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 */
29 #include <dlfcn.h>
30 #include <errno.h>
31 #include <fcntl.h>
32 #include <inttypes.h>
33 #include <pthread.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
37 #include <sys/mman.h>
38 #include <unistd.h>
40 #include <new>
42 // Private C library headers.
43 #include "private/bionic_tls.h"
44 #include "private/KernelArgumentBlock.h"
45 #include "private/ScopedPthreadMutexLocker.h"
46 #include "private/ScopedFd.h"
47 #include "private/ScopeGuard.h"
48 #include "private/UniquePtr.h"
50 #include "linker.h"
51 #include "linker_debug.h"
52 #include "linker_environ.h"
53 #include "linker_phdr.h"
54 #include "linker_allocator.h"
56 /* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<<
57 *
58 * Do NOT use malloc() and friends or pthread_*() code here.
59 * Don't use printf() either; it's caused mysterious memory
60 * corruption in the past.
61 * The linker runs before we bring up libc and it's easiest
62 * to make sure it does not depend on any complex libc features
63 *
64 * open issues / todo:
65 *
66 * - cleaner error reporting
67 * - after linking, set as much stuff as possible to READONLY
68 * and NOEXEC
69 */
71 #if defined(__LP64__)
72 #define SEARCH_NAME(x) x
73 #else
74 // Nvidia drivers are relying on the bug:
75 // http://code.google.com/p/android/issues/detail?id=6670
76 // so we continue to use base-name lookup for lp32
77 static const char* get_base_name(const char* name) {
78 const char* bname = strrchr(name, '/');
79 return bname ? bname + 1 : name;
80 }
81 #define SEARCH_NAME(x) get_base_name(x)
82 #endif
84 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
86 static LinkerAllocator<soinfo> g_soinfo_allocator;
87 static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator;
89 static soinfo* solist;
90 static soinfo* sonext;
91 static soinfo* somain; // main process, always the one after libdl_info
93 static const char* const kDefaultLdPaths[] = {
94 #if defined(__LP64__)
95 "/vendor/lib64",
96 "/system/lib64",
97 #else
98 "/vendor/lib",
99 "/system/lib",
100 #endif
101 nullptr
102 };
104 #define LDPATH_BUFSIZE (LDPATH_MAX*64)
105 #define LDPATH_MAX 8
107 #define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64)
108 #define LDPRELOAD_MAX 8
110 static char g_ld_library_paths_buffer[LDPATH_BUFSIZE];
111 static const char* g_ld_library_paths[LDPATH_MAX + 1];
113 static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE];
114 static const char* g_ld_preload_names[LDPRELOAD_MAX + 1];
116 static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1];
118 __LIBC_HIDDEN__ int g_ld_debug_verbosity;
120 __LIBC_HIDDEN__ abort_msg_t* g_abort_message = nullptr; // For debuggerd.
122 enum RelocationKind {
123 kRelocAbsolute = 0,
124 kRelocRelative,
125 kRelocCopy,
126 kRelocSymbol,
127 kRelocMax
128 };
130 #if STATS
131 struct linker_stats_t {
132 int count[kRelocMax];
133 };
135 static linker_stats_t linker_stats;
137 static void count_relocation(RelocationKind kind) {
138 ++linker_stats.count[kind];
139 }
140 #else
141 static void count_relocation(RelocationKind) {
142 }
143 #endif
145 #if COUNT_PAGES
146 static unsigned bitmask[4096];
147 #if defined(__LP64__)
148 #define MARK(offset) \
149 do { \
150 if ((((offset) >> 12) >> 5) < 4096) \
151 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \
152 } while (0)
153 #else
154 #define MARK(offset) \
155 do { \
156 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \
157 } while (0)
158 #endif
159 #else
160 #define MARK(x) do {} while (0)
161 #endif
163 // You shouldn't try to call memory-allocating functions in the dynamic linker.
164 // Guard against the most obvious ones.
165 #define DISALLOW_ALLOCATION(return_type, name, ...) \
166 return_type name __VA_ARGS__ \
167 { \
168 __libc_fatal("ERROR: " #name " called from the dynamic linker!\n"); \
169 }
170 DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused));
171 DISALLOW_ALLOCATION(void, free, (void* u __unused));
172 DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused));
173 DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused));
175 static char __linker_dl_err_buf[768];
177 char* linker_get_error_buffer() {
178 return &__linker_dl_err_buf[0];
179 }
181 size_t linker_get_error_buffer_size() {
182 return sizeof(__linker_dl_err_buf);
183 }
185 // This function is an empty stub where GDB locates a breakpoint to get notified
186 // about linker activity.
187 extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity();
189 static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER;
190 static r_debug _r_debug = {1, nullptr, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0};
191 static link_map* r_debug_tail = 0;
193 static void insert_soinfo_into_debug_map(soinfo* info) {
194 // Copy the necessary fields into the debug structure.
195 link_map* map = &(info->link_map_head);
196 map->l_addr = info->load_bias;
197 map->l_name = info->name;
198 map->l_ld = info->dynamic;
200 // Stick the new library at the end of the list.
201 // gdb tends to care more about libc than it does
202 // about leaf libraries, and ordering it this way
203 // reduces the back-and-forth over the wire.
204 if (r_debug_tail) {
205 r_debug_tail->l_next = map;
206 map->l_prev = r_debug_tail;
207 map->l_next = 0;
208 } else {
209 _r_debug.r_map = map;
210 map->l_prev = 0;
211 map->l_next = 0;
212 }
213 r_debug_tail = map;
214 }
216 static void remove_soinfo_from_debug_map(soinfo* info) {
217 link_map* map = &(info->link_map_head);
219 if (r_debug_tail == map) {
220 r_debug_tail = map->l_prev;
221 }
223 if (map->l_prev) {
224 map->l_prev->l_next = map->l_next;
225 }
226 if (map->l_next) {
227 map->l_next->l_prev = map->l_prev;
228 }
229 }
231 static void notify_gdb_of_load(soinfo* info) {
232 if (info->flags & FLAG_EXE) {
233 // GDB already knows about the main executable
234 return;
235 }
237 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
239 _r_debug.r_state = r_debug::RT_ADD;
240 rtld_db_dlactivity();
242 insert_soinfo_into_debug_map(info);
244 _r_debug.r_state = r_debug::RT_CONSISTENT;
245 rtld_db_dlactivity();
246 }
248 static void notify_gdb_of_unload(soinfo* info) {
249 if (info->flags & FLAG_EXE) {
250 // GDB already knows about the main executable
251 return;
252 }
254 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
256 _r_debug.r_state = r_debug::RT_DELETE;
257 rtld_db_dlactivity();
259 remove_soinfo_from_debug_map(info);
261 _r_debug.r_state = r_debug::RT_CONSISTENT;
262 rtld_db_dlactivity();
263 }
265 void notify_gdb_of_libraries() {
266 _r_debug.r_state = r_debug::RT_ADD;
267 rtld_db_dlactivity();
268 _r_debug.r_state = r_debug::RT_CONSISTENT;
269 rtld_db_dlactivity();
270 }
272 LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() {
273 return g_soinfo_links_allocator.alloc();
274 }
276 void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) {
277 g_soinfo_links_allocator.free(entry);
278 }
280 static void protect_data(int protection) {
281 g_soinfo_allocator.protect_all(protection);
282 g_soinfo_links_allocator.protect_all(protection);
283 }
285 static soinfo* soinfo_alloc(const char* name, struct stat* file_stat, off64_t file_offset, uint32_t rtld_flags) {
286 if (strlen(name) >= SOINFO_NAME_LEN) {
287 DL_ERR("library name \"%s\" too long", name);
288 return nullptr;
289 }
291 soinfo* si = new (g_soinfo_allocator.alloc()) soinfo(name, file_stat, file_offset, rtld_flags);
293 sonext->next = si;
294 sonext = si;
296 TRACE("name %s: allocated soinfo @ %p", name, si);
297 return si;
298 }
300 static void soinfo_free(soinfo* si) {
301 if (si == nullptr) {
302 return;
303 }
305 if (si->base != 0 && si->size != 0) {
306 munmap(reinterpret_cast<void*>(si->base), si->size);
307 }
309 soinfo *prev = nullptr, *trav;
311 TRACE("name %s: freeing soinfo @ %p", si->name, si);
313 for (trav = solist; trav != nullptr; trav = trav->next) {
314 if (trav == si) {
315 break;
316 }
317 prev = trav;
318 }
319 if (trav == nullptr) {
320 // si was not in solist
321 DL_ERR("name \"%s\" is not in solist!", si->name);
322 return;
323 }
325 // clear links to/from si
326 si->remove_all_links();
328 // prev will never be null, because the first entry in solist is
329 // always the static libdl_info.
330 prev->next = si->next;
331 if (si == sonext) {
332 sonext = prev;
333 }
335 g_soinfo_allocator.free(si);
336 }
339 static void parse_path(const char* path, const char* delimiters,
340 const char** array, char* buf, size_t buf_size, size_t max_count) {
341 if (path == nullptr) {
342 return;
343 }
345 size_t len = strlcpy(buf, path, buf_size);
347 size_t i = 0;
348 char* buf_p = buf;
349 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) {
350 if (*array[i] != '\0') {
351 ++i;
352 }
353 }
355 // Forget the last path if we had to truncate; this occurs if the 2nd to
356 // last char isn't '\0' (i.e. wasn't originally a delimiter).
357 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') {
358 array[i - 1] = nullptr;
359 } else {
360 array[i] = nullptr;
361 }
362 }
364 static void parse_LD_LIBRARY_PATH(const char* path) {
365 parse_path(path, ":", g_ld_library_paths,
366 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX);
367 }
369 static void parse_LD_PRELOAD(const char* path) {
370 // We have historically supported ':' as well as ' ' in LD_PRELOAD.
371 parse_path(path, " :", g_ld_preload_names,
372 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX);
373 }
375 #if defined(__arm__)
377 // For a given PC, find the .so that it belongs to.
378 // Returns the base address of the .ARM.exidx section
379 // for that .so, and the number of 8-byte entries
380 // in that section (via *pcount).
381 //
382 // Intended to be called by libc's __gnu_Unwind_Find_exidx().
383 //
384 // This function is exposed via dlfcn.cpp and libdl.so.
385 _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
386 unsigned addr = (unsigned)pc;
388 for (soinfo* si = solist; si != 0; si = si->next) {
389 if ((addr >= si->base) && (addr < (si->base + si->size))) {
390 *pcount = si->ARM_exidx_count;
391 return (_Unwind_Ptr)si->ARM_exidx;
392 }
393 }
394 *pcount = 0;
395 return nullptr;
396 }
398 #endif
400 // Here, we only have to provide a callback to iterate across all the
401 // loaded libraries. gcc_eh does the rest.
402 int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
403 int rv = 0;
404 for (soinfo* si = solist; si != nullptr; si = si->next) {
405 dl_phdr_info dl_info;
406 dl_info.dlpi_addr = si->link_map_head.l_addr;
407 dl_info.dlpi_name = si->link_map_head.l_name;
408 dl_info.dlpi_phdr = si->phdr;
409 dl_info.dlpi_phnum = si->phnum;
410 rv = cb(&dl_info, sizeof(dl_phdr_info), data);
411 if (rv != 0) {
412 break;
413 }
414 }
415 return rv;
416 }
418 static ElfW(Sym)* soinfo_elf_lookup(const soinfo* si, unsigned hash, const char* name) {
419 ElfW(Sym)* symtab = si->symtab;
421 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd",
422 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
424 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) {
425 ElfW(Sym)* s = symtab + n;
426 if (strcmp(si->get_string(s->st_name), name)) continue;
428 // only concern ourselves with global and weak symbol definitions
429 switch (ELF_ST_BIND(s->st_info)) {
430 case STB_GLOBAL:
431 case STB_WEAK:
432 if (s->st_shndx == SHN_UNDEF) {
433 continue;
434 }
436 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
437 name, si->name, reinterpret_cast<void*>(s->st_value),
438 static_cast<size_t>(s->st_size));
439 return s;
440 case STB_LOCAL:
441 continue;
442 default:
443 __libc_fatal("ERROR: Unexpected ST_BIND value: %d for '%s' in '%s'",
444 ELF_ST_BIND(s->st_info), name, si->name);
445 }
446 }
448 TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd",
449 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
452 return nullptr;
453 }
455 soinfo::soinfo(const char* name, const struct stat* file_stat, off64_t file_offset, int rtld_flags) {
456 memset(this, 0, sizeof(*this));
458 strlcpy(this->name, name, sizeof(this->name));
459 flags = FLAG_NEW_SOINFO;
460 version = SOINFO_VERSION;
462 if (file_stat != nullptr) {
463 this->st_dev = file_stat->st_dev;
464 this->st_ino = file_stat->st_ino;
465 this->file_offset = file_offset;
466 }
468 this->rtld_flags = rtld_flags;
469 }
471 static unsigned elfhash(const char* _name) {
472 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
473 unsigned h = 0, g;
475 while (*name) {
476 h = (h << 4) + *name++;
477 g = h & 0xf0000000;
478 h ^= g;
479 h ^= g >> 24;
480 }
481 return h;
482 }
484 static ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** si_found_in,
485 const soinfo::soinfo_list_t& global_group, const soinfo::soinfo_list_t& local_group) {
486 unsigned elf_hash = elfhash(name);
487 ElfW(Sym)* s = nullptr;
489 /* "This element's presence in a shared object library alters the dynamic linker's
490 * symbol resolution algorithm for references within the library. Instead of starting
491 * a symbol search with the executable file, the dynamic linker starts from the shared
492 * object itself. If the shared object fails to supply the referenced symbol, the
493 * dynamic linker then searches the executable file and other shared objects as usual."
494 *
495 * http://www.sco.com/developers/gabi/2012-12-31/ch5.dynamic.html
496 *
497 * Note that this is unlikely since static linker avoids generating
498 * relocations for -Bsymbolic linked dynamic executables.
499 */
500 if (si_from->has_DT_SYMBOLIC) {
501 DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si_from->name, name);
502 s = soinfo_elf_lookup(si_from, elf_hash, name);
503 if (s != nullptr) {
504 *si_found_in = si_from;
505 }
506 }
508 // 1. Look for it in global_group
509 if (s == nullptr) {
510 global_group.visit([&](soinfo* global_si) {
511 DEBUG("%s: looking up %s in %s (from global group)", si_from->name, name, global_si->name);
512 s = soinfo_elf_lookup(global_si, elf_hash, name);
513 if (s != nullptr) {
514 *si_found_in = global_si;
515 return false;
516 }
518 return true;
519 });
520 }
522 // 2. Look for it in the local group
523 if (s == nullptr) {
524 local_group.visit([&](soinfo* local_si) {
525 if (local_si == si_from && si_from->has_DT_SYMBOLIC) {
526 // we already did this - skip
527 return true;
528 }
530 DEBUG("%s: looking up %s in %s (from local group)", si_from->name, name, local_si->name);
531 s = soinfo_elf_lookup(local_si, elf_hash, name);
532 if (s != nullptr) {
533 *si_found_in = local_si;
534 return false;
535 }
537 return true;
538 });
539 }
541 if (s != nullptr) {
542 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
543 "found in %s, base = %p, load bias = %p",
544 si_from->name, name, reinterpret_cast<void*>(s->st_value),
545 (*si_found_in)->name, reinterpret_cast<void*>((*si_found_in)->base),
546 reinterpret_cast<void*>((*si_found_in)->load_bias));
547 }
549 return s;
550 }
552 // Each size has it's own allocator.
553 template<size_t size>
554 class SizeBasedAllocator {
555 public:
556 static void* alloc() {
557 return allocator_.alloc();
558 }
560 static void free(void* ptr) {
561 allocator_.free(ptr);
562 }
564 private:
565 static LinkerBlockAllocator allocator_;
566 };
568 template<size_t size>
569 LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
571 template<typename T>
572 class TypeBasedAllocator {
573 public:
574 static T* alloc() {
575 return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
576 }
578 static void free(T* ptr) {
579 SizeBasedAllocator<sizeof(T)>::free(ptr);
580 }
581 };
583 class LoadTask {
584 public:
585 struct deleter_t {
586 void operator()(LoadTask* t) {
587 TypeBasedAllocator<LoadTask>::free(t);
588 }
589 };
591 typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
593 static deleter_t deleter;
595 static LoadTask* create(const char* name, soinfo* needed_by) {
596 LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
597 return new (ptr) LoadTask(name, needed_by);
598 }
600 const char* get_name() const {
601 return name_;
602 }
604 soinfo* get_needed_by() const {
605 return needed_by_;
606 }
607 private:
608 LoadTask(const char* name, soinfo* needed_by)
609 : name_(name), needed_by_(needed_by) {}
611 const char* name_;
612 soinfo* needed_by_;
614 DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
615 };
617 LoadTask::deleter_t LoadTask::deleter;
619 template <typename T>
620 using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
622 typedef linked_list_t<soinfo> SoinfoLinkedList;
623 typedef linked_list_t<const char> StringLinkedList;
624 typedef linked_list_t<LoadTask> LoadTaskList;
627 // This function walks down the tree of soinfo dependencies
628 // in breadth-first order and
629 // * calls action(soinfo* si) for each node, and
630 // * terminates walk if action returns false.
631 //
632 // walk_dependencies_tree returns false if walk was terminated
633 // by the action and true otherwise.
634 template<typename F>
635 static bool walk_dependencies_tree(soinfo* root_soinfos[], size_t root_soinfos_size, F action) {
636 SoinfoLinkedList visit_list;
637 SoinfoLinkedList visited;
639 for (size_t i = 0; i < root_soinfos_size; ++i) {
640 visit_list.push_back(root_soinfos[i]);
641 }
643 soinfo* si;
644 while ((si = visit_list.pop_front()) != nullptr) {
645 if (visited.contains(si)) {
646 continue;
647 }
649 if (!action(si)) {
650 return false;
651 }
653 visited.push_back(si);
655 si->get_children().for_each([&](soinfo* child) {
656 visit_list.push_back(child);
657 });
658 }
660 return true;
661 }
664 // This is used by dlsym(3). It performs symbol lookup only within the
665 // specified soinfo object and its dependencies in breadth first order.
666 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
667 ElfW(Sym)* result = nullptr;
668 uint32_t elf_hash = elfhash(name);
671 walk_dependencies_tree(&si, 1, [&](soinfo* current_soinfo) {
672 result = soinfo_elf_lookup(current_soinfo, elf_hash, name);
673 if (result != nullptr) {
674 *found = current_soinfo;
675 return false;
676 }
678 return true;
679 });
681 return result;
682 }
684 /* This is used by dlsym(3) to performs a global symbol lookup. If the
685 start value is null (for RTLD_DEFAULT), the search starts at the
686 beginning of the global solist. Otherwise the search starts at the
687 specified soinfo (for RTLD_NEXT).
688 */
689 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
690 unsigned elf_hash = elfhash(name);
692 if (start == nullptr) {
693 start = solist;
694 }
696 ElfW(Sym)* s = nullptr;
697 for (soinfo* si = start; (s == nullptr) && (si != nullptr); si = si->next) {
698 if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0) {
699 continue;
700 }
702 s = soinfo_elf_lookup(si, elf_hash, name);
703 if (s != nullptr) {
704 *found = si;
705 break;
706 }
707 }
709 if (s != nullptr) {
710 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
711 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
712 }
714 return s;
715 }
717 soinfo* find_containing_library(const void* p) {
718 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
719 for (soinfo* si = solist; si != nullptr; si = si->next) {
720 if (address >= si->base && address - si->base < si->size) {
721 return si;
722 }
723 }
724 return nullptr;
725 }
727 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
728 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
730 // Search the library's symbol table for any defined symbol which
731 // contains this address.
732 for (size_t i = 0; i < si->nchain; ++i) {
733 ElfW(Sym)* sym = &si->symtab[i];
734 if (sym->st_shndx != SHN_UNDEF &&
735 soaddr >= sym->st_value &&
736 soaddr < sym->st_value + sym->st_size) {
737 return sym;
738 }
739 }
741 return nullptr;
742 }
744 static int open_library_on_path(const char* name, const char* const paths[]) {
745 char buf[512];
746 for (size_t i = 0; paths[i] != nullptr; ++i) {
747 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
748 if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
749 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
750 continue;
751 }
752 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
753 if (fd != -1) {
754 return fd;
755 }
756 }
757 return -1;
758 }
760 static int open_library(const char* name) {
761 TRACE("[ opening %s ]", name);
763 // If the name contains a slash, we should attempt to open it directly and not search the paths.
764 if (strchr(name, '/') != nullptr) {
765 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
766 if (fd != -1) {
767 return fd;
768 }
769 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
770 #if defined(__LP64__)
771 return -1;
772 #endif
773 }
775 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
776 int fd = open_library_on_path(name, g_ld_library_paths);
777 if (fd == -1) {
778 fd = open_library_on_path(name, kDefaultLdPaths);
779 }
780 return fd;
781 }
783 template<typename F>
784 static void for_each_dt_needed(const soinfo* si, F action) {
785 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
786 if (d->d_tag == DT_NEEDED) {
787 action(si->get_string(d->d_un.d_val));
788 }
789 }
790 }
792 static soinfo* load_library(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
793 int fd = -1;
794 off64_t file_offset = 0;
795 ScopedFd file_guard(-1);
797 if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
798 fd = extinfo->library_fd;
799 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
800 file_offset = extinfo->library_fd_offset;
801 }
802 } else {
803 // Open the file.
804 fd = open_library(name);
805 if (fd == -1) {
806 DL_ERR("library \"%s\" not found", name);
807 return nullptr;
808 }
810 file_guard.reset(fd);
811 }
813 if ((file_offset % PAGE_SIZE) != 0) {
814 DL_ERR("file offset for the library \"%s\" is not page-aligned: %" PRId64, name, file_offset);
815 return nullptr;
816 }
818 struct stat file_stat;
819 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
820 DL_ERR("unable to stat file for the library \"%s\": %s", name, strerror(errno));
821 return nullptr;
822 }
824 // Check for symlink and other situations where
825 // file can have different names.
826 for (soinfo* si = solist; si != nullptr; si = si->next) {
827 if (si->get_st_dev() != 0 &&
828 si->get_st_ino() != 0 &&
829 si->get_st_dev() == file_stat.st_dev &&
830 si->get_st_ino() == file_stat.st_ino &&
831 si->get_file_offset() == file_offset) {
832 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
833 return si;
834 }
835 }
837 if ((rtld_flags & RTLD_NOLOAD) != 0) {
838 DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
839 return nullptr;
840 }
842 // Read the ELF header and load the segments.
843 ElfReader elf_reader(name, fd, file_offset);
844 if (!elf_reader.Load(extinfo)) {
845 return nullptr;
846 }
848 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat, file_offset, rtld_flags);
849 if (si == nullptr) {
850 return nullptr;
851 }
852 si->base = elf_reader.load_start();
853 si->size = elf_reader.load_size();
854 si->load_bias = elf_reader.load_bias();
855 si->phnum = elf_reader.phdr_count();
856 si->phdr = elf_reader.loaded_phdr();
858 if (!si->PrelinkImage()) {
859 soinfo_free(si);
860 return nullptr;
861 }
863 for_each_dt_needed(si, [&] (const char* name) {
864 load_tasks.push_back(LoadTask::create(name, si));
865 });
867 return si;
868 }
870 static soinfo *find_loaded_library_by_name(const char* name) {
871 const char* search_name = SEARCH_NAME(name);
872 for (soinfo* si = solist; si != nullptr; si = si->next) {
873 if (!strcmp(search_name, si->name)) {
874 return si;
875 }
876 }
877 return nullptr;
878 }
880 static soinfo* find_library_internal(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
882 soinfo* si = find_loaded_library_by_name(name);
884 // Library might still be loaded, the accurate detection
885 // of this fact is done by load_library.
886 if (si == nullptr) {
887 TRACE("[ '%s' has not been found by name. Trying harder...]", name);
888 si = load_library(load_tasks, name, rtld_flags, extinfo);
889 }
891 return si;
892 }
894 static void soinfo_unload(soinfo* si);
896 static bool is_recursive(soinfo* si, soinfo* parent) {
897 if (parent == nullptr) {
898 return false;
899 }
901 if (si == parent) {
902 DL_ERR("recursive link to \"%s\"", si->name);
903 return true;
904 }
906 return !parent->get_parents().visit([&](soinfo* grandparent) {
907 return !is_recursive(si, grandparent);
908 });
909 }
911 // TODO: this is slightly unusual way to construct
912 // the global group for relocation. Not every RTLD_GLOBAL
913 // library is included in this group for backwards-compatibility
914 // reasons.
915 //
916 // This group consists of the main executable, LD_PRELOADs
917 // and libraries with the DF_1_GLOBAL flag set.
918 static soinfo::soinfo_list_t make_global_group() {
919 soinfo::soinfo_list_t global_group;
920 for (soinfo* si = somain; si != nullptr; si = si->next) {
921 if ((si->get_dt_flags_1() & DF_1_GLOBAL) != 0) {
922 global_group.push_back(si);
923 }
924 }
926 return global_group;
927 }
929 static bool find_libraries(soinfo* start_with, const char* const library_names[], size_t library_names_count, soinfo* soinfos[],
930 soinfo* ld_preloads[], size_t ld_preloads_count, int rtld_flags, const android_dlextinfo* extinfo) {
931 // Step 0: prepare.
932 LoadTaskList load_tasks;
933 for (size_t i = 0; i < library_names_count; ++i) {
934 const char* name = library_names[i];
935 load_tasks.push_back(LoadTask::create(name, start_with));
936 }
938 // Construct global_group.
939 soinfo::soinfo_list_t global_group = make_global_group();
941 // If soinfos array is null allocate one on stack.
942 // The array is needed in case of failure; for example
943 // when library_names[] = {libone.so, libtwo.so} and libone.so
944 // is loaded correctly but libtwo.so failed for some reason.
945 // In this case libone.so should be unloaded on return.
946 // See also implementation of failure_guard below.
948 if (soinfos == nullptr) {
949 size_t soinfos_size = sizeof(soinfo*)*library_names_count;
950 soinfos = reinterpret_cast<soinfo**>(alloca(soinfos_size));
951 memset(soinfos, 0, soinfos_size);
952 }
954 // list of libraries to link - see step 2.
955 size_t soinfos_count = 0;
957 auto failure_guard = make_scope_guard([&]() {
958 // Housekeeping
959 load_tasks.for_each([] (LoadTask* t) {
960 LoadTask::deleter(t);
961 });
963 for (size_t i = 0; i<soinfos_count; ++i) {
964 soinfo_unload(soinfos[i]);
965 }
966 });
968 // Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
969 for (LoadTask::unique_ptr task(load_tasks.pop_front()); task.get() != nullptr; task.reset(load_tasks.pop_front())) {
970 soinfo* si = find_library_internal(load_tasks, task->get_name(), rtld_flags, extinfo);
971 if (si == nullptr) {
972 return false;
973 }
975 soinfo* needed_by = task->get_needed_by();
977 if (is_recursive(si, needed_by)) {
978 return false;
979 }
981 si->ref_count++;
982 if (needed_by != nullptr) {
983 needed_by->add_child(si);
984 }
986 // When ld_preloads is not null, the first
987 // ld_preloads_count libs are in fact ld_preloads.
988 if (ld_preloads != nullptr && soinfos_count < ld_preloads_count) {
989 // Add LD_PRELOADed libraries to the global group for future runs.
990 // There is no need to explicitly add them to the global group
991 // for this run because they are going to appear in the local
992 // group in the correct order.
993 si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
994 ld_preloads[soinfos_count] = si;
995 }
997 if (soinfos_count < library_names_count) {
998 soinfos[soinfos_count++] = si;
999 }
1000 }
1002 // Step 2: link libraries.
1003 soinfo::soinfo_list_t local_group;
1004 walk_dependencies_tree(
1005 start_with == nullptr ? soinfos : &start_with,
1006 start_with == nullptr ? soinfos_count : 1,
1007 [&] (soinfo* si) {
1008 local_group.push_back(si);
1009 return true;
1010 });
1012 bool linked = local_group.visit([&](soinfo* si) {
1013 if ((si->flags & FLAG_LINKED) == 0) {
1014 if (!si->LinkImage(global_group, local_group, extinfo)) {
1015 return false;
1016 }
1017 si->flags |= FLAG_LINKED;
1018 }
1020 return true;
1021 });
1023 if (linked) {
1024 failure_guard.disable();
1025 }
1027 return linked;
1028 }
1030 static soinfo* find_library(const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
1031 if (name == nullptr) {
1032 somain->ref_count++;
1033 return somain;
1034 }
1036 soinfo* si;
1038 if (!find_libraries(nullptr, &name, 1, &si, nullptr, 0, rtld_flags, extinfo)) {
1039 return nullptr;
1040 }
1042 return si;
1043 }
1045 static void soinfo_unload(soinfo* si) {
1046 if (!si->can_unload()) {
1047 TRACE("not unloading '%s' - the binary is flagged with NODELETE", si->name);
1048 return;
1049 }
1051 if (si->ref_count == 1) {
1052 TRACE("unloading '%s'", si->name);
1053 si->CallDestructors();
1055 if (si->has_min_version(0)) {
1056 soinfo* child = nullptr;
1057 while ((child = si->get_children().pop_front()) != nullptr) {
1058 TRACE("%s needs to unload %s", si->name, child->name);
1059 soinfo_unload(child);
1060 }
1061 } else {
1062 for_each_dt_needed(si, [&] (const char* library_name) {
1063 TRACE("deprecated (old format of soinfo): %s needs to unload %s", si->name, library_name);
1064 soinfo* needed = find_library(library_name, RTLD_NOLOAD, nullptr);
1065 if (needed != nullptr) {
1066 soinfo_unload(needed);
1067 } else {
1068 // Not found: for example if symlink was deleted between dlopen and dlclose
1069 // Since we cannot really handle errors at this point - print and continue.
1070 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name);
1071 }
1072 });
1073 }
1075 notify_gdb_of_unload(si);
1076 si->ref_count = 0;
1077 soinfo_free(si);
1078 } else {
1079 si->ref_count--;
1080 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
1081 }
1082 }
1084 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
1085 // Use basic string manipulation calls to avoid snprintf.
1086 // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
1087 // When debug malloc is enabled, this call returns 0. This in turn causes
1088 // snprintf to do nothing, which causes libraries to fail to load.
1089 // See b/17302493 for further details.
1090 // Once the above bug is fixed, this code can be modified to use
1091 // snprintf again.
1092 size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
1093 if (buffer_size < required_len) {
1094 __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu",
1095 buffer_size, required_len);
1096 }
1097 char* end = stpcpy(buffer, kDefaultLdPaths[0]);
1098 *end = ':';
1099 strcpy(end + 1, kDefaultLdPaths[1]);
1100 }
1102 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
1103 if (!get_AT_SECURE()) {
1104 parse_LD_LIBRARY_PATH(ld_library_path);
1105 }
1106 }
1108 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
1109 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
1110 DL_ERR("invalid flags to dlopen: %x", flags);
1111 return nullptr;
1112 }
1113 if (extinfo != nullptr) {
1114 if ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0) {
1115 DL_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
1116 return nullptr;
1117 }
1118 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
1119 (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
1120 DL_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET without ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
1121 return nullptr;
1122 }
1123 }
1124 protect_data(PROT_READ | PROT_WRITE);
1125 soinfo* si = find_library(name, flags, extinfo);
1126 if (si != nullptr) {
1127 si->CallConstructors();
1128 }
1129 protect_data(PROT_READ);
1130 return si;
1131 }
1133 void do_dlclose(soinfo* si) {
1134 protect_data(PROT_READ | PROT_WRITE);
1135 soinfo_unload(si);
1136 protect_data(PROT_READ);
1137 }
1139 static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
1140 typedef ElfW(Addr) (*ifunc_resolver_t)(void);
1141 ifunc_resolver_t ifunc_resolver = reinterpret_cast<ifunc_resolver_t>(resolver_addr);
1142 ElfW(Addr) ifunc_addr = ifunc_resolver();
1143 TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p", ifunc_resolver, reinterpret_cast<void*>(ifunc_addr));
1145 return ifunc_addr;
1146 }
1148 #if defined(USE_RELA)
1149 int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& global_group, const soinfo_list_t& local_group) {
1150 for (size_t idx = 0; idx < count; ++idx, ++rela) {
1151 unsigned type = ELFW(R_TYPE)(rela->r_info);
1152 unsigned sym = ELFW(R_SYM)(rela->r_info);
1153 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + load_bias);
1154 ElfW(Addr) sym_addr = 0;
1155 const char* sym_name = nullptr;
1157 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1158 if (type == 0) { // R_*_NONE
1159 continue;
1160 }
1162 ElfW(Sym)* s = nullptr;
1163 soinfo* lsi = nullptr;
1165 if (sym != 0) {
1166 sym_name = get_string(symtab[sym].st_name);
1167 s = soinfo_do_lookup(this, sym_name, &lsi, global_group,local_group);
1168 if (s == nullptr) {
1169 // We only allow an undefined symbol if this is a weak reference...
1170 s = &symtab[sym];
1171 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1172 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1173 return -1;
1174 }
1176 /* IHI0044C AAELF 4.5.1.1:
1178 Libraries are not searched to resolve weak references.
1179 It is not an error for a weak reference to remain unsatisfied.
1181 During linking, the value of an undefined weak reference is:
1182 - Zero if the relocation type is absolute
1183 - The address of the place if the relocation is pc-relative
1184 - The address of nominal base address if the relocation
1185 type is base-relative.
1186 */
1188 switch (type) {
1189 #if defined(__aarch64__)
1190 case R_AARCH64_JUMP_SLOT:
1191 case R_AARCH64_GLOB_DAT:
1192 case R_AARCH64_ABS64:
1193 case R_AARCH64_ABS32:
1194 case R_AARCH64_ABS16:
1195 case R_AARCH64_RELATIVE:
1196 case R_AARCH64_IRELATIVE:
1197 /*
1198 * The sym_addr was initialized to be zero above, or the relocation
1199 * code below does not care about value of sym_addr.
1200 * No need to do anything.
1201 */
1202 break;
1203 #elif defined(__x86_64__)
1204 case R_X86_64_JUMP_SLOT:
1205 case R_X86_64_GLOB_DAT:
1206 case R_X86_64_32:
1207 case R_X86_64_64:
1208 case R_X86_64_RELATIVE:
1209 case R_X86_64_IRELATIVE:
1210 // No need to do anything.
1211 break;
1212 case R_X86_64_PC32:
1213 sym_addr = reloc;
1214 break;
1215 #endif
1216 default:
1217 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
1218 return -1;
1219 }
1220 } else {
1221 // We got a definition.
1222 sym_addr = lsi->resolve_symbol_address(s);
1223 }
1224 count_relocation(kRelocSymbol);
1225 }
1227 switch (type) {
1228 #if defined(__aarch64__)
1229 case R_AARCH64_JUMP_SLOT:
1230 count_relocation(kRelocAbsolute);
1231 MARK(rela->r_offset);
1232 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
1233 reloc, (sym_addr + rela->r_addend), sym_name);
1234 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1235 break;
1236 case R_AARCH64_GLOB_DAT:
1237 count_relocation(kRelocAbsolute);
1238 MARK(rela->r_offset);
1239 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
1240 reloc, (sym_addr + rela->r_addend), sym_name);
1241 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1242 break;
1243 case R_AARCH64_ABS64:
1244 count_relocation(kRelocAbsolute);
1245 MARK(rela->r_offset);
1246 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
1247 reloc, (sym_addr + rela->r_addend), sym_name);
1248 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1249 break;
1250 case R_AARCH64_ABS32:
1251 count_relocation(kRelocAbsolute);
1252 MARK(rela->r_offset);
1253 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
1254 reloc, (sym_addr + rela->r_addend), sym_name);
1255 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1256 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1257 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1258 } else {
1259 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1260 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1261 static_cast<ElfW(Addr)>(INT32_MIN),
1262 static_cast<ElfW(Addr)>(UINT32_MAX));
1263 return -1;
1264 }
1265 break;
1266 case R_AARCH64_ABS16:
1267 count_relocation(kRelocAbsolute);
1268 MARK(rela->r_offset);
1269 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
1270 reloc, (sym_addr + rela->r_addend), sym_name);
1271 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1272 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1273 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1274 } else {
1275 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1276 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1277 static_cast<ElfW(Addr)>(INT16_MIN),
1278 static_cast<ElfW(Addr)>(UINT16_MAX));
1279 return -1;
1280 }
1281 break;
1282 case R_AARCH64_PREL64:
1283 count_relocation(kRelocRelative);
1284 MARK(rela->r_offset);
1285 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
1286 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1287 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
1288 break;
1289 case R_AARCH64_PREL32:
1290 count_relocation(kRelocRelative);
1291 MARK(rela->r_offset);
1292 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
1293 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1294 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1295 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1296 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1297 } else {
1298 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1299 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1300 static_cast<ElfW(Addr)>(INT32_MIN),
1301 static_cast<ElfW(Addr)>(UINT32_MAX));
1302 return -1;
1303 }
1304 break;
1305 case R_AARCH64_PREL16:
1306 count_relocation(kRelocRelative);
1307 MARK(rela->r_offset);
1308 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
1309 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1310 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1311 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1312 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1313 } else {
1314 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1315 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1316 static_cast<ElfW(Addr)>(INT16_MIN),
1317 static_cast<ElfW(Addr)>(UINT16_MAX));
1318 return -1;
1319 }
1320 break;
1322 case R_AARCH64_RELATIVE:
1323 count_relocation(kRelocRelative);
1324 MARK(rela->r_offset);
1325 if (sym) {
1326 DL_ERR("odd RELATIVE form...");
1327 return -1;
1328 }
1329 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
1330 reloc, (base + rela->r_addend));
1331 *reinterpret_cast<ElfW(Addr)*>(reloc) = (base + rela->r_addend);
1332 break;
1334 case R_AARCH64_IRELATIVE:
1335 count_relocation(kRelocRelative);
1336 MARK(rela->r_offset);
1337 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1338 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1339 break;
1341 case R_AARCH64_COPY:
1342 /*
1343 * ET_EXEC is not supported so this should not happen.
1344 *
1345 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1346 *
1347 * Section 4.7.1.10 "Dynamic relocations"
1348 * R_AARCH64_COPY may only appear in executable objects where e_type is
1349 * set to ET_EXEC.
1350 */
1351 DL_ERR("%s R_AARCH64_COPY relocations are not supported", name);
1352 return -1;
1353 case R_AARCH64_TLS_TPREL64:
1354 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
1355 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1356 break;
1357 case R_AARCH64_TLS_DTPREL32:
1358 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
1359 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1360 break;
1361 #elif defined(__x86_64__)
1362 case R_X86_64_JUMP_SLOT:
1363 count_relocation(kRelocAbsolute);
1364 MARK(rela->r_offset);
1365 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1366 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1367 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1368 break;
1369 case R_X86_64_GLOB_DAT:
1370 count_relocation(kRelocAbsolute);
1371 MARK(rela->r_offset);
1372 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1373 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1374 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1375 break;
1376 case R_X86_64_RELATIVE:
1377 count_relocation(kRelocRelative);
1378 MARK(rela->r_offset);
1379 if (sym) {
1380 DL_ERR("odd RELATIVE form...");
1381 return -1;
1382 }
1383 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
1384 static_cast<size_t>(base));
1385 *reinterpret_cast<ElfW(Addr)*>(reloc) = base + rela->r_addend;
1386 break;
1387 case R_X86_64_IRELATIVE:
1388 count_relocation(kRelocRelative);
1389 MARK(rela->r_offset);
1390 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1391 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1392 break;
1393 case R_X86_64_32:
1394 count_relocation(kRelocRelative);
1395 MARK(rela->r_offset);
1396 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1397 static_cast<size_t>(sym_addr), sym_name);
1398 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1399 break;
1400 case R_X86_64_64:
1401 count_relocation(kRelocRelative);
1402 MARK(rela->r_offset);
1403 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1404 static_cast<size_t>(sym_addr), sym_name);
1405 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1406 break;
1407 case R_X86_64_PC32:
1408 count_relocation(kRelocRelative);
1409 MARK(rela->r_offset);
1410 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
1411 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
1412 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
1413 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc;
1414 break;
1415 #endif
1417 default:
1418 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
1419 return -1;
1420 }
1421 }
1422 return 0;
1423 }
1425 #else // REL, not RELA.
1426 int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& global_group, const soinfo_list_t& local_group) {
1427 for (size_t idx = 0; idx < count; ++idx, ++rel) {
1428 unsigned type = ELFW(R_TYPE)(rel->r_info);
1429 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
1430 unsigned sym = ELFW(R_SYM)(rel->r_info);
1431 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
1432 ElfW(Addr) sym_addr = 0;
1433 const char* sym_name = nullptr;
1435 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1436 if (type == 0) { // R_*_NONE
1437 continue;
1438 }
1440 ElfW(Sym)* s = nullptr;
1441 soinfo* lsi = nullptr;
1443 if (sym != 0) {
1444 sym_name = get_string(symtab[sym].st_name);
1445 s = soinfo_do_lookup(this, sym_name, &lsi, global_group, local_group);
1446 if (s == nullptr) {
1447 // We only allow an undefined symbol if this is a weak reference...
1448 s = &symtab[sym];
1449 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1450 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1451 return -1;
1452 }
1454 /* IHI0044C AAELF 4.5.1.1:
1456 Libraries are not searched to resolve weak references.
1457 It is not an error for a weak reference to remain
1458 unsatisfied.
1460 During linking, the value of an undefined weak reference is:
1461 - Zero if the relocation type is absolute
1462 - The address of the place if the relocation is pc-relative
1463 - The address of nominal base address if the relocation
1464 type is base-relative.
1465 */
1467 switch (type) {
1468 #if defined(__arm__)
1469 case R_ARM_JUMP_SLOT:
1470 case R_ARM_GLOB_DAT:
1471 case R_ARM_ABS32:
1472 case R_ARM_RELATIVE: /* Don't care. */
1473 // sym_addr was initialized to be zero above or relocation
1474 // code below does not care about value of sym_addr.
1475 // No need to do anything.
1476 break;
1477 #elif defined(__i386__)
1478 case R_386_JMP_SLOT:
1479 case R_386_GLOB_DAT:
1480 case R_386_32:
1481 case R_386_RELATIVE: /* Don't care. */
1482 case R_386_IRELATIVE:
1483 // sym_addr was initialized to be zero above or relocation
1484 // code below does not care about value of sym_addr.
1485 // No need to do anything.
1486 break;
1487 case R_386_PC32:
1488 sym_addr = reloc;
1489 break;
1490 #endif
1492 #if defined(__arm__)
1493 case R_ARM_COPY:
1494 // Fall through. Can't really copy if weak symbol is not found at run-time.
1495 #endif
1496 default:
1497 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
1498 return -1;
1499 }
1500 } else {
1501 // We got a definition.
1502 sym_addr = lsi->resolve_symbol_address(s);
1503 }
1504 count_relocation(kRelocSymbol);
1505 }
1507 switch (type) {
1508 #if defined(__arm__)
1509 case R_ARM_JUMP_SLOT:
1510 count_relocation(kRelocAbsolute);
1511 MARK(rel->r_offset);
1512 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1513 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1514 break;
1515 case R_ARM_GLOB_DAT:
1516 count_relocation(kRelocAbsolute);
1517 MARK(rel->r_offset);
1518 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1519 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1520 break;
1521 case R_ARM_ABS32:
1522 count_relocation(kRelocAbsolute);
1523 MARK(rel->r_offset);
1524 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
1525 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1526 break;
1527 case R_ARM_REL32:
1528 count_relocation(kRelocRelative);
1529 MARK(rel->r_offset);
1530 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
1531 reloc, sym_addr, rel->r_offset, sym_name);
1532 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
1533 break;
1534 case R_ARM_COPY:
1535 /*
1536 * ET_EXEC is not supported so this should not happen.
1537 *
1538 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1539 *
1540 * Section 4.7.1.10 "Dynamic relocations"
1541 * R_ARM_COPY may only appear in executable objects where e_type is
1542 * set to ET_EXEC.
1543 */
1544 DL_ERR("%s R_ARM_COPY relocations are not supported", name);
1545 return -1;
1546 #elif defined(__i386__)
1547 case R_386_JMP_SLOT:
1548 count_relocation(kRelocAbsolute);
1549 MARK(rel->r_offset);
1550 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1551 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1552 break;
1553 case R_386_GLOB_DAT:
1554 count_relocation(kRelocAbsolute);
1555 MARK(rel->r_offset);
1556 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1557 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1558 break;
1559 case R_386_32:
1560 count_relocation(kRelocRelative);
1561 MARK(rel->r_offset);
1562 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
1563 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1564 break;
1565 case R_386_PC32:
1566 count_relocation(kRelocRelative);
1567 MARK(rel->r_offset);
1568 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
1569 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
1570 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
1571 break;
1572 #elif defined(__mips__)
1573 case R_MIPS_REL32:
1574 #if defined(__LP64__)
1575 // MIPS Elf64_Rel entries contain compound relocations
1576 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
1577 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
1578 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
1579 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
1580 type, (unsigned)ELF64_R_TYPE2(rel->r_info),
1581 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
1582 return -1;
1583 }
1584 #endif
1585 count_relocation(kRelocAbsolute);
1586 MARK(rel->r_offset);
1587 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
1588 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
1589 if (s) {
1590 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1591 } else {
1592 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1593 }
1594 break;
1595 #endif
1597 #if defined(__arm__)
1598 case R_ARM_RELATIVE:
1599 #elif defined(__i386__)
1600 case R_386_RELATIVE:
1601 #endif
1602 count_relocation(kRelocRelative);
1603 MARK(rel->r_offset);
1604 if (sym) {
1605 DL_ERR("odd RELATIVE form...");
1606 return -1;
1607 }
1608 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
1609 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1610 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1611 break;
1612 #if defined(__i386__)
1613 case R_386_IRELATIVE:
1614 count_relocation(kRelocRelative);
1615 MARK(rel->r_offset);
1616 TRACE_TYPE(RELO, "RELO IRELATIVE %p <- %p", reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1617 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + *reinterpret_cast<ElfW(Addr)*>(reloc));
1618 break;
1619 #endif
1621 default:
1622 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
1623 return -1;
1624 }
1625 }
1626 return 0;
1627 }
1628 #endif
1630 #if defined(__mips__)
1631 static bool mips_relocate_got(soinfo* si, const soinfo::soinfo_list_t& global_group, const soinfo::soinfo_list_t& local_group) {
1632 ElfW(Addr)** got = si->plt_got;
1633 if (got == nullptr) {
1634 return true;
1635 }
1636 unsigned local_gotno = si->mips_local_gotno;
1637 unsigned gotsym = si->mips_gotsym;
1638 unsigned symtabno = si->mips_symtabno;
1639 ElfW(Sym)* symtab = si->symtab;
1641 // got[0] is the address of the lazy resolver function.
1642 // got[1] may be used for a GNU extension.
1643 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
1644 // FIXME: maybe this should be in a separate routine?
1645 if ((si->flags & FLAG_LINKER) == 0) {
1646 size_t g = 0;
1647 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
1648 if (reinterpret_cast<intptr_t>(got[g]) < 0) {
1649 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
1650 }
1651 // Relocate the local GOT entries.
1652 for (; g < local_gotno; g++) {
1653 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
1654 }
1655 }
1657 // Now for the global GOT entries...
1658 ElfW(Sym)* sym = symtab + gotsym;
1659 got = si->plt_got + local_gotno;
1660 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
1661 // This is an undefined reference... try to locate it.
1662 const char* sym_name = si->get_string(sym->st_name);
1663 soinfo* lsi = nullptr;
1664 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, global_group, local_group);
1665 if (s == nullptr) {
1666 // We only allow an undefined symbol if this is a weak reference.
1667 s = &symtab[g];
1668 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1669 DL_ERR("cannot locate \"%s\"...", sym_name);
1670 return false;
1671 }
1672 *got = 0;
1673 } else {
1674 // FIXME: is this sufficient?
1675 // For reference see NetBSD link loader
1676 // 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
1677 *got = reinterpret_cast<ElfW(Addr)*>(lsi->resolve_symbol_address(s));
1678 }
1679 }
1680 return true;
1681 }
1682 #endif
1684 void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
1685 if (functions == nullptr) {
1686 return;
1687 }
1689 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
1691 int begin = reverse ? (count - 1) : 0;
1692 int end = reverse ? -1 : count;
1693 int step = reverse ? -1 : 1;
1695 for (int i = begin; i != end; i += step) {
1696 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
1697 CallFunction("function", functions[i]);
1698 }
1700 TRACE("[ Done calling %s for '%s' ]", array_name, name);
1701 }
1703 void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
1704 if (function == nullptr || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
1705 return;
1706 }
1708 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
1709 function();
1710 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
1712 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
1713 // are still writable. This happens with our debug malloc (see http://b/7941716).
1714 protect_data(PROT_READ | PROT_WRITE);
1715 }
1717 void soinfo::CallPreInitConstructors() {
1718 // DT_PREINIT_ARRAY functions are called before any other constructors for executables,
1719 // but ignored in a shared library.
1720 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
1721 }
1723 void soinfo::CallConstructors() {
1724 if (constructors_called) {
1725 return;
1726 }
1728 // We set constructors_called before actually calling the constructors, otherwise it doesn't
1729 // protect against recursive constructor calls. One simple example of constructor recursion
1730 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
1731 // 1. The program depends on libc, so libc's constructor is called here.
1732 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
1733 // 3. dlopen() calls the constructors on the newly created
1734 // soinfo for libc_malloc_debug_leak.so.
1735 // 4. The debug .so depends on libc, so CallConstructors is
1736 // called again with the libc soinfo. If it doesn't trigger the early-
1737 // out above, the libc constructor will be called again (recursively!).
1738 constructors_called = true;
1740 if ((flags & FLAG_EXE) == 0 && preinit_array != nullptr) {
1741 // The GNU dynamic linker silently ignores these, but we warn the developer.
1742 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
1743 name, preinit_array_count);
1744 }
1746 get_children().for_each([] (soinfo* si) {
1747 si->CallConstructors();
1748 });
1750 TRACE("\"%s\": calling constructors", name);
1752 // DT_INIT should be called before DT_INIT_ARRAY if both are present.
1753 CallFunction("DT_INIT", init_func);
1754 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
1755 }
1757 void soinfo::CallDestructors() {
1758 if (!constructors_called) {
1759 return;
1760 }
1761 TRACE("\"%s\": calling destructors", name);
1763 // DT_FINI_ARRAY must be parsed in reverse order.
1764 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
1766 // DT_FINI should be called after DT_FINI_ARRAY if both are present.
1767 CallFunction("DT_FINI", fini_func);
1769 // This is needed on second call to dlopen
1770 // after library has been unloaded with RTLD_NODELETE
1771 constructors_called = false;
1772 }
1774 void soinfo::add_child(soinfo* child) {
1775 if (has_min_version(0)) {
1776 child->parents.push_back(this);
1777 this->children.push_back(child);
1778 }
1779 }
1781 void soinfo::remove_all_links() {
1782 if (!has_min_version(0)) {
1783 return;
1784 }
1786 // 1. Untie connected soinfos from 'this'.
1787 children.for_each([&] (soinfo* child) {
1788 child->parents.remove_if([&] (const soinfo* parent) {
1789 return parent == this;
1790 });
1791 });
1793 parents.for_each([&] (soinfo* parent) {
1794 parent->children.remove_if([&] (const soinfo* child) {
1795 return child == this;
1796 });
1797 });
1799 // 2. Once everything untied - clear local lists.
1800 parents.clear();
1801 children.clear();
1802 }
1804 dev_t soinfo::get_st_dev() const {
1805 if (has_min_version(0)) {
1806 return st_dev;
1807 }
1809 return 0;
1810 };
1812 ino_t soinfo::get_st_ino() const {
1813 if (has_min_version(0)) {
1814 return st_ino;
1815 }
1817 return 0;
1818 }
1820 off64_t soinfo::get_file_offset() const {
1821 if (has_min_version(1)) {
1822 return file_offset;
1823 }
1825 return 0;
1826 }
1828 uint32_t soinfo::get_rtld_flags() const {
1829 if (has_min_version(1)) {
1830 return rtld_flags;
1831 }
1833 return 0;
1834 }
1836 uint32_t soinfo::get_dt_flags_1() const {
1837 if (has_min_version(1)) {
1838 return dt_flags_1;
1839 }
1841 return 0;
1842 }
1843 void soinfo::set_dt_flags_1(uint32_t dt_flags_1) {
1844 if (has_min_version(1)) {
1845 if ((dt_flags_1 & DF_1_GLOBAL) != 0) {
1846 rtld_flags |= RTLD_GLOBAL;
1847 }
1849 if ((dt_flags_1 & DF_1_NODELETE) != 0) {
1850 rtld_flags |= RTLD_NODELETE;
1851 }
1853 this->dt_flags_1 = dt_flags_1;
1854 }
1855 }
1857 // This is a return on get_children()/get_parents() if
1858 // 'this->flags' does not have FLAG_NEW_SOINFO set.
1859 static soinfo::soinfo_list_t g_empty_list;
1861 soinfo::soinfo_list_t& soinfo::get_children() {
1862 if (has_min_version(0)) {
1863 return this->children;
1864 }
1866 return g_empty_list;
1867 }
1869 soinfo::soinfo_list_t& soinfo::get_parents() {
1870 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1871 return g_empty_list;
1872 }
1874 return this->parents;
1875 }
1877 ElfW(Addr) soinfo::resolve_symbol_address(ElfW(Sym)* s) {
1878 if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
1879 return call_ifunc_resolver(s->st_value + load_bias);
1880 }
1882 return static_cast<ElfW(Addr)>(s->st_value + load_bias);
1883 }
1885 const char* soinfo::get_string(ElfW(Word) index) const {
1886 if (has_min_version(1) && (index >= strtab_size)) {
1887 __libc_fatal("%s: strtab out of bounds error; STRSZ=%zd, name=%d", name, strtab_size, index);
1888 }
1890 return strtab + index;
1891 }
1893 bool soinfo::can_unload() const {
1894 return (get_rtld_flags() & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
1895 }
1897 /* Force any of the closed stdin, stdout and stderr to be associated with
1898 /dev/null. */
1899 static int nullify_closed_stdio() {
1900 int dev_null, i, status;
1901 int return_value = 0;
1903 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
1904 if (dev_null < 0) {
1905 DL_ERR("cannot open /dev/null: %s", strerror(errno));
1906 return -1;
1907 }
1908 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
1910 /* If any of the stdio file descriptors is valid and not associated
1911 with /dev/null, dup /dev/null to it. */
1912 for (i = 0; i < 3; i++) {
1913 /* If it is /dev/null already, we are done. */
1914 if (i == dev_null) {
1915 continue;
1916 }
1918 TRACE("[ Nullifying stdio file descriptor %d]", i);
1919 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
1921 /* If file is opened, we are good. */
1922 if (status != -1) {
1923 continue;
1924 }
1926 /* The only error we allow is that the file descriptor does not
1927 exist, in which case we dup /dev/null to it. */
1928 if (errno != EBADF) {
1929 DL_ERR("fcntl failed: %s", strerror(errno));
1930 return_value = -1;
1931 continue;
1932 }
1934 /* Try dupping /dev/null to this stdio file descriptor and
1935 repeat if there is a signal. Note that any errors in closing
1936 the stdio descriptor are lost. */
1937 status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
1938 if (status < 0) {
1939 DL_ERR("dup2 failed: %s", strerror(errno));
1940 return_value = -1;
1941 continue;
1942 }
1943 }
1945 /* If /dev/null is not one of the stdio file descriptors, close it. */
1946 if (dev_null > 2) {
1947 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
1948 status = TEMP_FAILURE_RETRY(close(dev_null));
1949 if (status == -1) {
1950 DL_ERR("close failed: %s", strerror(errno));
1951 return_value = -1;
1952 }
1953 }
1955 return return_value;
1956 }
1958 bool soinfo::PrelinkImage() {
1959 /* Extract dynamic section */
1960 ElfW(Word) dynamic_flags = 0;
1961 phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
1963 /* We can't log anything until the linker is relocated */
1964 bool relocating_linker = (flags & FLAG_LINKER) != 0;
1965 if (!relocating_linker) {
1966 INFO("[ linking %s ]", name);
1967 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags);
1968 }
1970 if (dynamic == nullptr) {
1971 if (!relocating_linker) {
1972 DL_ERR("missing PT_DYNAMIC in \"%s\"", name);
1973 }
1974 return false;
1975 } else {
1976 if (!relocating_linker) {
1977 DEBUG("dynamic = %p", dynamic);
1978 }
1979 }
1981 #if defined(__arm__)
1982 (void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
1983 &ARM_exidx, &ARM_exidx_count);
1984 #endif
1986 // Extract useful information from dynamic section.
1987 uint32_t needed_count = 0;
1988 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
1989 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
1990 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1991 switch (d->d_tag) {
1992 case DT_SONAME:
1993 // TODO: glibc dynamic linker uses this name for
1994 // initial library lookup; consider doing the same here.
1995 break;
1997 case DT_HASH:
1998 nbucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
1999 nchain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
2000 bucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
2001 chain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket * 4);
2002 break;
2004 case DT_STRTAB:
2005 strtab = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
2006 break;
2008 case DT_STRSZ:
2009 strtab_size = d->d_un.d_val;
2010 break;
2012 case DT_SYMTAB:
2013 symtab = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
2014 break;
2016 case DT_SYMENT:
2017 if (d->d_un.d_val != sizeof(ElfW(Sym))) {
2018 DL_ERR("invalid DT_SYMENT: %zd", static_cast<size_t>(d->d_un.d_val));
2019 return false;
2020 }
2021 break;
2023 case DT_PLTREL:
2024 #if defined(USE_RELA)
2025 if (d->d_un.d_val != DT_RELA) {
2026 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_RELA", name);
2027 return false;
2028 }
2029 #else
2030 if (d->d_un.d_val != DT_REL) {
2031 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_REL", name);
2032 return false;
2033 }
2034 #endif
2035 break;
2037 case DT_JMPREL:
2038 #if defined(USE_RELA)
2039 plt_rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2040 #else
2041 plt_rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2042 #endif
2043 break;
2045 case DT_PLTRELSZ:
2046 #if defined(USE_RELA)
2047 plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
2048 #else
2049 plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
2050 #endif
2051 break;
2053 case DT_PLTGOT:
2054 #if defined(__mips__)
2055 // Used by mips and mips64.
2056 plt_got = reinterpret_cast<ElfW(Addr)**>(load_bias + d->d_un.d_ptr);
2057 #endif
2058 // Ignore for other platforms... (because RTLD_LAZY is not supported)
2059 break;
2061 case DT_DEBUG:
2062 // Set the DT_DEBUG entry to the address of _r_debug for GDB
2063 // if the dynamic table is writable
2064 // FIXME: not working currently for N64
2065 // The flags for the LOAD and DYNAMIC program headers do not agree.
2066 // The LOAD section containing the dynamic table has been mapped as
2067 // read-only, but the DYNAMIC header claims it is writable.
2068 #if !(defined(__mips__) && defined(__LP64__))
2069 if ((dynamic_flags & PF_W) != 0) {
2070 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
2071 }
2072 break;
2073 #endif
2074 #if defined(USE_RELA)
2075 case DT_RELA:
2076 rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2077 break;
2079 case DT_RELASZ:
2080 rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
2081 break;
2083 case DT_RELAENT:
2084 if (d->d_un.d_val != sizeof(ElfW(Rela))) {
2085 DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
2086 return false;
2087 }
2088 break;
2090 // ignored (see DT_RELCOUNT comments for details)
2091 case DT_RELACOUNT:
2092 break;
2094 case DT_REL:
2095 DL_ERR("unsupported DT_REL in \"%s\"", name);
2096 return false;
2098 case DT_RELSZ:
2099 DL_ERR("unsupported DT_RELSZ in \"%s\"", name);
2100 return false;
2101 #else
2102 case DT_REL:
2103 rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2104 break;
2106 case DT_RELSZ:
2107 rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
2108 break;
2110 case DT_RELENT:
2111 if (d->d_un.d_val != sizeof(ElfW(Rel))) {
2112 DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
2113 return false;
2114 }
2115 break;
2117 // "Indicates that all RELATIVE relocations have been concatenated together,
2118 // and specifies the RELATIVE relocation count."
2119 //
2120 // TODO: Spec also mentions that this can be used to optimize relocation process;
2121 // Not currently used by bionic linker - ignored.
2122 case DT_RELCOUNT:
2123 break;
2124 case DT_RELA:
2125 DL_ERR("unsupported DT_RELA in \"%s\"", name);
2126 return false;
2127 #endif
2128 case DT_INIT:
2129 init_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2130 DEBUG("%s constructors (DT_INIT) found at %p", name, init_func);
2131 break;
2133 case DT_FINI:
2134 fini_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2135 DEBUG("%s destructors (DT_FINI) found at %p", name, fini_func);
2136 break;
2138 case DT_INIT_ARRAY:
2139 init_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2140 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", name, init_array);
2141 break;
2143 case DT_INIT_ARRAYSZ:
2144 init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2145 break;
2147 case DT_FINI_ARRAY:
2148 fini_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2149 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", name, fini_array);
2150 break;
2152 case DT_FINI_ARRAYSZ:
2153 fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2154 break;
2156 case DT_PREINIT_ARRAY:
2157 preinit_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2158 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", name, preinit_array);
2159 break;
2161 case DT_PREINIT_ARRAYSZ:
2162 preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2163 break;
2165 case DT_TEXTREL:
2166 #if defined(__LP64__)
2167 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2168 return false;
2169 #else
2170 has_text_relocations = true;
2171 break;
2172 #endif
2174 case DT_SYMBOLIC:
2175 has_DT_SYMBOLIC = true;
2176 break;
2178 case DT_NEEDED:
2179 ++needed_count;
2180 break;
2182 case DT_FLAGS:
2183 if (d->d_un.d_val & DF_TEXTREL) {
2184 #if defined(__LP64__)
2185 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2186 return false;
2187 #else
2188 has_text_relocations = true;
2189 #endif
2190 }
2191 if (d->d_un.d_val & DF_SYMBOLIC) {
2192 has_DT_SYMBOLIC = true;
2193 }
2194 break;
2196 case DT_FLAGS_1:
2197 set_dt_flags_1(d->d_un.d_val);
2199 if ((d->d_un.d_val & ~SUPPORTED_DT_FLAGS_1) != 0) {
2200 DL_WARN("Unsupported flags DT_FLAGS_1=%p", reinterpret_cast<void*>(d->d_un.d_val));
2201 }
2202 break;
2203 #if defined(__mips__)
2204 case DT_MIPS_RLD_MAP:
2205 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
2206 {
2207 r_debug** dp = reinterpret_cast<r_debug**>(load_bias + d->d_un.d_ptr);
2208 *dp = &_r_debug;
2209 }
2210 break;
2212 case DT_MIPS_RLD_VERSION:
2213 case DT_MIPS_FLAGS:
2214 case DT_MIPS_BASE_ADDRESS:
2215 case DT_MIPS_UNREFEXTNO:
2216 break;
2218 case DT_MIPS_SYMTABNO:
2219 mips_symtabno = d->d_un.d_val;
2220 break;
2222 case DT_MIPS_LOCAL_GOTNO:
2223 mips_local_gotno = d->d_un.d_val;
2224 break;
2226 case DT_MIPS_GOTSYM:
2227 mips_gotsym = d->d_un.d_val;
2228 break;
2229 #endif
2230 // Ignored: "Its use has been superseded by the DF_BIND_NOW flag"
2231 case DT_BIND_NOW:
2232 break;
2234 // Ignore: bionic does not support symbol versioning...
2235 case DT_VERSYM:
2236 case DT_VERDEF:
2237 case DT_VERDEFNUM:
2238 break;
2240 default:
2241 if (!relocating_linker) {
2242 DL_WARN("%s: unused DT entry: type %p arg %p", name,
2243 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
2244 }
2245 break;
2246 }
2247 }
2249 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
2250 reinterpret_cast<void*>(base), strtab, symtab);
2252 // Sanity checks.
2253 if (relocating_linker && needed_count != 0) {
2254 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
2255 return false;
2256 }
2257 if (nbucket == 0) {
2258 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", name);
2259 return false;
2260 }
2261 if (strtab == 0) {
2262 DL_ERR("empty/missing DT_STRTAB in \"%s\"", name);
2263 return false;
2264 }
2265 if (symtab == 0) {
2266 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", name);
2267 return false;
2268 }
2269 return true;
2270 }
2272 bool soinfo::LinkImage(const soinfo_list_t& global_group, const soinfo_list_t& local_group, const android_dlextinfo* extinfo) {
2274 #if !defined(__LP64__)
2275 if (has_text_relocations) {
2276 // Make segments writable to allow text relocations to work properly. We will later call
2277 // phdr_table_protect_segments() after all of them are applied and all constructors are run.
2278 DL_WARN("%s has text relocations. This is wasting memory and prevents "
2279 "security hardening. Please fix.", name);
2280 if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
2281 DL_ERR("can't unprotect loadable segments for \"%s\": %s",
2282 name, strerror(errno));
2283 return false;
2284 }
2285 }
2286 #endif
2288 #if defined(USE_RELA)
2289 if (rela != nullptr) {
2290 DEBUG("[ relocating %s ]", name);
2291 if (Relocate(rela, rela_count, global_group, local_group)) {
2292 return false;
2293 }
2294 }
2295 if (plt_rela != nullptr) {
2296 DEBUG("[ relocating %s plt ]", name);
2297 if (Relocate(plt_rela, plt_rela_count, global_group, local_group)) {
2298 return false;
2299 }
2300 }
2301 #else
2302 if (rel != nullptr) {
2303 DEBUG("[ relocating %s ]", name);
2304 if (Relocate(rel, rel_count, global_group, local_group)) {
2305 return false;
2306 }
2307 }
2308 if (plt_rel != nullptr) {
2309 DEBUG("[ relocating %s plt ]", name);
2310 if (Relocate(plt_rel, plt_rel_count, global_group, local_group)) {
2311 return false;
2312 }
2313 }
2314 #endif
2316 #if defined(__mips__)
2317 if (!mips_relocate_got(this, global_group, local_group)) {
2318 return false;
2319 }
2320 #endif
2322 DEBUG("[ finished linking %s ]", name);
2324 #if !defined(__LP64__)
2325 if (has_text_relocations) {
2326 // All relocations are done, we can protect our segments back to read-only.
2327 if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
2328 DL_ERR("can't protect segments for \"%s\": %s",
2329 name, strerror(errno));
2330 return false;
2331 }
2332 }
2333 #endif
2335 /* We can also turn on GNU RELRO protection */
2336 if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
2337 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
2338 name, strerror(errno));
2339 return false;
2340 }
2342 /* Handle serializing/sharing the RELRO segment */
2343 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
2344 if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
2345 extinfo->relro_fd) < 0) {
2346 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
2347 name, strerror(errno));
2348 return false;
2349 }
2350 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
2351 if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
2352 extinfo->relro_fd) < 0) {
2353 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
2354 name, strerror(errno));
2355 return false;
2356 }
2357 }
2359 notify_gdb_of_load(this);
2360 return true;
2361 }
2363 /*
2364 * This function add vdso to internal dso list.
2365 * It helps to stack unwinding through signal handlers.
2366 * Also, it makes bionic more like glibc.
2367 */
2368 static void add_vdso(KernelArgumentBlock& args __unused) {
2369 #if defined(AT_SYSINFO_EHDR)
2370 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
2371 if (ehdr_vdso == nullptr) {
2372 return;
2373 }
2375 soinfo* si = soinfo_alloc("[vdso]", nullptr, 0, 0);
2377 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
2378 si->phnum = ehdr_vdso->e_phnum;
2379 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
2380 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2381 si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
2383 si->PrelinkImage();
2384 si->LinkImage(g_empty_list, soinfo::soinfo_list_t::make_list(si), nullptr);
2385 #endif
2386 }
2388 /*
2389 * This is linker soinfo for GDB. See details below.
2390 */
2391 #if defined(__LP64__)
2392 #define LINKER_PATH "/system/bin/linker64"
2393 #else
2394 #define LINKER_PATH "/system/bin/linker"
2395 #endif
2396 static soinfo linker_soinfo_for_gdb(LINKER_PATH, nullptr, 0, 0);
2398 /* gdb expects the linker to be in the debug shared object list.
2399 * Without this, gdb has trouble locating the linker's ".text"
2400 * and ".plt" sections. Gdb could also potentially use this to
2401 * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
2402 * Don't use soinfo_alloc(), because the linker shouldn't
2403 * be on the soinfo list.
2404 */
2405 static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
2406 linker_soinfo_for_gdb.base = linker_base;
2408 /*
2409 * Set the dynamic field in the link map otherwise gdb will complain with
2410 * the following:
2411 * warning: .dynamic section for "/system/bin/linker" is not at the
2412 * expected address (wrong library or version mismatch?)
2413 */
2414 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
2415 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
2416 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
2417 &linker_soinfo_for_gdb.dynamic, nullptr);
2418 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
2419 }
2421 /*
2422 * This code is called after the linker has linked itself and
2423 * fixed it's own GOT. It is safe to make references to externs
2424 * and other non-local data at this point.
2425 */
2426 static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
2427 #if TIMING
2428 struct timeval t0, t1;
2429 gettimeofday(&t0, 0);
2430 #endif
2432 // Initialize environment functions, and get to the ELF aux vectors table.
2433 linker_env_init(args);
2435 // If this is a setuid/setgid program, close the security hole described in
2436 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2437 if (get_AT_SECURE()) {
2438 nullify_closed_stdio();
2439 }
2441 debuggerd_init();
2443 // Get a few environment variables.
2444 const char* LD_DEBUG = linker_env_get("LD_DEBUG");
2445 if (LD_DEBUG != nullptr) {
2446 g_ld_debug_verbosity = atoi(LD_DEBUG);
2447 }
2449 // Normally, these are cleaned by linker_env_init, but the test
2450 // doesn't cost us anything.
2451 const char* ldpath_env = nullptr;
2452 const char* ldpreload_env = nullptr;
2453 if (!get_AT_SECURE()) {
2454 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2455 ldpreload_env = linker_env_get("LD_PRELOAD");
2456 }
2458 INFO("[ android linker & debugger ]");
2460 soinfo* si = soinfo_alloc(args.argv[0], nullptr, 0, RTLD_GLOBAL);
2461 if (si == nullptr) {
2462 exit(EXIT_FAILURE);
2463 }
2465 /* bootstrap the link map, the main exe always needs to be first */
2466 si->flags |= FLAG_EXE;
2467 link_map* map = &(si->link_map_head);
2469 map->l_addr = 0;
2470 map->l_name = args.argv[0];
2471 map->l_prev = nullptr;
2472 map->l_next = nullptr;
2474 _r_debug.r_map = map;
2475 r_debug_tail = map;
2477 init_linker_info_for_gdb(linker_base);
2479 // Extract information passed from the kernel.
2480 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
2481 si->phnum = args.getauxval(AT_PHNUM);
2482 si->entry = args.getauxval(AT_ENTRY);
2484 /* Compute the value of si->base. We can't rely on the fact that
2485 * the first entry is the PHDR because this will not be true
2486 * for certain executables (e.g. some in the NDK unit test suite)
2487 */
2488 si->base = 0;
2489 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2490 si->load_bias = 0;
2491 for (size_t i = 0; i < si->phnum; ++i) {
2492 if (si->phdr[i].p_type == PT_PHDR) {
2493 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
2494 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
2495 break;
2496 }
2497 }
2498 si->dynamic = nullptr;
2499 si->ref_count = 1;
2501 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
2502 if (elf_hdr->e_type != ET_DYN) {
2503 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
2504 exit(EXIT_FAILURE);
2505 }
2507 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
2508 parse_LD_LIBRARY_PATH(ldpath_env);
2509 parse_LD_PRELOAD(ldpreload_env);
2511 somain = si;
2513 si->PrelinkImage();
2515 // add somain to global group
2516 si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
2518 // Load ld_preloads and dependencies.
2519 StringLinkedList needed_library_name_list;
2520 size_t needed_libraries_count = 0;
2521 size_t ld_preloads_count = 0;
2522 while (g_ld_preload_names[ld_preloads_count] != nullptr) {
2523 needed_library_name_list.push_back(g_ld_preload_names[ld_preloads_count++]);
2524 ++needed_libraries_count;
2525 }
2527 for_each_dt_needed(si, [&](const char* name) {
2528 needed_library_name_list.push_back(name);
2529 ++needed_libraries_count;
2530 });
2532 const char* needed_library_names[needed_libraries_count];
2534 memset(needed_library_names, 0, sizeof(needed_library_names));
2535 needed_library_name_list.copy_to_array(needed_library_names, needed_libraries_count);
2537 if (needed_libraries_count > 0 && !find_libraries(si, needed_library_names, needed_libraries_count, nullptr, g_ld_preloads, ld_preloads_count, RTLD_GLOBAL, nullptr)) {
2538 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
2539 exit(EXIT_FAILURE);
2540 }
2542 add_vdso(args);
2544 si->CallPreInitConstructors();
2546 /* After the PrelinkImage, the si->load_bias is initialized.
2547 * For so lib, the map->l_addr will be updated in notify_gdb_of_load.
2548 * We need to update this value for so exe here. So Unwind_Backtrace
2549 * for some arch like x86 could work correctly within so exe.
2550 */
2551 map->l_addr = si->load_bias;
2552 si->CallConstructors();
2554 #if TIMING
2555 gettimeofday(&t1, nullptr);
2556 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
2557 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2558 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
2559 #endif
2560 #if STATS
2561 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
2562 linker_stats.count[kRelocAbsolute],
2563 linker_stats.count[kRelocRelative],
2564 linker_stats.count[kRelocCopy],
2565 linker_stats.count[kRelocSymbol]);
2566 #endif
2567 #if COUNT_PAGES
2568 {
2569 unsigned n;
2570 unsigned i;
2571 unsigned count = 0;
2572 for (n = 0; n < 4096; n++) {
2573 if (bitmask[n]) {
2574 unsigned x = bitmask[n];
2575 #if defined(__LP64__)
2576 for (i = 0; i < 32; i++) {
2577 #else
2578 for (i = 0; i < 8; i++) {
2579 #endif
2580 if (x & 1) {
2581 count++;
2582 }
2583 x >>= 1;
2584 }
2585 }
2586 }
2587 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
2588 }
2589 #endif
2591 #if TIMING || STATS || COUNT_PAGES
2592 fflush(stdout);
2593 #endif
2595 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry));
2596 return si->entry;
2597 }
2599 /* Compute the load-bias of an existing executable. This shall only
2600 * be used to compute the load bias of an executable or shared library
2601 * that was loaded by the kernel itself.
2602 *
2603 * Input:
2604 * elf -> address of ELF header, assumed to be at the start of the file.
2605 * Return:
2606 * load bias, i.e. add the value of any p_vaddr in the file to get
2607 * the corresponding address in memory.
2608 */
2609 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
2610 ElfW(Addr) offset = elf->e_phoff;
2611 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
2612 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
2614 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
2615 if (phdr->p_type == PT_LOAD) {
2616 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
2617 }
2618 }
2619 return 0;
2620 }
2622 extern "C" void _start();
2624 /*
2625 * This is the entry point for the linker, called from begin.S. This
2626 * method is responsible for fixing the linker's own relocations, and
2627 * then calling __linker_init_post_relocation().
2628 *
2629 * Because this method is called before the linker has fixed it's own
2630 * relocations, any attempt to reference an extern variable, extern
2631 * function, or other GOT reference will generate a segfault.
2632 */
2633 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
2634 KernelArgumentBlock args(raw_args);
2636 ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
2637 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY);
2638 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
2639 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
2641 soinfo linker_so("[dynamic linker]", nullptr, 0, 0);
2643 // If the linker is not acting as PT_INTERP entry_point is equal to
2644 // _start. Which means that the linker is running as an executable and
2645 // already linked by PT_INTERP.
2646 //
2647 // This happens when user tries to run 'adb shell /system/bin/linker'
2648 // see also https://code.google.com/p/android/issues/detail?id=63174
2649 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) {
2650 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]);
2651 }
2653 linker_so.base = linker_addr;
2654 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
2655 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
2656 linker_so.dynamic = nullptr;
2657 linker_so.phdr = phdr;
2658 linker_so.phnum = elf_hdr->e_phnum;
2659 linker_so.flags |= FLAG_LINKER;
2661 // This might not be obvious... The reasons why we pass g_empty_list
2662 // in place of local_group here are (1) we do not really need it, because
2663 // linker is built with DT_SYMBOLIC and therefore relocates its symbols against
2664 // itself without having to look into local_group and (2) allocators
2665 // are not yet initialized, and therefore we cannot use linked_list.push_*
2666 // functions at this point.
2667 if (!(linker_so.PrelinkImage() && linker_so.LinkImage(g_empty_list, g_empty_list, nullptr))) {
2668 // It would be nice to print an error message, but if the linker
2669 // can't link itself, there's no guarantee that we'll be able to
2670 // call write() (because it involves a GOT reference). We may as
2671 // well try though...
2672 const char* msg = "CANNOT LINK EXECUTABLE: ";
2673 write(2, msg, strlen(msg));
2674 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2675 write(2, "\n", 1);
2676 _exit(EXIT_FAILURE);
2677 }
2679 __libc_init_tls(args);
2681 // Initialize the linker's own global variables
2682 linker_so.CallConstructors();
2684 // Initialize static variables. Note that in order to
2685 // get correct libdl_info we need to call constructors
2686 // before get_libdl_info().
2687 solist = get_libdl_info();
2688 sonext = get_libdl_info();
2690 // We have successfully fixed our own relocations. It's safe to run
2691 // the main part of the linker now.
2692 args.abort_message_ptr = &g_abort_message;
2693 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
2695 protect_data(PROT_READ);
2697 // Return the address that the calling assembly stub should jump to.
2698 return start_address;
2699 }