r_debug.r_map = map; 218 map->l_prev = 0; 219 map->l_next = 0; 220 } 221 r_debug_tail = map; 222} 223 224static void remove_soinfo_from_debug_map(soinfo* info) { 225 link_map* map = &(info->link_map_head); 226 227 if (r_debug_tail == map) { 228 r_debug_tail = map->l_prev; 229 } 230 231 if (map->l_prev) { 232 map->l_prev->l_next = map->l_next; 233 } 234 if (map->l_next) { 235 map->l_next->l_prev = map->l_prev; 236 } 237} 238 239static void notify_gdb_of_load(soinfo* info) { 240 if (info->flags & FLAG_EXE) { 241 // GDB already knows about the main executable 242 return; 243 } 244 245 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 246 247 _r_debug.r_state = r_debug::RT_ADD; 248 rtld_db_dlactivity(); 249 250 insert_soinfo_into_debug_map(info); 251 252 _r_debug.r_state = r_debug::RT_CONSISTENT; 253 rtld_db_dlactivity(); 254} 255 256static void notify_gdb_of_unload(soinfo* info) { 257 if (info->flags & FLAG_EXE) { 258 // GDB already knows about the main executable 259 return; 260 } 261 262 ScopedPthreadMutexLocker locker(&g__r_debug_mutex); 263 264 _r_debug.r_state = r_debug::RT_DELETE; 265 rtld_db_dlactivity(); 266 267 remove_soinfo_from_debug_map(info); 268 269 _r_debug.r_state = r_debug::RT_CONSISTENT; 270 rtld_db_dlactivity(); 271} 272 273void notify_gdb_of_libraries() { 274 _r_debug.r_state = r_debug::RT_ADD; 275 rtld_db_dlactivity(); 276 _r_debug.r_state = r_debug::RT_CONSISTENT; 277 rtld_db_dlactivity(); 278} 279 280LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() { 281 return g_soinfo_links_allocator.alloc(); 282} 283 284void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) { 285 g_soinfo_links_allocator.free(entry); 286} 287 288static void protect_data(int protection) { 289 g_soinfo_allocator.protect_all(protection); 290 g_soinfo_links_allocator.protect_all(protection); 291} 292 293static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) { 294 if (strlen(name) >= SOINFO_NAME_LEN) { 295 DL_ERR("library name \"%s\" too long", name); 296 return NULL; 297 } 298 299 soinfo* si = g_soinfo_allocator.alloc(); 300 301 // Initialize the new element. 302 memset(si, 0, sizeof(soinfo)); 303 strlcpy(si->name, name, sizeof(si->name)); 304 si->flags = FLAG_NEW_SOINFO; 305 306 if (file_stat != NULL) { 307 si->set_st_dev(file_stat->st_dev); 308 si->set_st_ino(file_stat->st_ino); 309 } 310 311 sonext->next = si; 312 sonext = si; 313 314 TRACE("name %s: allocated soinfo @ %p", name, si); 315 return si; 316} 317 318static void soinfo_free(soinfo* si) { 319 if (si == NULL) { 320 return; 321 } 322 323 if (si->base != 0 && si->size != 0) { 324 munmap(reinterpret_cast<void*>(si->base), si->size); 325 } 326 327 soinfo *prev = NULL, *trav; 328 329 TRACE("name %s: freeing soinfo @ %p", si->name, si); 330 331 for (trav = solist; trav != NULL; trav = trav->next) { 332 if (trav == si) 333 break; 334 prev = trav; 335 } 336 if (trav == NULL) { 337 /* si was not in solist */ 338 DL_ERR("name \"%s\" is not in solist!", si->name); 339 return; 340 } 341 342 // clear links to/from si 343 si->remove_all_links(); 344 345 /* prev will never be NULL, because the first entry in solist is 346 always the static libdl_info. 347 */ 348 prev->next = si->next; 349 if (si == sonext) { 350 sonext = prev; 351 } 352 353 g_soinfo_allocator.free(si); 354} 355 356 357static void parse_path(const char* path, const char* delimiters, 358 const char** array, char* buf, size_t buf_size, size_t max_count) { 359 if (path == NULL) { 360 return; 361 } 362 363 size_t len = strlcpy(buf, path, buf_size); 364 365 size_t i = 0; 366 char* buf_p = buf; 367 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 368 if (*array[i] != '\0') { 369 ++i; 370 } 371 } 372 373 // Forget the last path if we had to truncate; this occurs if the 2nd to 374 // last char isn't '\0' (i.e. wasn't originally a delimiter). 375 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 376 array[i - 1] = NULL; 377 } else { 378 array[i] = NULL; 379 } 380} 381 382static void parse_LD_LIBRARY_PATH(const char* path) { 383 parse_path(path, ":", g_ld_library_paths, 384 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX); 385} 386 387static void parse_LD_PRELOAD(const char* path) { 388 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 389 parse_path(path, " :", g_ld_preload_names, 390 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX); 391} 392 393#if defined(__arm__) 394 395/* For a given PC, find the .so that it belongs to. 396 * Returns the base address of the .ARM.exidx section 397 * for that .so, and the number of 8-byte entries 398 * in that section (via *pcount). 399 * 400 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 401 * 402 * This function is exposed via dlfcn.cpp and libdl.so. 403 */ 404_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 405 unsigned addr = (unsigned)pc; 406 407 for (soinfo* si = solist; si != 0; si = si->next) { 408 if ((addr >= si->base) && (addr < (si->base + si->size))) { 409 *pcount = si->ARM_exidx_count; 410 return (_Unwind_Ptr)si->ARM_exidx; 411 } 412 } 413 *pcount = 0; 414 return NULL; 415} 416 417#endif 418 419/* Here, we only have to provide a callback to iterate across all the 420 * loaded libraries. gcc_eh does the rest. */ 421int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 422 int rv = 0; 423 for (soinfo* si = solist; si != NULL; si = si->next) { 424 dl_phdr_info dl_info; 425 dl_info.dlpi_addr = si->link_map_head.l_addr; 426 dl_info.dlpi_name = si->link_map_head.l_name; 427 dl_info.dlpi_phdr = si->phdr; 428 dl_info.dlpi_phnum = si->phnum; 429 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 430 if (rv != 0) { 431 break; 432 } 433 } 434 return rv; 435} 436 437static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name, const SymbolLookupScope& lookup_scope) { 438 ElfW(Sym)* symtab = si->symtab; 439 const char* strtab = si->strtab; 440 441 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 442 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 443 444 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 445 ElfW(Sym)* s = symtab + n; 446 if (strcmp(strtab + s->st_name, name)) continue; 447 448 switch (ELF_ST_BIND(s->st_info)) { 449 case STB_GLOBAL: 450 case STB_WEAK: 451 if (s->st_shndx == SHN_UNDEF) { 452 continue; 453 } 454 455 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 456 name, si->name, reinterpret_cast<void*>(s->st_value), 457 static_cast<size_t>(s->st_size)); 458 return s; 459 case STB_LOCAL: 460 if (lookup_scope != SymbolLookupScope::kAllowLocal) { 461 continue; 462 } 463 TRACE_TYPE(LOOKUP, "FOUND LOCAL %s in %s (%p) %zd", 464 name, si->name, reinterpret_cast<void*>(s->st_value), 465 static_cast<size_t>(s->st_size)); 466 return s; 467 default: 468 __libc_fatal("ERROR: Unexpected ST_BIND value: %d for '%s' in '%s'", 469 ELF_ST_BIND(s->st_info), name, si->name); 470 } 471 } 472 473 return NULL; 474} 475 476static unsigned elfhash(const char* _name) { 477 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 478 unsigned h = 0, g; 479 480 while (*name) { 481 h = (h << 4) + *name++; 482 g = h & 0xf0000000; 483 h ^= g; 484 h ^= g >> 24; 485 } 486 return h; 487} 488 489static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 490 unsigned elf_hash = elfhash(name); 491 ElfW(Sym)* s = NULL; 492 493 if (si != NULL && somain != NULL) { 494 /* 495 * Local scope is executable scope. Just start looking into it right away 496 * for the shortcut. 497 */ 498 499 if (si == somain) { 500 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 501 if (s != NULL) { 502 *lsi = si; 503 goto done; 504 } 505 } else { 506 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 507 508 /* 509 * If this object was built with symbolic relocations disabled, the 510 * first place to look to resolve external references is the main 511 * executable. 512 */ 513 514 if (!si->has_DT_SYMBOLIC) { 515 DEBUG("%s: looking up %s in executable %s", 516 si->name, name, somain->name); 517 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 518 if (s != NULL) { 519 *lsi = somain; 520 goto done; 521 } 522 } 523 524 /* Look for symbols in the local scope (the object who is 525 * searching). This happens with C++ templates on x86 for some 526 * reason. 527 * 528 * Notes on weak symbols: 529 * The ELF specs are ambiguous about treatment of weak definitions in 530 * dynamic linking. Some systems return the first definition found 531 * and some the first non-weak definition. This is system dependent. 532 * Here we return the first definition found for simplicity. */ 533 534 s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal); 535 if (s != NULL) { 536 *lsi = si; 537 goto done; 538 } 539 540 /* 541 * If this object was built with -Bsymbolic and symbol is not found 542 * in the local scope, try to find the symbol in the main executable. 543 */ 544 545 if (si->has_DT_SYMBOLIC) { 546 DEBUG("%s: looking up %s in executable %s after local scope", 547 si->name, name, somain->name); 548 s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal); 549 if (s != NULL) { 550 *lsi = somain; 551 goto done; 552 } 553 } 554 } 555 } 556 557 /* Next, look for it in the preloads list */ 558 for (int i = 0; g_ld_preloads[i] != NULL; i++) { 559 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 560 if (s != NULL) { 561 *lsi = g_ld_preloads[i]; 562 goto done; 563 } 564 } 565 566 for (int i = 0; needed[i] != NULL; i++) { 567 DEBUG("%s: looking up %s in %s", 568 si->name, name, needed[i]->name); 569 s = soinfo_elf_lookup(needed[i], elf_hash, name, SymbolLookupScope::kExcludeLocal); 570 if (s != NULL) { 571 *lsi = needed[i]; 572 goto done; 573 } 574 } 575 576done: 577 if (s != NULL) { 578 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 579 "found in %s, base = %p, load bias = %p", 580 si->name, name, reinterpret_cast<void*>(s->st_value), 581 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 582 reinterpret_cast<void*>((*lsi)->load_bias)); 583 return s; 584 } 585 586 return NULL; 587} 588 589/* This is used by dlsym(3). It performs symbol lookup only within the 590 specified soinfo object and not in any of its dependencies. 591 592 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 593 that it should do a breadth first search through the dependency 594 tree. This agrees with the ELF spec (aka System V Application 595 Binary Interface) where in Chapter 5 it discuss resolving "Shared 596 Object Dependencies" in breadth first search order. 597 */ 598ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name, soinfo* caller) { 599 return soinfo_elf_lookup(si, elfhash(name), name, 600 caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 601} 602 603/* This is used by dlsym(3) to performs a global symbol lookup. If the 604 start value is null (for RTLD_DEFAULT), the search starts at the 605 beginning of the global solist. Otherwise the search starts at the 606 specified soinfo (for RTLD_NEXT). 607 */ 608ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start, soinfo* caller) { 609 unsigned elf_hash = elfhash(name); 610 611 if (start == NULL) { 612 start = solist; 613 } 614 615 ElfW(Sym)* s = NULL; 616 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 617 s = soinfo_elf_lookup(si, elf_hash, name, 618 caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal); 619 if (s != NULL) { 620 *found = si; 621 break; 622 } 623 } 624 625 if (s != NULL) { 626 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 627 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 628 } 629 630 return s; 631} 632 633soinfo* find_containing_library(const void* p) { 634 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 635 for (soinfo* si = solist; si != NULL; si = si->next) { 636 if (address >= si->base && address - si->base < si->size) { 637 return si; 638 } 639 } 640 return NULL; 641} 642 643ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 644 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 645 646 // Search the library's symbol table for any defined symbol which 647 // contains this address. 648 for (size_t i = 0; i < si->nchain; ++i) { 649 ElfW(Sym)* sym = &si->symtab[i]; 650 if (sym->st_shndx != SHN_UNDEF && 651 soaddr >= sym->st_value && 652 soaddr < sym->st_value + sym->st_size) { 653 return sym; 654 } 655 } 656 657 return NULL; 658} 659 660static int open_library_on_path(const char* name, const char* const paths[]) { 661 char buf[512]; 662 for (size_t i = 0; paths[i] != NULL; ++i) { 663 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 664 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 665 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 666 continue; 667 } 668 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 669 if (fd != -1) { 670 return fd; 671 } 672 } 673 return -1; 674} 675 676static int open_library(const char* name) { 677 TRACE("[ opening %s ]", name); 678 679 // If the name contains a slash, we should attempt to open it directly and not search the paths. 680 if (strchr(name, '/') != NULL) { 681 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 682 if (fd != -1) { 683 return fd; 684 } 685 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 686#if defined(__LP64__) 687 return -1; 688#endif 689 } 690 691 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 692 int fd = open_library_on_path(name, g_ld_library_paths); 693 if (fd == -1) { 694 fd = open_library_on_path(name, kDefaultLdPaths); 695 } 696 return fd; 697} 698 699static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 700 int fd = -1; 701 ScopedFd file_guard(-1); 702 703 if (extinfo != NULL && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) { 704 fd = extinfo->library_fd; 705 } else { 706 // Open the file. 707 fd = open_library(name); 708 if (fd == -1) { 709 DL_ERR("library \"%s\" not found", name); 710 return NULL; 711 } 712 713 file_guard.reset(fd); 714 } 715 716 ElfReader elf_reader(name, fd); 717 718 struct stat file_stat; 719 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) { 720 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno)); 721 return NULL; 722 } 723 724 // Check for symlink and other situations where 725 // file can have different names. 726 for (soinfo* si = solist; si != NULL; si = si->next) { 727 if (si->get_st_dev() != 0 && 728 si->get_st_ino() != 0 && 729 si->get_st_dev() == file_stat.st_dev && 730 si->get_st_ino() == file_stat.st_ino) { 731 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name); 732 return si; 733 } 734 } 735 736 if ((dlflags & RTLD_NOLOAD) != 0) { 737 return NULL; 738 } 739 740 // Read the ELF header and load the segments. 741 if (!elf_reader.Load(extinfo)) { 742 return NULL; 743 } 744 745 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat); 746 if (si == NULL) { 747 return NULL; 748 } 749 si->base = elf_reader.load_start(); 750 si->size = elf_reader.load_size(); 751 si->load_bias = elf_reader.load_bias(); 752 si->phnum = elf_reader.phdr_count(); 753 si->phdr = elf_reader.loaded_phdr(); 754 755 // At this point we know that whatever is loaded @ base is a valid ELF 756 // shared library whose segments are properly mapped in. 757 TRACE("[ load_library base=%p size=%zu name='%s' ]", 758 reinterpret_cast<void*>(si->base), si->size, si->name); 759 760 if (!soinfo_link_image(si, extinfo)) { 761 soinfo_free(si); 762 return NULL; 763 } 764 765 return si; 766} 767 768static soinfo *find_loaded_library_by_name(const char* name) { 769 const char* search_name = SEARCH_NAME(name); 770 for (soinfo* si = solist; si != NULL; si = si->next) { 771 if (!strcmp(search_name, si->name)) { 772 return si; 773 } 774 } 775 return NULL; 776} 777 778static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) { 779 if (name == NULL) { 780 return somain; 781 } 782 783 soinfo* si = find_loaded_library_by_name(name); 784 785 // Library might still be loaded, the accurate detection 786 // of this fact is done by load_library 787 if (si == NULL) { 788 TRACE("[ '%s' has not been found by name. Trying harder...]", name); 789 si = load_library(name, dlflags, extinfo); 790 } 791 792 if (si != NULL && (si->flags & FLAG_LINKED) == 0) { 793 DL_ERR("recursive link to \"%s\"", si->name); 794 return NULL; 795 } 796 797 return si; 798} 799 800static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) { 801 soinfo* si = find_library_internal(name, dlflags, extinfo); 802 if (si != NULL) { 803 si->ref_count++; 804 } 805 return si; 806} 807 808static void soinfo_unload(soinfo* si) { 809 if (si->ref_count == 1) { 810 TRACE("unloading '%s'", si->name); 811 si->CallDestructors(); 812 813 if ((si->flags | FLAG_NEW_SOINFO) != 0) { 814 si->get_children().for_each([&] (soinfo* child) { 815 TRACE("%s needs to unload %s", si->name, child->name); 816 soinfo_unload(child); 817 }); 818 } else { 819 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 820 if (d->d_tag == DT_NEEDED) { 821 const char* library_name = si->strtab + d->d_un.d_val; 822 TRACE("%s needs to unload %s", si->name, library_name); 823 soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL); 824 if (needed != NULL) { 825 soinfo_unload(needed); 826 } else { 827 // Not found: for example if symlink was deleted between dlopen and dlclose 828 // Since we cannot really handle errors at this point - print and continue. 829 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name); 830 } 831 } 832 } 833 } 834 835 notify_gdb_of_unload(si); 836 si->ref_count = 0; 837 soinfo_free(si); 838 } else { 839 si->ref_count--; 840 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 841 } 842} 843 844void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 845 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]); 846} 847 848void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 849 if (!get_AT_SECURE()) { 850 parse_LD_LIBRARY_PATH(ld_library_path); 851 } 852} 853 854soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 855 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) { 856 DL_ERR("invalid flags to dlopen: %x", flags); 857 return NULL; 858 } 859 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 860 DL_ERR("invalid extended flags to android_dlopen_ext: %llx", extinfo->flags); 861 return NULL; 862 } 863 protect_data(PROT_READ | PROT_WRITE); 864 soinfo* si = find_library(name, flags, extinfo); 865 if (si != NULL) { 866 si->CallConstructors(); 867 } 868 protect_data(PROT_READ); 869 return si; 870} 871 872void do_dlclose(soinfo* si) { 873 protect_data(PROT_READ | PROT_WRITE); 874 soinfo_unload(si); 875 protect_data(PROT_READ); 876} 877 878#if defined(USE_RELA) 879static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 880 ElfW(Sym)* s; 881 soinfo* lsi; 882 883 for (size_t idx = 0; idx < count; ++idx, ++rela) { 884 unsigned type = ELFW(R_TYPE)(rela->r_info); 885 unsigned sym = ELFW(R_SYM)(rela->r_info); 886 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 887 ElfW(Addr) sym_addr = 0; 888 const char* sym_name = NULL; 889 890 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 891 if (type == 0) { // R_*_NONE 892 continue; 893 } 894 if (sym != 0) { 895 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 896 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 897 if (s == NULL) { 898 // We only allow an undefined symbol if this is a weak reference... 899 s = &si->symtab[sym]; 900 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 901 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 902 return -1; 903 } 904 905 /* IHI0044C AAELF 4.5.1.1: 906 907 Libraries are not searched to resolve weak references. 908 It is not an error for a weak reference to remain unsatisfied. 909 910 During linking, the value of an undefined weak reference is: 911 - Zero if the relocation type is absolute 912 - The address of the place if the relocation is pc-relative 913 - The address of nominal base address if the relocation 914 type is base-relative. 915 */ 916 917 switch (type) { 918#if defined(__aarch64__) 919 case R_AARCH64_JUMP_SLOT: 920 case R_AARCH64_GLOB_DAT: 921 case R_AARCH64_ABS64: 922 case R_AARCH64_ABS32: 923 case R_AARCH64_ABS16: 924 case R_AARCH64_RELATIVE: 925 /* 926 * The sym_addr was initialized to be zero above, or the relocation 927 * code below does not care about value of sym_addr. 928 * No need to do anything. 929 */ 930 break; 931#elif defined(__x86_64__) 932 case R_X86_64_JUMP_SLOT: 933 case R_X86_64_GLOB_DAT: 934 case R_X86_64_32: 935 case R_X86_64_64: 936 case R_X86_64_RELATIVE: 937 // No need to do anything. 938 break; 939 case R_X86_64_PC32: 940 sym_addr = reloc; 941 break; 942#endif 943 default: 944 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 945 return -1; 946 } 947 } else { 948 // We got a definition. 949 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 950 } 951 count_relocation(kRelocSymbol); 952 } else { 953 s = NULL; 954 } 955 956 switch (type) { 957#if defined(__aarch64__) 958 case R_AARCH64_JUMP_SLOT: 959 count_relocation(kRelocAbsolute); 960 MARK(rela->r_offset); 961 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 962 reloc, (sym_addr + rela->r_addend), sym_name); 963 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 964 break; 965 case R_AARCH64_GLOB_DAT: 966 count_relocation(kRelocAbsolute); 967 MARK(rela->r_offset); 968 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 969 reloc, (sym_addr + rela->r_addend), sym_name); 970 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 971 break; 972 case R_AARCH64_ABS64: 973 count_relocation(kRelocAbsolute); 974 MARK(rela->r_offset); 975 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 976 reloc, (sym_addr + rela->r_addend), sym_name); 977 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 978 break; 979 case R_AARCH64_ABS32: 980 count_relocation(kRelocAbsolute); 981 MARK(rela->r_offset); 982 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 983 reloc, (sym_addr + rela->r_addend), sym_name); 984 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 985 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 986 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 987 } else { 988 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 989 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 990 static_cast<ElfW(Addr)>(INT32_MIN), 991 static_cast<ElfW(Addr)>(UINT32_MAX)); 992 return -1; 993 } 994 break; 995 case R_AARCH64_ABS16: 996 count_relocation(kRelocAbsolute); 997 MARK(rela->r_offset); 998 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 999 reloc, (sym_addr + rela->r_addend), sym_name); 1000 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 1001 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1002 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 1003 } else { 1004 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1005 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 1006 static_cast<ElfW(Addr)>(INT16_MIN), 1007 static_cast<ElfW(Addr)>(UINT16_MAX)); 1008 return -1; 1009 } 1010 break; 1011 case R_AARCH64_PREL64: 1012 count_relocation(kRelocRelative); 1013 MARK(rela->r_offset); 1014 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 1015 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1016 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 1017 break; 1018 case R_AARCH64_PREL32: 1019 count_relocation(kRelocRelative); 1020 MARK(rela->r_offset); 1021 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 1022 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1023 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1024 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 1025 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1026 } else { 1027 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1028 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1029 static_cast<ElfW(Addr)>(INT32_MIN), 1030 static_cast<ElfW(Addr)>(UINT32_MAX)); 1031 return -1; 1032 } 1033 break; 1034 case R_AARCH64_PREL16: 1035 count_relocation(kRelocRelative); 1036 MARK(rela->r_offset); 1037 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1038 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1039 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1040 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1041 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1042 } else { 1043 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1044 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1045 static_cast<ElfW(Addr)>(INT16_MIN), 1046 static_cast<ElfW(Addr)>(UINT16_MAX)); 1047 return -1; 1048 } 1049 break; 1050 1051 case R_AARCH64_RELATIVE: 1052 count_relocation(kRelocRelative); 1053 MARK(rela->r_offset); 1054 if (sym) { 1055 DL_ERR("odd RELATIVE form..."); 1056 return -1; 1057 } 1058 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1059 reloc, (si->base + rela->r_addend)); 1060 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1061 break; 1062 1063 case R_AARCH64_COPY: 1064 if ((si->flags & FLAG_EXE) == 0) { 1065 /* 1066 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1067 * 1068 * Section 4.7.1.10 "Dynamic relocations" 1069 * R_AARCH64_COPY may only appear in executable objects where e_type is 1070 * set to ET_EXEC. 1071 * 1072 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1073 * We should explicitly disallow ET_DYN executables from having 1074 * R_AARCH64_COPY relocations. 1075 */ 1076 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1077 return -1; 1078 } 1079 count_relocation(kRelocCopy); 1080 MARK(rela->r_offset); 1081 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1082 reloc, 1083 s->st_size, 1084 (sym_addr + rela->r_addend), 1085 sym_name); 1086 if (reloc == (sym_addr + rela->r_addend)) { 1087 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1088 1089 if (src == NULL) { 1090 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1091 return -1; 1092 } 1093 if (lsi->has_DT_SYMBOLIC) { 1094 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1095 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1096 return -1; 1097 } 1098 if (s->st_size < src->st_size) { 1099 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1100 si->name, s->st_size, src->st_size); 1101 return -1; 1102 } 1103 memcpy(reinterpret_cast<void*>(reloc), 1104 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1105 } else { 1106 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1107 return -1; 1108 } 1109 break; 1110 case R_AARCH64_TLS_TPREL64: 1111 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1112 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1113 break; 1114 case R_AARCH64_TLS_DTPREL32: 1115 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1116 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1117 break; 1118#elif defined(__x86_64__) 1119 case R_X86_64_JUMP_SLOT: 1120 count_relocation(kRelocAbsolute); 1121 MARK(rela->r_offset); 1122 TRACE_TYPE(RELO, "RELO JMP_SLOT %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_GLOB_DAT: 1127 count_relocation(kRelocAbsolute); 1128 MARK(rela->r_offset); 1129 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1130 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1131 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1132 break; 1133 case R_X86_64_RELATIVE: 1134 count_relocation(kRelocRelative); 1135 MARK(rela->r_offset); 1136 if (sym) { 1137 DL_ERR("odd RELATIVE form..."); 1138 return -1; 1139 } 1140 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1141 static_cast<size_t>(si->base)); 1142 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1143 break; 1144 case R_X86_64_32: 1145 count_relocation(kRelocRelative); 1146 MARK(rela->r_offset); 1147 TRACE_TYPE(RELO, "RELO R_X86_64_32 %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_64: 1152 count_relocation(kRelocRelative); 1153 MARK(rela->r_offset); 1154 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1155 static_cast<size_t>(sym_addr), sym_name); 1156 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1157 break; 1158 case R_X86_64_PC32: 1159 count_relocation(kRelocRelative); 1160 MARK(rela->r_offset); 1161 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1162 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1163 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1164 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1165 break; 1166#endif 1167 1168 default: 1169 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1170 return -1; 1171 } 1172 } 1173 return 0; 1174} 1175 1176#else // REL, not RELA. 1177 1178static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1179 ElfW(Sym)* s; 1180 soinfo* lsi; 1181 1182 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1183 unsigned type = ELFW(R_TYPE)(rel->r_info); 1184 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1185 unsigned sym = ELFW(R_SYM)(rel->r_info); 1186 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1187 ElfW(Addr) sym_addr = 0; 1188 const char* sym_name = NULL; 1189 1190 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1191 if (type == 0) { // R_*_NONE 1192 continue; 1193 } 1194 if (sym != 0) { 1195 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1196 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1197 if (s == NULL) { 1198 // We only allow an undefined symbol if this is a weak reference... 1199 s = &si->symtab[sym]; 1200 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1201 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1202 return -1; 1203 } 1204 1205 /* IHI0044C AAELF 4.5.1.1: 1206 1207 Libraries are not searched to resolve weak references. 1208 It is not an error for a weak reference to remain 1209 unsatisfied. 1210 1211 During linking, the value of an undefined weak reference is: 1212 - Zero if the relocation type is absolute 1213 - The address of the place if the relocation is pc-relative 1214 - The address of nominal base address if the relocation 1215 type is base-relative. 1216 */ 1217 1218 switch (type) { 1219#if defined(__arm__) 1220 case R_ARM_JUMP_SLOT: 1221 case R_ARM_GLOB_DAT: 1222 case R_ARM_ABS32: 1223 case R_ARM_RELATIVE: /* Don't care. */ 1224 // sym_addr was initialized to be zero above or relocation 1225 // code below does not care about value of sym_addr. 1226 // No need to do anything. 1227 break; 1228#elif defined(__i386__) 1229 case R_386_JMP_SLOT: 1230 case R_386_GLOB_DAT: 1231 case R_386_32: 1232 case R_386_RELATIVE: /* Don't care. */ 1233 // sym_addr was initialized to be zero above or relocation 1234 // code below does not care about value of sym_addr. 1235 // No need to do anything. 1236 break; 1237 case R_386_PC32: 1238 sym_addr = reloc; 1239 break; 1240#endif 1241 1242#if defined(__arm__) 1243 case R_ARM_COPY: 1244 // Fall through. Can't really copy if weak symbol is not found at run-time. 1245#endif 1246 default: 1247 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1248 return -1; 1249 } 1250 } else { 1251 // We got a definition. 1252 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1253 } 1254 count_relocation(kRelocSymbol); 1255 } else { 1256 s = NULL; 1257 } 1258 1259 switch (type) { 1260#if defined(__arm__) 1261 case R_ARM_JUMP_SLOT: 1262 count_relocation(kRelocAbsolute); 1263 MARK(rel->r_offset); 1264 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1265 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1266 break; 1267 case R_ARM_GLOB_DAT: 1268 count_relocation(kRelocAbsolute); 1269 MARK(rel->r_offset); 1270 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1271 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1272 break; 1273 case R_ARM_ABS32: 1274 count_relocation(kRelocAbsolute); 1275 MARK(rel->r_offset); 1276 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1277 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1278 break; 1279 case R_ARM_REL32: 1280 count_relocation(kRelocRelative); 1281 MARK(rel->r_offset); 1282 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1283 reloc, sym_addr, rel->r_offset, sym_name); 1284 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1285 break; 1286 case R_ARM_COPY: 1287 if ((si->flags & FLAG_EXE) == 0) { 1288 /* 1289 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1290 * 1291 * Section 4.7.1.10 "Dynamic relocations" 1292 * R_ARM_COPY may only appear in executable objects where e_type is 1293 * set to ET_EXEC. 1294 * 1295 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1296 * We should explicitly disallow ET_DYN executables from having 1297 * R_ARM_COPY relocations. 1298 */ 1299 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1300 return -1; 1301 } 1302 count_relocation(kRelocCopy); 1303 MARK(rel->r_offset); 1304 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1305 if (reloc == sym_addr) { 1306 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1307 1308 if (src == NULL) { 1309 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1310 return -1; 1311 } 1312 if (lsi->has_DT_SYMBOLIC) { 1313 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1314 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1315 return -1; 1316 } 1317 if (s->st_size < src->st_size) { 1318 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1319 si->name, s->st_size, src->st_size); 1320 return -1; 1321 } 1322 memcpy(reinterpret_cast<void*>(reloc), 1323 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1324 } else { 1325 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1326 return -1; 1327 } 1328 break; 1329#elif defined(__i386__) 1330 case R_386_JMP_SLOT: 1331 count_relocation(kRelocAbsolute); 1332 MARK(rel->r_offset); 1333 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1334 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1335 break; 1336 case R_386_GLOB_DAT: 1337 count_relocation(kRelocAbsolute); 1338 MARK(rel->r_offset); 1339 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1340 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1341 break; 1342 case R_386_32: 1343 count_relocation(kRelocRelative); 1344 MARK(rel->r_offset); 1345 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1346 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1347 break; 1348 case R_386_PC32: 1349 count_relocation(kRelocRelative); 1350 MARK(rel->r_offset); 1351 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1352 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1353 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1354 break; 1355#elif defined(__mips__) 1356 case R_MIPS_REL32: 1357#if defined(__LP64__) 1358 // MIPS Elf64_Rel entries contain compound relocations 1359 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1360 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1361 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1362 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1363 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1364 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1365 return -1; 1366 } 1367#endif 1368 count_relocation(kRelocAbsolute); 1369 MARK(rel->r_offset); 1370 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1371 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1372 if (s) { 1373 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1374 } else { 1375 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1376 } 1377 break; 1378#endif 1379 1380#if defined(__arm__) 1381 case R_ARM_RELATIVE: 1382#elif defined(__i386__) 1383 case R_386_RELATIVE: 1384#endif 1385 count_relocation(kRelocRelative); 1386 MARK(rel->r_offset); 1387 if (sym) { 1388 DL_ERR("odd RELATIVE form..."); 1389 return -1; 1390 } 1391 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1392 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1393 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1394 break; 1395 1396 default: 1397 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1398 return -1; 1399 } 1400 } 1401 return 0; 1402} 1403#endif 1404 1405#if defined(__mips__) 1406static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1407 ElfW(Addr)** got = si->plt_got; 1408 if (got == NULL) { 1409 return true; 1410 } 1411 unsigned local_gotno = si->mips_local_gotno; 1412 unsigned gotsym = si->mips_gotsym; 1413 unsigned symtabno = si->mips_symtabno; 1414 ElfW(Sym)* symtab = si->symtab; 1415 1416 // got[0] is the address of the lazy resolver function. 1417 // got[1] may be used for a GNU extension. 1418 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1419 // FIXME: maybe this should be in a separate routine? 1420 if ((si->flags & FLAG_LINKER) == 0) { 1421 size_t g = 0; 1422 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1423 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1424 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1425 } 1426 // Relocate the local GOT entries. 1427 for (; g < local_gotno; g++) { 1428 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1429 } 1430 } 1431 1432 // Now for the global GOT entries... 1433 ElfW(Sym)* sym = symtab + gotsym; 1434 got = si->plt_got + local_gotno; 1435 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1436 // This is an undefined reference... try to locate it. 1437 const char* sym_name = si->strtab + sym->st_name; 1438 soinfo* lsi; 1439 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1440 if (s == NULL) { 1441 // We only allow an undefined symbol if this is a weak reference. 1442 s = &symtab[g]; 1443 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1444 DL_ERR("cannot locate \"%s\"...", sym_name); 1445 return false; 1446 } 1447 *got = 0; 1448 } else { 1449 // FIXME: is this sufficient? 1450 // For reference see NetBSD link loader 1451 // 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 1452 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1453 } 1454 } 1455 return true; 1456} 1457#endif 1458 1459void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1460 if (functions == NULL) { 1461 return; 1462 } 1463 1464 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1465 1466 int begin = reverse ? (count - 1) : 0; 1467 int end = reverse ? -1 : count; 1468 int step = reverse ? -1 : 1; 1469 1470 for (int i = begin; i != end; i += step) { 1471 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1472 CallFunction("function", functions[i]); 1473 } 1474 1475 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1476} 1477 1478void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1479 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1480 return; 1481 } 1482 1483 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1484 function(); 1485 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1486 1487 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1488 // are still writable. This happens with our debug malloc (see http://b/7941716). 1489 protect_data(PROT_READ | PROT_WRITE); 1490} 1491 1492void soinfo::CallPreInitConstructors() { 1493 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1494 // but ignored in a shared library. 1495 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1496} 1497 1498void soinfo::CallConstructors() { 1499 if (constructors_called) { 1500 return; 1501 } 1502 1503 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1504 // protect against recursive constructor calls. One simple example of constructor recursion 1505 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1506 // 1. The program depends on libc, so libc's constructor is called here. 1507 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1508 // 3. dlopen() calls the constructors on the newly created 1509 // soinfo for libc_malloc_debug_leak.so. 1510 // 4. The debug .so depends on libc, so CallConstructors is 1511 // called again with the libc soinfo. If it doesn't trigger the early- 1512 // out above, the libc constructor will be called again (recursively!). 1513 constructors_called = true; 1514 1515 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1516 // The GNU dynamic linker silently ignores these, but we warn the developer. 1517 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1518 name, preinit_array_count); 1519 } 1520 1521 get_children().for_each([] (soinfo* si) { 1522 si->CallConstructors(); 1523 }); 1524 1525 TRACE("\"%s\": calling constructors", name); 1526 1527 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1528 CallFunction("DT_INIT", init_func); 1529 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1530} 1531 1532void soinfo::CallDestructors() { 1533 TRACE("\"%s\": calling destructors", name); 1534 1535 // DT_FINI_ARRAY must be parsed in reverse order. 1536 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1537 1538 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1539 CallFunction("DT_FINI", fini_func); 1540 1541 // This is needed on second call to dlopen 1542 // after library has been unloaded with RTLD_NODELETE 1543 constructors_called = false; 1544} 1545 1546void soinfo::add_child(soinfo* child) { 1547 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1548 return; 1549 } 1550 1551 this->children.push_front(child); 1552 child->parents.push_front(this); 1553} 1554 1555void soinfo::remove_all_links() { 1556 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1557 return; 1558 } 1559 1560 // 1. Untie connected soinfos from 'this'. 1561 children.for_each([&] (soinfo* child) { 1562 child->parents.remove_if([&] (const soinfo* parent) { 1563 return parent == this; 1564 }); 1565 }); 1566 1567 parents.for_each([&] (soinfo* parent) { 1568 parent->children.for_each([&] (const soinfo* child) { 1569 return child == this; 1570 }); 1571 }); 1572 1573 // 2. Once everything untied - clear local lists. 1574 parents.clear(); 1575 children.clear(); 1576} 1577 1578void soinfo::set_st_dev(dev_t dev) { 1579 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1580 return; 1581 } 1582 1583 st_dev = dev; 1584} 1585 1586void soinfo::set_st_ino(ino_t ino) { 1587 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1588 return; 1589 } 1590 1591 st_ino = ino; 1592} 1593 1594dev_t soinfo::get_st_dev() { 1595 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1596 return 0; 1597 } 1598 1599 return st_dev; 1600}; 1601 1602ino_t soinfo::get_st_ino() { 1603 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1604 return 0; 1605 } 1606 1607 return st_ino; 1608} 1609 1610// This is a return on get_children() in case 1611// 'this->flags' does not have FLAG_NEW_SOINFO set. 1612static soinfo::soinfo_list_t g_empty_list; 1613 1614soinfo::soinfo_list_t& soinfo::get_children() { 1615 if ((this->flags & FLAG_NEW_SOINFO) == 0) { 1616 return g_empty_list; 1617 } 1618 1619 return this->children; 1620} 1621 1622/* Force any of the closed stdin, stdout and stderr to be associated with 1623 /dev/null. */ 1624static int nullify_closed_stdio() { 1625 int dev_null, i, status; 1626 int return_value = 0; 1627 1628 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1629 if (dev_null < 0) { 1630 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1631 return -1; 1632 } 1633 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1634 1635 /* If any of the stdio file descriptors is valid and not associated 1636 with /dev/null, dup /dev/null to it. */ 1637 for (i = 0; i < 3; i++) { 1638 /* If it is /dev/null already, we are done. */ 1639 if (i == dev_null) { 1640 continue; 1641 } 1642 1643 TRACE("[ Nullifying stdio file descriptor %d]", i); 1644 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1645 1646 /* If file is opened, we are good. */ 1647 if (status != -1) { 1648 continue; 1649 } 1650 1651 /* The only error we allow is that the file descriptor does not 1652 exist, in which case we dup /dev/null to it. */ 1653 if (errno != EBADF) { 1654 DL_ERR("fcntl failed: %s", strerror(errno)); 1655 return_value = -1; 1656 continue; 1657 } 1658 1659 /* Try dupping /dev/null to this stdio file descriptor and 1660 repeat if there is a signal. Note that any errors in closing 1661 the stdio descriptor are lost. */ 1662 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1663 if (status < 0) { 1664 DL_ERR("dup2 failed: %s", strerror(errno)); 1665 return_value = -1; 1666 continue; 1667 } 1668 } 1669 1670 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1671 if (dev_null > 2) { 1672 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1673 status = TEMP_FAILURE_RETRY(close(dev_null)); 1674 if (status == -1) { 1675 DL_ERR("close failed: %s", strerror(errno)); 1676 return_value = -1; 1677 } 1678 } 1679 1680 return return_value; 1681} 1682 1683static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1684 /* "base" might wrap around UINT32_MAX. */ 1685 ElfW(Addr) base = si->load_bias; 1686 const ElfW(Phdr)* phdr = si->phdr; 1687 int phnum = si->phnum; 1688 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1689 1690 /* We can't debug anything until the linker is relocated */ 1691 if (!relocating_linker) { 1692 INFO("[ linking %s ]", si->name); 1693 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1694 } 1695 1696 /* Extract dynamic section */ 1697 size_t dynamic_count; 1698 ElfW(Word) dynamic_flags; 1699 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1700 &dynamic_count, &dynamic_flags); 1701 if (si->dynamic == NULL) { 1702 if (!relocating_linker) { 1703 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1704 } 1705 return false; 1706 } else { 1707 if (!relocating_linker) { 1708 DEBUG("dynamic = %p", si->dynamic); 1709 } 1710 } 1711 1712#if defined(__arm__) 1713 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1714 &si->ARM_exidx, &si->ARM_exidx_count); 1715#endif 1716 1717 // Extract useful information from dynamic section. 1718 uint32_t needed_count = 0; 1719 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1720 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1721 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1722 switch (d->d_tag) { 1723 case DT_HASH: 1724 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1725 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1726 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1727 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1728 break; 1729 case DT_STRTAB: 1730 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1731 break; 1732 case DT_SYMTAB: 1733 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1734 break; 1735#if !defined(__LP64__) 1736 case DT_PLTREL: 1737 if (d->d_un.d_val != DT_REL) { 1738 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1739 return false; 1740 } 1741 break; 1742#endif 1743 case DT_JMPREL: 1744#if defined(USE_RELA) 1745 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1746#else 1747 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1748#endif 1749 break; 1750 case DT_PLTRELSZ: 1751#if defined(USE_RELA) 1752 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1753#else 1754 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1755#endif 1756 break; 1757#if defined(__mips__) 1758 case DT_PLTGOT: 1759 // Used by mips and mips64. 1760 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1761 break; 1762#endif 1763 case DT_DEBUG: 1764 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1765 // if the dynamic table is writable 1766// FIXME: not working currently for N64 1767// The flags for the LOAD and DYNAMIC program headers do not agree. 1768// The LOAD section containng the dynamic table has been mapped as 1769// read-only, but the DYNAMIC header claims it is writable. 1770#if !(defined(__mips__) && defined(__LP64__)) 1771 if ((dynamic_flags & PF_W) != 0) { 1772 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1773 } 1774 break; 1775#endif 1776#if defined(USE_RELA) 1777 case DT_RELA: 1778 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1779 break; 1780 case DT_RELASZ: 1781 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1782 break; 1783 case DT_REL: 1784 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1785 return false; 1786 case DT_RELSZ: 1787 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1788 return false; 1789#else 1790 case DT_REL: 1791 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1792 break; 1793 case DT_RELSZ: 1794 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1795 break; 1796 case DT_RELA: 1797 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1798 return false; 1799#endif 1800 case DT_INIT: 1801 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1802 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1803 break; 1804 case DT_FINI: 1805 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1806 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1807 break; 1808 case DT_INIT_ARRAY: 1809 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1810 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1811 break; 1812 case DT_INIT_ARRAYSZ: 1813 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1814 break; 1815 case DT_FINI_ARRAY: 1816 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1817 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1818 break; 1819 case DT_FINI_ARRAYSZ: 1820 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1821 break; 1822 case DT_PREINIT_ARRAY: 1823 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1824 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1825 break; 1826 case DT_PREINIT_ARRAYSZ: 1827 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1828 break; 1829 case DT_TEXTREL: 1830#if defined(__LP64__) 1831 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1832 return false; 1833#else 1834 si->has_text_relocations = true; 1835 break; 1836#endif 1837 case DT_SYMBOLIC: 1838 si->has_DT_SYMBOLIC = true; 1839 break; 1840 case DT_NEEDED: 1841 ++needed_count; 1842 break; 1843 case DT_FLAGS: 1844 if (d->d_un.d_val & DF_TEXTREL) { 1845#if defined(__LP64__) 1846 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1847 return false; 1848#else 1849 si->has_text_relocations = true; 1850#endif 1851 } 1852 if (d->d_un.d_val & DF_SYMBOLIC) { 1853 si->has_DT_SYMBOLIC = true; 1854 } 1855 break; 1856#if defined(__mips__) 1857 case DT_STRSZ: 1858 case DT_SYMENT: 1859 case DT_RELENT: 1860 break; 1861 case DT_MIPS_RLD_MAP: 1862 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1863 { 1864 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1865 *dp = &_r_debug; 1866 } 1867 break; 1868 case DT_MIPS_RLD_VERSION: 1869 case DT_MIPS_FLAGS: 1870 case DT_MIPS_BASE_ADDRESS: 1871 case DT_MIPS_UNREFEXTNO: 1872 break; 1873 1874 case DT_MIPS_SYMTABNO: 1875 si->mips_symtabno = d->d_un.d_val; 1876 break; 1877 1878 case DT_MIPS_LOCAL_GOTNO: 1879 si->mips_local_gotno = d->d_un.d_val; 1880 break; 1881 1882 case DT_MIPS_GOTSYM: 1883 si->mips_gotsym = d->d_un.d_val; 1884 break; 1885#endif 1886 1887 default: 1888 DEBUG("Unused DT entry: type %p arg %p", 1889 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1890 break; 1891 } 1892 } 1893 1894 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1895 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1896 1897 // Sanity checks. 1898 if (relocating_linker && needed_count != 0) { 1899 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1900 return false; 1901 } 1902 if (si->nbucket == 0) { 1903 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1904 return false; 1905 } 1906 if (si->strtab == 0) { 1907 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1908 return false; 1909 } 1910 if (si->symtab == 0) { 1911 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1912 return false; 1913 } 1914 1915 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1916 if (si->flags & FLAG_EXE) { 1917 memset(g_ld_preloads, 0, sizeof(g_ld_preloads)); 1918 size_t preload_count = 0; 1919 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) { 1920 soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL); 1921 if (lsi != NULL) { 1922 g_ld_preloads[preload_count++] = lsi; 1923 } else { 1924 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1925 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1926 g_ld_preload_names[i], si->name, linker_get_error_buffer()); 1927 } 1928 } 1929 } 1930 1931 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1932 soinfo** pneeded = needed; 1933 1934 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1935 if (d->d_tag == DT_NEEDED) { 1936 const char* library_name = si->strtab + d->d_un.d_val; 1937 DEBUG("%s needs %s", si->name, library_name); 1938 soinfo* lsi = find_library(library_name, 0, NULL); 1939 if (lsi == NULL) { 1940 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1941 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1942 library_name, si->name, tmp_err_buf); 1943 return false; 1944 } 1945 1946 si->add_child(lsi); 1947 *pneeded++ = lsi; 1948 } 1949 } 1950 *pneeded = NULL; 1951 1952#if !defined(__LP64__) 1953 if (si->has_text_relocations) { 1954 // Make segments writable to allow text relocations to work properly. We will later call 1955 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1956 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1957 "security hardening. Please fix.", si->name); 1958 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1959 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1960 si->name, strerror(errno)); 1961 return false; 1962 } 1963 } 1964#endif 1965 1966#if defined(USE_RELA) 1967 if (si->plt_rela != NULL) { 1968 DEBUG("[ relocating %s plt ]\n", si->name); 1969 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1970 return false; 1971 } 1972 } 1973 if (si->rela != NULL) { 1974 DEBUG("[ relocating %s ]\n", si->name); 1975 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1976 return false; 1977 } 1978 } 1979#else 1980 if (si->plt_rel != NULL) { 1981 DEBUG("[ relocating %s plt ]", si->name); 1982 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1983 return false; 1984 } 1985 } 1986 if (si->rel != NULL) { 1987 DEBUG("[ relocating %s ]", si->name); 1988 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1989 return false; 1990 } 1991 } 1992#endif 1993 1994#if defined(__mips__) 1995 if (!mips_relocate_got(si, needed)) { 1996 return false; 1997 } 1998#endif 1999 2000 si->flags |= FLAG_LINKED; 2001 DEBUG("[ finished linking %s ]", si->name); 2002 2003#if !defined(__LP64__) 2004 if (si->has_text_relocations) { 2005 // All relocations are done, we can protect our segments back to read-only. 2006 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 2007 DL_ERR("can't protect segments for \"%s\": %s", 2008 si->name, strerror(errno)); 2009 return false; 2010 } 2011 } 2012#endif 2013 2014 /* We can also turn on GNU RELRO protection */ 2015 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 2016 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 2017 si->name, strerror(errno)); 2018 return false; 2019 } 2020 2021 /* Handle serializing/sharing the RELRO segment */ 2022 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 2023 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 2024 extinfo->relro_fd) < 0) { 2025 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 2026 si->name, strerror(errno)); 2027 return false; 2028 } 2029 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 2030 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 2031 extinfo->relro_fd) < 0) { 2032 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 2033 si->name, strerror(errno)); 2034 return false; 2035 } 2036 } 2037 2038 notify_gdb_of_load(si); 2039 return true; 2040} 2041 2042/* 2043 * This function add vdso to internal dso list. 2044 * It helps to stack unwinding through signal handlers. 2045 * Also, it makes bionic more like glibc. 2046 */ 2047static void add_vdso(KernelArgumentBlock& args __unused) { 2048#if defined(AT_SYSINFO_EHDR) 2049 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 2050 if (ehdr_vdso == NULL) { 2051 return; 2052 } 2053 2054 soinfo* si = soinfo_alloc("[vdso]", NULL); 2055 2056 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 2057 si->phnum = ehdr_vdso->e_phnum; 2058 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 2059 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2060 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 2061 2062 soinfo_link_image(si, NULL); 2063#endif 2064} 2065 2066/* 2067 * This is linker soinfo for GDB. See details below. 2068 */ 2069static soinfo linker_soinfo_for_gdb; 2070 2071/* gdb expects the linker to be in the debug shared object list. 2072 * Without this, gdb has trouble locating the linker's ".text" 2073 * and ".plt" sections. Gdb could also potentially use this to 2074 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2075 * Don't use soinfo_alloc(), because the linker shouldn't 2076 * be on the soinfo list. 2077 */ 2078static void init_linker_info_for_gdb(ElfW(Addr) linker_base) { 2079#if defined(__LP64__) 2080 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name)); 2081#else 2082 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name)); 2083#endif 2084 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO; 2085 linker_soinfo_for_gdb.base = linker_base; 2086 2087 /* 2088 * Set the dynamic field in the link map otherwise gdb will complain with 2089 * the following: 2090 * warning: .dynamic section for "/system/bin/linker" is not at the 2091 * expected address (wrong library or version mismatch?) 2092 */ 2093 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2094 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2095 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2096 &linker_soinfo_for_gdb.dynamic, NULL, NULL); 2097 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb); 2098} 2099 2100/* 2101 * This code is called after the linker has linked itself and 2102 * fixed it's own GOT. It is safe to make references to externs 2103 * and other non-local data at this point. 2104 */ 2105static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 2106 /* NOTE: we store the args pointer on a special location 2107 * of the temporary TLS area in order to pass it to 2108 * the C Library's runtime initializer. 2109 * 2110 * The initializer must clear the slot and reset the TLS 2111 * to point to a different location to ensure that no other 2112 * shared library constructor can access it. 2113 */ 2114 __libc_init_tls(args); 2115 2116#if TIMING 2117 struct timeval t0, t1; 2118 gettimeofday(&t0, 0); 2119#endif 2120 2121 // Initialize environment functions, and get to the ELF aux vectors table. 2122 linker_env_init(args); 2123 2124 // If this is a setuid/setgid program, close the security hole described in 2125 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 2126 if (get_AT_SECURE()) { 2127 nullify_closed_stdio(); 2128 } 2129 2130 debuggerd_init(); 2131 2132 // Get a few environment variables. 2133 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 2134 if (LD_DEBUG != NULL) { 2135 g_ld_debug_verbosity = atoi(LD_DEBUG); 2136 } 2137 2138 // Normally, these are cleaned by linker_env_init, but the test 2139 // doesn't cost us anything. 2140 const char* ldpath_env = NULL; 2141 const char* ldpreload_env = NULL; 2142 if (!get_AT_SECURE()) { 2143 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2144 ldpreload_env = linker_env_get("LD_PRELOAD"); 2145 } 2146 2147 // Linker does not call constructors for its own 2148 // global variables so we need to initialize 2149 // the allocators explicitly. 2150 g_soinfo_allocator.init(); 2151 g_soinfo_links_allocator.init(); 2152 2153 INFO("[ android linker & debugger ]"); 2154 2155 soinfo* si = soinfo_alloc(args.argv[0], NULL); 2156 if (si == NULL) { 2157 exit(EXIT_FAILURE); 2158 } 2159 2160 /* bootstrap the link map, the main exe always needs to be first */ 2161 si->flags |= FLAG_EXE; 2162 link_map* map = &(si->link_map_head); 2163 2164 map->l_addr = 0; 2165 map->l_name = args.argv[0]; 2166 map->l_prev = NULL; 2167 map->l_next = NULL; 2168 2169 _r_debug.r_map = map; 2170 r_debug_tail = map; 2171 2172 init_linker_info_for_gdb(linker_base); 2173 2174 // Extract information passed from the kernel. 2175 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2176 si->phnum = args.getauxval(AT_PHNUM); 2177 si->entry = args.getauxval(AT_ENTRY); 2178 2179 /* Compute the value of si->base. We can't rely on the fact that 2180 * the first entry is the PHDR because this will not be true 2181 * for certain executables (e.g. some in the NDK unit test suite) 2182 */ 2183 si->base = 0; 2184 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2185 si->load_bias = 0; 2186 for (size_t i = 0; i < si->phnum; ++i) { 2187 if (si->phdr[i].p_type == PT_PHDR) { 2188 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2189 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2190 break; 2191 } 2192 } 2193 si->dynamic = NULL; 2194 si->ref_count = 1; 2195 2196#if defined(__LP64__) 2197 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base); 2198 if (elf_hdr->e_type != ET_DYN) { 2199 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n"); 2200 exit(EXIT_FAILURE); 2201 } 2202#endif 2203 2204 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2205 parse_LD_LIBRARY_PATH(ldpath_env); 2206 parse_LD_PRELOAD(ldpreload_env); 2207 2208 somain = si; 2209 2210 if (!soinfo_link_image(si, NULL)) { 2211 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2212 exit(EXIT_FAILURE); 2213 } 2214 2215 add_vdso(args); 2216 2217 si->CallPreInitConstructors(); 2218 2219 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) { 2220 g_ld_preloads[i]->CallConstructors(); 2221 } 2222 2223 /* After the link_image, the si->load_bias is initialized. 2224 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2225 * We need to update this value for so exe here. So Unwind_Backtrace 2226 * for some arch like x86 could work correctly within so exe. 2227 */ 2228 map->l_addr = si->load_bias; 2229 si->CallConstructors(); 2230 2231#if TIMING 2232 gettimeofday(&t1, NULL); 2233 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2234 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2235 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2236#endif 2237#if STATS 2238 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2239 linker_stats.count[kRelocAbsolute], 2240 linker_stats.count[kRelocRelative], 2241 linker_stats.count[kRelocCopy], 2242 linker_stats.count[kRelocSymbol]); 2243#endif 2244#if COUNT_PAGES 2245 { 2246 unsigned n; 2247 unsigned i; 2248 unsigned count = 0; 2249 for (n = 0; n < 4096; n++) { 2250 if (bitmask[n]) { 2251 unsigned x = bitmask[n]; 2252#if defined(__LP64__) 2253 for (i = 0; i < 32; i++) { 2254#else 2255 for (i = 0; i < 8; i++) { 2256#endif 2257 if (x & 1) { 2258 count++; 2259 } 2260 x >>= 1; 2261 } 2262 } 2263 } 2264 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2265 } 2266#endif 2267 2268#if TIMING || STATS || COUNT_PAGES 2269 fflush(stdout); 2270#endif 2271 2272 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2273 return si->entry; 2274} 2275 2276/* Compute the load-bias of an existing executable. This shall only 2277 * be used to compute the load bias of an executable or shared library 2278 * that was loaded by the kernel itself. 2279 * 2280 * Input: 2281 * elf -> address of ELF header, assumed to be at the start of the file. 2282 * Return: 2283 * load bias, i.e. add the value of any p_vaddr in the file to get 2284 * the corresponding address in memory. 2285 */ 2286static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2287 ElfW(Addr) offset = elf->e_phoff; 2288 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2289 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2290 2291 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2292 if (phdr->p_type == PT_LOAD) { 2293 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2294 } 2295 } 2296 return 0; 2297} 2298 2299/* 2300 * This is the entry point for the linker, called from begin.S. This 2301 * method is responsible for fixing the linker's own relocations, and 2302 * then calling __linker_init_post_relocation(). 2303 * 2304 * Because this method is called before the linker has fixed it's own 2305 * relocations, any attempt to reference an extern variable, extern 2306 * function, or other GOT reference will generate a segfault. 2307 */ 2308extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2309 // Initialize static variables. 2310 solist = get_libdl_info(); 2311 sonext = get_libdl_info(); 2312 2313 KernelArgumentBlock args(raw_args); 2314 2315 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2316 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2317 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2318 2319 soinfo linker_so; 2320 memset(&linker_so, 0, sizeof(soinfo)); 2321 2322 strcpy(linker_so.name, "[dynamic linker]"); 2323 linker_so.base = linker_addr; 2324 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2325 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2326 linker_so.dynamic = NULL; 2327 linker_so.phdr = phdr; 2328 linker_so.phnum = elf_hdr->e_phnum; 2329 linker_so.flags |= FLAG_LINKER; 2330 2331 if (!soinfo_link_image(&linker_so, NULL)) { 2332 // It would be nice to print an error message, but if the linker 2333 // can't link itself, there's no guarantee that we'll be able to 2334 // call write() (because it involves a GOT reference). We may as 2335 // well try though... 2336 const char* msg = "CANNOT LINK EXECUTABLE: "; 2337 write(2, msg, strlen(msg)); 2338 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2339 write(2, "\n", 1); 2340 _exit(EXIT_FAILURE); 2341 } 2342 2343 // We have successfully fixed our own relocations. It's safe to run 2344 // the main part of the linker now. 2345 args.abort_message_ptr = &g_abort_message; 2346 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2347 2348 protect_data(PROT_READ); 2349 2350 // Return the address that the calling assembly stub should jump to. 2351 return start_address; 2352} 2353