linker.cpp revision 812fd4263a005b88f3b4222baa910114f938d594
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); 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 } 684 685 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 686 int fd = open_library_on_path(name, gLdPaths); 687 if (fd == -1) { 688 fd = open_library_on_path(name, gDefaultLdPaths); 689 } 690 return fd; 691} 692 693static soinfo* load_library(const char* name) { 694 // Open the file. 695 int fd = open_library(name); 696 if (fd == -1) { 697 DL_ERR("library \"%s\" not found", name); 698 return NULL; 699 } 700 701 // Read the ELF header and load the segments. 702 ElfReader elf_reader(name, fd); 703 if (!elf_reader.Load()) { 704 return NULL; 705 } 706 707 const char* bname = strrchr(name, '/'); 708 soinfo* si = soinfo_alloc(bname ? bname + 1 : name); 709 if (si == NULL) { 710 return NULL; 711 } 712 si->base = elf_reader.load_start(); 713 si->size = elf_reader.load_size(); 714 si->load_bias = elf_reader.load_bias(); 715 si->flags = 0; 716 si->entry = 0; 717 si->dynamic = NULL; 718 si->phnum = elf_reader.phdr_count(); 719 si->phdr = elf_reader.loaded_phdr(); 720 return si; 721} 722 723static soinfo *find_loaded_library(const char* name) { 724 // TODO: don't use basename only for determining libraries 725 // http://code.google.com/p/android/issues/detail?id=6670 726 727 const char* bname = strrchr(name, '/'); 728 bname = bname ? bname + 1 : name; 729 730 for (soinfo* si = solist; si != NULL; si = si->next) { 731 if (!strcmp(bname, si->name)) { 732 return si; 733 } 734 } 735 return NULL; 736} 737 738static soinfo* find_library_internal(const char* name) { 739 if (name == NULL) { 740 return somain; 741 } 742 743 soinfo* si = find_loaded_library(name); 744 if (si != NULL) { 745 if (si->flags & FLAG_LINKED) { 746 return si; 747 } 748 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 749 return NULL; 750 } 751 752 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 753 si = load_library(name); 754 if (si == NULL) { 755 return NULL; 756 } 757 758 // At this point we know that whatever is loaded @ base is a valid ELF 759 // shared library whose segments are properly mapped in. 760 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 761 reinterpret_cast<void*>(si->base), si->size, si->name); 762 763 if (!soinfo_link_image(si)) { 764 munmap(reinterpret_cast<void*>(si->base), si->size); 765 soinfo_free(si); 766 return NULL; 767 } 768 769 return si; 770} 771 772static soinfo* find_library(const char* name) { 773 soinfo* si = find_library_internal(name); 774 if (si != NULL) { 775 si->ref_count++; 776 } 777 return si; 778} 779 780static int soinfo_unload(soinfo* si) { 781 if (si->ref_count == 1) { 782 TRACE("unloading '%s'", si->name); 783 si->CallDestructors(); 784 785 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 786 if (d->d_tag == DT_NEEDED) { 787 const char* library_name = si->strtab + d->d_un.d_val; 788 TRACE("%s needs to unload %s", si->name, library_name); 789 soinfo_unload(find_loaded_library(library_name)); 790 } 791 } 792 793 munmap(reinterpret_cast<void*>(si->base), si->size); 794 notify_gdb_of_unload(si); 795 soinfo_free(si); 796 si->ref_count = 0; 797 } else { 798 si->ref_count--; 799 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 800 } 801 return 0; 802} 803 804void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 805 snprintf(buffer, buffer_size, "%s:%s", gDefaultLdPaths[0], gDefaultLdPaths[1]); 806} 807 808void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 809 if (!get_AT_SECURE()) { 810 parse_LD_LIBRARY_PATH(ld_library_path); 811 } 812} 813 814soinfo* do_dlopen(const char* name, int flags) { 815 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 816 DL_ERR("invalid flags to dlopen: %x", flags); 817 return NULL; 818 } 819 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 820 soinfo* si = find_library(name); 821 if (si != NULL) { 822 si->CallConstructors(); 823 } 824 set_soinfo_pool_protection(PROT_READ); 825 return si; 826} 827 828int do_dlclose(soinfo* si) { 829 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 830 int result = soinfo_unload(si); 831 set_soinfo_pool_protection(PROT_READ); 832 return result; 833} 834 835#if defined(USE_RELA) 836static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 837 ElfW(Sym)* s; 838 soinfo* lsi; 839 840 for (size_t idx = 0; idx < count; ++idx, ++rela) { 841 unsigned type = ELFW(R_TYPE)(rela->r_info); 842 unsigned sym = ELFW(R_SYM)(rela->r_info); 843 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 844 ElfW(Addr) sym_addr = 0; 845 const char* sym_name = NULL; 846 847 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 848 if (type == 0) { // R_*_NONE 849 continue; 850 } 851 if (sym != 0) { 852 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 853 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 854 if (s == NULL) { 855 // We only allow an undefined symbol if this is a weak reference... 856 s = &si->symtab[sym]; 857 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 858 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 859 return -1; 860 } 861 862 /* IHI0044C AAELF 4.5.1.1: 863 864 Libraries are not searched to resolve weak references. 865 It is not an error for a weak reference to remain unsatisfied. 866 867 During linking, the value of an undefined weak reference is: 868 - Zero if the relocation type is absolute 869 - The address of the place if the relocation is pc-relative 870 - The address of nominal base address if the relocation 871 type is base-relative. 872 */ 873 874 switch (type) { 875#if defined(__aarch64__) 876 case R_AARCH64_JUMP_SLOT: 877 case R_AARCH64_GLOB_DAT: 878 case R_AARCH64_ABS64: 879 case R_AARCH64_ABS32: 880 case R_AARCH64_ABS16: 881 case R_AARCH64_RELATIVE: 882 /* 883 * The sym_addr was initialized to be zero above, or the relocation 884 * code below does not care about value of sym_addr. 885 * No need to do anything. 886 */ 887 break; 888#elif defined(__x86_64__) 889 case R_X86_64_JUMP_SLOT: 890 case R_X86_64_GLOB_DAT: 891 case R_X86_64_32: 892 case R_X86_64_RELATIVE: 893 // No need to do anything. 894 break; 895 case R_X86_64_PC32: 896 sym_addr = reloc; 897 break; 898#endif 899 default: 900 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 901 return -1; 902 } 903 } else { 904 // We got a definition. 905 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 906 } 907 count_relocation(kRelocSymbol); 908 } else { 909 s = NULL; 910 } 911 912 switch (type) { 913#if defined(__aarch64__) 914 case R_AARCH64_JUMP_SLOT: 915 count_relocation(kRelocAbsolute); 916 MARK(rela->r_offset); 917 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 918 reloc, (sym_addr + rela->r_addend), sym_name); 919 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 920 break; 921 case R_AARCH64_GLOB_DAT: 922 count_relocation(kRelocAbsolute); 923 MARK(rela->r_offset); 924 TRACE_TYPE(RELO, "RELO GLOB_DAT %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_ABS64: 929 count_relocation(kRelocAbsolute); 930 MARK(rela->r_offset); 931 TRACE_TYPE(RELO, "RELO ABS64 %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_ABS32: 936 count_relocation(kRelocAbsolute); 937 MARK(rela->r_offset); 938 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 939 reloc, (sym_addr + rela->r_addend), sym_name); 940 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 941 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 942 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 943 } else { 944 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 945 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 946 static_cast<ElfW(Addr)>(INT32_MIN), 947 static_cast<ElfW(Addr)>(UINT32_MAX)); 948 return -1; 949 } 950 break; 951 case R_AARCH64_ABS16: 952 count_relocation(kRelocAbsolute); 953 MARK(rela->r_offset); 954 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 955 reloc, (sym_addr + rela->r_addend), sym_name); 956 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 957 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 958 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 959 } else { 960 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 961 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 962 static_cast<ElfW(Addr)>(INT16_MIN), 963 static_cast<ElfW(Addr)>(UINT16_MAX)); 964 return -1; 965 } 966 break; 967 case R_AARCH64_PREL64: 968 count_relocation(kRelocRelative); 969 MARK(rela->r_offset); 970 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 971 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 972 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 973 break; 974 case R_AARCH64_PREL32: 975 count_relocation(kRelocRelative); 976 MARK(rela->r_offset); 977 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 978 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 979 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 980 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 981 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 982 } else { 983 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 984 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 985 static_cast<ElfW(Addr)>(INT32_MIN), 986 static_cast<ElfW(Addr)>(UINT32_MAX)); 987 return -1; 988 } 989 break; 990 case R_AARCH64_PREL16: 991 count_relocation(kRelocRelative); 992 MARK(rela->r_offset); 993 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 994 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 995 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 996 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 997 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 998 } else { 999 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1000 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1001 static_cast<ElfW(Addr)>(INT16_MIN), 1002 static_cast<ElfW(Addr)>(UINT16_MAX)); 1003 return -1; 1004 } 1005 break; 1006 1007 case R_AARCH64_RELATIVE: 1008 count_relocation(kRelocRelative); 1009 MARK(rela->r_offset); 1010 if (sym) { 1011 DL_ERR("odd RELATIVE form..."); 1012 return -1; 1013 } 1014 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1015 reloc, (si->base + rela->r_addend)); 1016 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1017 break; 1018 1019 case R_AARCH64_COPY: 1020 if ((si->flags & FLAG_EXE) == 0) { 1021 /* 1022 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1023 * 1024 * Section 4.7.1.10 "Dynamic relocations" 1025 * R_AARCH64_COPY may only appear in executable objects where e_type is 1026 * set to ET_EXEC. 1027 * 1028 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1029 * We should explicitly disallow ET_DYN executables from having 1030 * R_AARCH64_COPY relocations. 1031 */ 1032 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1033 return -1; 1034 } 1035 count_relocation(kRelocCopy); 1036 MARK(rela->r_offset); 1037 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1038 reloc, 1039 s->st_size, 1040 (sym_addr + rela->r_addend), 1041 sym_name); 1042 if (reloc == (sym_addr + rela->r_addend)) { 1043 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1044 1045 if (src == NULL) { 1046 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1047 return -1; 1048 } 1049 if (lsi->has_DT_SYMBOLIC) { 1050 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1051 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1052 return -1; 1053 } 1054 if (s->st_size < src->st_size) { 1055 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1056 si->name, s->st_size, src->st_size); 1057 return -1; 1058 } 1059 memcpy(reinterpret_cast<void*>(reloc), 1060 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1061 } else { 1062 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1063 return -1; 1064 } 1065 break; 1066 case R_AARCH64_TLS_TPREL64: 1067 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1068 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1069 break; 1070 case R_AARCH64_TLS_DTPREL32: 1071 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1072 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1073 break; 1074#elif defined(__x86_64__) 1075 case R_X86_64_JUMP_SLOT: 1076 count_relocation(kRelocAbsolute); 1077 MARK(rela->r_offset); 1078 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1079 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1080 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1081 break; 1082 case R_X86_64_GLOB_DAT: 1083 count_relocation(kRelocAbsolute); 1084 MARK(rela->r_offset); 1085 TRACE_TYPE(RELO, "RELO GLOB_DAT %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_RELATIVE: 1090 count_relocation(kRelocRelative); 1091 MARK(rela->r_offset); 1092 if (sym) { 1093 DL_ERR("odd RELATIVE form..."); 1094 return -1; 1095 } 1096 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1097 static_cast<size_t>(si->base)); 1098 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1099 break; 1100 case R_X86_64_32: 1101 count_relocation(kRelocRelative); 1102 MARK(rela->r_offset); 1103 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1104 static_cast<size_t>(sym_addr), sym_name); 1105 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1106 break; 1107 case R_X86_64_64: 1108 count_relocation(kRelocRelative); 1109 MARK(rela->r_offset); 1110 TRACE_TYPE(RELO, "RELO R_X86_64_64 %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_PC32: 1115 count_relocation(kRelocRelative); 1116 MARK(rela->r_offset); 1117 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1118 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1119 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1120 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1121 break; 1122#endif 1123 1124 default: 1125 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1126 return -1; 1127 } 1128 } 1129 return 0; 1130} 1131 1132#else // REL, not RELA. 1133 1134static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1135 ElfW(Sym)* s; 1136 soinfo* lsi; 1137 1138 for (size_t idx = 0; idx < count; ++idx, ++rel) { 1139 unsigned type = ELFW(R_TYPE)(rel->r_info); 1140 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead. 1141 unsigned sym = ELFW(R_SYM)(rel->r_info); 1142 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias); 1143 ElfW(Addr) sym_addr = 0; 1144 const char* sym_name = NULL; 1145 1146 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 1147 if (type == 0) { // R_*_NONE 1148 continue; 1149 } 1150 if (sym != 0) { 1151 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name); 1152 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1153 if (s == NULL) { 1154 // We only allow an undefined symbol if this is a weak reference... 1155 s = &si->symtab[sym]; 1156 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1157 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 1158 return -1; 1159 } 1160 1161 /* IHI0044C AAELF 4.5.1.1: 1162 1163 Libraries are not searched to resolve weak references. 1164 It is not an error for a weak reference to remain 1165 unsatisfied. 1166 1167 During linking, the value of an undefined weak reference is: 1168 - Zero if the relocation type is absolute 1169 - The address of the place if the relocation is pc-relative 1170 - The address of nominal base address if the relocation 1171 type is base-relative. 1172 */ 1173 1174 switch (type) { 1175#if defined(__arm__) 1176 case R_ARM_JUMP_SLOT: 1177 case R_ARM_GLOB_DAT: 1178 case R_ARM_ABS32: 1179 case R_ARM_RELATIVE: /* Don't care. */ 1180 // sym_addr was initialized to be zero above or relocation 1181 // code below does not care about value of sym_addr. 1182 // No need to do anything. 1183 break; 1184#elif defined(__i386__) 1185 case R_386_JMP_SLOT: 1186 case R_386_GLOB_DAT: 1187 case R_386_32: 1188 case R_386_RELATIVE: /* Don't care. */ 1189 // sym_addr was initialized to be zero above or relocation 1190 // code below does not care about value of sym_addr. 1191 // No need to do anything. 1192 break; 1193 case R_386_PC32: 1194 sym_addr = reloc; 1195 break; 1196#endif 1197 1198#if defined(__arm__) 1199 case R_ARM_COPY: 1200 // Fall through. Can't really copy if weak symbol is not found at run-time. 1201#endif 1202 default: 1203 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx); 1204 return -1; 1205 } 1206 } else { 1207 // We got a definition. 1208 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 1209 } 1210 count_relocation(kRelocSymbol); 1211 } else { 1212 s = NULL; 1213 } 1214 1215 switch (type) { 1216#if defined(__arm__) 1217 case R_ARM_JUMP_SLOT: 1218 count_relocation(kRelocAbsolute); 1219 MARK(rel->r_offset); 1220 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1221 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1222 break; 1223 case R_ARM_GLOB_DAT: 1224 count_relocation(kRelocAbsolute); 1225 MARK(rel->r_offset); 1226 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1227 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1228 break; 1229 case R_ARM_ABS32: 1230 count_relocation(kRelocAbsolute); 1231 MARK(rel->r_offset); 1232 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name); 1233 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1234 break; 1235 case R_ARM_REL32: 1236 count_relocation(kRelocRelative); 1237 MARK(rel->r_offset); 1238 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s", 1239 reloc, sym_addr, rel->r_offset, sym_name); 1240 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset; 1241 break; 1242 case R_ARM_COPY: 1243 if ((si->flags & FLAG_EXE) == 0) { 1244 /* 1245 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1246 * 1247 * Section 4.7.1.10 "Dynamic relocations" 1248 * R_ARM_COPY may only appear in executable objects where e_type is 1249 * set to ET_EXEC. 1250 * 1251 * TODO: FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1252 * We should explicitly disallow ET_DYN executables from having 1253 * R_ARM_COPY relocations. 1254 */ 1255 DL_ERR("%s R_ARM_COPY relocations only supported for ET_EXEC", si->name); 1256 return -1; 1257 } 1258 count_relocation(kRelocCopy); 1259 MARK(rel->r_offset); 1260 TRACE_TYPE(RELO, "RELO %08x <- %d @ %08x %s", reloc, s->st_size, sym_addr, sym_name); 1261 if (reloc == sym_addr) { 1262 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1263 1264 if (src == NULL) { 1265 DL_ERR("%s R_ARM_COPY relocation source cannot be resolved", si->name); 1266 return -1; 1267 } 1268 if (lsi->has_DT_SYMBOLIC) { 1269 DL_ERR("%s invalid R_ARM_COPY relocation against DT_SYMBOLIC shared " 1270 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1271 return -1; 1272 } 1273 if (s->st_size < src->st_size) { 1274 DL_ERR("%s R_ARM_COPY relocation size mismatch (%d < %d)", 1275 si->name, s->st_size, src->st_size); 1276 return -1; 1277 } 1278 memcpy(reinterpret_cast<void*>(reloc), 1279 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1280 } else { 1281 DL_ERR("%s R_ARM_COPY relocation target cannot be resolved", si->name); 1282 return -1; 1283 } 1284 break; 1285#elif defined(__i386__) 1286 case R_386_JMP_SLOT: 1287 count_relocation(kRelocAbsolute); 1288 MARK(rel->r_offset); 1289 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name); 1290 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1291 break; 1292 case R_386_GLOB_DAT: 1293 count_relocation(kRelocAbsolute); 1294 MARK(rel->r_offset); 1295 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name); 1296 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr; 1297 break; 1298 case R_386_32: 1299 count_relocation(kRelocRelative); 1300 MARK(rel->r_offset); 1301 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name); 1302 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1303 break; 1304 case R_386_PC32: 1305 count_relocation(kRelocRelative); 1306 MARK(rel->r_offset); 1307 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s", 1308 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name); 1309 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc); 1310 break; 1311#elif defined(__mips__) 1312 case R_MIPS_REL32: 1313#if defined(__LP64__) 1314 // MIPS Elf64_Rel entries contain compound relocations 1315 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case 1316 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 || 1317 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) { 1318 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)", 1319 type, (unsigned)ELF64_R_TYPE2(rel->r_info), 1320 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx); 1321 return -1; 1322 } 1323#endif 1324 count_relocation(kRelocAbsolute); 1325 MARK(rel->r_offset); 1326 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc), 1327 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*"); 1328 if (s) { 1329 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr; 1330 } else { 1331 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1332 } 1333 break; 1334#endif 1335 1336#if defined(__arm__) 1337 case R_ARM_RELATIVE: 1338#elif defined(__i386__) 1339 case R_386_RELATIVE: 1340#endif 1341 count_relocation(kRelocRelative); 1342 MARK(rel->r_offset); 1343 if (sym) { 1344 DL_ERR("odd RELATIVE form..."); 1345 return -1; 1346 } 1347 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p", 1348 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base)); 1349 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base; 1350 break; 1351 1352 default: 1353 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx); 1354 return -1; 1355 } 1356 } 1357 return 0; 1358} 1359#endif 1360 1361#if defined(__mips__) 1362static bool mips_relocate_got(soinfo* si, soinfo* needed[]) { 1363 ElfW(Addr)** got = si->plt_got; 1364 if (got == NULL) { 1365 return true; 1366 } 1367 unsigned local_gotno = si->mips_local_gotno; 1368 unsigned gotsym = si->mips_gotsym; 1369 unsigned symtabno = si->mips_symtabno; 1370 ElfW(Sym)* symtab = si->symtab; 1371 1372 // got[0] is the address of the lazy resolver function. 1373 // got[1] may be used for a GNU extension. 1374 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start). 1375 // FIXME: maybe this should be in a separate routine? 1376 if ((si->flags & FLAG_LINKER) == 0) { 1377 size_t g = 0; 1378 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef); 1379 if (reinterpret_cast<intptr_t>(got[g]) < 0) { 1380 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed); 1381 } 1382 // Relocate the local GOT entries. 1383 for (; g < local_gotno; g++) { 1384 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias); 1385 } 1386 } 1387 1388 // Now for the global GOT entries... 1389 ElfW(Sym)* sym = symtab + gotsym; 1390 got = si->plt_got + local_gotno; 1391 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) { 1392 // This is an undefined reference... try to locate it. 1393 const char* sym_name = si->strtab + sym->st_name; 1394 soinfo* lsi; 1395 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed); 1396 if (s == NULL) { 1397 // We only allow an undefined symbol if this is a weak reference. 1398 s = &symtab[g]; 1399 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 1400 DL_ERR("cannot locate \"%s\"...", sym_name); 1401 return false; 1402 } 1403 *got = 0; 1404 } else { 1405 // FIXME: is this sufficient? 1406 // For reference see NetBSD link loader 1407 // 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 1408 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value); 1409 } 1410 } 1411 return true; 1412} 1413#endif 1414 1415void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) { 1416 if (functions == NULL) { 1417 return; 1418 } 1419 1420 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name); 1421 1422 int begin = reverse ? (count - 1) : 0; 1423 int end = reverse ? -1 : count; 1424 int step = reverse ? -1 : 1; 1425 1426 for (int i = begin; i != end; i += step) { 1427 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]); 1428 CallFunction("function", functions[i]); 1429 } 1430 1431 TRACE("[ Done calling %s for '%s' ]", array_name, name); 1432} 1433 1434void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) { 1435 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) { 1436 return; 1437 } 1438 1439 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name); 1440 function(); 1441 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name); 1442 1443 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures 1444 // are still writable. This happens with our debug malloc (see http://b/7941716). 1445 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 1446} 1447 1448void soinfo::CallPreInitConstructors() { 1449 // DT_PREINIT_ARRAY functions are called before any other constructors for executables, 1450 // but ignored in a shared library. 1451 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false); 1452} 1453 1454void soinfo::CallConstructors() { 1455 if (constructors_called) { 1456 return; 1457 } 1458 1459 // We set constructors_called before actually calling the constructors, otherwise it doesn't 1460 // protect against recursive constructor calls. One simple example of constructor recursion 1461 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so: 1462 // 1. The program depends on libc, so libc's constructor is called here. 1463 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1464 // 3. dlopen() calls the constructors on the newly created 1465 // soinfo for libc_malloc_debug_leak.so. 1466 // 4. The debug .so depends on libc, so CallConstructors is 1467 // called again with the libc soinfo. If it doesn't trigger the early- 1468 // out above, the libc constructor will be called again (recursively!). 1469 constructors_called = true; 1470 1471 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) { 1472 // The GNU dynamic linker silently ignores these, but we warn the developer. 1473 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!", 1474 name, preinit_array_count); 1475 } 1476 1477 if (dynamic != NULL) { 1478 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) { 1479 if (d->d_tag == DT_NEEDED) { 1480 const char* library_name = strtab + d->d_un.d_val; 1481 TRACE("\"%s\": calling constructors in DT_NEEDED \"%s\"", name, library_name); 1482 find_loaded_library(library_name)->CallConstructors(); 1483 } 1484 } 1485 } 1486 1487 TRACE("\"%s\": calling constructors", name); 1488 1489 // DT_INIT should be called before DT_INIT_ARRAY if both are present. 1490 CallFunction("DT_INIT", init_func); 1491 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false); 1492} 1493 1494void soinfo::CallDestructors() { 1495 TRACE("\"%s\": calling destructors", name); 1496 1497 // DT_FINI_ARRAY must be parsed in reverse order. 1498 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true); 1499 1500 // DT_FINI should be called after DT_FINI_ARRAY if both are present. 1501 CallFunction("DT_FINI", fini_func); 1502} 1503 1504/* Force any of the closed stdin, stdout and stderr to be associated with 1505 /dev/null. */ 1506static int nullify_closed_stdio() { 1507 int dev_null, i, status; 1508 int return_value = 0; 1509 1510 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1511 if (dev_null < 0) { 1512 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1513 return -1; 1514 } 1515 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null); 1516 1517 /* If any of the stdio file descriptors is valid and not associated 1518 with /dev/null, dup /dev/null to it. */ 1519 for (i = 0; i < 3; i++) { 1520 /* If it is /dev/null already, we are done. */ 1521 if (i == dev_null) { 1522 continue; 1523 } 1524 1525 TRACE("[ Nullifying stdio file descriptor %d]", i); 1526 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1527 1528 /* If file is opened, we are good. */ 1529 if (status != -1) { 1530 continue; 1531 } 1532 1533 /* The only error we allow is that the file descriptor does not 1534 exist, in which case we dup /dev/null to it. */ 1535 if (errno != EBADF) { 1536 DL_ERR("fcntl failed: %s", strerror(errno)); 1537 return_value = -1; 1538 continue; 1539 } 1540 1541 /* Try dupping /dev/null to this stdio file descriptor and 1542 repeat if there is a signal. Note that any errors in closing 1543 the stdio descriptor are lost. */ 1544 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1545 if (status < 0) { 1546 DL_ERR("dup2 failed: %s", strerror(errno)); 1547 return_value = -1; 1548 continue; 1549 } 1550 } 1551 1552 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1553 if (dev_null > 2) { 1554 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null); 1555 status = TEMP_FAILURE_RETRY(close(dev_null)); 1556 if (status == -1) { 1557 DL_ERR("close failed: %s", strerror(errno)); 1558 return_value = -1; 1559 } 1560 } 1561 1562 return return_value; 1563} 1564 1565static bool soinfo_link_image(soinfo* si) { 1566 /* "base" might wrap around UINT32_MAX. */ 1567 ElfW(Addr) base = si->load_bias; 1568 const ElfW(Phdr)* phdr = si->phdr; 1569 int phnum = si->phnum; 1570 bool relocating_linker = (si->flags & FLAG_LINKER) != 0; 1571 1572 /* We can't debug anything until the linker is relocated */ 1573 if (!relocating_linker) { 1574 INFO("[ linking %s ]", si->name); 1575 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags); 1576 } 1577 1578 /* Extract dynamic section */ 1579 size_t dynamic_count; 1580 ElfW(Word) dynamic_flags; 1581 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1582 &dynamic_count, &dynamic_flags); 1583 if (si->dynamic == NULL) { 1584 if (!relocating_linker) { 1585 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name); 1586 } 1587 return false; 1588 } else { 1589 if (!relocating_linker) { 1590 DEBUG("dynamic = %p", si->dynamic); 1591 } 1592 } 1593 1594#if defined(__arm__) 1595 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1596 &si->ARM_exidx, &si->ARM_exidx_count); 1597#endif 1598 1599 // Extract useful information from dynamic section. 1600 uint32_t needed_count = 0; 1601 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1602 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p", 1603 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1604 switch (d->d_tag) { 1605 case DT_HASH: 1606 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0]; 1607 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1]; 1608 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8); 1609 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4); 1610 break; 1611 case DT_STRTAB: 1612 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr); 1613 break; 1614 case DT_SYMTAB: 1615 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr); 1616 break; 1617#if !defined(__LP64__) 1618 case DT_PLTREL: 1619 if (d->d_un.d_val != DT_REL) { 1620 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1621 return false; 1622 } 1623 break; 1624#endif 1625 case DT_JMPREL: 1626#if defined(USE_RELA) 1627 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1628#else 1629 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1630#endif 1631 break; 1632 case DT_PLTRELSZ: 1633#if defined(USE_RELA) 1634 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1635#else 1636 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1637#endif 1638 break; 1639#if defined(__mips__) 1640 case DT_PLTGOT: 1641 // Used by mips and mips64. 1642 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr); 1643 break; 1644#endif 1645 case DT_DEBUG: 1646 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1647 // if the dynamic table is writable 1648// FIXME: not working currently for N64 1649// The flags for the LOAD and DYNAMIC program headers do not agree. 1650// The LOAD section containng the dynamic table has been mapped as 1651// read-only, but the DYNAMIC header claims it is writable. 1652#if !(defined(__mips__) && defined(__LP64__)) 1653 if ((dynamic_flags & PF_W) != 0) { 1654 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug); 1655 } 1656 break; 1657#endif 1658#if defined(USE_RELA) 1659 case DT_RELA: 1660 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr); 1661 break; 1662 case DT_RELASZ: 1663 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela)); 1664 break; 1665 case DT_REL: 1666 DL_ERR("unsupported DT_REL in \"%s\"", si->name); 1667 return false; 1668 case DT_RELSZ: 1669 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name); 1670 return false; 1671#else 1672 case DT_REL: 1673 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr); 1674 break; 1675 case DT_RELSZ: 1676 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel)); 1677 break; 1678 case DT_RELA: 1679 DL_ERR("unsupported DT_RELA in \"%s\"", si->name); 1680 return false; 1681#endif 1682 case DT_INIT: 1683 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1684 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func); 1685 break; 1686 case DT_FINI: 1687 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr); 1688 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func); 1689 break; 1690 case DT_INIT_ARRAY: 1691 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1692 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array); 1693 break; 1694 case DT_INIT_ARRAYSZ: 1695 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1696 break; 1697 case DT_FINI_ARRAY: 1698 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1699 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array); 1700 break; 1701 case DT_FINI_ARRAYSZ: 1702 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1703 break; 1704 case DT_PREINIT_ARRAY: 1705 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr); 1706 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array); 1707 break; 1708 case DT_PREINIT_ARRAYSZ: 1709 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr)); 1710 break; 1711 case DT_TEXTREL: 1712#if defined(__LP64__) 1713 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1714 return false; 1715#else 1716 si->has_text_relocations = true; 1717 break; 1718#endif 1719 case DT_SYMBOLIC: 1720 si->has_DT_SYMBOLIC = true; 1721 break; 1722 case DT_NEEDED: 1723 ++needed_count; 1724 break; 1725 case DT_FLAGS: 1726 if (d->d_un.d_val & DF_TEXTREL) { 1727#if defined(__LP64__) 1728 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name); 1729 return false; 1730#else 1731 si->has_text_relocations = true; 1732#endif 1733 } 1734 if (d->d_un.d_val & DF_SYMBOLIC) { 1735 si->has_DT_SYMBOLIC = true; 1736 } 1737 break; 1738#if defined(__mips__) 1739 case DT_STRSZ: 1740 case DT_SYMENT: 1741 case DT_RELENT: 1742 break; 1743 case DT_MIPS_RLD_MAP: 1744 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1745 { 1746 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr); 1747 *dp = &_r_debug; 1748 } 1749 break; 1750 case DT_MIPS_RLD_VERSION: 1751 case DT_MIPS_FLAGS: 1752 case DT_MIPS_BASE_ADDRESS: 1753 case DT_MIPS_UNREFEXTNO: 1754 break; 1755 1756 case DT_MIPS_SYMTABNO: 1757 si->mips_symtabno = d->d_un.d_val; 1758 break; 1759 1760 case DT_MIPS_LOCAL_GOTNO: 1761 si->mips_local_gotno = d->d_un.d_val; 1762 break; 1763 1764 case DT_MIPS_GOTSYM: 1765 si->mips_gotsym = d->d_un.d_val; 1766 break; 1767#endif 1768 1769 default: 1770 DEBUG("Unused DT entry: type %p arg %p", 1771 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); 1772 break; 1773 } 1774 } 1775 1776 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p", 1777 reinterpret_cast<void*>(si->base), si->strtab, si->symtab); 1778 1779 // Sanity checks. 1780 if (relocating_linker && needed_count != 0) { 1781 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries"); 1782 return false; 1783 } 1784 if (si->nbucket == 0) { 1785 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name); 1786 return false; 1787 } 1788 if (si->strtab == 0) { 1789 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name); 1790 return false; 1791 } 1792 if (si->symtab == 0) { 1793 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name); 1794 return false; 1795 } 1796 1797 // If this is the main executable, then load all of the libraries from LD_PRELOAD now. 1798 if (si->flags & FLAG_EXE) { 1799 memset(gLdPreloads, 0, sizeof(gLdPreloads)); 1800 size_t preload_count = 0; 1801 for (size_t i = 0; gLdPreloadNames[i] != NULL; i++) { 1802 soinfo* lsi = find_library(gLdPreloadNames[i]); 1803 if (lsi != NULL) { 1804 gLdPreloads[preload_count++] = lsi; 1805 } else { 1806 // As with glibc, failure to load an LD_PRELOAD library is just a warning. 1807 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s", 1808 gLdPreloadNames[i], si->name, linker_get_error_buffer()); 1809 } 1810 } 1811 } 1812 1813 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*))); 1814 soinfo** pneeded = needed; 1815 1816 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 1817 if (d->d_tag == DT_NEEDED) { 1818 const char* library_name = si->strtab + d->d_un.d_val; 1819 DEBUG("%s needs %s", si->name, library_name); 1820 soinfo* lsi = find_library(library_name); 1821 if (lsi == NULL) { 1822 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf)); 1823 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1824 library_name, si->name, tmp_err_buf); 1825 return false; 1826 } 1827 *pneeded++ = lsi; 1828 } 1829 } 1830 *pneeded = NULL; 1831 1832#if !defined(__LP64__) 1833 if (si->has_text_relocations) { 1834 // Make segments writable to allow text relocations to work properly. We will later call 1835 // phdr_table_protect_segments() after all of them are applied and all constructors are run. 1836 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1837 "security hardening. Please fix.", si->name); 1838 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1839 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1840 si->name, strerror(errno)); 1841 return false; 1842 } 1843 } 1844#endif 1845 1846#if defined(USE_RELA) 1847 if (si->plt_rela != NULL) { 1848 DEBUG("[ relocating %s plt ]\n", si->name); 1849 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1850 return false; 1851 } 1852 } 1853 if (si->rela != NULL) { 1854 DEBUG("[ relocating %s ]\n", si->name); 1855 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1856 return false; 1857 } 1858 } 1859#else 1860 if (si->plt_rel != NULL) { 1861 DEBUG("[ relocating %s plt ]", si->name); 1862 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1863 return false; 1864 } 1865 } 1866 if (si->rel != NULL) { 1867 DEBUG("[ relocating %s ]", si->name); 1868 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1869 return false; 1870 } 1871 } 1872#endif 1873 1874#if defined(__mips__) 1875 if (!mips_relocate_got(si, needed)) { 1876 return false; 1877 } 1878#endif 1879 1880 si->flags |= FLAG_LINKED; 1881 DEBUG("[ finished linking %s ]", si->name); 1882 1883#if !defined(__LP64__) 1884 if (si->has_text_relocations) { 1885 // All relocations are done, we can protect our segments back to read-only. 1886 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1887 DL_ERR("can't protect segments for \"%s\": %s", 1888 si->name, strerror(errno)); 1889 return false; 1890 } 1891 } 1892#endif 1893 1894 /* We can also turn on GNU RELRO protection */ 1895 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1896 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1897 si->name, strerror(errno)); 1898 return false; 1899 } 1900 1901 notify_gdb_of_load(si); 1902 return true; 1903} 1904 1905/* 1906 * This function add vdso to internal dso list. 1907 * It helps to stack unwinding through signal handlers. 1908 * Also, it makes bionic more like glibc. 1909 */ 1910static void add_vdso(KernelArgumentBlock& args __unused) { 1911#if defined(AT_SYSINFO_EHDR) 1912 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1913 if (ehdr_vdso == NULL) { 1914 return; 1915 } 1916 1917 soinfo* si = soinfo_alloc("[vdso]"); 1918 1919 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1920 si->phnum = ehdr_vdso->e_phnum; 1921 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1922 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1923 si->flags = 0; 1924 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1925 1926 soinfo_link_image(si); 1927#endif 1928} 1929 1930/* 1931 * This code is called after the linker has linked itself and 1932 * fixed it's own GOT. It is safe to make references to externs 1933 * and other non-local data at this point. 1934 */ 1935static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 1936 /* NOTE: we store the args pointer on a special location 1937 * of the temporary TLS area in order to pass it to 1938 * the C Library's runtime initializer. 1939 * 1940 * The initializer must clear the slot and reset the TLS 1941 * to point to a different location to ensure that no other 1942 * shared library constructor can access it. 1943 */ 1944 __libc_init_tls(args); 1945 1946#if TIMING 1947 struct timeval t0, t1; 1948 gettimeofday(&t0, 0); 1949#endif 1950 1951 // Initialize environment functions, and get to the ELF aux vectors table. 1952 linker_env_init(args); 1953 1954 // If this is a setuid/setgid program, close the security hole described in 1955 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 1956 if (get_AT_SECURE()) { 1957 nullify_closed_stdio(); 1958 } 1959 1960 debuggerd_init(); 1961 1962 // Get a few environment variables. 1963 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 1964 if (LD_DEBUG != NULL) { 1965 gLdDebugVerbosity = atoi(LD_DEBUG); 1966 } 1967 1968 // Normally, these are cleaned by linker_env_init, but the test 1969 // doesn't cost us anything. 1970 const char* ldpath_env = NULL; 1971 const char* ldpreload_env = NULL; 1972 if (!get_AT_SECURE()) { 1973 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 1974 ldpreload_env = linker_env_get("LD_PRELOAD"); 1975 } 1976 1977 INFO("[ android linker & debugger ]"); 1978 1979 soinfo* si = soinfo_alloc(args.argv[0]); 1980 if (si == NULL) { 1981 exit(EXIT_FAILURE); 1982 } 1983 1984 /* bootstrap the link map, the main exe always needs to be first */ 1985 si->flags |= FLAG_EXE; 1986 link_map* map = &(si->link_map_head); 1987 1988 map->l_addr = 0; 1989 map->l_name = args.argv[0]; 1990 map->l_prev = NULL; 1991 map->l_next = NULL; 1992 1993 _r_debug.r_map = map; 1994 r_debug_tail = map; 1995 1996 /* gdb expects the linker to be in the debug shared object list. 1997 * Without this, gdb has trouble locating the linker's ".text" 1998 * and ".plt" sections. Gdb could also potentially use this to 1999 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2000 * Don't use soinfo_alloc(), because the linker shouldn't 2001 * be on the soinfo list. 2002 */ 2003 { 2004 static soinfo linker_soinfo; 2005#if defined(__LP64__) 2006 strlcpy(linker_soinfo.name, "/system/bin/linker64", sizeof(linker_soinfo.name)); 2007#else 2008 strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name)); 2009#endif 2010 linker_soinfo.flags = 0; 2011 linker_soinfo.base = linker_base; 2012 2013 /* 2014 * Set the dynamic field in the link map otherwise gdb will complain with 2015 * the following: 2016 * warning: .dynamic section for "/system/bin/linker" is not at the 2017 * expected address (wrong library or version mismatch?) 2018 */ 2019 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2020 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2021 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2022 &linker_soinfo.dynamic, NULL, NULL); 2023 insert_soinfo_into_debug_map(&linker_soinfo); 2024 } 2025 2026 // Extract information passed from the kernel. 2027 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2028 si->phnum = args.getauxval(AT_PHNUM); 2029 si->entry = args.getauxval(AT_ENTRY); 2030 2031 /* Compute the value of si->base. We can't rely on the fact that 2032 * the first entry is the PHDR because this will not be true 2033 * for certain executables (e.g. some in the NDK unit test suite) 2034 */ 2035 si->base = 0; 2036 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2037 si->load_bias = 0; 2038 for (size_t i = 0; i < si->phnum; ++i) { 2039 if (si->phdr[i].p_type == PT_PHDR) { 2040 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2041 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2042 break; 2043 } 2044 } 2045 si->dynamic = NULL; 2046 si->ref_count = 1; 2047 2048 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2049 parse_LD_LIBRARY_PATH(ldpath_env); 2050 parse_LD_PRELOAD(ldpreload_env); 2051 2052 somain = si; 2053 2054 if (!soinfo_link_image(si)) { 2055 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2056 exit(EXIT_FAILURE); 2057 } 2058 2059 add_vdso(args); 2060 2061 si->CallPreInitConstructors(); 2062 2063 for (size_t i = 0; gLdPreloads[i] != NULL; ++i) { 2064 gLdPreloads[i]->CallConstructors(); 2065 } 2066 2067 /* After the link_image, the si->load_bias is initialized. 2068 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2069 * We need to update this value for so exe here. So Unwind_Backtrace 2070 * for some arch like x86 could work correctly within so exe. 2071 */ 2072 map->l_addr = si->load_bias; 2073 si->CallConstructors(); 2074 2075#if TIMING 2076 gettimeofday(&t1, NULL); 2077 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2078 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2079 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2080#endif 2081#if STATS 2082 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2083 linker_stats.count[kRelocAbsolute], 2084 linker_stats.count[kRelocRelative], 2085 linker_stats.count[kRelocCopy], 2086 linker_stats.count[kRelocSymbol]); 2087#endif 2088#if COUNT_PAGES 2089 { 2090 unsigned n; 2091 unsigned i; 2092 unsigned count = 0; 2093 for (n = 0; n < 4096; n++) { 2094 if (bitmask[n]) { 2095 unsigned x = bitmask[n]; 2096#if defined(__LP64__) 2097 for (i = 0; i < 32; i++) { 2098#else 2099 for (i = 0; i < 8; i++) { 2100#endif 2101 if (x & 1) { 2102 count++; 2103 } 2104 x >>= 1; 2105 } 2106 } 2107 } 2108 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2109 } 2110#endif 2111 2112#if TIMING || STATS || COUNT_PAGES 2113 fflush(stdout); 2114#endif 2115 2116 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2117 return si->entry; 2118} 2119 2120/* Compute the load-bias of an existing executable. This shall only 2121 * be used to compute the load bias of an executable or shared library 2122 * that was loaded by the kernel itself. 2123 * 2124 * Input: 2125 * elf -> address of ELF header, assumed to be at the start of the file. 2126 * Return: 2127 * load bias, i.e. add the value of any p_vaddr in the file to get 2128 * the corresponding address in memory. 2129 */ 2130static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2131 ElfW(Addr) offset = elf->e_phoff; 2132 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2133 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2134 2135 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2136 if (phdr->p_type == PT_LOAD) { 2137 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2138 } 2139 } 2140 return 0; 2141} 2142 2143/* 2144 * This is the entry point for the linker, called from begin.S. This 2145 * method is responsible for fixing the linker's own relocations, and 2146 * then calling __linker_init_post_relocation(). 2147 * 2148 * Because this method is called before the linker has fixed it's own 2149 * relocations, any attempt to reference an extern variable, extern 2150 * function, or other GOT reference will generate a segfault. 2151 */ 2152extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2153 KernelArgumentBlock args(raw_args); 2154 2155 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2156 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2157 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2158 2159 soinfo linker_so; 2160 memset(&linker_so, 0, sizeof(soinfo)); 2161 2162 strcpy(linker_so.name, "[dynamic linker]"); 2163 linker_so.base = linker_addr; 2164 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2165 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2166 linker_so.dynamic = NULL; 2167 linker_so.phdr = phdr; 2168 linker_so.phnum = elf_hdr->e_phnum; 2169 linker_so.flags |= FLAG_LINKER; 2170 2171 if (!soinfo_link_image(&linker_so)) { 2172 // It would be nice to print an error message, but if the linker 2173 // can't link itself, there's no guarantee that we'll be able to 2174 // call write() (because it involves a GOT reference). We may as 2175 // well try though... 2176 const char* msg = "CANNOT LINK EXECUTABLE: "; 2177 write(2, msg, strlen(msg)); 2178 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2179 write(2, "\n", 1); 2180 _exit(EXIT_FAILURE); 2181 } 2182 2183 // We have successfully fixed our own relocations. It's safe to run 2184 // the main part of the linker now. 2185 args.abort_message_ptr = &gAbortMessage; 2186 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2187 2188 set_soinfo_pool_protection(PROT_READ); 2189 2190 // Return the address that the calling assembly stub should jump to. 2191 return start_address; 2192} 2193