linker.cpp revision faf05bacd45719291b371f24b1b89543881b37f6
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 } 166#define UNUSED __attribute__((unused)) 167DISALLOW_ALLOCATION(void*, malloc, (size_t u UNUSED)); 168DISALLOW_ALLOCATION(void, free, (void* u UNUSED)); 169DISALLOW_ALLOCATION(void*, realloc, (void* u1 UNUSED, size_t u2 UNUSED)); 170DISALLOW_ALLOCATION(void*, calloc, (size_t u1 UNUSED, size_t u2 UNUSED)); 171 172static char tmp_err_buf[768]; 173static char __linker_dl_err_buf[768]; 174 175char* linker_get_error_buffer() { 176 return &__linker_dl_err_buf[0]; 177} 178 179size_t linker_get_error_buffer_size() { 180 return sizeof(__linker_dl_err_buf); 181} 182 183/* 184 * This function is an empty stub where GDB locates a breakpoint to get notified 185 * about linker activity. 186 */ 187extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(); 188 189static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0}; 190static link_map* r_debug_tail = 0; 191 192static pthread_mutex_t gDebugMutex = PTHREAD_MUTEX_INITIALIZER; 193 194static void insert_soinfo_into_debug_map(soinfo* info) { 195 // Copy the necessary fields into the debug structure. 196 link_map* map = &(info->link_map_head); 197 map->l_addr = info->load_bias; 198 map->l_name = reinterpret_cast<char*>(info->name); 199 map->l_ld = info->dynamic; 200 201 /* Stick the new library at the end of the list. 202 * gdb tends to care more about libc than it does 203 * about leaf libraries, and ordering it this way 204 * reduces the back-and-forth over the wire. 205 */ 206 if (r_debug_tail) { 207 r_debug_tail->l_next = map; 208 map->l_prev = r_debug_tail; 209 map->l_next = 0; 210 } else { 211 _r_debug.r_map = map; 212 map->l_prev = 0; 213 map->l_next = 0; 214 } 215 r_debug_tail = map; 216} 217 218static void remove_soinfo_from_debug_map(soinfo* info) { 219 link_map* map = &(info->link_map_head); 220 221 if (r_debug_tail == map) { 222 r_debug_tail = map->l_prev; 223 } 224 225 if (map->l_prev) { 226 map->l_prev->l_next = map->l_next; 227 } 228 if (map->l_next) { 229 map->l_next->l_prev = map->l_prev; 230 } 231} 232 233static void notify_gdb_of_load(soinfo* info) { 234 if (info->flags & FLAG_EXE) { 235 // GDB already knows about the main executable 236 return; 237 } 238 239 ScopedPthreadMutexLocker locker(&gDebugMutex); 240 241 _r_debug.r_state = r_debug::RT_ADD; 242 rtld_db_dlactivity(); 243 244 insert_soinfo_into_debug_map(info); 245 246 _r_debug.r_state = r_debug::RT_CONSISTENT; 247 rtld_db_dlactivity(); 248} 249 250static void notify_gdb_of_unload(soinfo* info) { 251 if (info->flags & FLAG_EXE) { 252 // GDB already knows about the main executable 253 return; 254 } 255 256 ScopedPthreadMutexLocker locker(&gDebugMutex); 257 258 _r_debug.r_state = r_debug::RT_DELETE; 259 rtld_db_dlactivity(); 260 261 remove_soinfo_from_debug_map(info); 262 263 _r_debug.r_state = r_debug::RT_CONSISTENT; 264 rtld_db_dlactivity(); 265} 266 267void notify_gdb_of_libraries() { 268 _r_debug.r_state = r_debug::RT_ADD; 269 rtld_db_dlactivity(); 270 _r_debug.r_state = r_debug::RT_CONSISTENT; 271 rtld_db_dlactivity(); 272} 273 274static bool ensure_free_list_non_empty() { 275 if (gSoInfoFreeList != NULL) { 276 return true; 277 } 278 279 // Allocate a new pool. 280 soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool), 281 PROT_READ|PROT_WRITE, 282 MAP_PRIVATE|MAP_ANONYMOUS, 0, 0)); 283 if (pool == MAP_FAILED) { 284 return false; 285 } 286 287 // Add the pool to our list of pools. 288 pool->next = gSoInfoPools; 289 gSoInfoPools = pool; 290 291 // Chain the entries in the new pool onto the free list. 292 gSoInfoFreeList = &pool->info[0]; 293 soinfo* next = NULL; 294 for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) { 295 pool->info[i].next = next; 296 next = &pool->info[i]; 297 } 298 299 return true; 300} 301 302static void set_soinfo_pool_protection(int protection) { 303 for (soinfo_pool_t* p = gSoInfoPools; p != NULL; p = p->next) { 304 if (mprotect(p, sizeof(*p), protection) == -1) { 305 abort(); // Can't happen. 306 } 307 } 308} 309 310static soinfo* soinfo_alloc(const char* name) { 311 if (strlen(name) >= SOINFO_NAME_LEN) { 312 DL_ERR("library name \"%s\" too long", name); 313 return NULL; 314 } 315 316 if (!ensure_free_list_non_empty()) { 317 DL_ERR("out of memory when loading \"%s\"", name); 318 return NULL; 319 } 320 321 // Take the head element off the free list. 322 soinfo* si = gSoInfoFreeList; 323 gSoInfoFreeList = gSoInfoFreeList->next; 324 325 // Initialize the new element. 326 memset(si, 0, sizeof(soinfo)); 327 strlcpy(si->name, name, sizeof(si->name)); 328 sonext->next = si; 329 sonext = si; 330 331 TRACE("name %s: allocated soinfo @ %p", name, si); 332 return si; 333} 334 335static void soinfo_free(soinfo* si) { 336 if (si == NULL) { 337 return; 338 } 339 340 soinfo *prev = NULL, *trav; 341 342 TRACE("name %s: freeing soinfo @ %p", si->name, si); 343 344 for (trav = solist; trav != NULL; trav = trav->next) { 345 if (trav == si) 346 break; 347 prev = trav; 348 } 349 if (trav == NULL) { 350 /* si was not in solist */ 351 DL_ERR("name \"%s\" is not in solist!", si->name); 352 return; 353 } 354 355 /* prev will never be NULL, because the first entry in solist is 356 always the static libdl_info. 357 */ 358 prev->next = si->next; 359 if (si == sonext) { 360 sonext = prev; 361 } 362 si->next = gSoInfoFreeList; 363 gSoInfoFreeList = si; 364} 365 366 367static void parse_path(const char* path, const char* delimiters, 368 const char** array, char* buf, size_t buf_size, size_t max_count) { 369 if (path == NULL) { 370 return; 371 } 372 373 size_t len = strlcpy(buf, path, buf_size); 374 375 size_t i = 0; 376 char* buf_p = buf; 377 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 378 if (*array[i] != '\0') { 379 ++i; 380 } 381 } 382 383 // Forget the last path if we had to truncate; this occurs if the 2nd to 384 // last char isn't '\0' (i.e. wasn't originally a delimiter). 385 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 386 array[i - 1] = NULL; 387 } else { 388 array[i] = NULL; 389 } 390} 391 392static void parse_LD_LIBRARY_PATH(const char* path) { 393 parse_path(path, ":", gLdPaths, 394 gLdPathsBuffer, sizeof(gLdPathsBuffer), LDPATH_MAX); 395} 396 397static void parse_LD_PRELOAD(const char* path) { 398 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 399 parse_path(path, " :", gLdPreloadNames, 400 gLdPreloadsBuffer, sizeof(gLdPreloadsBuffer), LDPRELOAD_MAX); 401} 402 403#if defined(__arm__) 404 405/* For a given PC, find the .so that it belongs to. 406 * Returns the base address of the .ARM.exidx section 407 * for that .so, and the number of 8-byte entries 408 * in that section (via *pcount). 409 * 410 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 411 * 412 * This function is exposed via dlfcn.cpp and libdl.so. 413 */ 414_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) { 415 unsigned addr = (unsigned)pc; 416 417 for (soinfo* si = solist; si != 0; si = si->next) { 418 if ((addr >= si->base) && (addr < (si->base + si->size))) { 419 *pcount = si->ARM_exidx_count; 420 return (_Unwind_Ptr)si->ARM_exidx; 421 } 422 } 423 *pcount = 0; 424 return NULL; 425} 426 427#endif 428 429/* Here, we only have to provide a callback to iterate across all the 430 * loaded libraries. gcc_eh does the rest. */ 431int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 432 int rv = 0; 433 for (soinfo* si = solist; si != NULL; si = si->next) { 434 dl_phdr_info dl_info; 435 dl_info.dlpi_addr = si->link_map_head.l_addr; 436 dl_info.dlpi_name = si->link_map_head.l_name; 437 dl_info.dlpi_phdr = si->phdr; 438 dl_info.dlpi_phnum = si->phnum; 439 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 440 if (rv != 0) { 441 break; 442 } 443 } 444 return rv; 445} 446 447static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) { 448 ElfW(Sym)* symtab = si->symtab; 449 const char* strtab = si->strtab; 450 451 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd", 452 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket); 453 454 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) { 455 ElfW(Sym)* s = symtab + n; 456 if (strcmp(strtab + s->st_name, name)) continue; 457 458 /* only concern ourselves with global and weak symbol definitions */ 459 switch (ELF_ST_BIND(s->st_info)) { 460 case STB_GLOBAL: 461 case STB_WEAK: 462 if (s->st_shndx == SHN_UNDEF) { 463 continue; 464 } 465 466 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd", 467 name, si->name, reinterpret_cast<void*>(s->st_value), 468 static_cast<size_t>(s->st_size)); 469 return s; 470 } 471 } 472 473 return NULL; 474} 475 476static unsigned elfhash(const char* _name) { 477 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name); 478 unsigned h = 0, g; 479 480 while (*name) { 481 h = (h << 4) + *name++; 482 g = h & 0xf0000000; 483 h ^= g; 484 h ^= g >> 24; 485 } 486 return h; 487} 488 489static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) { 490 unsigned elf_hash = elfhash(name); 491 ElfW(Sym)* s = NULL; 492 493 if (si != NULL && somain != NULL) { 494 /* 495 * Local scope is executable scope. Just start looking into it right away 496 * for the shortcut. 497 */ 498 499 if (si == somain) { 500 s = soinfo_elf_lookup(si, elf_hash, name); 501 if (s != NULL) { 502 *lsi = si; 503 goto done; 504 } 505 } else { 506 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */ 507 508 /* 509 * If this object was built with symbolic relocations disabled, the 510 * first place to look to resolve external references is the main 511 * executable. 512 */ 513 514 if (!si->has_DT_SYMBOLIC) { 515 DEBUG("%s: looking up %s in executable %s", 516 si->name, name, somain->name); 517 s = soinfo_elf_lookup(somain, elf_hash, name); 518 if (s != NULL) { 519 *lsi = somain; 520 goto done; 521 } 522 } 523 524 /* Look for symbols in the local scope (the object who is 525 * searching). This happens with C++ templates on x86 for some 526 * reason. 527 * 528 * Notes on weak symbols: 529 * The ELF specs are ambiguous about treatment of weak definitions in 530 * dynamic linking. Some systems return the first definition found 531 * and some the first non-weak definition. This is system dependent. 532 * Here we return the first definition found for simplicity. */ 533 534 s = soinfo_elf_lookup(si, elf_hash, name); 535 if (s != NULL) { 536 *lsi = si; 537 goto done; 538 } 539 540 /* 541 * If this object was built with -Bsymbolic and symbol is not found 542 * in the local scope, try to find the symbol in the main executable. 543 */ 544 545 if (si->has_DT_SYMBOLIC) { 546 DEBUG("%s: looking up %s in executable %s after local scope", 547 si->name, name, somain->name); 548 s = soinfo_elf_lookup(somain, elf_hash, name); 549 if (s != NULL) { 550 *lsi = somain; 551 goto done; 552 } 553 } 554 } 555 } 556 557 /* Next, look for it in the preloads list */ 558 for (int i = 0; gLdPreloads[i] != NULL; i++) { 559 s = soinfo_elf_lookup(gLdPreloads[i], elf_hash, name); 560 if (s != NULL) { 561 *lsi = gLdPreloads[i]; 562 goto done; 563 } 564 } 565 566 for (int i = 0; needed[i] != NULL; i++) { 567 DEBUG("%s: looking up %s in %s", 568 si->name, name, needed[i]->name); 569 s = soinfo_elf_lookup(needed[i], elf_hash, name); 570 if (s != NULL) { 571 *lsi = needed[i]; 572 goto done; 573 } 574 } 575 576done: 577 if (s != NULL) { 578 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, " 579 "found in %s, base = %p, load bias = %p", 580 si->name, name, reinterpret_cast<void*>(s->st_value), 581 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base), 582 reinterpret_cast<void*>((*lsi)->load_bias)); 583 return s; 584 } 585 586 return NULL; 587} 588 589/* This is used by dlsym(3). It performs symbol lookup only within the 590 specified soinfo object and not in any of its dependencies. 591 592 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says 593 that it should do a breadth first search through the dependency 594 tree. This agrees with the ELF spec (aka System V Application 595 Binary Interface) where in Chapter 5 it discuss resolving "Shared 596 Object Dependencies" in breadth first search order. 597 */ 598ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) { 599 return soinfo_elf_lookup(si, elfhash(name), name); 600} 601 602/* This is used by dlsym(3) to performs a global symbol lookup. If the 603 start value is null (for RTLD_DEFAULT), the search starts at the 604 beginning of the global solist. Otherwise the search starts at the 605 specified soinfo (for RTLD_NEXT). 606 */ 607ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) { 608 unsigned elf_hash = elfhash(name); 609 610 if (start == NULL) { 611 start = solist; 612 } 613 614 ElfW(Sym)* s = NULL; 615 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) { 616 s = soinfo_elf_lookup(si, elf_hash, name); 617 if (s != NULL) { 618 *found = si; 619 break; 620 } 621 } 622 623 if (s != NULL) { 624 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p", 625 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base)); 626 } 627 628 return s; 629} 630 631soinfo* find_containing_library(const void* p) { 632 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p); 633 for (soinfo* si = solist; si != NULL; si = si->next) { 634 if (address >= si->base && address - si->base < si->size) { 635 return si; 636 } 637 } 638 return NULL; 639} 640 641ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) { 642 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base; 643 644 // Search the library's symbol table for any defined symbol which 645 // contains this address. 646 for (size_t i = 0; i < si->nchain; ++i) { 647 ElfW(Sym)* sym = &si->symtab[i]; 648 if (sym->st_shndx != SHN_UNDEF && 649 soaddr >= sym->st_value && 650 soaddr < sym->st_value + sym->st_size) { 651 return sym; 652 } 653 } 654 655 return NULL; 656} 657 658static int open_library_on_path(const char* name, const char* const paths[]) { 659 char buf[512]; 660 for (size_t i = 0; paths[i] != NULL; ++i) { 661 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name); 662 if (n < 0 || n >= static_cast<int>(sizeof(buf))) { 663 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name); 664 continue; 665 } 666 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC)); 667 if (fd != -1) { 668 return fd; 669 } 670 } 671 return -1; 672} 673 674static int open_library(const char* name) { 675 TRACE("[ opening %s ]", name); 676 677 // If the name contains a slash, we should attempt to open it directly and not search the paths. 678 if (strchr(name, '/') != NULL) { 679 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC)); 680 if (fd != -1) { 681 return fd; 682 } 683 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now. 684 } 685 686 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths. 687 int fd = open_library_on_path(name, gLdPaths); 688 if (fd == -1) { 689 fd = open_library_on_path(name, gDefaultLdPaths); 690 } 691 return fd; 692} 693 694static soinfo* load_library(const char* name) { 695 // Open the file. 696 int fd = open_library(name); 697 if (fd == -1) { 698 DL_ERR("library \"%s\" not found", name); 699 return NULL; 700 } 701 702 // Read the ELF header and load the segments. 703 ElfReader elf_reader(name, fd); 704 if (!elf_reader.Load()) { 705 return NULL; 706 } 707 708 const char* bname = strrchr(name, '/'); 709 soinfo* si = soinfo_alloc(bname ? bname + 1 : name); 710 if (si == NULL) { 711 return NULL; 712 } 713 si->base = elf_reader.load_start(); 714 si->size = elf_reader.load_size(); 715 si->load_bias = elf_reader.load_bias(); 716 si->flags = 0; 717 si->entry = 0; 718 si->dynamic = NULL; 719 si->phnum = elf_reader.phdr_count(); 720 si->phdr = elf_reader.loaded_phdr(); 721 return si; 722} 723 724static soinfo *find_loaded_library(const char* name) { 725 // TODO: don't use basename only for determining libraries 726 // http://code.google.com/p/android/issues/detail?id=6670 727 728 const char* bname = strrchr(name, '/'); 729 bname = bname ? bname + 1 : name; 730 731 for (soinfo* si = solist; si != NULL; si = si->next) { 732 if (!strcmp(bname, si->name)) { 733 return si; 734 } 735 } 736 return NULL; 737} 738 739static soinfo* find_library_internal(const char* name) { 740 if (name == NULL) { 741 return somain; 742 } 743 744 soinfo* si = find_loaded_library(name); 745 if (si != NULL) { 746 if (si->flags & FLAG_LINKED) { 747 return si; 748 } 749 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 750 return NULL; 751 } 752 753 TRACE("[ '%s' has not been loaded yet. Locating...]", name); 754 si = load_library(name); 755 if (si == NULL) { 756 return NULL; 757 } 758 759 // At this point we know that whatever is loaded @ base is a valid ELF 760 // shared library whose segments are properly mapped in. 761 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]", 762 reinterpret_cast<void*>(si->base), si->size, si->name); 763 764 if (!soinfo_link_image(si)) { 765 munmap(reinterpret_cast<void*>(si->base), si->size); 766 soinfo_free(si); 767 return NULL; 768 } 769 770 return si; 771} 772 773static soinfo* find_library(const char* name) { 774 soinfo* si = find_library_internal(name); 775 if (si != NULL) { 776 si->ref_count++; 777 } 778 return si; 779} 780 781static int soinfo_unload(soinfo* si) { 782 if (si->ref_count == 1) { 783 TRACE("unloading '%s'", si->name); 784 si->CallDestructors(); 785 786 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) { 787 if (d->d_tag == DT_NEEDED) { 788 const char* library_name = si->strtab + d->d_un.d_val; 789 TRACE("%s needs to unload %s", si->name, library_name); 790 soinfo_unload(find_loaded_library(library_name)); 791 } 792 } 793 794 munmap(reinterpret_cast<void*>(si->base), si->size); 795 notify_gdb_of_unload(si); 796 soinfo_free(si); 797 si->ref_count = 0; 798 } else { 799 si->ref_count--; 800 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count); 801 } 802 return 0; 803} 804 805void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 806 snprintf(buffer, buffer_size, "%s:%s", gDefaultLdPaths[0], gDefaultLdPaths[1]); 807} 808 809void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 810 if (!get_AT_SECURE()) { 811 parse_LD_LIBRARY_PATH(ld_library_path); 812 } 813} 814 815soinfo* do_dlopen(const char* name, int flags) { 816 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) { 817 DL_ERR("invalid flags to dlopen: %x", flags); 818 return NULL; 819 } 820 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 821 soinfo* si = find_library(name); 822 if (si != NULL) { 823 si->CallConstructors(); 824 } 825 set_soinfo_pool_protection(PROT_READ); 826 return si; 827} 828 829int do_dlclose(soinfo* si) { 830 set_soinfo_pool_protection(PROT_READ | PROT_WRITE); 831 int result = soinfo_unload(si); 832 set_soinfo_pool_protection(PROT_READ); 833 return result; 834} 835 836#if defined(USE_RELA) 837static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) { 838 ElfW(Sym)* symtab = si->symtab; 839 const char* strtab = si->strtab; 840 ElfW(Sym)* s; 841 ElfW(Rela)* start = rela; 842 soinfo* lsi; 843 844 for (size_t idx = 0; idx < count; ++idx, ++rela) { 845 unsigned type = ELFW(R_TYPE)(rela->r_info); 846 unsigned sym = ELFW(R_SYM)(rela->r_info); 847 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias); 848 ElfW(Addr) sym_addr = 0; 849 const char* sym_name = NULL; 850 851 DEBUG("Processing '%s' relocation at index %zd", si->name, idx); 852 if (type == 0) { // R_*_NONE 853 continue; 854 } 855 if (sym != 0) { 856 sym_name = reinterpret_cast<const char*>(strtab + symtab[sym].st_name); 857 s = soinfo_do_lookup(si, sym_name, &lsi, needed); 858 if (s == NULL) { 859 // We only allow an undefined symbol if this is a weak reference... 860 s = &symtab[sym]; 861 if (ELF_ST_BIND(s->st_info) != STB_WEAK) { 862 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name); 863 return -1; 864 } 865 866 /* IHI0044C AAELF 4.5.1.1: 867 868 Libraries are not searched to resolve weak references. 869 It is not an error for a weak reference to remain unsatisfied. 870 871 During linking, the value of an undefined weak reference is: 872 - Zero if the relocation type is absolute 873 - The address of the place if the relocation is pc-relative 874 - The address of nominal base address if the relocation 875 type is base-relative. 876 */ 877 878 switch (type) { 879#if defined(__aarch64__) 880 case R_AARCH64_JUMP_SLOT: 881 case R_AARCH64_GLOB_DAT: 882 case R_AARCH64_ABS64: 883 case R_AARCH64_ABS32: 884 case R_AARCH64_ABS16: 885 case R_AARCH64_RELATIVE: 886 /* 887 * The sym_addr was initialized to be zero above, or the relocation 888 * code below does not care about value of sym_addr. 889 * No need to do anything. 890 */ 891 break; 892#elif defined(__x86_64__) 893 case R_X86_64_JUMP_SLOT: 894 case R_X86_64_GLOB_DAT: 895 case R_X86_64_32: 896 case R_X86_64_RELATIVE: 897 // No need to do anything. 898 break; 899 case R_X86_64_PC32: 900 sym_addr = reloc; 901 break; 902#endif 903 default: 904 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx); 905 return -1; 906 } 907 } else { 908 // We got a definition. 909 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias); 910 } 911 count_relocation(kRelocSymbol); 912 } else { 913 s = NULL; 914 } 915 916 switch (type) { 917#if defined(__aarch64__) 918 case R_AARCH64_JUMP_SLOT: 919 count_relocation(kRelocAbsolute); 920 MARK(rela->r_offset); 921 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n", 922 reloc, (sym_addr + rela->r_addend), sym_name); 923 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 924 break; 925 case R_AARCH64_GLOB_DAT: 926 count_relocation(kRelocAbsolute); 927 MARK(rela->r_offset); 928 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n", 929 reloc, (sym_addr + rela->r_addend), sym_name); 930 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend); 931 break; 932 case R_AARCH64_ABS64: 933 count_relocation(kRelocAbsolute); 934 MARK(rela->r_offset); 935 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n", 936 reloc, (sym_addr + rela->r_addend), sym_name); 937 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 938 break; 939 case R_AARCH64_ABS32: 940 count_relocation(kRelocAbsolute); 941 MARK(rela->r_offset); 942 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n", 943 reloc, (sym_addr + rela->r_addend), sym_name); 944 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 945 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 946 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 947 } else { 948 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 949 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 950 static_cast<ElfW(Addr)>(INT32_MIN), 951 static_cast<ElfW(Addr)>(UINT32_MAX)); 952 return -1; 953 } 954 break; 955 case R_AARCH64_ABS16: 956 count_relocation(kRelocAbsolute); 957 MARK(rela->r_offset); 958 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n", 959 reloc, (sym_addr + rela->r_addend), sym_name); 960 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) && 961 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 962 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend); 963 } else { 964 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 965 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)), 966 static_cast<ElfW(Addr)>(INT16_MIN), 967 static_cast<ElfW(Addr)>(UINT16_MAX)); 968 return -1; 969 } 970 break; 971 case R_AARCH64_PREL64: 972 count_relocation(kRelocRelative); 973 MARK(rela->r_offset); 974 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n", 975 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 976 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset; 977 break; 978 case R_AARCH64_PREL32: 979 count_relocation(kRelocRelative); 980 MARK(rela->r_offset); 981 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n", 982 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 983 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 984 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) { 985 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 986 } else { 987 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 988 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 989 static_cast<ElfW(Addr)>(INT32_MIN), 990 static_cast<ElfW(Addr)>(UINT32_MAX)); 991 return -1; 992 } 993 break; 994 case R_AARCH64_PREL16: 995 count_relocation(kRelocRelative); 996 MARK(rela->r_offset); 997 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n", 998 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name); 999 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) && 1000 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) { 1001 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset); 1002 } else { 1003 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx", 1004 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)), 1005 static_cast<ElfW(Addr)>(INT16_MIN), 1006 static_cast<ElfW(Addr)>(UINT16_MAX)); 1007 return -1; 1008 } 1009 break; 1010 1011 case R_AARCH64_RELATIVE: 1012 count_relocation(kRelocRelative); 1013 MARK(rela->r_offset); 1014 if (sym) { 1015 DL_ERR("odd RELATIVE form..."); 1016 return -1; 1017 } 1018 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n", 1019 reloc, (si->base + rela->r_addend)); 1020 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend); 1021 break; 1022 1023 case R_AARCH64_COPY: 1024 if ((si->flags & FLAG_EXE) == 0) { 1025 /* 1026 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf 1027 * 1028 * Section 4.7.1.10 "Dynamic relocations" 1029 * R_AARCH64_COPY may only appear in executable objects where e_type is 1030 * set to ET_EXEC. 1031 * 1032 * FLAG_EXE is set for both ET_DYN and ET_EXEC executables. 1033 * We should explicitly disallow ET_DYN executables from having 1034 * R_AARCH64_COPY relocations. 1035 */ 1036 DL_ERR("%s R_AARCH64_COPY relocations only supported for ET_EXEC", si->name); 1037 return -1; 1038 } 1039 count_relocation(kRelocCopy); 1040 MARK(rela->r_offset); 1041 TRACE_TYPE(RELO, "RELO COPY %16llx <- %lld @ %16llx %s\n", 1042 reloc, 1043 s->st_size, 1044 (sym_addr + rela->r_addend), 1045 sym_name); 1046 if (reloc == (sym_addr + rela->r_addend)) { 1047 ElfW(Sym)* src = soinfo_do_lookup(NULL, sym_name, &lsi, needed); 1048 1049 if (src == NULL) { 1050 DL_ERR("%s R_AARCH64_COPY relocation source cannot be resolved", si->name); 1051 return -1; 1052 } 1053 if (lsi->has_DT_SYMBOLIC) { 1054 DL_ERR("%s invalid R_AARCH64_COPY relocation against DT_SYMBOLIC shared " 1055 "library %s (built with -Bsymbolic?)", si->name, lsi->name); 1056 return -1; 1057 } 1058 if (s->st_size < src->st_size) { 1059 DL_ERR("%s R_AARCH64_COPY relocation size mismatch (%lld < %lld)", 1060 si->name, s->st_size, src->st_size); 1061 return -1; 1062 } 1063 memcpy(reinterpret_cast<void*>(reloc), 1064 reinterpret_cast<void*>(src->st_value + lsi->load_bias), src->st_size); 1065 } else { 1066 DL_ERR("%s R_AARCH64_COPY relocation target cannot be resolved", si->name); 1067 return -1; 1068 } 1069 break; 1070 case R_AARCH64_TLS_TPREL64: 1071 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n", 1072 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1073 break; 1074 case R_AARCH64_TLS_DTPREL32: 1075 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n", 1076 reloc, (sym_addr + rela->r_addend), rela->r_offset); 1077 break; 1078#elif defined(__x86_64__) 1079 case R_X86_64_JUMP_SLOT: 1080 count_relocation(kRelocAbsolute); 1081 MARK(rela->r_offset); 1082 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1083 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1084 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1085 break; 1086 case R_X86_64_GLOB_DAT: 1087 count_relocation(kRelocAbsolute); 1088 MARK(rela->r_offset); 1089 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc), 1090 static_cast<size_t>(sym_addr + rela->r_addend), sym_name); 1091 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1092 break; 1093 case R_X86_64_RELATIVE: 1094 count_relocation(kRelocRelative); 1095 MARK(rela->r_offset); 1096 if (sym) { 1097 DL_ERR("odd RELATIVE form..."); 1098 return -1; 1099 } 1100 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc), 1101 static_cast<size_t>(si->base)); 1102 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend; 1103 break; 1104 case R_X86_64_32: 1105 count_relocation(kRelocRelative); 1106 MARK(rela->r_offset); 1107 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1108 static_cast<size_t>(sym_addr), sym_name); 1109 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1110 break; 1111 case R_X86_64_64: 1112 count_relocation(kRelocRelative); 1113 MARK(rela->r_offset); 1114 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc), 1115 static_cast<size_t>(sym_addr), sym_name); 1116 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend; 1117 break; 1118 case R_X86_64_PC32: 1119 count_relocation(kRelocRelative); 1120 MARK(rela->r_offset); 1121 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s", 1122 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc), 1123 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name); 1124 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc; 1125 break; 1126#endif 1127 1128 default: 1129 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx); 1130 return -1; 1131 } 1132 } 1133 return 0; 1134} 1135 1136#else // REL, not RELA. 1137 1138static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) { 1139 ElfW(Sym)* symtab = si->symtab; 1140 const char* strtab = si->strtab; 1141 ElfW(Sym)* s; 1142 ElfW(Rel)* start = rel; 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*>(strtab + 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 = &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) { 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**>(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]); 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); 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 DL_WARN("%s has text relocations. This is wasting memory and prevents " 1844 "security hardening. Please fix.", si->name); 1845 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1846 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1847 si->name, strerror(errno)); 1848 return false; 1849 } 1850 } 1851#endif 1852 1853#if defined(USE_RELA) 1854 if (si->plt_rela != NULL) { 1855 DEBUG("[ relocating %s plt ]\n", si->name); 1856 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) { 1857 return false; 1858 } 1859 } 1860 if (si->rela != NULL) { 1861 DEBUG("[ relocating %s ]\n", si->name); 1862 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) { 1863 return false; 1864 } 1865 } 1866#else 1867 if (si->plt_rel != NULL) { 1868 DEBUG("[ relocating %s plt ]", si->name); 1869 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) { 1870 return false; 1871 } 1872 } 1873 if (si->rel != NULL) { 1874 DEBUG("[ relocating %s ]", si->name); 1875 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) { 1876 return false; 1877 } 1878 } 1879#endif 1880 1881#if defined(__mips__) 1882 if (!mips_relocate_got(si, needed)) { 1883 return false; 1884 } 1885#endif 1886 1887 si->flags |= FLAG_LINKED; 1888 DEBUG("[ finished linking %s ]", si->name); 1889 1890#if !defined(__LP64__) 1891 if (si->has_text_relocations) { 1892 // All relocations are done, we can protect our segments back to read-only. 1893 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1894 DL_ERR("can't protect segments for \"%s\": %s", 1895 si->name, strerror(errno)); 1896 return false; 1897 } 1898 } 1899#endif 1900 1901 /* We can also turn on GNU RELRO protection */ 1902 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1903 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1904 si->name, strerror(errno)); 1905 return false; 1906 } 1907 1908 notify_gdb_of_load(si); 1909 return true; 1910} 1911 1912/* 1913 * This function add vdso to internal dso list. 1914 * It helps to stack unwinding through signal handlers. 1915 * Also, it makes bionic more like glibc. 1916 */ 1917static void add_vdso(KernelArgumentBlock& args UNUSED) { 1918#if defined(AT_SYSINFO_EHDR) 1919 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR)); 1920 if (ehdr_vdso == NULL) { 1921 return; 1922 } 1923 1924 soinfo* si = soinfo_alloc("[vdso]"); 1925 1926 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff); 1927 si->phnum = ehdr_vdso->e_phnum; 1928 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso); 1929 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1930 si->flags = 0; 1931 si->load_bias = get_elf_exec_load_bias(ehdr_vdso); 1932 1933 soinfo_link_image(si); 1934#endif 1935} 1936 1937/* 1938 * This code is called after the linker has linked itself and 1939 * fixed it's own GOT. It is safe to make references to externs 1940 * and other non-local data at this point. 1941 */ 1942static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) { 1943 /* NOTE: we store the args pointer on a special location 1944 * of the temporary TLS area in order to pass it to 1945 * the C Library's runtime initializer. 1946 * 1947 * The initializer must clear the slot and reset the TLS 1948 * to point to a different location to ensure that no other 1949 * shared library constructor can access it. 1950 */ 1951 __libc_init_tls(args); 1952 1953#if TIMING 1954 struct timeval t0, t1; 1955 gettimeofday(&t0, 0); 1956#endif 1957 1958 // Initialize environment functions, and get to the ELF aux vectors table. 1959 linker_env_init(args); 1960 1961 // If this is a setuid/setgid program, close the security hole described in 1962 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 1963 if (get_AT_SECURE()) { 1964 nullify_closed_stdio(); 1965 } 1966 1967 debuggerd_init(); 1968 1969 // Get a few environment variables. 1970 const char* LD_DEBUG = linker_env_get("LD_DEBUG"); 1971 if (LD_DEBUG != NULL) { 1972 gLdDebugVerbosity = atoi(LD_DEBUG); 1973 } 1974 1975 // Normally, these are cleaned by linker_env_init, but the test 1976 // doesn't cost us anything. 1977 const char* ldpath_env = NULL; 1978 const char* ldpreload_env = NULL; 1979 if (!get_AT_SECURE()) { 1980 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 1981 ldpreload_env = linker_env_get("LD_PRELOAD"); 1982 } 1983 1984 INFO("[ android linker & debugger ]"); 1985 1986 soinfo* si = soinfo_alloc(args.argv[0]); 1987 if (si == NULL) { 1988 exit(EXIT_FAILURE); 1989 } 1990 1991 /* bootstrap the link map, the main exe always needs to be first */ 1992 si->flags |= FLAG_EXE; 1993 link_map* map = &(si->link_map_head); 1994 1995 map->l_addr = 0; 1996 map->l_name = args.argv[0]; 1997 map->l_prev = NULL; 1998 map->l_next = NULL; 1999 2000 _r_debug.r_map = map; 2001 r_debug_tail = map; 2002 2003 /* gdb expects the linker to be in the debug shared object list. 2004 * Without this, gdb has trouble locating the linker's ".text" 2005 * and ".plt" sections. Gdb could also potentially use this to 2006 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 2007 * Don't use soinfo_alloc(), because the linker shouldn't 2008 * be on the soinfo list. 2009 */ 2010 { 2011 static soinfo linker_soinfo; 2012#if defined(__LP64__) 2013 strlcpy(linker_soinfo.name, "/system/bin/linker64", sizeof(linker_soinfo.name)); 2014#else 2015 strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name)); 2016#endif 2017 linker_soinfo.flags = 0; 2018 linker_soinfo.base = linker_base; 2019 2020 /* 2021 * Set the dynamic field in the link map otherwise gdb will complain with 2022 * the following: 2023 * warning: .dynamic section for "/system/bin/linker" is not at the 2024 * expected address (wrong library or version mismatch?) 2025 */ 2026 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base); 2027 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff); 2028 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 2029 &linker_soinfo.dynamic, NULL, NULL); 2030 insert_soinfo_into_debug_map(&linker_soinfo); 2031 } 2032 2033 // Extract information passed from the kernel. 2034 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)); 2035 si->phnum = args.getauxval(AT_PHNUM); 2036 si->entry = args.getauxval(AT_ENTRY); 2037 2038 /* Compute the value of si->base. We can't rely on the fact that 2039 * the first entry is the PHDR because this will not be true 2040 * for certain executables (e.g. some in the NDK unit test suite) 2041 */ 2042 si->base = 0; 2043 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 2044 si->load_bias = 0; 2045 for (size_t i = 0; i < si->phnum; ++i) { 2046 if (si->phdr[i].p_type == PT_PHDR) { 2047 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr; 2048 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset; 2049 break; 2050 } 2051 } 2052 si->dynamic = NULL; 2053 si->ref_count = 1; 2054 2055 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 2056 parse_LD_LIBRARY_PATH(ldpath_env); 2057 parse_LD_PRELOAD(ldpreload_env); 2058 2059 somain = si; 2060 2061 if (!soinfo_link_image(si)) { 2062 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer()); 2063 exit(EXIT_FAILURE); 2064 } 2065 2066 add_vdso(args); 2067 2068 si->CallPreInitConstructors(); 2069 2070 for (size_t i = 0; gLdPreloads[i] != NULL; ++i) { 2071 gLdPreloads[i]->CallConstructors(); 2072 } 2073 2074 /* After the link_image, the si->load_bias is initialized. 2075 * For so lib, the map->l_addr will be updated in notify_gdb_of_load. 2076 * We need to update this value for so exe here. So Unwind_Backtrace 2077 * for some arch like x86 could work correctly within so exe. 2078 */ 2079 map->l_addr = si->load_bias; 2080 si->CallConstructors(); 2081 2082#if TIMING 2083 gettimeofday(&t1, NULL); 2084 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) ( 2085 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 2086 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec))); 2087#endif 2088#if STATS 2089 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0], 2090 linker_stats.count[kRelocAbsolute], 2091 linker_stats.count[kRelocRelative], 2092 linker_stats.count[kRelocCopy], 2093 linker_stats.count[kRelocSymbol]); 2094#endif 2095#if COUNT_PAGES 2096 { 2097 unsigned n; 2098 unsigned i; 2099 unsigned count = 0; 2100 for (n = 0; n < 4096; n++) { 2101 if (bitmask[n]) { 2102 unsigned x = bitmask[n]; 2103#if defined(__LP64__) 2104 for (i = 0; i < 32; i++) { 2105#else 2106 for (i = 0; i < 8; i++) { 2107#endif 2108 if (x & 1) { 2109 count++; 2110 } 2111 x >>= 1; 2112 } 2113 } 2114 } 2115 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4); 2116 } 2117#endif 2118 2119#if TIMING || STATS || COUNT_PAGES 2120 fflush(stdout); 2121#endif 2122 2123 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry)); 2124 return si->entry; 2125} 2126 2127/* Compute the load-bias of an existing executable. This shall only 2128 * be used to compute the load bias of an executable or shared library 2129 * that was loaded by the kernel itself. 2130 * 2131 * Input: 2132 * elf -> address of ELF header, assumed to be at the start of the file. 2133 * Return: 2134 * load bias, i.e. add the value of any p_vaddr in the file to get 2135 * the corresponding address in memory. 2136 */ 2137static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) { 2138 ElfW(Addr) offset = elf->e_phoff; 2139 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset); 2140 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum; 2141 2142 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) { 2143 if (phdr->p_type == PT_LOAD) { 2144 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr; 2145 } 2146 } 2147 return 0; 2148} 2149 2150/* 2151 * This is the entry point for the linker, called from begin.S. This 2152 * method is responsible for fixing the linker's own relocations, and 2153 * then calling __linker_init_post_relocation(). 2154 * 2155 * Because this method is called before the linker has fixed it's own 2156 * relocations, any attempt to reference an extern variable, extern 2157 * function, or other GOT reference will generate a segfault. 2158 */ 2159extern "C" ElfW(Addr) __linker_init(void* raw_args) { 2160 KernelArgumentBlock args(raw_args); 2161 2162 ElfW(Addr) linker_addr = args.getauxval(AT_BASE); 2163 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr); 2164 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff); 2165 2166 soinfo linker_so; 2167 memset(&linker_so, 0, sizeof(soinfo)); 2168 2169 strcpy(linker_so.name, "[dynamic linker]"); 2170 linker_so.base = linker_addr; 2171 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2172 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2173 linker_so.dynamic = NULL; 2174 linker_so.phdr = phdr; 2175 linker_so.phnum = elf_hdr->e_phnum; 2176 linker_so.flags |= FLAG_LINKER; 2177 2178 if (!soinfo_link_image(&linker_so)) { 2179 // It would be nice to print an error message, but if the linker 2180 // can't link itself, there's no guarantee that we'll be able to 2181 // call write() (because it involves a GOT reference). We may as 2182 // well try though... 2183 const char* msg = "CANNOT LINK EXECUTABLE: "; 2184 write(2, msg, strlen(msg)); 2185 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 2186 write(2, "\n", 1); 2187 _exit(EXIT_FAILURE); 2188 } 2189 2190 // We have successfully fixed our own relocations. It's safe to run 2191 // the main part of the linker now. 2192 args.abort_message_ptr = &gAbortMessage; 2193 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr); 2194 2195 set_soinfo_pool_protection(PROT_READ); 2196 2197 // Return the address that the calling assembly stub should jump to. 2198 return start_address; 2199} 2200