linker.cpp revision 5ca7ed9005ea16733d7c87d7154473b7a500be0c
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/atomics.h> 38#include <sys/mman.h> 39#include <sys/stat.h> 40#include <unistd.h> 41 42// Private C library headers. 43#include "private/bionic_tls.h" 44#include "private/KernelArgumentBlock.h" 45#include "private/ScopedPthreadMutexLocker.h" 46 47#include "linker.h" 48#include "linker_debug.h" 49#include "linker_environ.h" 50#include "linker_phdr.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 68static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo); 69static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf); 70 71// We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous 72// maps, each a single page in size. The pages are broken up into as many struct soinfo 73// objects as will fit, and they're all threaded together on a free list. 74#define SOINFO_PER_POOL ((PAGE_SIZE - sizeof(soinfo_pool_t*)) / sizeof(soinfo)) 75struct soinfo_pool_t { 76 soinfo_pool_t* next; 77 soinfo info[SOINFO_PER_POOL]; 78}; 79static struct soinfo_pool_t* gSoInfoPools = NULL; 80static soinfo* gSoInfoFreeList = NULL; 81 82static soinfo* solist = &libdl_info; 83static soinfo* sonext = &libdl_info; 84static soinfo* somain; /* main process, always the one after libdl_info */ 85 86static const char* const gDefaultLdPaths[] = { 87#if defined(__LP64__) 88 "/vendor/lib64", 89 "/system/lib64", 90#else 91 "/vendor/lib", 92 "/system/lib", 93#endif 94 NULL 95}; 96 97#define LDPATH_BUFSIZE (LDPATH_MAX*64) 98#define LDPATH_MAX 8 99 100#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64) 101#define LDPRELOAD_MAX 8 102 103static char gLdPathsBuffer[LDPATH_BUFSIZE]; 104static const char* gLdPaths[LDPATH_MAX + 1]; 105 106static char gLdPreloadsBuffer[LDPRELOAD_BUFSIZE]; 107static const char* gLdPreloadNames[LDPRELOAD_MAX + 1]; 108 109static soinfo* gLdPreloads[LDPRELOAD_MAX + 1]; 110 111__LIBC_HIDDEN__ int gLdDebugVerbosity; 112 113__LIBC_HIDDEN__ abort_msg_t* gAbortMessage = NULL; // For debuggerd. 114 115enum RelocationKind { 116 kRelocAbsolute = 0, 117 kRelocRelative, 118 kRelocCopy, 119 kRelocSymbol, 120 kRelocMax 121}; 122 123#if STATS 124struct linker_stats_t { 125 int count[kRelocMax]; 126}; 127 128static linker_stats_t linker_stats; 129 130static void count_relocation(RelocationKind kind) { 131 ++linker_stats.count[kind]; 132} 133#else 134static void count_relocation(RelocationKind) { 135} 136#endif 137 138#if COUNT_PAGES 139static unsigned bitmask[4096]; 140#if defined(__LP64__) 141#define MARK(offset) \ 142 do { \ 143 if ((((offset) >> 12) >> 5) < 4096) \ 144 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \ 145 } while (0) 146#else 147#define MARK(offset) \ 148 do { \ 149 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 150 } while (0) 151#endif 152#else 153#define MARK(x) do {} while (0) 154#endif 155 156// You shouldn't try to call memory-allocating functions in the dynamic linker. 157// Guard against the most obvious ones. 158#define DISALLOW_ALLOCATION(return_type, name, ...) \ 159 return_type name __VA_ARGS__ \ 160 { \ 161 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 162 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \ 163 write(2, msg, strlen(msg)); \ 164 abort(); \ 165 } 166DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused)); 167DISALLOW_ALLOCATION(void, free, (void* u __unused)); 168DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused)); 169DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused)); 170 171static char tmp_err_buf[768]; 172static char __linker_dl_err_buf[768]; 173 174char* linker_get_error_buffer() { 175 return &__linker_dl_err_buf[0]; 176} 177 178size_t linker_get_error_buffer_size() { 179 return sizeof(__linker_dl_err_buf); 180} 181 182/* 183 * This function is an empty stub where GDB locates a breakpoint to get notified 184 * about linker activity. 185 */ 186extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 187 188static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 189static link_map* r_debug_tail = 0; 190 191static pthread_mutex_t gDebugMutex = PTHREAD_MUTEX_INITIALIZER; 192 193static void insert_soinfo_into_debug_map(soinfo* info) { 194 // Copy the necessary fields into the debug structure. 195 link_map* map = &(info->link_map_head); 196 map->l_addr = info->load_bias; 197 map->l_name = reinterpret_cast<char*>(info->name); 198 map->l_ld = info->dynamic; 199 200 /* Stick the new library at the end of the list. 201 * gdb tends to care more about libc than it does 202 * about leaf libraries, and ordering it this way 203 * reduces the back-and-forth over the wire. 204 */ 205 if (r_debug_tail) { 206 r_debug_tail->l_next = map; 207 map->l_prev = r_debug_tail; 208 map->l_next = 0; 209 } else { 210 _r_debug.r_map = map; 211 map->l_prev = 0; 212 map->l_next = 0; 213 } 214 r_debug_tail = map; 215} 216 217static void remove_soinfo_from_debug_map(soinfo* info) { 218 link_map* map = &(info->link_map_head); 219 220 if (r_debug_tail == map) { 221 r_debug_tail = map->l_prev; 222 } 223 224 if (map->l_prev) { 225 map->l_prev->l_next = map->l_next; 226 } 227 if (map->l_next) { 228 map->l_next->l_prev = map->l_prev; 229 } 230} 231 232static void notify_gdb_of_load(soinfo* info) { 233 if (info->flags & FLAG_EXE) { 234 // GDB already knows about the main executable 235 return; 236 } 237 238 ScopedPthreadMutexLocker locker(&gDebugMutex); 239 240 _r_debug.r_state = r_debug::RT_ADD; 241 rtld_db_dlactivity(); 242 243 insert_soinfo_into_debug_map(info); 244 245 _r_debug.r_state = r_debug::RT_CONSISTENT; 246 rtld_db_dlactivity(); 247} 248 249static void notify_gdb_of_unload(soinfo* info) { 250 if (info->flags & FLAG_EXE) { 251 // GDB already knows about the main executable 252 return; 253 } 254 255 ScopedPthreadMutexLocker locker(&gDebugMutex); 256 257 _r_debug.r_state = r_debug::RT_DELETE; 258 rtld_db_dlactivity(); 259 260 remove_soinfo_from_debug_map(info); 261 262 _r_debug.r_state = r_debug::RT_CONSISTENT; 263 rtld_db_dlactivity(); 264} 265 266void notify_gdb_of_libraries() { 267 _r_debug.r_state = r_debug::RT_ADD; 268 rtld_db_dlactivity(); 269 _r_debug.r_state = r_debug::RT_CONSISTENT; 270 rtld_db_dlactivity(); 271} 272 273static bool ensure_free_list_non_empty() { 274 if (gSoInfoFreeList != NULL) { 275 return true; 276 } 277 278 // Allocate a new pool. 279 soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool), 280 PROT_READ|PROT_WRITE, 281 MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); 282 if (pool == MAP_FAILED) { 283 return false; 284 } 285 286 // Add the pool to our list of pools. 287 pool->next = gSoInfoPools; 288 gSoInfoPools = pool; 289 290 // Chain the entries in the new pool onto the free list. 291 gSoInfoFreeList = &pool->info[0]; 292 soinfo* next = NULL; 293 for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) { 294 pool->info[i].next = next; 295 next = &pool->info[i]; 296 } 297 298 return true; 299} 300 301static void set_soinfo_pool_protection(int protection) { 302 for (soinfo_pool_t* p = gSoInfoPools; p != NULL; p = p->next) { 303 if (mprotect(p, sizeof(*p), protection) == -1) { 304 abort(); // Can't happen. 305 } 306 } 307} 308 309static soinfo* soinfo_alloc(const char* name) { 310 if (strlen(name) >= SOINFO_NAME_LEN) { 311 DL_ERR("library name \"%s\" too long", name); 312 return NULL; 313 } 314 315 if (!ensure_free_list_non_empty()) { 316 DL_ERR("out of memory when loading \"%s\"", name); 317 return NULL; 318 } 319 320 // Take the head element off the free list. 321 soinfo* si = gSoInfoFreeList; 322 gSoInfoFreeList = gSoInfoFreeList->next; 323 324 // Initialize the new element. 325 memset(si, 0, sizeof(soinfo)); 326 strlcpy(si->name, name, sizeof(si->name)); 327 sonext->next = si; 328 sonext = si; 329 330 TRACE("name %s: allocated soinfo @ %p", name, si); 331 return si; 332} 333 334static void soinfo_free(soinfo* si) { 335 if (si == NULL) { 336 return; 337 } 338 339 soinfo *prev = NULL, *trav; 340 341 TRACE("name %s: freeing soinfo @ %p", si->name, si); 342 343 for (trav = solist; trav != NULL; trav = trav->next) { 344 if (trav == si) 345 break; 346 prev = trav; 347 } 348 if (trav == NULL) { 349 /* si was not in solist */ 350 DL_ERR("name \"%s\" is not in solist!", si->name); 351 return; 352 } 353 354 /* prev will never be NULL, because the first entry in solist is 355 always the static libdl_info. 356 */ 357 prev->next = si->next; 358 if (si == sonext) { 359 sonext = prev; 360 } 361 si->next = gSoInfoFreeList; 362 gSoInfoFreeList = si; 363} 364 365 366static void parse_path(const char* path, const char* delimiters, 367 const char** array, char* buf, size_t buf_size, size_t max_count) { 368 if (path == NULL) { 369 return; 370 } 371 372 size_t len = strlcpy(buf, path, buf_size); 373 374 size_t i = 0; 375 char* buf_p = buf; 376 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 377 if (*array[i] != '\0') { 378 ++i; 379 } 380 } 381 382 // Forget the last path if we had to truncate; this occurs if the 2nd to 383 // last char isn't '\0' (i.e. wasn't originally a delimiter). 384 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 385 array[i - 1] = NULL; 386 } else { 387 array[i] = NULL; 388 } 389} 390 391static void parse_LD_LIBRARY_PATH(const char* path) { 392 parse_path(path, ":", gLdPaths, 393 gLdPathsBuffer, sizeof(gLdPathsBuffer), LDPATH_MAX); 394} 395 396static void parse_LD_PRELOAD(const char* path) { 397 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 398 parse_path(path, " :", gLdPreloadNames, 399 gLdPreloadsBuffer, sizeof(gLdPreloadsBuffer), LDPRELOAD_MAX); 400} 401 402#if defined(__arm__) 403 404/* For a given PC, find the .so that it belongs to. 405 * Returns the base address of the .ARM.exidx section 406 * for that .so, and the number of 8-byte entries 407 * in that section (via *pcount). 408 * 409 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 410 * 411 * This function is exposed via dlfcn.cpp and libdl.so. 412 */ 413_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 414 unsigned addr = (unsigned)pc; 415 416 for (soinfo* si = solist; si != 0; si = si->next) { 417 if ((addr >= si->base) && (addr < (si->base + si->size))) { 418 *pcount = si->ARM_exidx_count; 419 return (_Unwind_Ptr)si->ARM_exidx; 420 } 421 } 422 *pcount = 0; 423 return NULL; 424} 425 426#endif 427 428/* Here, we only have to provide a callback to iterate across all the 429 * loaded libraries. gcc_eh does the rest. */ 430int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 431 int rv = 0; 432 for (soinfo* si = solist; si != NULL; si = si->next) { 433 dl_phdr_info dl_info; 434 dl_info.dlpi_addr = si->link_map_head.l_addr; 435 dl_info.dlpi_name = si->link_map_head.l_name; 436 dl_info.dlpi_phdr = si->phdr; 437 dl_info.dlpi_phnum = si->phnum; 438 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 439 if (rv != 0) { 440 break; 441 } 442 } 443 return rv; 444} 445 446static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 447 ElfW(Sym)* symtab = si->symtab; 448 const char* strtab = si->strtab; 449 450 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 451 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 452 453 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 454 ElfW(Sym)* s = symtab + n; 455 if (strcmp(strtab + s->st_name, name)) continue; 456 457 /* only concern ourselves with global and weak symbol definitions */ 458 switch (ELF_ST_BIND(s->st_info)) { 459 case STB_GLOBAL: 460 case STB_WEAK: 461 if (s->st_shndx == SHN_UNDEF) { 462 continue; 463 } 464 465 TRACE_TYPE(LOOKUP, "FOUND %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 } 470 } 471 472 return NULL; 473} 474 475static unsigned elfhash(const char* _name) { 476 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 477 unsigned h = 0, g; 478 479 while (*name) { 480 h = (h << 4) + *name++; 481 g = h & 0xf0000000; 482 h ^= g; 483 h ^= g >> 24; 484 } 485 return h; 486} 487 488static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 489 unsigned elf_hash = elfhash(name); 490 ElfW(Sym)* s = NULL; 491 492 if (si != NULL && somain != NULL) { 493 /* 494 * Local scope is executable scope. Just start looking into it right away 495 * for the shortcut. 496 */ 497 498 if (si == somain) { 499 s = soinfo_elf_lookup(si, elf_hash, name); 500 if (s != NULL) { 501 *lsi = si; 502 goto done; 503 } 504 } else { 505 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 506 507 /* 508 * If this object was built with symbolic relocations disabled, the 509 * first place to look to resolve external references is the main 510 * executable. 511 */ 512 513 if (!si->has_DT_SYMBOLIC) { 514 DEBUG("%s: looking up %s in executable %s", 515 si->name, name, somain->name); 516 s = soinfo_elf_lookup(somain, elf_hash, name); 517 if (s != NULL) { 518 *lsi = somain; 519 goto done; 520 } 521 } 522 523 /* Look for symbols in the local scope (the object who is 524 * searching). This happens with C++ templates on x86 for some 525 * reason. 526 * 527 * Notes on weak symbols: 528 * The ELF specs are ambiguous about treatment of weak definitions in 529 * dynamic linking. Some systems return the first definition found 530 * and some the first non-weak definition. This is system dependent. 531 * Here we return the first definition found for simplicity. */ 532 533 s = soinfo_elf_lookup(si, elf_hash, name); 534 if (s != NULL) { 535 *lsi = si; 536 goto done; 537 } 538 539 /* 540 * If this object was built with -Bsymbolic and symbol is not found 541 * in the local scope, try to find the symbol in the main executable. 542 */ 543 544 if (si->has_DT_SYMBOLIC) { 545 DEBUG("%s: looking up %s in executable %s after local scope", 546 si->name, name, somain->name); 547 s = soinfo_elf_lookup(somain, elf_hash, name); 548 if (s != NULL) { 549 *lsi = somain; 550 goto done; 551 } 552 } 553 } 554 } 555 556 /* Next, look for it in the preloads list */ 557 for (int i = 0; gLdPreloads[i] != NULL; i++) { 558 s = soinfo_elf_lookup(gLdPreloads[i], elf_hash, name); 559 if (s != NULL) { 560 *lsi = gLdPreloads[i]; 561 goto done; 562 } 563 } 564 565 for (int i = 0; needed[i] != NULL; i++) { 566 DEBUG("%s: looking up %s in %s", 567 si->name, name, needed[i]->name); 568 s = soinfo_elf_lookup(needed[i], elf_hash, name); 569 if (s != NULL) { 570 *lsi = needed[i]; 571 goto done; 572 } 573 } 574 575done: 576 if (s != NULL) { 577 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 578 "found in %s, base = %p, load bias = %p", 579 si->name, name, reinterpret_cast<void*>(s->st_value), 580 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 581 reinterpret_cast<void*>((*lsi)->load_bias)); 582 return s; 583 } 584 585 return NULL; 586} 587 588/* This is used by dlsym(3). It performs symbol lookup only within the 589 specified soinfo object and not in any of its dependencies. 590 591 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 592 that it should do a breadth first search through the dependency 593 tree. This agrees with the ELF spec (aka System V Application 594 Binary Interface) where in Chapter 5 it discuss resolving "Shared 595 Object Dependencies" in breadth first search order. 596 */ 597ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) { 598 return soinfo_elf_lookup(si, elfhash(name), name); 599} 600 601/* This is used by dlsym(3) to performs a global symbol lookup. If the 602 start value is null (for RTLD_DEFAULT), the search starts at the 603 beginning of the global solist. Otherwise the search starts at the 604 specified soinfo (for RTLD_NEXT). 605 */ 606ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 607 unsigned elf_hash = elfhash(name); 608 609 if (start == NULL) { 610 start = solist; 611 } 612 613 ElfW(Sym)* s = NULL; 614 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 615 s = soinfo_elf_lookup(si, elf_hash, name); 616 if (s != NULL) { 617 *found = si; 618 break; 619 } 620 } 621 622 if (s != NULL) { 623 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 624 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 625 } 626 627 return s; 628} 629 630soinfo* find_containing_library(const void* p) { 631 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 632 for (soinfo* si = solist; si != NULL; si = si->next) { 633 if (address >= si->base && address - si->base < si->size) { 634 return si; 635 } 636 } 637 return NULL; 638} 639 640ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 641 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 642 643 // Search the library's symbol table for any defined symbol which 644 // contains this address. 645 for (size_t i = 0; i < si->nchain; ++i) { 646 ElfW(Sym)* sym = &si->symtab[i]; 647 if (sym->st_shndx != SHN_UNDEF && 648 soaddr >= sym->st_value && 649 soaddr < sym->st_value + sym->st_size) { 650 return sym; 651 } 652 } 653 654 return NULL; 655} 656 657static int open_library_on_path(const char* name, const char* const paths[]) { 658 char buf[512]; 659 for (size_t i = 0; paths[i] != NULL; ++i) { 660 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 661 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 662 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 663 continue; 664 } 665 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 666 if (fd != -1) { 667 return fd; 668 } 669 } 670 return -1; 671} 672 673static int open_library(const char* name) { 674 TRACE("[ opening %s ]", name); 675 676 // If the name contains a slash, we should attempt to open it directly and not search the paths. 677 if (strchr(name, '/') != NULL) { 678 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 679 if (fd != -1) { 680 return fd; 681 } 682 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 683#if defined(__LP64__) 684 return -1; 685#endif 686 } 687 688 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 689 int fd = open_library_on_path(name, gLdPaths); 690 if (fd == -1) { 691 fd = open_library_on_path(name, gDefaultLdPaths); 692 } 693 return fd; 694} 695 696static soinfo* load_library(const char* name, const android_dlextinfo* extinfo) { 697 // Open the file. 698 int fd = open_library(name); 699 if (fd == -1) { 700 DL_ERR("library \"%s\" not found", name); 701 return NULL; 702 } 703 704 // Read the ELF header and load the segments. 705 ElfReader elf_reader(name, fd); 706 if (!elf_reader.Load(extinfo)) { 707 return NULL; 708 } 709 710 const char* bname = strrchr(name, '/'); 711 soinfo* si = soinfo_alloc(bname ? bname + 1 : name); 712 if (si == NULL) { 713 return NULL; 714 } 715 si->base = elf_reader.load_start(); 716 si->size = elf_reader.load_size(); 717 si->load_bias = elf_reader.load_bias(); 718 si->flags = 0; 719 si->entry = 0; 720 si->dynamic = NULL; 721 si->phnum = elf_reader.phdr_count(); 722 si->phdr = elf_reader.loaded_phdr(); 723 return si; 724} 725 726static soinfo *find_loaded_library(const char* name) { 727 // TODO: don't use basename only for determining libraries 728 // http://code.google.com/p/android/issues/detail?id=6670 729 730 const char* bname = strrchr(name, '/'); 731 bname = bname ? bname + 1 : name; 732 733 for (soinfo* si = solist; si != NULL; si = si->next) { 734 if (!strcmp(bname, si->name)) { 735 return si; 736 } 737 } 738 return NULL; 739} 740 741static soinfo* find_library_internal(const char* name, const android_dlextinfo* extinfo) { 742 if (name == NULL) { 743 return somain; 744 } 745 746 soinfo* si = find_loaded_library(name); 747 if (si != NULL) { 748 if (si->flags & FLAG_LINKED) { 749 return si; 750 } 751 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 752 return NULL; 753 } 754 755 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 756 si = load_library(name, extinfo); 757 if (si == NULL) { 758 return NULL; 759 } 760 761 // At this point we know that whatever is loaded @ base is a valid ELF 762 // shared library whose segments are properly mapped in. 763 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 764 reinterpret_cast<void*>(si->base), si->size, si->name); 765 766 if (!soinfo_link_image(si, extinfo)) { 767 munmap(reinterpret_cast<void*>(si->base), si->size); 768 soinfo_free(si); 769 return NULL; 770 } 771 772 return si; 773} 774 775static soinfo* find_library(const char* name, const android_dlextinfo* extinfo) { 776 soinfo* si = find_library_internal(name, extinfo); 777 if (si != NULL) { 778 si->ref_count++; 779 } 780 return si; 781} 782 783static int soinfo_unload(soinfo* si) { 784 if (si->ref_count == 1) { 785 TRACE("unloading '%s'", si->name); 786 si->CallDestructors(); 787 788 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 789 if (d->d_tag == DT_NEEDED) { 790 const char* library_name = si->strtab + d->d_un.d_val; 791 TRACE("%s needs to unload %s", si->name, library_name); 792 soinfo_unload(find_loaded_library(library_name)); 793 } 794 } 795 796 munmap(reinterpret_cast<void*>(si->base), si->size); 797 notify_gdb_of_unload(si); 798 soinfo_free(si); 799 si->ref_count = 0; 800 } else { 801 si->ref_count--; 802 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 803 } 804 return 0; 805} 806 807void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 808 snprintf(buffer, buffer_size, "%s:%s", gDefaultLdPaths[0], gDefaultLdPaths[1]); 809} 810 811void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 812 if (!get_AT_SECURE()) { 813 parse_LD_LIBRARY_PATH(ld_library_path); 814 } 815} 816 817soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) { 818 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 819 DL_ERR("invalid flags to dlopen: %x", flags); 820 return NULL; 821 } 822 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) { 823 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags); 824 return NULL; 825 } 826 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 827 soinfo* si = find_library(name, extinfo); 828 if (si != NULL) { 829 si->CallConstructors(); 830 } 831 set_soinfo_pool_protection(PROT_READ); 832 return si; 833} 834 835int do_dlclose(soinfo* si) { 836 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 837 int result = soinfo_unload(si); 838 set_soinfo_pool_protection(PROT_READ); 839 return result; 840} 841 842#if defined(USE_RELA) 843static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 844 ElfW(Sym)* s; 845 soinfo* lsi; 846 847 for (size_t idx = 0; idx < count; ++idx, ++rela) { 848 unsigned type = ELFW(R_TYPE)(rela->r_info); 849 unsigned sym = ELFW(R_SYM)(rela->r_info); 850 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 851 ElfW(Addr) sym_addr = 0; 852 const char* sym_name = NULL; 853 854 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 855 if (type == 0) { // R_*_NONE 856 continue; 857 } 858 if (sym != 0) { 859 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 860 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 861 if (s == NULL) { 862 // We only allow an undefined symbol if this is a weak reference... 863 s = &si->symtab[sym]; 864 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 865 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 866 return -1; 867 } 868 869 /* IHI0044C AAELF 4.5.1.1: 870 871 Libraries are not searched to resolve weak references. 872 It is not an error for a weak reference to remain unsatisfied. 873 874 During linking, the value of an undefined weak reference is: 875 - Zero if the relocation type is absolute 876 - The address of the place if the relocation is pc-relative 877 - The address of nominal base address if the relocation 878 type is base-relative. 879 */ 880 881 switch (type) { 882#if defined(__aarch64__) 883 case R_AARCH64_JUMP_SLOT: 884 case R_AARCH64_GLOB_DAT: 885 case R_AARCH64_ABS64: 886 case R_AARCH64_ABS32: 887 case R_AARCH64_ABS16: 888 case R_AARCH64_RELATIVE: 889 /* 890 * The sym_addr was initialized to be zero above, or the relocation 891 * code below does not care about value of sym_addr. 892 * No need to do anything. 893 */ 894 break; 895#elif defined(__x86_64__) 896 case R_X86_64_JUMP_SLOT: 897 case R_X86_64_GLOB_DAT: 898 case R_X86_64_32: 899 case R_X86_64_RELATIVE: 900 // No need to do anything. 901 break; 902 case R_X86_64_PC32: 903 sym_addr = reloc; 904 break; 905#endif 906 default: 907 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 908 return -1; 909 } 910 } else { 911 // We got a definition. 912 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 913 } 914 count_relocation(kRelocSymbol); 915 } else { 916 s = NULL; 917 } 918 919 switch (type) { 920#if defined(__aarch64__) 921 case R_AARCH64_JUMP_SLOT: 922 count_relocation(kRelocAbsolute); 923 MARK(rela->r_offset); 924 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 925 reloc, (sym_addr + rela->r_addend), sym_name); 926 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 927 break; 928 case R_AARCH64_GLOB_DAT: 929 count_relocation(kRelocAbsolute); 930 MARK(rela->r_offset); 931 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 932 reloc, (sym_addr + rela->r_addend), sym_name); 933 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 934 break; 935 case R_AARCH64_ABS64: 936 count_relocation(kRelocAbsolute); 937 MARK(rela->r_offset); 938 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 939 reloc, (sym_addr + rela->r_addend), sym_name); 940 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 941 break; 942 case R_AARCH64_ABS32: 943 count_relocation(kRelocAbsolute); 944 MARK(rela->r_offset); 945 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 946 reloc, (sym_addr + rela->r_addend), sym_name); 947 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 948 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 949 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 950 } else { 951 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 952 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 953 static_cast<ElfW(Addr)>(INT32_MIN), 954 static_cast<ElfW(Addr)>(UINT32_MAX)); 955 return -1; 956 } 957 break; 958 case R_AARCH64_ABS16: 959 count_relocation(kRelocAbsolute); 960 MARK(rela->r_offset); 961 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 962 reloc, (sym_addr + rela->r_addend), sym_name); 963 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 964 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 965 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 966 } else { 967 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 968 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 969 static_cast<ElfW(Addr)>(INT16_MIN), 970 static_cast<ElfW(Addr)>(UINT16_MAX)); 971 return -1; 972 } 973 break; 974 case R_AARCH64_PREL64: 975 count_relocation(kRelocRelative); 976 MARK(rela->r_offset); 977 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 978 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 979 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 980 break; 981 case R_AARCH64_PREL32: 982 count_relocation(kRelocRelative); 983 MARK(rela->r_offset); 984 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 985 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 986 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 987 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 988 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 989 } else { 990 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 991 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 992 static_cast<ElfW(Addr)>(INT32_MIN), 993 static_cast<ElfW(Addr)>(UINT32_MAX)); 994 return -1; 995 } 996 break; 997 case R_AARCH64_PREL16: 998 count_relocation(kRelocRelative); 999 MARK(rela->r_offset); 1000 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 1001 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 1002 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1003 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1004 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1005 } else { 1006 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1007 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1008 static_cast<ElfW(Addr)>(INT16_MIN), 1009 static_cast<ElfW(Addr)>(UINT16_MAX)); 1010 return -1; 1011 } 1012 break; 1013 1014 case R_AARCH64_RELATIVE: 1015 count_relocation(kRelocRelative); 1016 MARK(rela->r_offset); 1017 if (sym) { 1018 DL_ERR("odd RELATIVE form..."); 1019 return -1; 1020 } 1021 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1022 reloc, (si->base + rela->r_addend)); 1023 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1024 break; 1025 1026 case R_AARCH64_COPY: 1027 if ((si->flags & FLAG_EXE) == 0) { 1028 /* 1029 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1030 * 1031 * Section 4.7.1.10 "Dynamic relocations" 1032 * R_AARCH64_COPY may only appear in executable objects where e_type is 1033 * set to ET_EXEC. 1034 * 1035 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1036 * We should explicitly disallow ET_DYN executables from having 1037 * R_AARCH64_COPY relocations. 1038 */ 1039 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1040 return -1; 1041 } 1042 count_relocation(kRelocCopy); 1043 MARK(rela->r_offset); 1044 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1045 reloc, 1046 s->st_size, 1047 (sym_addr + rela->r_addend), 1048 sym_name); 1049 if (reloc == (sym_addr + rela->r_addend)) { 1050 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1051 1052 if (src == NULL) { 1053 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1054 return -1; 1055 } 1056 if (lsi->has_DT_SYMBOLIC) { 1057 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1058 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1059 return -1; 1060 } 1061 if (s->st_size < src->st_size) { 1062 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1063 si->name, s->st_size, src->st_size); 1064 return -1; 1065 } 1066 memcpy(reinterpret_cast<void*>(reloc), 1067 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1068 } else { 1069 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1070 return -1; 1071 } 1072 break; 1073 case R_AARCH64_TLS_TPREL64: 1074 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1075 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1076 break; 1077 case R_AARCH64_TLS_DTPREL32: 1078 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1079 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1080 break; 1081#elif defined(__x86_64__) 1082 case R_X86_64_JUMP_SLOT: 1083 count_relocation(kRelocAbsolute); 1084 MARK(rela->r_offset); 1085 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1086 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1087 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1088 break; 1089 case R_X86_64_GLOB_DAT: 1090 count_relocation(kRelocAbsolute); 1091 MARK(rela->r_offset); 1092 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1093 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1094 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1095 break; 1096 case R_X86_64_RELATIVE: 1097 count_relocation(kRelocRelative); 1098 MARK(rela->r_offset); 1099 if (sym) { 1100 DL_ERR("odd RELATIVE form..."); 1101 return -1; 1102 } 1103 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1104 static_cast<size_t>(si->base)); 1105 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1106 break; 1107 case R_X86_64_32: 1108 count_relocation(kRelocRelative); 1109 MARK(rela->r_offset); 1110 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1111 static_cast<size_t>(sym_addr), sym_name); 1112 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1113 break; 1114 case R_X86_64_64: 1115 count_relocation(kRelocRelative); 1116 MARK(rela->r_offset); 1117 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1118 static_cast<size_t>(sym_addr), sym_name); 1119 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1120 break; 1121 case R_X86_64_PC32: 1122 count_relocation(kRelocRelative); 1123 MARK(rela->r_offset); 1124 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1125 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1126 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1127 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1128 break; 1129#endif 1130 1131 default: 1132 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1133 return -1; 1134 } 1135 } 1136 return 0; 1137} 1138 1139#else // REL, not RELA. 1140 1141static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1142 ElfW(Sym)* s; 1143 soinfo* lsi; 1144 1145 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1146 unsigned type = ELFW(R_TYPE)(rel->r_info); 1147 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1148 unsigned sym = ELFW(R_SYM)(rel->r_info); 1149 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1150 ElfW(Addr) sym_addr = 0; 1151 const char* sym_name = NULL; 1152 1153 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1154 if (type == 0) { // R_*_NONE 1155 continue; 1156 } 1157 if (sym != 0) { 1158 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1159 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1160 if (s == NULL) { 1161 // We only allow an undefined symbol if this is a weak reference... 1162 s = &si->symtab[sym]; 1163 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1164 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1165 return -1; 1166 } 1167 1168 /* IHI0044C AAELF 4.5.1.1: 1169 1170 Libraries are not searched to resolve weak references. 1171 It is not an error for a weak reference to remain 1172 unsatisfied. 1173 1174 During linking, the value of an undefined weak reference is: 1175 - Zero if the relocation type is absolute 1176 - The address of the place if the relocation is pc-relative 1177 - The address of nominal base address if the relocation 1178 type is base-relative. 1179 */ 1180 1181 switch (type) { 1182#if defined(__arm__) 1183 case R_ARM_JUMP_SLOT: 1184 case R_ARM_GLOB_DAT: 1185 case R_ARM_ABS32: 1186 case R_ARM_RELATIVE: /* Don't care. */ 1187 // sym_addr was initialized to be zero above or relocation 1188 // code below does not care about value of sym_addr. 1189 // No need to do anything. 1190 break; 1191#elif defined(__i386__) 1192 case R_386_JMP_SLOT: 1193 case R_386_GLOB_DAT: 1194 case R_386_32: 1195 case R_386_RELATIVE: /* Don't care. */ 1196 // sym_addr was initialized to be zero above or relocation 1197 // code below does not care about value of sym_addr. 1198 // No need to do anything. 1199 break; 1200 case R_386_PC32: 1201 sym_addr = reloc; 1202 break; 1203#endif 1204 1205#if defined(__arm__) 1206 case R_ARM_COPY: 1207 // Fall through. Can't really copy if weak symbol is not found at run-time. 1208#endif 1209 default: 1210 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1211 return -1; 1212 } 1213 } else { 1214 // We got a definition. 1215 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1216 } 1217 count_relocation(kRelocSymbol); 1218 } else { 1219 s = NULL; 1220 } 1221 1222 switch (type) { 1223#if defined(__arm__) 1224 case R_ARM_JUMP_SLOT: 1225 count_relocation(kRelocAbsolute); 1226 MARK(rel->r_offset); 1227 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1228 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1229 break; 1230 case R_ARM_GLOB_DAT: 1231 count_relocation(kRelocAbsolute); 1232 MARK(rel->r_offset); 1233 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1234 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1235 break; 1236 case R_ARM_ABS32: 1237 count_relocation(kRelocAbsolute); 1238 MARK(rel->r_offset); 1239 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1240 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1241 break; 1242 case R_ARM_REL32: 1243 count_relocation(kRelocRelative); 1244 MARK(rel->r_offset); 1245 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1246 reloc, sym_addr, rel->r_offset, sym_name); 1247 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1248 break; 1249 case R_ARM_COPY: 1250 if ((si->flags & FLAG_EXE) == 0) { 1251 /* 1252 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1253 * 1254 * Section 4.7.1.10 "Dynamic relocations" 1255 * R_ARM_COPY may only appear in executable objects where e_type is 1256 * set to ET_EXEC. 1257 * 1258 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1259 * We should explicitly disallow ET_DYN executables from having 1260 * R_ARM_COPY relocations. 1261 */ 1262 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1263 return -1; 1264 } 1265 count_relocation(kRelocCopy); 1266 MARK(rel->r_offset); 1267 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1268 if (reloc == sym_addr) { 1269 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1270 1271 if (src == NULL) { 1272 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1273 return -1; 1274 } 1275 if (lsi->has_DT_SYMBOLIC) { 1276 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1277 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1278 return -1; 1279 } 1280 if (s->st_size < src->st_size) { 1281 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1282 si->name, s->st_size, src->st_size); 1283 return -1; 1284 } 1285 memcpy(reinterpret_cast<void*>(reloc), 1286 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1287 } else { 1288 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1289 return -1; 1290 } 1291 break; 1292#elif defined(__i386__) 1293 case R_386_JMP_SLOT: 1294 count_relocation(kRelocAbsolute); 1295 MARK(rel->r_offset); 1296 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1297 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1298 break; 1299 case R_386_GLOB_DAT: 1300 count_relocation(kRelocAbsolute); 1301 MARK(rel->r_offset); 1302 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1303 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1304 break; 1305 case R_386_32: 1306 count_relocation(kRelocRelative); 1307 MARK(rel->r_offset); 1308 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1309 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1310 break; 1311 case R_386_PC32: 1312 count_relocation(kRelocRelative); 1313 MARK(rel->r_offset); 1314 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1315 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1316 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1317 break; 1318#elif defined(__mips__) 1319 case R_MIPS_REL32: 1320#if defined(__LP64__) 1321 // MIPS Elf64_Rel entries contain compound relocations 1322 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1323 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1324 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1325 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1326 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1327 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1328 return -1; 1329 } 1330#endif 1331 count_relocation(kRelocAbsolute); 1332 MARK(rel->r_offset); 1333 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1334 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1335 if (s) { 1336 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1337 } else { 1338 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1339 } 1340 break; 1341#endif 1342 1343#if defined(__arm__) 1344 case R_ARM_RELATIVE: 1345#elif defined(__i386__) 1346 case R_386_RELATIVE: 1347#endif 1348 count_relocation(kRelocRelative); 1349 MARK(rel->r_offset); 1350 if (sym) { 1351 DL_ERR("odd RELATIVE form..."); 1352 return -1; 1353 } 1354 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1355 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1356 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1357 break; 1358 1359 default: 1360 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1361 return -1; 1362 } 1363 } 1364 return 0; 1365} 1366#endif 1367 1368#if defined(__mips__) 1369static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1370 ElfW(Addr)** got = si->plt_got; 1371 if (got == NULL) { 1372 return true; 1373 } 1374 unsigned local_gotno = si->mips_local_gotno; 1375 unsigned gotsym = si->mips_gotsym; 1376 unsigned symtabno = si->mips_symtabno; 1377 ElfW(Sym)* symtab = si->symtab; 1378 1379 // got[0] is the address of the lazy resolver function. 1380 // got[1] may be used for a GNU extension. 1381 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1382 // FIXME: maybe this should be in a separate routine? 1383 if ((si->flags & FLAG_LINKER) == 0) { 1384 size_t g = 0; 1385 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1386 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1387 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1388 } 1389 // Relocate the local GOT entries. 1390 for (; g < local_gotno; g++) { 1391 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1392 } 1393 } 1394 1395 // Now for the global GOT entries... 1396 ElfW(Sym)* sym = symtab + gotsym; 1397 got = si->plt_got + local_gotno; 1398 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1399 // This is an undefined reference... try to locate it. 1400 const char* sym_name = si->strtab + sym->st_name; 1401 soinfo* lsi; 1402 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1403 if (s == NULL) { 1404 // We only allow an undefined symbol if this is a weak reference. 1405 s = &symtab[g]; 1406 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1407 DL_ERR("cannot locate \"%s\"...", sym_name); 1408 return false; 1409 } 1410 *got = 0; 1411 } else { 1412 // FIXME: is this sufficient? 1413 // For reference see NetBSD link loader 1414 // 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 1415 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1416 } 1417 } 1418 return true; 1419} 1420#endif 1421 1422void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1423 if (functions == NULL) { 1424 return; 1425 } 1426 1427 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1428 1429 int begin = reverse ? (count - 1) : 0; 1430 int end = reverse ? -1 : count; 1431 int step = reverse ? -1 : 1; 1432 1433 for (int i = begin; i != end; i += step) { 1434 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1435 CallFunction("function", functions[i]); 1436 } 1437 1438 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1439} 1440 1441void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1442 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1443 return; 1444 } 1445 1446 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1447 function(); 1448 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1449 1450 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1451 // are still writable. This happens with our debug malloc (see http://b/7941716). 1452 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 1453} 1454 1455void soinfo::CallPreInitConstructors() { 1456 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1457 // but ignored in a shared library. 1458 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1459} 1460 1461void soinfo::CallConstructors() { 1462 if (constructors_called) { 1463 return; 1464 } 1465 1466 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1467 // protect against recursive constructor calls. One simple example of constructor recursion 1468 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1469 // 1. The program depends on libc, so libc's constructor is called here. 1470 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1471 // 3. dlopen() calls the constructors on the newly created 1472 // soinfo for libc_malloc_debug_leak.so. 1473 // 4. The debug .so depends on libc, so CallConstructors is 1474 // called again with the libc soinfo. If it doesn't trigger the early- 1475 // out above, the libc constructor will be called again (recursively!). 1476 constructors_called = true; 1477 1478 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1479 // The GNU dynamic linker silently ignores these, but we warn the developer. 1480 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1481 name, preinit_array_count); 1482 } 1483 1484 if (dynamic != NULL) { 1485 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) { 1486 if (d->d_tag == DT_NEEDED) { 1487 const char* library_name = strtab + d->d_un.d_val; 1488 TRACE("\"%s\": calling constructors in DT_NEEDED \"%s\"", name, library_name); 1489 find_loaded_library(library_name)->CallConstructors(); 1490 } 1491 } 1492 } 1493 1494 TRACE("\"%s\": calling constructors", name); 1495 1496 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1497 CallFunction("DT_INIT", init_func); 1498 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1499} 1500 1501void soinfo::CallDestructors() { 1502 TRACE("\"%s\": calling destructors", name); 1503 1504 // DT_FINI_ARRAY must be parsed in reverse order. 1505 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1506 1507 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1508 CallFunction("DT_FINI", fini_func); 1509} 1510 1511/* Force any of the closed stdin, stdout and stderr to be associated with 1512 /dev/null. */ 1513static int nullify_closed_stdio() { 1514 int dev_null, i, status; 1515 int return_value = 0; 1516 1517 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1518 if (dev_null < 0) { 1519 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1520 return -1; 1521 } 1522 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1523 1524 /* If any of the stdio file descriptors is valid and not associated 1525 with /dev/null, dup /dev/null to it. */ 1526 for (i = 0; i < 3; i++) { 1527 /* If it is /dev/null already, we are done. */ 1528 if (i == dev_null) { 1529 continue; 1530 } 1531 1532 TRACE("[ Nullifying stdio file descriptor %d]", i); 1533 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1534 1535 /* If file is opened, we are good. */ 1536 if (status != -1) { 1537 continue; 1538 } 1539 1540 /* The only error we allow is that the file descriptor does not 1541 exist, in which case we dup /dev/null to it. */ 1542 if (errno != EBADF) { 1543 DL_ERR("fcntl failed: %s", strerror(errno)); 1544 return_value = -1; 1545 continue; 1546 } 1547 1548 /* Try dupping /dev/null to this stdio file descriptor and 1549 repeat if there is a signal. Note that any errors in closing 1550 the stdio descriptor are lost. */ 1551 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1552 if (status < 0) { 1553 DL_ERR("dup2 failed: %s", strerror(errno)); 1554 return_value = -1; 1555 continue; 1556 } 1557 } 1558 1559 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1560 if (dev_null > 2) { 1561 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1562 status = TEMP_FAILURE_RETRY(close(dev_null)); 1563 if (status == -1) { 1564 DL_ERR("close failed: %s", strerror(errno)); 1565 return_value = -1; 1566 } 1567 } 1568 1569 return return_value; 1570} 1571 1572static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) { 1573 /* "base" might wrap around UINT32_MAX. */ 1574 ElfW(Addr) base = si->load_bias; 1575 const ElfW(Phdr)* phdr = si->phdr; 1576 int phnum = si->phnum; 1577 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1578 1579 /* We can't debug anything until the linker is relocated */ 1580 if (!relocating_linker) { 1581 INFO("[ linking %s ]", si->name); 1582 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1583 } 1584 1585 /* Extract dynamic section */ 1586 size_t dynamic_count; 1587 ElfW(Word) dynamic_flags; 1588 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1589 &dynamic_count, &dynamic_flags); 1590 if (si->dynamic == NULL) { 1591 if (!relocating_linker) { 1592 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1593 } 1594 return false; 1595 } else { 1596 if (!relocating_linker) { 1597 DEBUG("dynamic = %p", si->dynamic); 1598 } 1599 } 1600 1601#if defined(__arm__) 1602 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1603 &si->ARM_exidx, &si->ARM_exidx_count); 1604#endif 1605 1606 // Extract useful information from dynamic section. 1607 uint32_t needed_count = 0; 1608 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1609 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1610 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1611 switch (d->d_tag) { 1612 case DT_HASH: 1613 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1614 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1615 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1616 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1617 break; 1618 case DT_STRTAB: 1619 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1620 break; 1621 case DT_SYMTAB: 1622 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1623 break; 1624#if !defined(__LP64__) 1625 case DT_PLTREL: 1626 if (d->d_un.d_val != DT_REL) { 1627 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1628 return false; 1629 } 1630 break; 1631#endif 1632 case DT_JMPREL: 1633#if defined(USE_RELA) 1634 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1635#else 1636 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1637#endif 1638 break; 1639 case DT_PLTRELSZ: 1640#if defined(USE_RELA) 1641 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1642#else 1643 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1644#endif 1645 break; 1646#if defined(__mips__) 1647 case DT_PLTGOT: 1648 // Used by mips and mips64. 1649 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1650 break; 1651#endif 1652 case DT_DEBUG: 1653 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1654 // if the dynamic table is writable 1655// FIXME: not working currently for N64 1656// The flags for the LOAD and DYNAMIC program headers do not agree. 1657// The LOAD section containng the dynamic table has been mapped as 1658// read-only, but the DYNAMIC header claims it is writable. 1659#if !(defined(__mips__) && defined(__LP64__)) 1660 if ((dynamic_flags & PF_W) != 0) { 1661 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1662 } 1663 break; 1664#endif 1665#if defined(USE_RELA) 1666 case DT_RELA: 1667 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1668 break; 1669 case DT_RELASZ: 1670 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1671 break; 1672 case DT_REL: 1673 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1674 return false; 1675 case DT_RELSZ: 1676 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1677 return false; 1678#else 1679 case DT_REL: 1680 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1681 break; 1682 case DT_RELSZ: 1683 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1684 break; 1685 case DT_RELA: 1686 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1687 return false; 1688#endif 1689 case DT_INIT: 1690 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1691 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1692 break; 1693 case DT_FINI: 1694 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1695 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1696 break; 1697 case DT_INIT_ARRAY: 1698 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1699 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1700 break; 1701 case DT_INIT_ARRAYSZ: 1702 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1703 break; 1704 case DT_FINI_ARRAY: 1705 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1706 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1707 break; 1708 case DT_FINI_ARRAYSZ: 1709 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1710 break; 1711 case DT_PREINIT_ARRAY: 1712 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1713 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1714 break; 1715 case DT_PREINIT_ARRAYSZ: 1716 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1717 break; 1718 case DT_TEXTREL: 1719#if defined(__LP64__) 1720 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1721 return false; 1722#else 1723 si->has_text_relocations = true; 1724 break; 1725#endif 1726 case DT_SYMBOLIC: 1727 si->has_DT_SYMBOLIC = true; 1728 break; 1729 case DT_NEEDED: 1730 ++needed_count; 1731 break; 1732 case DT_FLAGS: 1733 if (d->d_un.d_val & DF_TEXTREL) { 1734#if defined(__LP64__) 1735 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1736 return false; 1737#else 1738 si->has_text_relocations = true; 1739#endif 1740 } 1741 if (d->d_un.d_val & DF_SYMBOLIC) { 1742 si->has_DT_SYMBOLIC = true; 1743 } 1744 break; 1745#if defined(__mips__) 1746 case DT_STRSZ: 1747 case DT_SYMENT: 1748 case DT_RELENT: 1749 break; 1750 case DT_MIPS_RLD_MAP: 1751 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1752 { 1753 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1754 *dp = &_r_debug; 1755 } 1756 break; 1757 case DT_MIPS_RLD_VERSION: 1758 case DT_MIPS_FLAGS: 1759 case DT_MIPS_BASE_ADDRESS: 1760 case DT_MIPS_UNREFEXTNO: 1761 break; 1762 1763 case DT_MIPS_SYMTABNO: 1764 si->mips_symtabno = d->d_un.d_val; 1765 break; 1766 1767 case DT_MIPS_LOCAL_GOTNO: 1768 si->mips_local_gotno = d->d_un.d_val; 1769 break; 1770 1771 case DT_MIPS_GOTSYM: 1772 si->mips_gotsym = d->d_un.d_val; 1773 break; 1774#endif 1775 1776 default: 1777 DEBUG("Unused DT entry: type %p arg %p", 1778 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1779 break; 1780 } 1781 } 1782 1783 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1784 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1785 1786 // Sanity checks. 1787 if (relocating_linker && needed_count != 0) { 1788 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1789 return false; 1790 } 1791 if (si->nbucket == 0) { 1792 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1793 return false; 1794 } 1795 if (si->strtab == 0) { 1796 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1797 return false; 1798 } 1799 if (si->symtab == 0) { 1800 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1801 return false; 1802 } 1803 1804 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1805 if (si->flags & FLAG_EXE) { 1806 memset(gLdPreloads, 0, sizeof(gLdPreloads)); 1807 size_t preload_count = 0; 1808 for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) { 1809 soinfo* lsi = find_library(gLdPreloadNames[i], NULL); 1810 if (lsi != NULL) { 1811 gLdPreloads[preload_count++] = lsi; 1812 } else { 1813 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1814 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1815 gLdPreloadNames[i], si->name, linker_get_error_buffer()); 1816 } 1817 } 1818 } 1819 1820 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1821 soinfo** pneeded = needed; 1822 1823 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1824 if (d->d_tag == DT_NEEDED) { 1825 const char* library_name = si->strtab + d->d_un.d_val; 1826 DEBUG("%s needs %s", si->name, library_name); 1827 soinfo* lsi = find_library(library_name, NULL); 1828 if (lsi == NULL) { 1829 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1830 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1831 library_name, si->name, tmp_err_buf); 1832 return false; 1833 } 1834 *pneeded++ = lsi; 1835 } 1836 } 1837 *pneeded = NULL; 1838 1839#if !defined(__LP64__) 1840 if (si->has_text_relocations) { 1841 // Make segments writable to allow text relocations to work properly. We will later call 1842 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1843#if !defined(__i386__) // The platform itself has too many text relocations on x86. 1844 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1845 "security hardening. Please fix.", si->name); 1846#endif 1847 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1848 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1849 si->name, strerror(errno)); 1850 return false; 1851 } 1852 } 1853#endif 1854 1855#if defined(USE_RELA) 1856 if (si->plt_rela != NULL) { 1857 DEBUG("[ relocating %s plt ]\n", si->name); 1858 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1859 return false; 1860 } 1861 } 1862 if (si->rela != NULL) { 1863 DEBUG("[ relocating %s ]\n", si->name); 1864 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1865 return false; 1866 } 1867 } 1868#else 1869 if (si->plt_rel != NULL) { 1870 DEBUG("[ relocating %s plt ]", si->name); 1871 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1872 return false; 1873 } 1874 } 1875 if (si->rel != NULL) { 1876 DEBUG("[ relocating %s ]", si->name); 1877 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1878 return false; 1879 } 1880 } 1881#endif 1882 1883#if defined(__mips__) 1884 if (!mips_relocate_got(si, needed)) { 1885 return false; 1886 } 1887#endif 1888 1889 si->flags |= FLAG_LINKED; 1890 DEBUG("[ finished linking %s ]", si->name); 1891 1892#if !defined(__LP64__) 1893 if (si->has_text_relocations) { 1894 // All relocations are done, we can protect our segments back to read-only. 1895 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1896 DL_ERR("can't protect segments for \"%s\": %s", 1897 si->name, strerror(errno)); 1898 return false; 1899 } 1900 } 1901#endif 1902 1903 /* We can also turn on GNU RELRO protection */ 1904 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1905 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1906 si->name, strerror(errno)); 1907 return false; 1908 } 1909 1910 /* Handle serializing/sharing the RELRO segment */ 1911 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) { 1912 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias, 1913 extinfo->relro_fd) < 0) { 1914 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s", 1915 si->name, strerror(errno)); 1916 return false; 1917 } 1918 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) { 1919 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias, 1920 extinfo->relro_fd) < 0) { 1921 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s", 1922 si->name, strerror(errno)); 1923 return false; 1924 } 1925 } 1926 1927 notify_gdb_of_load(si); 1928 return true; 1929} 1930 1931/* 1932 * This function add vdso to internal dso list. 1933 * It helps to stack unwinding through signal handlers. 1934 * Also, it makes bionic more like glibc. 1935 */ 1936static void add_vdso(KernelArgumentBlock& args __unused) { 1937#if defined(AT_SYSINFO_EHDR) 1938 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1939 if (ehdr_vdso == NULL) { 1940 return; 1941 } 1942 1943 soinfo* si = soinfo_alloc("[vdso]"); 1944 1945 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1946 si->phnum = ehdr_vdso->e_phnum; 1947 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1948 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1949 si->flags = 0; 1950 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1951 1952 soinfo_link_image(si, NULL); 1953#endif 1954} 1955 1956/* 1957 * This code is called after the linker has linked itself and 1958 * fixed it's own GOT. It is safe to make references to externs 1959 * and other non-local data at this point. 1960 */ 1961static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 1962 /* NOTE: we store the args pointer on a special location 1963 * of the temporary TLS area in order to pass it to 1964 * the C Library's runtime initializer. 1965 * 1966 * The initializer must clear the slot and reset the TLS 1967 * to point to a different location to ensure that no other 1968 * shared library constructor can access it. 1969 */ 1970 __libc_init_tls(args); 1971 1972#if TIMING 1973 struct timeval t0, t1; 1974 gettimeofday(&t0, 0); 1975#endif 1976 1977 // Initialize environment functions, and get to the ELF aux vectors table. 1978 linker_env_init(args); 1979 1980 // If this is a setuid/setgid program, close the security hole described in 1981 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 1982 if (get_AT_SECURE()) { 1983 nullify_closed_stdio(); 1984 } 1985 1986 debuggerd_init(); 1987 1988 // Get a few environment variables. 1989 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 1990 if (LD_DEBUG != NULL) { 1991 gLdDebugVerbosity = atoi(LD_DEBUG); 1992 } 1993 1994 // Normally, these are cleaned by linker_env_init, but the test 1995 // doesn't cost us anything. 1996 const char* ldpath_env = NULL; 1997 const char* ldpreload_env = NULL; 1998 if (!get_AT_SECURE()) { 1999 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 2000 ldpreload_env = linker_env_get("LD_PRELOAD"); 2001 } 2002 2003 INFO("[ android linker & debugger ]"); 2004 2005 soinfo* si = soinfo_alloc(args.argv[0]); 2006 if (si == NULL) { 2007 exit(EXIT_FAILURE); 2008 } 2009 2010 /* bootstrap the link map, the main exe always needs to be first */ 2011 si->flags |= FLAG_EXE; 2012 link_map* map = &(si->link_map_head); 2013 2014 map->l_addr = 0; 2015 map->l_name = args.argv[0]; 2016 map->l_prev = NULL; 2017 map->l_next = NULL; 2018 2019 _r_debug.r_map = map; 2020 r_debug_tail = map; 2021 2022 /* gdb expects the linker to be in the debug shared object list. 2023 * Without this, gdb has trouble locating the linker's ".text" 2024 * and ".plt" sections. Gdb could also potentially use this to 2025 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2026 * Don't use soinfo_alloc(), because the linker shouldn't 2027 * be on the soinfo list. 2028 */ 2029 { 2030 static soinfo linker_soinfo; 2031#if defined(__LP64__) 2032 strlcpy(linker_soinfo.name, "/system/bin/linker64", sizeof(linker_soinfo.name)); 2033#else 2034 strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name)); 2035#endif 2036 linker_soinfo.flags = 0; 2037 linker_soinfo.base = linker_base; 2038 2039 /* 2040 * Set the dynamic field in the link map otherwise gdb will complain with 2041 * the following: 2042 * warning: .dynamic section for "/system/bin/linker" is not at the 2043 * expected address (wrong library or version mismatch?) 2044 */ 2045 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2046 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2047 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2048 &linker_soinfo.dynamic, NULL, NULL); 2049 insert_soinfo_into_debug_map(&linker_soinfo); 2050 } 2051 2052 // Extract information passed from the kernel. 2053 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2054 si->phnum = args.getauxval(AT_PHNUM); 2055 si->entry = args.getauxval(AT_ENTRY); 2056 2057 /* Compute the value of si->base. We can't rely on the fact that 2058 * the first entry is the PHDR because this will not be true 2059 * for certain executables (e.g. some in the NDK unit test suite) 2060 */ 2061 si->base = 0; 2062 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2063 si->load_bias = 0; 2064 for (size_t i = 0; i < si->phnum; ++i) { 2065 if (si->phdr[i].p_type == PT_PHDR) { 2066 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2067 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2068 break; 2069 } 2070 } 2071 si->dynamic = NULL; 2072 si->ref_count = 1; 2073 2074 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2075 parse_LD_LIBRARY_PATH(ldpath_env); 2076 parse_LD_PRELOAD(ldpreload_env); 2077 2078 somain = si; 2079 2080 if (!soinfo_link_image(si, NULL)) { 2081 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2082 exit(EXIT_FAILURE); 2083 } 2084 2085 add_vdso(args); 2086 2087 si->CallPreInitConstructors(); 2088 2089 for (size_t i = 0; gLdPreloads[i] != NULL; ++i) { 2090 gLdPreloads[i]->CallConstructors(); 2091 } 2092 2093 /* After the link_image, the si->load_bias is initialized. 2094 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2095 * We need to update this value for so exe here. So Unwind_Backtrace 2096 * for some arch like x86 could work correctly within so exe. 2097 */ 2098 map->l_addr = si->load_bias; 2099 si->CallConstructors(); 2100 2101#if TIMING 2102 gettimeofday(&t1, NULL); 2103 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2104 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2105 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2106#endif 2107#if STATS 2108 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2109 linker_stats.count[kRelocAbsolute], 2110 linker_stats.count[kRelocRelative], 2111 linker_stats.count[kRelocCopy], 2112 linker_stats.count[kRelocSymbol]); 2113#endif 2114#if COUNT_PAGES 2115 { 2116 unsigned n; 2117 unsigned i; 2118 unsigned count = 0; 2119 for (n = 0; n < 4096; n++) { 2120 if (bitmask[n]) { 2121 unsigned x = bitmask[n]; 2122#if defined(__LP64__) 2123 for (i = 0; i < 32; i++) { 2124#else 2125 for (i = 0; i < 8; i++) { 2126#endif 2127 if (x & 1) { 2128 count++; 2129 } 2130 x >>= 1; 2131 } 2132 } 2133 } 2134 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2135 } 2136#endif 2137 2138#if TIMING || STATS || COUNT_PAGES 2139 fflush(stdout); 2140#endif 2141 2142 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2143 return si->entry; 2144} 2145 2146/* Compute the load-bias of an existing executable. This shall only 2147 * be used to compute the load bias of an executable or shared library 2148 * that was loaded by the kernel itself. 2149 * 2150 * Input: 2151 * elf -> address of ELF header, assumed to be at the start of the file. 2152 * Return: 2153 * load bias, i.e. add the value of any p_vaddr in the file to get 2154 * the corresponding address in memory. 2155 */ 2156static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2157 ElfW(Addr) offset = elf->e_phoff; 2158 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2159 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2160 2161 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2162 if (phdr->p_type == PT_LOAD) { 2163 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2164 } 2165 } 2166 return 0; 2167} 2168 2169/* 2170 * This is the entry point for the linker, called from begin.S. This 2171 * method is responsible for fixing the linker's own relocations, and 2172 * then calling __linker_init_post_relocation(). 2173 * 2174 * Because this method is called before the linker has fixed it's own 2175 * relocations, any attempt to reference an extern variable, extern 2176 * function, or other GOT reference will generate a segfault. 2177 */ 2178extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2179 KernelArgumentBlock args(raw_args); 2180 2181 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2182 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2183 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2184 2185 soinfo linker_so; 2186 memset(&linker_so, 0, sizeof(soinfo)); 2187 2188 strcpy(linker_so.name, "[dynamic linker]"); 2189 linker_so.base = linker_addr; 2190 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2191 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2192 linker_so.dynamic = NULL; 2193 linker_so.phdr = phdr; 2194 linker_so.phnum = elf_hdr->e_phnum; 2195 linker_so.flags |= FLAG_LINKER; 2196 2197 if (!soinfo_link_image(&linker_so, NULL)) { 2198 // It would be nice to print an error message, but if the linker 2199 // can't link itself, there's no guarantee that we'll be able to 2200 // call write() (because it involves a GOT reference). We may as 2201 // well try though... 2202 const char* msg = "CANNOT LINK EXECUTABLE: "; 2203 write(2, msg, strlen(msg)); 2204 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2205 write(2, "\n", 1); 2206 _exit(EXIT_FAILURE); 2207 } 2208 2209 // We have successfully fixed our own relocations. It's safe to run 2210 // the main part of the linker now. 2211 args.abort_message_ptr = &gAbortMessage; 2212 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2213 2214 set_soinfo_pool_protection(PROT_READ); 2215 2216 // Return the address that the calling assembly stub should jump to. 2217 return start_address; 2218} 2219