linker.cpp revision bedfe38b8ba512dd6236c00e8b4a9b01c2bd1281
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 <linux/auxvec.h> 33#include <pthread.h> 34#include <stdbool.h> 35#include <stdio.h> 36#include <stdlib.h> 37#include <string.h> 38#include <sys/atomics.h> 39#include <sys/mman.h> 40#include <sys/stat.h> 41#include <unistd.h> 42 43// Private C library headers. 44#include <private/bionic_tls.h> 45#include <private/logd.h> 46 47#include "linker.h" 48#include "linker_debug.h" 49#include "linker_environ.h" 50#include "linker_format.h" 51#include "linker_phdr.h" 52 53#define ALLOW_SYMBOLS_FROM_MAIN 1 54#define SO_MAX 128 55 56/* Assume average path length of 64 and max 8 paths */ 57#define LDPATH_BUFSIZE 512 58#define LDPATH_MAX 8 59 60#define LDPRELOAD_BUFSIZE 512 61#define LDPRELOAD_MAX 8 62 63/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<< 64 * 65 * Do NOT use malloc() and friends or pthread_*() code here. 66 * Don't use printf() either; it's caused mysterious memory 67 * corruption in the past. 68 * The linker runs before we bring up libc and it's easiest 69 * to make sure it does not depend on any complex libc features 70 * 71 * open issues / todo: 72 * 73 * - are we doing everything we should for ARM_COPY relocations? 74 * - cleaner error reporting 75 * - after linking, set as much stuff as possible to READONLY 76 * and NOEXEC 77 * - linker hardcodes PAGE_SIZE and PAGE_MASK because the kernel 78 * headers provide versions that are negative... 79 * - allocate space for soinfo structs dynamically instead of 80 * having a hard limit (SO_MAX) 81 */ 82 83 84static int soinfo_link_image(soinfo *si); 85 86static int socount = 0; 87static soinfo sopool[SO_MAX]; 88static soinfo *freelist = NULL; 89static soinfo *solist = &libdl_info; 90static soinfo *sonext = &libdl_info; 91#if ALLOW_SYMBOLS_FROM_MAIN 92static soinfo *somain; /* main process, always the one after libdl_info */ 93#endif 94 95 96static char ldpaths_buf[LDPATH_BUFSIZE]; 97static const char *ldpaths[LDPATH_MAX + 1]; 98 99static char ldpreloads_buf[LDPRELOAD_BUFSIZE]; 100static const char *ldpreload_names[LDPRELOAD_MAX + 1]; 101 102static soinfo *preloads[LDPRELOAD_MAX + 1]; 103 104#if LINKER_DEBUG 105int debug_verbosity; 106#endif 107 108static int pid; 109 110/* This boolean is set if the program being loaded is setuid */ 111static bool program_is_setuid; 112 113enum RelocationKind { 114 kRelocAbsolute = 0, 115 kRelocRelative, 116 kRelocCopy, 117 kRelocSymbol, 118 kRelocMax 119}; 120 121#if STATS 122struct linker_stats_t { 123 int count[kRelocMax]; 124}; 125 126static linker_stats_t linker_stats; 127 128static void count_relocation(RelocationKind kind) { 129 ++linker_stats.count[kind]; 130} 131#else 132static void count_relocation(RelocationKind) { 133} 134#endif 135 136#if COUNT_PAGES 137static unsigned bitmask[4096]; 138#define MARK(offset) \ 139 do { \ 140 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \ 141 } while(0) 142#else 143#define MARK(x) do {} while (0) 144#endif 145 146// You shouldn't try to call memory-allocating functions in the dynamic linker. 147// Guard against the most obvious ones. 148#define DISALLOW_ALLOCATION(return_type, name, ...) \ 149 return_type name __VA_ARGS__ \ 150 { \ 151 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \ 152 __libc_android_log_write(ANDROID_LOG_FATAL, "linker", msg); \ 153 write(2, msg, sizeof(msg)); \ 154 abort(); \ 155 } 156#define UNUSED __attribute__((unused)) 157DISALLOW_ALLOCATION(void*, malloc, (size_t u UNUSED)); 158DISALLOW_ALLOCATION(void, free, (void* u UNUSED)); 159DISALLOW_ALLOCATION(void*, realloc, (void* u1 UNUSED, size_t u2 UNUSED)); 160DISALLOW_ALLOCATION(void*, calloc, (size_t u1 UNUSED, size_t u2 UNUSED)); 161 162static char tmp_err_buf[768]; 163static char __linker_dl_err_buf[768]; 164#define BASENAME(s) (strrchr(s, '/') != NULL ? strrchr(s, '/') + 1 : s) 165#define DL_ERR(fmt, x...) \ 166 do { \ 167 format_buffer(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), \ 168 "(%s:%d, pid %d) %s: " fmt, \ 169 BASENAME(__FILE__), __LINE__, pid, __func__, ##x); \ 170 ERROR(fmt "\n", ##x); \ 171 } while(0) 172 173const char *linker_get_error(void) 174{ 175 return (const char *)&__linker_dl_err_buf[0]; 176} 177 178/* 179 * This function is an empty stub where GDB locates a breakpoint to get notified 180 * about linker activity. 181 */ 182extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity(void); 183 184static r_debug _r_debug = {1, NULL, &rtld_db_dlactivity, 185 RT_CONSISTENT, 0}; 186static link_map* r_debug_tail = 0; 187 188static pthread_mutex_t _r_debug_lock = PTHREAD_MUTEX_INITIALIZER; 189 190static void insert_soinfo_into_debug_map(soinfo * info) { 191 // Copy the necessary fields into the debug structure. 192 link_map* map = &(info->linkmap); 193 map->l_addr = info->base; 194 map->l_name = (char*) info->name; 195 map->l_ld = (uintptr_t)info->dynamic; 196 197 /* Stick the new library at the end of the list. 198 * gdb tends to care more about libc than it does 199 * about leaf libraries, and ordering it this way 200 * reduces the back-and-forth over the wire. 201 */ 202 if (r_debug_tail) { 203 r_debug_tail->l_next = map; 204 map->l_prev = r_debug_tail; 205 map->l_next = 0; 206 } else { 207 _r_debug.r_map = map; 208 map->l_prev = 0; 209 map->l_next = 0; 210 } 211 r_debug_tail = map; 212} 213 214static void remove_soinfo_from_debug_map(soinfo* info) { 215 link_map* map = &(info->linkmap); 216 217 if (r_debug_tail == map) { 218 r_debug_tail = map->l_prev; 219 } 220 221 if (map->l_prev) { 222 map->l_prev->l_next = map->l_next; 223 } 224 if (map->l_next) { 225 map->l_next->l_prev = map->l_prev; 226 } 227} 228 229static void notify_gdb_of_load(soinfo* info) { 230 if (info->flags & FLAG_EXE) { 231 // GDB already knows about the main executable 232 return; 233 } 234 235 pthread_mutex_lock(&_r_debug_lock); 236 237 _r_debug.r_state = RT_ADD; 238 rtld_db_dlactivity(); 239 240 insert_soinfo_into_debug_map(info); 241 242 _r_debug.r_state = RT_CONSISTENT; 243 rtld_db_dlactivity(); 244 245 pthread_mutex_unlock(&_r_debug_lock); 246} 247 248static void notify_gdb_of_unload(soinfo* info) { 249 if (info->flags & FLAG_EXE) { 250 // GDB already knows about the main executable 251 return; 252 } 253 254 pthread_mutex_lock(&_r_debug_lock); 255 256 _r_debug.r_state = RT_DELETE; 257 rtld_db_dlactivity(); 258 259 remove_soinfo_from_debug_map(info); 260 261 _r_debug.r_state = RT_CONSISTENT; 262 rtld_db_dlactivity(); 263 264 pthread_mutex_unlock(&_r_debug_lock); 265} 266 267extern "C" void notify_gdb_of_libraries() 268{ 269 _r_debug.r_state = RT_ADD; 270 rtld_db_dlactivity(); 271 _r_debug.r_state = RT_CONSISTENT; 272 rtld_db_dlactivity(); 273} 274 275static soinfo *soinfo_alloc(const char *name) 276{ 277 if (strlen(name) >= SOINFO_NAME_LEN) { 278 DL_ERR("library name \"%s\" too long", name); 279 return NULL; 280 } 281 282 /* The freelist is populated when we call soinfo_free(), which in turn is 283 done only by dlclose(), which is not likely to be used. 284 */ 285 if (!freelist) { 286 if (socount == SO_MAX) { 287 DL_ERR("too many libraries when loading \"%s\"", name); 288 return NULL; 289 } 290 freelist = sopool + socount++; 291 freelist->next = NULL; 292 } 293 294 soinfo* si = freelist; 295 freelist = freelist->next; 296 297 /* Make sure we get a clean block of soinfo */ 298 memset(si, 0, sizeof(soinfo)); 299 strlcpy((char*) si->name, name, sizeof(si->name)); 300 sonext->next = si; 301 si->next = NULL; 302 si->refcount = 0; 303 sonext = si; 304 305 TRACE("%5d name %s: allocated soinfo @ %p\n", pid, name, si); 306 return si; 307} 308 309static void soinfo_free(soinfo* si) 310{ 311 if (si == NULL) { 312 return; 313 } 314 315 soinfo *prev = NULL, *trav; 316 317 TRACE("%5d name %s: freeing soinfo @ %p\n", pid, si->name, si); 318 319 for(trav = solist; trav != NULL; trav = trav->next){ 320 if (trav == si) 321 break; 322 prev = trav; 323 } 324 if (trav == NULL) { 325 /* si was not ni solist */ 326 DL_ERR("name \"%s\" is not in solist!", si->name); 327 return; 328 } 329 330 /* prev will never be NULL, because the first entry in solist is 331 always the static libdl_info. 332 */ 333 prev->next = si->next; 334 if (si == sonext) sonext = prev; 335 si->next = freelist; 336 freelist = si; 337} 338 339#ifdef ANDROID_ARM_LINKER 340 341/* For a given PC, find the .so that it belongs to. 342 * Returns the base address of the .ARM.exidx section 343 * for that .so, and the number of 8-byte entries 344 * in that section (via *pcount). 345 * 346 * Intended to be called by libc's __gnu_Unwind_Find_exidx(). 347 * 348 * This function is exposed via dlfcn.c and libdl.so. 349 */ 350_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount) 351{ 352 soinfo *si; 353 unsigned addr = (unsigned)pc; 354 355 for (si = solist; si != 0; si = si->next){ 356 if ((addr >= si->base) && (addr < (si->base + si->size))) { 357 *pcount = si->ARM_exidx_count; 358 return (_Unwind_Ptr)si->ARM_exidx; 359 } 360 } 361 *pcount = 0; 362 return NULL; 363} 364 365#elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER) 366 367/* Here, we only have to provide a callback to iterate across all the 368 * loaded libraries. gcc_eh does the rest. */ 369int 370dl_iterate_phdr(int (*cb)(dl_phdr_info *info, size_t size, void *data), 371 void *data) 372{ 373 int rv = 0; 374 for (soinfo* si = solist; si != NULL; si = si->next) { 375 dl_phdr_info dl_info; 376 dl_info.dlpi_addr = si->linkmap.l_addr; 377 dl_info.dlpi_name = si->linkmap.l_name; 378 dl_info.dlpi_phdr = si->phdr; 379 dl_info.dlpi_phnum = si->phnum; 380 rv = cb(&dl_info, sizeof(dl_phdr_info), data); 381 if (rv != 0) { 382 break; 383 } 384 } 385 return rv; 386} 387 388#endif 389 390static Elf32_Sym *soinfo_elf_lookup(soinfo *si, unsigned hash, const char *name) 391{ 392 Elf32_Sym *s; 393 Elf32_Sym *symtab = si->symtab; 394 const char *strtab = si->strtab; 395 unsigned n; 396 397 TRACE_TYPE(LOOKUP, "%5d SEARCH %s in %s@0x%08x %08x %d\n", pid, 398 name, si->name, si->base, hash, hash % si->nbucket); 399 n = hash % si->nbucket; 400 401 for(n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]){ 402 s = symtab + n; 403 if(strcmp(strtab + s->st_name, name)) continue; 404 405 /* only concern ourselves with global and weak symbol definitions */ 406 switch(ELF32_ST_BIND(s->st_info)){ 407 case STB_GLOBAL: 408 case STB_WEAK: 409 if(s->st_shndx == SHN_UNDEF) 410 continue; 411 412 TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", pid, 413 name, si->name, s->st_value, s->st_size); 414 return s; 415 } 416 } 417 418 return NULL; 419} 420 421static unsigned elfhash(const char *_name) 422{ 423 const unsigned char *name = (const unsigned char *) _name; 424 unsigned h = 0, g; 425 426 while(*name) { 427 h = (h << 4) + *name++; 428 g = h & 0xf0000000; 429 h ^= g; 430 h ^= g >> 24; 431 } 432 return h; 433} 434 435static Elf32_Sym * 436soinfo_do_lookup(soinfo *si, const char *name, Elf32_Addr *offset, 437 soinfo *needed[]) 438{ 439 unsigned elf_hash = elfhash(name); 440 Elf32_Sym *s; 441 soinfo *lsi = si; 442 int i; 443 444 /* Look for symbols in the local scope (the object who is 445 * searching). This happens with C++ templates on i386 for some 446 * reason. 447 * 448 * Notes on weak symbols: 449 * The ELF specs are ambiguous about treatment of weak definitions in 450 * dynamic linking. Some systems return the first definition found 451 * and some the first non-weak definition. This is system dependent. 452 * Here we return the first definition found for simplicity. */ 453 454 s = soinfo_elf_lookup(si, elf_hash, name); 455 if(s != NULL) 456 goto done; 457 458 /* Next, look for it in the preloads list */ 459 for(i = 0; preloads[i] != NULL; i++) { 460 lsi = preloads[i]; 461 s = soinfo_elf_lookup(lsi, elf_hash, name); 462 if(s != NULL) 463 goto done; 464 } 465 466 for(i = 0; needed[i] != NULL; i++) { 467 lsi = needed[i]; 468 DEBUG("%5d %s: looking up %s in %s\n", 469 pid, si->name, name, lsi->name); 470 s = soinfo_elf_lookup(lsi, elf_hash, name); 471 if (s != NULL) 472 goto done; 473 } 474 475#if ALLOW_SYMBOLS_FROM_MAIN 476 /* If we are resolving relocations while dlopen()ing a library, it's OK for 477 * the library to resolve a symbol that's defined in the executable itself, 478 * although this is rare and is generally a bad idea. 479 */ 480 if (somain) { 481 lsi = somain; 482 DEBUG("%5d %s: looking up %s in executable %s\n", 483 pid, si->name, name, lsi->name); 484 s = soinfo_elf_lookup(lsi, elf_hash, name); 485 } 486#endif 487 488done: 489 if(s != NULL) { 490 TRACE_TYPE(LOOKUP, "%5d si %s sym %s s->st_value = 0x%08x, " 491 "found in %s, base = 0x%08x, load bias = 0x%08x\n", 492 pid, si->name, name, s->st_value, 493 lsi->name, lsi->base, lsi->load_bias); 494 *offset = lsi->load_bias; 495 return s; 496 } 497 498 return NULL; 499} 500 501/* This is used by dl_sym(). It performs symbol lookup only within the 502 specified soinfo object and not in any of its dependencies. 503 */ 504Elf32_Sym *soinfo_lookup(soinfo *si, const char *name) 505{ 506 return soinfo_elf_lookup(si, elfhash(name), name); 507} 508 509/* This is used by dl_sym(). It performs a global symbol lookup. 510 */ 511Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start) 512{ 513 unsigned elf_hash = elfhash(name); 514 Elf32_Sym *s = NULL; 515 soinfo *si; 516 517 if(start == NULL) { 518 start = solist; 519 } 520 521 for(si = start; (s == NULL) && (si != NULL); si = si->next) 522 { 523 if(si->flags & FLAG_ERROR) 524 continue; 525 s = soinfo_elf_lookup(si, elf_hash, name); 526 if (s != NULL) { 527 *found = si; 528 break; 529 } 530 } 531 532 if(s != NULL) { 533 TRACE_TYPE(LOOKUP, "%5d %s s->st_value = 0x%08x, " 534 "si->base = 0x%08x\n", pid, name, s->st_value, si->base); 535 return s; 536 } 537 538 return NULL; 539} 540 541soinfo *find_containing_library(const void *addr) 542{ 543 soinfo *si; 544 545 for(si = solist; si != NULL; si = si->next) 546 { 547 if((unsigned)addr >= si->base && (unsigned)addr - si->base < si->size) { 548 return si; 549 } 550 } 551 552 return NULL; 553} 554 555Elf32_Sym *soinfo_find_symbol(soinfo* si, const void *addr) 556{ 557 unsigned int i; 558 unsigned soaddr = (unsigned)addr - si->base; 559 560 /* Search the library's symbol table for any defined symbol which 561 * contains this address */ 562 for(i=0; i<si->nchain; i++) { 563 Elf32_Sym *sym = &si->symtab[i]; 564 565 if(sym->st_shndx != SHN_UNDEF && 566 soaddr >= sym->st_value && 567 soaddr < sym->st_value + sym->st_size) { 568 return sym; 569 } 570 } 571 572 return NULL; 573} 574 575#if 0 576static void dump(soinfo *si) 577{ 578 Elf32_Sym *s = si->symtab; 579 unsigned n; 580 581 for(n = 0; n < si->nchain; n++) { 582 TRACE("%5d %04d> %08x: %02x %04x %08x %08x %s\n", pid, n, s, 583 s->st_info, s->st_shndx, s->st_value, s->st_size, 584 si->strtab + s->st_name); 585 s++; 586 } 587} 588#endif 589 590static const char * const sopaths[] = { 591 "/vendor/lib", 592 "/system/lib", 593 0 594}; 595 596static int _open_lib(const char* name) { 597 // TODO: why not just call open? 598 struct stat sb; 599 if (stat(name, &sb) == -1 || !S_ISREG(sb.st_mode)) { 600 return -1; 601 } 602 return TEMP_FAILURE_RETRY(open(name, O_RDONLY)); 603} 604 605static int open_library(const char *name) 606{ 607 int fd; 608 char buf[512]; 609 const char * const*path; 610 int n; 611 612 TRACE("[ %5d opening %s ]\n", pid, name); 613 614 if(name == 0) return -1; 615 if(strlen(name) > 256) return -1; 616 617 if ((name[0] == '/') && ((fd = _open_lib(name)) >= 0)) 618 return fd; 619 620 for (path = ldpaths; *path; path++) { 621 n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name); 622 if (n < 0 || n >= (int)sizeof(buf)) { 623 WARN("Ignoring very long library path: %s/%s\n", *path, name); 624 continue; 625 } 626 if ((fd = _open_lib(buf)) >= 0) 627 return fd; 628 } 629 for (path = sopaths; *path; path++) { 630 n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name); 631 if (n < 0 || n >= (int)sizeof(buf)) { 632 WARN("Ignoring very long library path: %s/%s\n", *path, name); 633 continue; 634 } 635 if ((fd = _open_lib(buf)) >= 0) 636 return fd; 637 } 638 639 return -1; 640} 641 642// Returns 'true' if the library is prelinked or on failure so we error out 643// either way. We no longer support prelinking. 644static bool is_prelinked(int fd, const char* name) 645{ 646 struct prelink_info_t { 647 long mmap_addr; 648 char tag[4]; // "PRE ". 649 }; 650 651 off_t sz = lseek(fd, -sizeof(prelink_info_t), SEEK_END); 652 if (sz < 0) { 653 DL_ERR("lseek failed: %s", strerror(errno)); 654 return true; 655 } 656 657 prelink_info_t info; 658 int rc = TEMP_FAILURE_RETRY(read(fd, &info, sizeof(info))); 659 if (rc != sizeof(info)) { 660 DL_ERR("could not read prelink_info_t structure for \"%s\":", name, strerror(errno)); 661 return true; 662 } 663 664 if (memcmp(info.tag, "PRE ", 4) == 0) { 665 DL_ERR("prelinked libraries no longer supported: %s", name); 666 return true; 667 } 668 return false; 669} 670 671/* verify_elf_header 672 * Verifies the content of an ELF header. 673 * 674 * Args: 675 * 676 * Returns: 677 * 0 on success 678 * -1 if no valid ELF object is found @ base. 679 */ 680static int 681verify_elf_header(const Elf32_Ehdr* hdr) 682{ 683 if (hdr->e_ident[EI_MAG0] != ELFMAG0) return -1; 684 if (hdr->e_ident[EI_MAG1] != ELFMAG1) return -1; 685 if (hdr->e_ident[EI_MAG2] != ELFMAG2) return -1; 686 if (hdr->e_ident[EI_MAG3] != ELFMAG3) return -1; 687 688 /* TODO: Should we verify anything else in the header? */ 689#ifdef ANDROID_ARM_LINKER 690 if (hdr->e_machine != EM_ARM) return -1; 691#elif defined(ANDROID_X86_LINKER) 692 if (hdr->e_machine != EM_386) return -1; 693#elif defined(ANDROID_MIPS_LINKER) 694 if (hdr->e_machine != EM_MIPS) return -1; 695#endif 696 return 0; 697} 698 699struct scoped_fd { 700 ~scoped_fd() { 701 if (fd != -1) { 702 close(fd); 703 } 704 } 705 int fd; 706}; 707 708struct soinfo_ptr { 709 soinfo_ptr(const char* name) { 710 const char* bname = strrchr(name, '/'); 711 ptr = soinfo_alloc(bname ? bname + 1 : name); 712 } 713 ~soinfo_ptr() { 714 soinfo_free(ptr); 715 } 716 soinfo* release() { 717 soinfo* result = ptr; 718 ptr = NULL; 719 return result; 720 } 721 soinfo* ptr; 722}; 723 724// TODO: rewrite linker_phdr.h to use a class, then lose this. 725struct phdr_ptr { 726 phdr_ptr() : phdr_mmap(NULL) {} 727 ~phdr_ptr() { 728 if (phdr_mmap != NULL) { 729 phdr_table_unload(phdr_mmap, phdr_size); 730 } 731 } 732 void* phdr_mmap; 733 Elf32_Addr phdr_size; 734}; 735 736static soinfo* load_library(const char* name) 737{ 738 // Open the file. 739 scoped_fd fd; 740 fd.fd = open_library(name); 741 if (fd.fd == -1) { 742 DL_ERR("library \"%s\" not found", name); 743 return NULL; 744 } 745 746 // Read the ELF header. 747 Elf32_Ehdr header[1]; 748 int ret = TEMP_FAILURE_RETRY(read(fd.fd, (void*)header, sizeof(header))); 749 if (ret < 0) { 750 DL_ERR("can't read file \"%s\": %s", name, strerror(errno)); 751 return NULL; 752 } 753 if (ret != (int)sizeof(header)) { 754 DL_ERR("too small to be an ELF executable: %s", name); 755 return NULL; 756 } 757 if (verify_elf_header(header) < 0) { 758 DL_ERR("not a valid ELF executable: %s", name); 759 return NULL; 760 } 761 762 // Read the program header table. 763 const Elf32_Phdr* phdr_table; 764 phdr_ptr phdr_holder; 765 ret = phdr_table_load(fd.fd, header->e_phoff, header->e_phnum, 766 &phdr_holder.phdr_mmap, &phdr_holder.phdr_size, &phdr_table); 767 if (ret < 0) { 768 DL_ERR("can't load program header table: %s: %s", name, strerror(errno)); 769 return NULL; 770 } 771 size_t phdr_count = header->e_phnum; 772 773 // Get the load extents. 774 Elf32_Addr ext_sz = phdr_table_get_load_size(phdr_table, phdr_count); 775 TRACE("[ %5d - '%s' wants sz=0x%08x ]\n", pid, name, ext_sz); 776 if (ext_sz == 0) { 777 DL_ERR("no loadable segments in file: %s", name); 778 return NULL; 779 } 780 781 // We no longer support pre-linked libraries. 782 if (is_prelinked(fd.fd, name)) { 783 return NULL; 784 } 785 786 // Reserve address space for all loadable segments. 787 void* load_start = NULL; 788 Elf32_Addr load_size = 0; 789 Elf32_Addr load_bias = 0; 790 ret = phdr_table_reserve_memory(phdr_table, 791 phdr_count, 792 &load_start, 793 &load_size, 794 &load_bias); 795 if (ret < 0) { 796 DL_ERR("can't reserve %d bytes in address space for \"%s\": %s", 797 ext_sz, name, strerror(errno)); 798 return NULL; 799 } 800 801 TRACE("[ %5d allocated memory for %s @ %p (0x%08x) ]\n", 802 pid, name, load_start, load_size); 803 804 /* Map all the segments in our address space with default protections */ 805 ret = phdr_table_load_segments(phdr_table, 806 phdr_count, 807 load_bias, 808 fd.fd); 809 if (ret < 0) { 810 DL_ERR("can't map loadable segments for \"%s\": %s", 811 name, strerror(errno)); 812 return NULL; 813 } 814 815 soinfo_ptr si(name); 816 if (si.ptr == NULL) { 817 return NULL; 818 } 819 820 si.ptr->base = (Elf32_Addr) load_start; 821 si.ptr->size = load_size; 822 si.ptr->load_bias = load_bias; 823 si.ptr->flags = 0; 824 si.ptr->entry = 0; 825 si.ptr->dynamic = (unsigned *)-1; 826 si.ptr->phnum = phdr_count; 827 si.ptr->phdr = phdr_table_get_loaded_phdr(phdr_table, phdr_count, load_bias); 828 if (si.ptr->phdr == NULL) { 829 DL_ERR("can't find loaded PHDR for \"%s\"", name); 830 return NULL; 831 } 832 833 return si.release(); 834} 835 836static soinfo * 837init_library(soinfo *si) 838{ 839 /* At this point we know that whatever is loaded @ base is a valid ELF 840 * shared library whose segments are properly mapped in. */ 841 TRACE("[ %5d init_library base=0x%08x sz=0x%08x name='%s') ]\n", 842 pid, si->base, si->size, si->name); 843 844 if(soinfo_link_image(si)) { 845 munmap((void *)si->base, si->size); 846 return NULL; 847 } 848 849 return si; 850} 851 852static soinfo *find_loaded_library(const char *name) 853{ 854 soinfo *si; 855 const char *bname; 856 857 // TODO: don't use basename only for determining libraries 858 // http://code.google.com/p/android/issues/detail?id=6670 859 860 bname = strrchr(name, '/'); 861 bname = bname ? bname + 1 : name; 862 863 for(si = solist; si != NULL; si = si->next){ 864 if(!strcmp(bname, si->name)) { 865 return si; 866 } 867 } 868 return NULL; 869} 870 871soinfo *find_library(const char *name) 872{ 873 soinfo *si; 874 875#if ALLOW_SYMBOLS_FROM_MAIN 876 if (name == NULL) 877 return somain; 878#else 879 if (name == NULL) 880 return NULL; 881#endif 882 883 si = find_loaded_library(name); 884 if (si != NULL) { 885 if(si->flags & FLAG_ERROR) { 886 DL_ERR("\"%s\" failed to load previously", name); 887 return NULL; 888 } 889 if(si->flags & FLAG_LINKED) return si; 890 DL_ERR("OOPS: recursive link to \"%s\"", si->name); 891 return NULL; 892 } 893 894 TRACE("[ %5d '%s' has not been loaded yet. Locating...]\n", pid, name); 895 si = load_library(name); 896 if(si == NULL) 897 return NULL; 898 return init_library(si); 899} 900 901static void call_destructors(soinfo *si); 902 903int soinfo_unload(soinfo* si) { 904 if (si->refcount == 1) { 905 TRACE("%5d unloading '%s'\n", pid, si->name); 906 call_destructors(si); 907 908 for (unsigned* d = si->dynamic; *d; d += 2) { 909 if(d[0] == DT_NEEDED){ 910 soinfo *lsi = find_loaded_library(si->strtab + d[1]); 911 if (lsi) { 912 TRACE("%5d %s needs to unload %s\n", pid, 913 si->name, lsi->name); 914 soinfo_unload(lsi); 915 } else { 916 // TODO: should we return -1 in this case? 917 DL_ERR("\"%s\": could not unload dependent library", 918 si->name); 919 } 920 } 921 } 922 923 munmap((char *)si->base, si->size); 924 notify_gdb_of_unload(si); 925 soinfo_free(si); 926 si->refcount = 0; 927 } else { 928 si->refcount--; 929 PRINT("%5d not unloading '%s', decrementing refcount to %d\n", 930 pid, si->name, si->refcount); 931 } 932 return 0; 933} 934 935/* TODO: don't use unsigned for addrs below. It works, but is not 936 * ideal. They should probably be either uint32_t, Elf32_Addr, or unsigned 937 * long. 938 */ 939static int soinfo_relocate(soinfo *si, Elf32_Rel *rel, unsigned count, 940 soinfo *needed[]) 941{ 942 Elf32_Sym *symtab = si->symtab; 943 const char *strtab = si->strtab; 944 Elf32_Sym *s; 945 Elf32_Addr offset; 946 Elf32_Rel *start = rel; 947 948 for (size_t idx = 0; idx < count; ++idx, ++rel) { 949 unsigned type = ELF32_R_TYPE(rel->r_info); 950 unsigned sym = ELF32_R_SYM(rel->r_info); 951 unsigned reloc = (unsigned)(rel->r_offset + si->load_bias); 952 unsigned sym_addr = 0; 953 char *sym_name = NULL; 954 955 DEBUG("%5d Processing '%s' relocation at index %d\n", pid, 956 si->name, idx); 957 if (type == 0) { // R_*_NONE 958 continue; 959 } 960 if(sym != 0) { 961 sym_name = (char *)(strtab + symtab[sym].st_name); 962 s = soinfo_do_lookup(si, sym_name, &offset, needed); 963 if(s == NULL) { 964 /* We only allow an undefined symbol if this is a weak 965 reference.. */ 966 s = &symtab[sym]; 967 if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { 968 DL_ERR("cannot locate \"%s\"...", sym_name); 969 return -1; 970 } 971 972 /* IHI0044C AAELF 4.5.1.1: 973 974 Libraries are not searched to resolve weak references. 975 It is not an error for a weak reference to remain 976 unsatisfied. 977 978 During linking, the value of an undefined weak reference is: 979 - Zero if the relocation type is absolute 980 - The address of the place if the relocation is pc-relative 981 - The address of nominal base address if the relocation 982 type is base-relative. 983 */ 984 985 switch (type) { 986#if defined(ANDROID_ARM_LINKER) 987 case R_ARM_JUMP_SLOT: 988 case R_ARM_GLOB_DAT: 989 case R_ARM_ABS32: 990 case R_ARM_RELATIVE: /* Don't care. */ 991#elif defined(ANDROID_X86_LINKER) 992 case R_386_JMP_SLOT: 993 case R_386_GLOB_DAT: 994 case R_386_32: 995 case R_386_RELATIVE: /* Dont' care. */ 996#endif /* ANDROID_*_LINKER */ 997 /* sym_addr was initialized to be zero above or relocation 998 code below does not care about value of sym_addr. 999 No need to do anything. */ 1000 break; 1001 1002#if defined(ANDROID_X86_LINKER) 1003 case R_386_PC32: 1004 sym_addr = reloc; 1005 break; 1006#endif /* ANDROID_X86_LINKER */ 1007 1008#if defined(ANDROID_ARM_LINKER) 1009 case R_ARM_COPY: 1010 /* Fall through. Can't really copy if weak symbol is 1011 not found in run-time. */ 1012#endif /* ANDROID_ARM_LINKER */ 1013 default: 1014 DL_ERR("unknown weak reloc type %d @ %p (%d)", 1015 type, rel, (int) (rel - start)); 1016 return -1; 1017 } 1018 } else { 1019 /* We got a definition. */ 1020#if 0 1021 if((base == 0) && (si->base != 0)){ 1022 /* linking from libraries to main image is bad */ 1023 DL_ERR("cannot locate \"%s\"...", 1024 strtab + symtab[sym].st_name); 1025 return -1; 1026 } 1027#endif 1028 sym_addr = (unsigned)(s->st_value + offset); 1029 } 1030 count_relocation(kRelocSymbol); 1031 } else { 1032 s = NULL; 1033 } 1034 1035/* TODO: This is ugly. Split up the relocations by arch into 1036 * different files. 1037 */ 1038 switch(type){ 1039#if defined(ANDROID_ARM_LINKER) 1040 case R_ARM_JUMP_SLOT: 1041 count_relocation(kRelocAbsolute); 1042 MARK(rel->r_offset); 1043 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid, 1044 reloc, sym_addr, sym_name); 1045 *((unsigned*)reloc) = sym_addr; 1046 break; 1047 case R_ARM_GLOB_DAT: 1048 count_relocation(kRelocAbsolute); 1049 MARK(rel->r_offset); 1050 TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", pid, 1051 reloc, sym_addr, sym_name); 1052 *((unsigned*)reloc) = sym_addr; 1053 break; 1054 case R_ARM_ABS32: 1055 count_relocation(kRelocAbsolute); 1056 MARK(rel->r_offset); 1057 TRACE_TYPE(RELO, "%5d RELO ABS %08x <- %08x %s\n", pid, 1058 reloc, sym_addr, sym_name); 1059 *((unsigned*)reloc) += sym_addr; 1060 break; 1061 case R_ARM_REL32: 1062 count_relocation(kRelocRelative); 1063 MARK(rel->r_offset); 1064 TRACE_TYPE(RELO, "%5d RELO REL32 %08x <- %08x - %08x %s\n", pid, 1065 reloc, sym_addr, rel->r_offset, sym_name); 1066 *((unsigned*)reloc) += sym_addr - rel->r_offset; 1067 break; 1068#elif defined(ANDROID_X86_LINKER) 1069 case R_386_JMP_SLOT: 1070 count_relocation(kRelocAbsolute); 1071 MARK(rel->r_offset); 1072 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid, 1073 reloc, sym_addr, sym_name); 1074 *((unsigned*)reloc) = sym_addr; 1075 break; 1076 case R_386_GLOB_DAT: 1077 count_relocation(kRelocAbsolute); 1078 MARK(rel->r_offset); 1079 TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", pid, 1080 reloc, sym_addr, sym_name); 1081 *((unsigned*)reloc) = sym_addr; 1082 break; 1083#elif defined(ANDROID_MIPS_LINKER) 1084 case R_MIPS_JUMP_SLOT: 1085 count_relocation(kRelocAbsolute); 1086 MARK(rel->r_offset); 1087 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid, 1088 reloc, sym_addr, sym_name); 1089 *((unsigned*)reloc) = sym_addr; 1090 break; 1091 case R_MIPS_REL32: 1092 count_relocation(kRelocAbsolute); 1093 MARK(rel->r_offset); 1094 TRACE_TYPE(RELO, "%5d RELO REL32 %08x <- %08x %s\n", pid, 1095 reloc, sym_addr, (sym_name) ? sym_name : "*SECTIONHDR*"); 1096 if (s) { 1097 *((unsigned*)reloc) += sym_addr; 1098 } else { 1099 *((unsigned*)reloc) += si->base; 1100 } 1101 break; 1102#endif /* ANDROID_*_LINKER */ 1103 1104#if defined(ANDROID_ARM_LINKER) 1105 case R_ARM_RELATIVE: 1106#elif defined(ANDROID_X86_LINKER) 1107 case R_386_RELATIVE: 1108#endif /* ANDROID_*_LINKER */ 1109 count_relocation(kRelocRelative); 1110 MARK(rel->r_offset); 1111 if (sym) { 1112 DL_ERR("odd RELATIVE form...", pid); 1113 return -1; 1114 } 1115 TRACE_TYPE(RELO, "%5d RELO RELATIVE %08x <- +%08x\n", pid, 1116 reloc, si->base); 1117 *((unsigned*)reloc) += si->base; 1118 break; 1119 1120#if defined(ANDROID_X86_LINKER) 1121 case R_386_32: 1122 count_relocation(kRelocRelative); 1123 MARK(rel->r_offset); 1124 1125 TRACE_TYPE(RELO, "%5d RELO R_386_32 %08x <- +%08x %s\n", pid, 1126 reloc, sym_addr, sym_name); 1127 *((unsigned *)reloc) += (unsigned)sym_addr; 1128 break; 1129 1130 case R_386_PC32: 1131 count_relocation(kRelocRelative); 1132 MARK(rel->r_offset); 1133 TRACE_TYPE(RELO, "%5d RELO R_386_PC32 %08x <- " 1134 "+%08x (%08x - %08x) %s\n", pid, reloc, 1135 (sym_addr - reloc), sym_addr, reloc, sym_name); 1136 *((unsigned *)reloc) += (unsigned)(sym_addr - reloc); 1137 break; 1138#endif /* ANDROID_X86_LINKER */ 1139 1140#ifdef ANDROID_ARM_LINKER 1141 case R_ARM_COPY: 1142 count_relocation(kRelocCopy); 1143 MARK(rel->r_offset); 1144 TRACE_TYPE(RELO, "%5d RELO %08x <- %d @ %08x %s\n", pid, 1145 reloc, s->st_size, sym_addr, sym_name); 1146 memcpy((void*)reloc, (void*)sym_addr, s->st_size); 1147 break; 1148#endif /* ANDROID_ARM_LINKER */ 1149 1150 default: 1151 DL_ERR("unknown reloc type %d @ %p (%d)", 1152 type, rel, (int) (rel - start)); 1153 return -1; 1154 } 1155 } 1156 return 0; 1157} 1158 1159#ifdef ANDROID_MIPS_LINKER 1160static int mips_relocate_got(soinfo* si, soinfo* needed[]) { 1161 unsigned *got; 1162 unsigned local_gotno, gotsym, symtabno; 1163 Elf32_Sym *symtab, *sym; 1164 unsigned g; 1165 1166 got = si->plt_got; 1167 local_gotno = si->mips_local_gotno; 1168 gotsym = si->mips_gotsym; 1169 symtabno = si->mips_symtabno; 1170 symtab = si->symtab; 1171 1172 /* 1173 * got[0] is address of lazy resolver function 1174 * got[1] may be used for a GNU extension 1175 * set it to a recognizable address in case someone calls it 1176 * (should be _rtld_bind_start) 1177 * FIXME: maybe this should be in a separate routine 1178 */ 1179 1180 if ((si->flags & FLAG_LINKER) == 0) { 1181 g = 0; 1182 got[g++] = 0xdeadbeef; 1183 if (got[g] & 0x80000000) { 1184 got[g++] = 0xdeadfeed; 1185 } 1186 /* 1187 * Relocate the local GOT entries need to be relocated 1188 */ 1189 for (; g < local_gotno; g++) { 1190 got[g] += si->load_bias; 1191 } 1192 } 1193 1194 /* Now for the global GOT entries */ 1195 sym = symtab + gotsym; 1196 got = si->plt_got + local_gotno; 1197 for (g = gotsym; g < symtabno; g++, sym++, got++) { 1198 const char *sym_name; 1199 unsigned base; 1200 Elf32_Sym *s; 1201 1202 /* This is an undefined reference... try to locate it */ 1203 sym_name = si->strtab + sym->st_name; 1204 s = soinfo_do_lookup(si, sym_name, &base, needed); 1205 if (s == NULL) { 1206 /* We only allow an undefined symbol if this is a weak 1207 reference.. */ 1208 s = &symtab[g]; 1209 if (ELF32_ST_BIND(s->st_info) != STB_WEAK) { 1210 DL_ERR("cannot locate \"%s\"...", sym_name); 1211 return -1; 1212 } 1213 *got = 0; 1214 } 1215 else { 1216 /* FIXME: is this sufficient? 1217 * For reference see NetBSD link loader 1218 * 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 1219 */ 1220 *got = base + s->st_value; 1221 } 1222 } 1223 return 0; 1224} 1225#endif 1226 1227/* Please read the "Initialization and Termination functions" functions. 1228 * of the linker design note in bionic/linker/README.TXT to understand 1229 * what the following code is doing. 1230 * 1231 * The important things to remember are: 1232 * 1233 * DT_PREINIT_ARRAY must be called first for executables, and should 1234 * not appear in shared libraries. 1235 * 1236 * DT_INIT should be called before DT_INIT_ARRAY if both are present 1237 * 1238 * DT_FINI should be called after DT_FINI_ARRAY if both are present 1239 * 1240 * DT_FINI_ARRAY must be parsed in reverse order. 1241 */ 1242 1243static void call_array(unsigned *ctor, int count, int reverse) 1244{ 1245 int n, inc = 1; 1246 1247 if (reverse) { 1248 ctor += (count-1); 1249 inc = -1; 1250 } 1251 1252 for(n = count; n > 0; n--) { 1253 TRACE("[ %5d Looking at %s *0x%08x == 0x%08x ]\n", pid, 1254 reverse ? "dtor" : "ctor", 1255 (unsigned)ctor, (unsigned)*ctor); 1256 void (*func)() = (void (*)()) *ctor; 1257 ctor += inc; 1258 if(((int) func == 0) || ((int) func == -1)) continue; 1259 TRACE("[ %5d Calling func @ 0x%08x ]\n", pid, (unsigned)func); 1260 func(); 1261 } 1262} 1263 1264static void soinfo_call_preinit_constructors(soinfo *si) 1265{ 1266 TRACE("[ %5d Calling preinit_array @ 0x%08x [%d] for '%s' ]\n", 1267 pid, (unsigned)si->preinit_array, si->preinit_array_count, 1268 si->name); 1269 call_array(si->preinit_array, si->preinit_array_count, 0); 1270 TRACE("[ %5d Done calling preinit_array for '%s' ]\n", pid, si->name); 1271} 1272 1273void soinfo_call_constructors(soinfo *si) 1274{ 1275 if (si->constructors_called) 1276 return; 1277 1278 // Set this before actually calling the constructors, otherwise it doesn't 1279 // protect against recursive constructor calls. One simple example of 1280 // constructor recursion is the libc debug malloc, which is implemented in 1281 // libc_malloc_debug_leak.so: 1282 // 1. The program depends on libc, so libc's constructor is called here. 1283 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so. 1284 // 3. dlopen() calls soinfo_call_constructors() with the newly created 1285 // soinfo for libc_malloc_debug_leak.so. 1286 // 4. The debug so depends on libc, so soinfo_call_constructors() is 1287 // called again with the libc soinfo. If it doesn't trigger the early- 1288 // out above, the libc constructor will be called again (recursively!). 1289 si->constructors_called = 1; 1290 1291 if (!(si->flags & FLAG_EXE) && si->preinit_array) { 1292 DL_ERR("shared library \"%s\" has a preinit_array table @ 0x%08x. " 1293 "This is INVALID.", si->name, (unsigned) si->preinit_array); 1294 } 1295 1296 if (si->dynamic) { 1297 unsigned *d; 1298 for(d = si->dynamic; *d; d += 2) { 1299 if(d[0] == DT_NEEDED){ 1300 soinfo* lsi = find_loaded_library(si->strtab + d[1]); 1301 if (!lsi) { 1302 DL_ERR("\"%s\": could not initialize dependent library", 1303 si->name); 1304 } else { 1305 soinfo_call_constructors(lsi); 1306 } 1307 } 1308 } 1309 } 1310 1311 if (si->init_func) { 1312 TRACE("[ %5d Calling init_func @ 0x%08x for '%s' ]\n", pid, 1313 (unsigned)si->init_func, si->name); 1314 si->init_func(); 1315 TRACE("[ %5d Done calling init_func for '%s' ]\n", pid, si->name); 1316 } 1317 1318 if (si->init_array) { 1319 TRACE("[ %5d Calling init_array @ 0x%08x [%d] for '%s' ]\n", pid, 1320 (unsigned)si->init_array, si->init_array_count, si->name); 1321 call_array(si->init_array, si->init_array_count, 0); 1322 TRACE("[ %5d Done calling init_array for '%s' ]\n", pid, si->name); 1323 } 1324 1325} 1326 1327static void call_destructors(soinfo *si) 1328{ 1329 if (si->fini_array) { 1330 TRACE("[ %5d Calling fini_array @ 0x%08x [%d] for '%s' ]\n", pid, 1331 (unsigned)si->fini_array, si->fini_array_count, si->name); 1332 call_array(si->fini_array, si->fini_array_count, 1); 1333 TRACE("[ %5d Done calling fini_array for '%s' ]\n", pid, si->name); 1334 } 1335 1336 if (si->fini_func) { 1337 TRACE("[ %5d Calling fini_func @ 0x%08x for '%s' ]\n", pid, 1338 (unsigned)si->fini_func, si->name); 1339 si->fini_func(); 1340 TRACE("[ %5d Done calling fini_func for '%s' ]\n", pid, si->name); 1341 } 1342} 1343 1344/* Force any of the closed stdin, stdout and stderr to be associated with 1345 /dev/null. */ 1346static int nullify_closed_stdio (void) 1347{ 1348 int dev_null, i, status; 1349 int return_value = 0; 1350 1351 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)); 1352 if (dev_null < 0) { 1353 DL_ERR("cannot open /dev/null: %s", strerror(errno)); 1354 return -1; 1355 } 1356 TRACE("[ %5d Opened /dev/null file-descriptor=%d]\n", pid, dev_null); 1357 1358 /* If any of the stdio file descriptors is valid and not associated 1359 with /dev/null, dup /dev/null to it. */ 1360 for (i = 0; i < 3; i++) { 1361 /* If it is /dev/null already, we are done. */ 1362 if (i == dev_null) { 1363 continue; 1364 } 1365 1366 TRACE("[ %5d Nullifying stdio file descriptor %d]\n", pid, i); 1367 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL)); 1368 1369 /* If file is opened, we are good. */ 1370 if (status != -1) { 1371 continue; 1372 } 1373 1374 /* The only error we allow is that the file descriptor does not 1375 exist, in which case we dup /dev/null to it. */ 1376 if (errno != EBADF) { 1377 DL_ERR("fcntl failed: %s", strerror(errno)); 1378 return_value = -1; 1379 continue; 1380 } 1381 1382 /* Try dupping /dev/null to this stdio file descriptor and 1383 repeat if there is a signal. Note that any errors in closing 1384 the stdio descriptor are lost. */ 1385 status = TEMP_FAILURE_RETRY(dup2(dev_null, i)); 1386 if (status < 0) { 1387 DL_ERR("dup2 failed: %s", strerror(errno)); 1388 return_value = -1; 1389 continue; 1390 } 1391 } 1392 1393 /* If /dev/null is not one of the stdio file descriptors, close it. */ 1394 if (dev_null > 2) { 1395 TRACE("[ %5d Closing /dev/null file-descriptor=%d]\n", pid, dev_null); 1396 status = TEMP_FAILURE_RETRY(close(dev_null)); 1397 if (status == -1) { 1398 DL_ERR("close failed: %s", strerror(errno)); 1399 return_value = -1; 1400 } 1401 } 1402 1403 return return_value; 1404} 1405 1406static int soinfo_link_image(soinfo *si) 1407{ 1408 unsigned *d; 1409 /* "base" might wrap around UINT32_MAX. */ 1410 Elf32_Addr base = si->load_bias; 1411 const Elf32_Phdr *phdr = si->phdr; 1412 int phnum = si->phnum; 1413 int relocating_linker = (si->flags & FLAG_LINKER) != 0; 1414 soinfo **needed, **pneeded; 1415 size_t dynamic_count; 1416 1417 /* We can't debug anything until the linker is relocated */ 1418 if (!relocating_linker) { 1419 INFO("[ %5d linking %s ]\n", pid, si->name); 1420 DEBUG("%5d si->base = 0x%08x si->flags = 0x%08x\n", pid, 1421 si->base, si->flags); 1422 } 1423 1424 /* Extract dynamic section */ 1425 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic, 1426 &dynamic_count); 1427 if (si->dynamic == NULL) { 1428 if (!relocating_linker) { 1429 DL_ERR("missing PT_DYNAMIC?!"); 1430 } 1431 goto fail; 1432 } else { 1433 if (!relocating_linker) { 1434 DEBUG("%5d dynamic = %p\n", pid, si->dynamic); 1435 } 1436 } 1437 1438#ifdef ANDROID_ARM_LINKER 1439 (void) phdr_table_get_arm_exidx(phdr, phnum, base, 1440 &si->ARM_exidx, &si->ARM_exidx_count); 1441#endif 1442 1443 /* extract useful information from dynamic section */ 1444 for(d = si->dynamic; *d; d++){ 1445 DEBUG("%5d d = %p, d[0] = 0x%08x d[1] = 0x%08x\n", pid, d, d[0], d[1]); 1446 switch(*d++){ 1447 case DT_HASH: 1448 si->nbucket = ((unsigned *) (base + *d))[0]; 1449 si->nchain = ((unsigned *) (base + *d))[1]; 1450 si->bucket = (unsigned *) (base + *d + 8); 1451 si->chain = (unsigned *) (base + *d + 8 + si->nbucket * 4); 1452 break; 1453 case DT_STRTAB: 1454 si->strtab = (const char *) (base + *d); 1455 break; 1456 case DT_SYMTAB: 1457 si->symtab = (Elf32_Sym *) (base + *d); 1458 break; 1459 case DT_PLTREL: 1460 if(*d != DT_REL) { 1461 DL_ERR("DT_RELA not supported"); 1462 goto fail; 1463 } 1464 break; 1465 case DT_JMPREL: 1466 si->plt_rel = (Elf32_Rel*) (base + *d); 1467 break; 1468 case DT_PLTRELSZ: 1469 si->plt_rel_count = *d / 8; 1470 break; 1471 case DT_REL: 1472 si->rel = (Elf32_Rel*) (base + *d); 1473 break; 1474 case DT_RELSZ: 1475 si->rel_count = *d / 8; 1476 break; 1477 case DT_PLTGOT: 1478 /* Save this in case we decide to do lazy binding. We don't yet. */ 1479 si->plt_got = (unsigned *)(base + *d); 1480 break; 1481 case DT_DEBUG: 1482#if !defined(ANDROID_MIPS_LINKER) 1483 // Set the DT_DEBUG entry to the address of _r_debug for GDB 1484 *d = (int) &_r_debug; 1485#endif 1486 break; 1487 case DT_RELA: 1488 DL_ERR("DT_RELA not supported"); 1489 goto fail; 1490 case DT_INIT: 1491 si->init_func = (void (*)(void))(base + *d); 1492 DEBUG("%5d %s constructors (init func) found at %p\n", 1493 pid, si->name, si->init_func); 1494 break; 1495 case DT_FINI: 1496 si->fini_func = (void (*)(void))(base + *d); 1497 DEBUG("%5d %s destructors (fini func) found at %p\n", 1498 pid, si->name, si->fini_func); 1499 break; 1500 case DT_INIT_ARRAY: 1501 si->init_array = (unsigned *)(base + *d); 1502 DEBUG("%5d %s constructors (init_array) found at %p\n", 1503 pid, si->name, si->init_array); 1504 break; 1505 case DT_INIT_ARRAYSZ: 1506 si->init_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); 1507 break; 1508 case DT_FINI_ARRAY: 1509 si->fini_array = (unsigned *)(base + *d); 1510 DEBUG("%5d %s destructors (fini_array) found at %p\n", 1511 pid, si->name, si->fini_array); 1512 break; 1513 case DT_FINI_ARRAYSZ: 1514 si->fini_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); 1515 break; 1516 case DT_PREINIT_ARRAY: 1517 si->preinit_array = (unsigned *)(base + *d); 1518 DEBUG("%5d %s constructors (preinit_array) found at %p\n", 1519 pid, si->name, si->preinit_array); 1520 break; 1521 case DT_PREINIT_ARRAYSZ: 1522 si->preinit_array_count = ((unsigned)*d) / sizeof(Elf32_Addr); 1523 break; 1524 case DT_TEXTREL: 1525 si->has_text_relocations = true; 1526 break; 1527#if defined(ANDROID_MIPS_LINKER) 1528 case DT_NEEDED: 1529 case DT_STRSZ: 1530 case DT_SYMENT: 1531 case DT_RELENT: 1532 break; 1533 case DT_MIPS_RLD_MAP: 1534 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB. 1535 { 1536 r_debug** dp = (r_debug**) *d; 1537 *dp = &_r_debug; 1538 } 1539 break; 1540 case DT_MIPS_RLD_VERSION: 1541 case DT_MIPS_FLAGS: 1542 case DT_MIPS_BASE_ADDRESS: 1543 case DT_MIPS_UNREFEXTNO: 1544 case DT_MIPS_RWPLT: 1545 break; 1546 1547 case DT_MIPS_PLTGOT: 1548#if 0 1549 /* not yet... */ 1550 si->mips_pltgot = (unsigned *)(si->base + *d); 1551#endif 1552 break; 1553 1554 case DT_MIPS_SYMTABNO: 1555 si->mips_symtabno = *d; 1556 break; 1557 1558 case DT_MIPS_LOCAL_GOTNO: 1559 si->mips_local_gotno = *d; 1560 break; 1561 1562 case DT_MIPS_GOTSYM: 1563 si->mips_gotsym = *d; 1564 break; 1565 1566 default: 1567 DEBUG("%5d Unused DT entry: type 0x%08x arg 0x%08x\n", 1568 pid, d[-1], d[0]); 1569 break; 1570#endif 1571 } 1572 } 1573 1574 DEBUG("%5d si->base = 0x%08x, si->strtab = %p, si->symtab = %p\n", 1575 pid, si->base, si->strtab, si->symtab); 1576 1577 if((si->strtab == 0) || (si->symtab == 0)) { 1578 DL_ERR("missing essential tables"); 1579 goto fail; 1580 } 1581 1582 /* if this is the main executable, then load all of the preloads now */ 1583 if(si->flags & FLAG_EXE) { 1584 int i; 1585 memset(preloads, 0, sizeof(preloads)); 1586 for(i = 0; ldpreload_names[i] != NULL; i++) { 1587 soinfo *lsi = find_library(ldpreload_names[i]); 1588 if(lsi == 0) { 1589 strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf)); 1590 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1591 ldpreload_names[i], si->name, tmp_err_buf); 1592 goto fail; 1593 } 1594 lsi->refcount++; 1595 preloads[i] = lsi; 1596 } 1597 } 1598 1599 /* dynamic_count is an upper bound for the number of needed libs */ 1600 pneeded = needed = (soinfo**) alloca((1 + dynamic_count) * sizeof(soinfo*)); 1601 1602 for(d = si->dynamic; *d; d += 2) { 1603 if(d[0] == DT_NEEDED){ 1604 DEBUG("%5d %s needs %s\n", pid, si->name, si->strtab + d[1]); 1605 soinfo *lsi = find_library(si->strtab + d[1]); 1606 if(lsi == 0) { 1607 strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf)); 1608 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s", 1609 si->strtab + d[1], si->name, tmp_err_buf); 1610 goto fail; 1611 } 1612 *pneeded++ = lsi; 1613 lsi->refcount++; 1614 } 1615 } 1616 *pneeded = NULL; 1617 1618 if (si->has_text_relocations) { 1619 /* Unprotect the segments, i.e. make them writable, to allow 1620 * text relocations to work properly. We will later call 1621 * phdr_table_protect_segments() after all of them are applied 1622 * and all constructors are run. 1623 */ 1624 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1625 DL_ERR("can't unprotect loadable segments for \"%s\": %s", 1626 si->name, strerror(errno)); 1627 goto fail; 1628 } 1629 } 1630 1631 if(si->plt_rel) { 1632 DEBUG("[ %5d relocating %s plt ]\n", pid, si->name ); 1633 if(soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) 1634 goto fail; 1635 } 1636 if(si->rel) { 1637 DEBUG("[ %5d relocating %s ]\n", pid, si->name ); 1638 if(soinfo_relocate(si, si->rel, si->rel_count, needed)) 1639 goto fail; 1640 } 1641 1642#ifdef ANDROID_MIPS_LINKER 1643 if(mips_relocate_got(si, needed)) { 1644 goto fail; 1645 } 1646#endif 1647 1648 si->flags |= FLAG_LINKED; 1649 DEBUG("[ %5d finished linking %s ]\n", pid, si->name); 1650 1651 if (si->has_text_relocations) { 1652 /* All relocations are done, we can protect our segments back to 1653 * read-only. */ 1654 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) { 1655 DL_ERR("can't protect segments for \"%s\": %s", 1656 si->name, strerror(errno)); 1657 goto fail; 1658 } 1659 } 1660 1661 /* We can also turn on GNU RELRO protection */ 1662 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) { 1663 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s", 1664 si->name, strerror(errno)); 1665 goto fail; 1666 } 1667 1668 /* If this is a SET?ID program, dup /dev/null to opened stdin, 1669 stdout and stderr to close a security hole described in: 1670 1671 ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc 1672 1673 */ 1674 if (program_is_setuid) { 1675 nullify_closed_stdio(); 1676 } 1677 notify_gdb_of_load(si); 1678 return 0; 1679 1680fail: 1681 ERROR("failed to link %s\n", si->name); 1682 si->flags |= FLAG_ERROR; 1683 return -1; 1684} 1685 1686static void parse_path(const char* path, const char* delimiters, 1687 const char** array, char* buf, size_t buf_size, size_t max_count) 1688{ 1689 if (path == NULL) { 1690 return; 1691 } 1692 1693 size_t len = strlcpy(buf, path, buf_size); 1694 1695 size_t i = 0; 1696 char* buf_p = buf; 1697 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) { 1698 if (*array[i] != '\0') { 1699 ++i; 1700 } 1701 } 1702 1703 // Forget the last path if we had to truncate; this occurs if the 2nd to 1704 // last char isn't '\0' (i.e. wasn't originally a delimiter). 1705 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') { 1706 array[i - 1] = NULL; 1707 } else { 1708 array[i] = NULL; 1709 } 1710} 1711 1712static void parse_LD_LIBRARY_PATH(const char* path) { 1713 parse_path(path, ":", ldpaths, 1714 ldpaths_buf, sizeof(ldpaths_buf), LDPATH_MAX); 1715} 1716 1717static void parse_LD_PRELOAD(const char* path) { 1718 // We have historically supported ':' as well as ' ' in LD_PRELOAD. 1719 parse_path(path, " :", ldpreload_names, 1720 ldpreloads_buf, sizeof(ldpreloads_buf), LDPRELOAD_MAX); 1721} 1722 1723/* 1724 * This code is called after the linker has linked itself and 1725 * fixed it's own GOT. It is safe to make references to externs 1726 * and other non-local data at this point. 1727 */ 1728static unsigned __linker_init_post_relocation(unsigned **elfdata, unsigned linker_base) 1729{ 1730 static soinfo linker_soinfo; 1731 1732 int argc = (int) *elfdata; 1733 char **argv = (char**) (elfdata + 1); 1734 unsigned *vecs = (unsigned*) (argv + argc + 1); 1735 unsigned *v; 1736 soinfo *si; 1737 int i; 1738 const char *ldpath_env = NULL; 1739 const char *ldpreload_env = NULL; 1740 1741 /* NOTE: we store the elfdata pointer on a special location 1742 * of the temporary TLS area in order to pass it to 1743 * the C Library's runtime initializer. 1744 * 1745 * The initializer must clear the slot and reset the TLS 1746 * to point to a different location to ensure that no other 1747 * shared library constructor can access it. 1748 */ 1749 __libc_init_tls(elfdata); 1750 1751 pid = getpid(); 1752 1753#if TIMING 1754 struct timeval t0, t1; 1755 gettimeofday(&t0, 0); 1756#endif 1757 1758 /* Initialize environment functions, and get to the ELF aux vectors table */ 1759 vecs = linker_env_init(vecs); 1760 1761 /* Check auxv for AT_SECURE first to see if program is setuid, setgid, 1762 has file caps, or caused a SELinux/AppArmor domain transition. */ 1763 for (v = vecs; v[0]; v += 2) { 1764 if (v[0] == AT_SECURE) { 1765 /* kernel told us whether to enable secure mode */ 1766 program_is_setuid = v[1]; 1767 goto sanitize; 1768 } 1769 } 1770 1771 /* Kernel did not provide AT_SECURE - fall back on legacy test. */ 1772 program_is_setuid = (getuid() != geteuid()) || (getgid() != getegid()); 1773 1774sanitize: 1775 /* Sanitize environment if we're loading a setuid program */ 1776 if (program_is_setuid) { 1777 linker_env_secure(); 1778 } 1779 1780 debugger_init(); 1781 1782 /* Get a few environment variables */ 1783 { 1784#if LINKER_DEBUG 1785 const char* env; 1786 env = linker_env_get("DEBUG"); /* XXX: TODO: Change to LD_DEBUG */ 1787 if (env) 1788 debug_verbosity = atoi(env); 1789#endif 1790 1791 /* Normally, these are cleaned by linker_env_secure, but the test 1792 * against program_is_setuid doesn't cost us anything */ 1793 if (!program_is_setuid) { 1794 ldpath_env = linker_env_get("LD_LIBRARY_PATH"); 1795 ldpreload_env = linker_env_get("LD_PRELOAD"); 1796 } 1797 } 1798 1799 INFO("[ android linker & debugger ]\n"); 1800 DEBUG("%5d elfdata @ 0x%08x\n", pid, (unsigned)elfdata); 1801 1802 si = soinfo_alloc(argv[0]); 1803 if(si == 0) { 1804 exit(-1); 1805 } 1806 1807 /* bootstrap the link map, the main exe always needs to be first */ 1808 si->flags |= FLAG_EXE; 1809 link_map* map = &(si->linkmap); 1810 1811 map->l_addr = 0; 1812 map->l_name = argv[0]; 1813 map->l_prev = NULL; 1814 map->l_next = NULL; 1815 1816 _r_debug.r_map = map; 1817 r_debug_tail = map; 1818 1819 /* gdb expects the linker to be in the debug shared object list. 1820 * Without this, gdb has trouble locating the linker's ".text" 1821 * and ".plt" sections. Gdb could also potentially use this to 1822 * relocate the offset of our exported 'rtld_db_dlactivity' symbol. 1823 * Don't use soinfo_alloc(), because the linker shouldn't 1824 * be on the soinfo list. 1825 */ 1826 strlcpy((char*) linker_soinfo.name, "/system/bin/linker", sizeof linker_soinfo.name); 1827 linker_soinfo.flags = 0; 1828 linker_soinfo.base = linker_base; 1829 /* 1830 * Set the dynamic field in the link map otherwise gdb will complain with 1831 * the following: 1832 * warning: .dynamic section for "/system/bin/linker" is not at the 1833 * expected address (wrong library or version mismatch?) 1834 */ 1835 Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_base; 1836 Elf32_Phdr *phdr = 1837 (Elf32_Phdr *)((unsigned char *) linker_base + elf_hdr->e_phoff); 1838 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base, 1839 &linker_soinfo.dynamic, NULL); 1840 insert_soinfo_into_debug_map(&linker_soinfo); 1841 1842 /* extract information passed from the kernel */ 1843 while(vecs[0] != 0){ 1844 switch(vecs[0]){ 1845 case AT_PHDR: 1846 si->phdr = (Elf32_Phdr*) vecs[1]; 1847 break; 1848 case AT_PHNUM: 1849 si->phnum = (int) vecs[1]; 1850 break; 1851 case AT_ENTRY: 1852 si->entry = vecs[1]; 1853 break; 1854 } 1855 vecs += 2; 1856 } 1857 1858 /* Compute the value of si->base. We can't rely on the fact that 1859 * the first entry is the PHDR because this will not be true 1860 * for certain executables (e.g. some in the NDK unit test suite) 1861 */ 1862 int nn; 1863 si->base = 0; 1864 si->size = phdr_table_get_load_size(si->phdr, si->phnum); 1865 si->load_bias = 0; 1866 for ( nn = 0; nn < si->phnum; nn++ ) { 1867 if (si->phdr[nn].p_type == PT_PHDR) { 1868 si->load_bias = (Elf32_Addr)si->phdr - si->phdr[nn].p_vaddr; 1869 si->base = (Elf32_Addr) si->phdr - si->phdr[nn].p_offset; 1870 break; 1871 } 1872 } 1873 si->dynamic = (unsigned *)-1; 1874 si->refcount = 1; 1875 1876 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid). 1877 parse_LD_LIBRARY_PATH(ldpath_env); 1878 parse_LD_PRELOAD(ldpreload_env); 1879 1880 if(soinfo_link_image(si)) { 1881 char errmsg[] = "CANNOT LINK EXECUTABLE\n"; 1882 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); 1883 write(2, errmsg, sizeof(errmsg)); 1884 exit(-1); 1885 } 1886 1887 soinfo_call_preinit_constructors(si); 1888 1889 for(i = 0; preloads[i] != NULL; i++) { 1890 soinfo_call_constructors(preloads[i]); 1891 } 1892 1893 soinfo_call_constructors(si); 1894 1895#if ALLOW_SYMBOLS_FROM_MAIN 1896 /* Set somain after we've loaded all the libraries in order to prevent 1897 * linking of symbols back to the main image, which is not set up at that 1898 * point yet. 1899 */ 1900 somain = si; 1901#endif 1902 1903#if TIMING 1904 gettimeofday(&t1,NULL); 1905 PRINT("LINKER TIME: %s: %d microseconds\n", argv[0], (int) ( 1906 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) - 1907 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec) 1908 )); 1909#endif 1910#if STATS 1911 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol\n", argv[0], 1912 linker_stats.count[kRelocAbsolute], 1913 linker_stats.count[kRelocRelative], 1914 linker_stats.count[kRelocCopy], 1915 linker_stats.count[kRelocSymbol]); 1916#endif 1917#if COUNT_PAGES 1918 { 1919 unsigned n; 1920 unsigned i; 1921 unsigned count = 0; 1922 for(n = 0; n < 4096; n++){ 1923 if(bitmask[n]){ 1924 unsigned x = bitmask[n]; 1925 for(i = 0; i < 8; i++){ 1926 if(x & 1) count++; 1927 x >>= 1; 1928 } 1929 } 1930 } 1931 PRINT("PAGES MODIFIED: %s: %d (%dKB)\n", argv[0], count, count * 4); 1932 } 1933#endif 1934 1935#if TIMING || STATS || COUNT_PAGES 1936 fflush(stdout); 1937#endif 1938 1939 TRACE("[ %5d Ready to execute '%s' @ 0x%08x ]\n", pid, si->name, 1940 si->entry); 1941 return si->entry; 1942} 1943 1944/* 1945 * Find the value of AT_BASE passed to us by the kernel. This is the load 1946 * location of the linker. 1947 */ 1948static unsigned find_linker_base(unsigned **elfdata) { 1949 int argc = (int) *elfdata; 1950 char **argv = (char**) (elfdata + 1); 1951 unsigned *vecs = (unsigned*) (argv + argc + 1); 1952 while (vecs[0] != 0) { 1953 vecs++; 1954 } 1955 1956 /* The end of the environment block is marked by two NULL pointers */ 1957 vecs++; 1958 1959 while(vecs[0]) { 1960 if (vecs[0] == AT_BASE) { 1961 return vecs[1]; 1962 } 1963 vecs += 2; 1964 } 1965 1966 return 0; // should never happen 1967} 1968 1969/* Compute the load-bias of an existing executable. This shall only 1970 * be used to compute the load bias of an executable or shared library 1971 * that was loaded by the kernel itself. 1972 * 1973 * Input: 1974 * elf -> address of ELF header, assumed to be at the start of the file. 1975 * Return: 1976 * load bias, i.e. add the value of any p_vaddr in the file to get 1977 * the corresponding address in memory. 1978 */ 1979static Elf32_Addr 1980get_elf_exec_load_bias(const Elf32_Ehdr* elf) 1981{ 1982 Elf32_Addr offset = elf->e_phoff; 1983 const Elf32_Phdr* phdr_table = (const Elf32_Phdr*)((char*)elf + offset); 1984 const Elf32_Phdr* phdr_end = phdr_table + elf->e_phnum; 1985 const Elf32_Phdr* phdr; 1986 1987 for (phdr = phdr_table; phdr < phdr_end; phdr++) { 1988 if (phdr->p_type == PT_LOAD) { 1989 return (Elf32_Addr)elf + phdr->p_offset - phdr->p_vaddr; 1990 } 1991 } 1992 return 0; 1993} 1994 1995/* 1996 * This is the entry point for the linker, called from begin.S. This 1997 * method is responsible for fixing the linker's own relocations, and 1998 * then calling __linker_init_post_relocation(). 1999 * 2000 * Because this method is called before the linker has fixed it's own 2001 * relocations, any attempt to reference an extern variable, extern 2002 * function, or other GOT reference will generate a segfault. 2003 */ 2004extern "C" unsigned __linker_init(unsigned **elfdata) { 2005 unsigned linker_addr = find_linker_base(elfdata); 2006 Elf32_Ehdr *elf_hdr = (Elf32_Ehdr *) linker_addr; 2007 Elf32_Phdr *phdr = 2008 (Elf32_Phdr *)((unsigned char *) linker_addr + elf_hdr->e_phoff); 2009 2010 soinfo linker_so; 2011 memset(&linker_so, 0, sizeof(soinfo)); 2012 2013 linker_so.base = linker_addr; 2014 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum); 2015 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr); 2016 linker_so.dynamic = (unsigned *) -1; 2017 linker_so.phdr = phdr; 2018 linker_so.phnum = elf_hdr->e_phnum; 2019 linker_so.flags |= FLAG_LINKER; 2020 2021 if (soinfo_link_image(&linker_so)) { 2022 // It would be nice to print an error message, but if the linker 2023 // can't link itself, there's no guarantee that we'll be able to 2024 // call write() (because it involves a GOT reference). 2025 // 2026 // This situation should never occur unless the linker itself 2027 // is corrupt. 2028 exit(-1); 2029 } 2030 2031 // We have successfully fixed our own relocations. It's safe to run 2032 // the main part of the linker now. 2033 return __linker_init_post_relocation(elfdata, linker_addr); 2034} 2035