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 = reinterpret_cast<char*>(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, int 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(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, const char* name, soinfo** lsi) {
485 unsigned elf_hash = elfhash(name);
486 ElfW(Sym)* s = nullptr;
488 /* "This element's presence in a shared object library alters the dynamic linker's
489 * symbol resolution algorithm for references within the library. Instead of starting
490 * a symbol search with the executable file, the dynamic linker starts from the shared
491 * object itself. If the shared object fails to supply the referenced symbol, the
492 * dynamic linker then searches the executable file and other shared objects as usual."
493 *
494 * http://www.sco.com/developers/gabi/2012-12-31/ch5.dynamic.html
495 *
496 * Note that this is unlikely since static linker avoids generating
497 * relocations for -Bsymbolic linked dynamic executables.
498 */
499 if (si->has_DT_SYMBOLIC) {
500 DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si->name, name);
501 s = soinfo_elf_lookup(si, elf_hash, name);
502 if (s != nullptr) {
503 *lsi = si;
504 }
505 }
507 if (s == nullptr && somain != nullptr) {
508 // 1. Look for it in the main executable unless we already did.
509 if (si != somain || !si->has_DT_SYMBOLIC) {
510 DEBUG("%s: looking up %s in executable %s",
511 si->name, name, somain->name);
512 s = soinfo_elf_lookup(somain, elf_hash, name);
513 if (s != nullptr) {
514 *lsi = somain;
515 }
516 }
518 // 2. Look for it in the ld_preloads
519 if (s == nullptr) {
520 for (int i = 0; g_ld_preloads[i] != NULL; i++) {
521 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
522 if (s != nullptr) {
523 *lsi = g_ld_preloads[i];
524 break;
525 }
526 }
527 }
528 }
530 /* Look for symbols in the local scope (the object who is
531 * searching). This happens with C++ templates on x86 for some
532 * reason.
533 *
534 * Notes on weak symbols:
535 * The ELF specs are ambiguous about treatment of weak definitions in
536 * dynamic linking. Some systems return the first definition found
537 * and some the first non-weak definition. This is system dependent.
538 * Here we return the first definition found for simplicity. */
540 if (s == nullptr && !si->has_DT_SYMBOLIC) {
541 DEBUG("%s: looking up %s in local scope", si->name, name);
542 s = soinfo_elf_lookup(si, elf_hash, name);
543 if (s != nullptr) {
544 *lsi = si;
545 }
546 }
548 if (s == nullptr) {
549 si->get_children().visit([&](soinfo* child) {
550 DEBUG("%s: looking up %s in %s", si->name, name, child->name);
551 s = soinfo_elf_lookup(child, elf_hash, name);
552 if (s != nullptr) {
553 *lsi = child;
554 return false;
555 }
556 return true;
557 });
558 }
560 if (s != nullptr) {
561 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
562 "found in %s, base = %p, load bias = %p",
563 si->name, name, reinterpret_cast<void*>(s->st_value),
564 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
565 reinterpret_cast<void*>((*lsi)->load_bias));
566 }
568 return s;
569 }
571 // Each size has it's own allocator.
572 template<size_t size>
573 class SizeBasedAllocator {
574 public:
575 static void* alloc() {
576 return allocator_.alloc();
577 }
579 static void free(void* ptr) {
580 allocator_.free(ptr);
581 }
583 private:
584 static LinkerBlockAllocator allocator_;
585 };
587 template<size_t size>
588 LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
590 template<typename T>
591 class TypeBasedAllocator {
592 public:
593 static T* alloc() {
594 return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
595 }
597 static void free(T* ptr) {
598 SizeBasedAllocator<sizeof(T)>::free(ptr);
599 }
600 };
602 class LoadTask {
603 public:
604 struct deleter_t {
605 void operator()(LoadTask* t) {
606 TypeBasedAllocator<LoadTask>::free(t);
607 }
608 };
610 typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
612 static deleter_t deleter;
614 static LoadTask* create(const char* name, soinfo* needed_by) {
615 LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
616 return new (ptr) LoadTask(name, needed_by);
617 }
619 const char* get_name() const {
620 return name_;
621 }
623 soinfo* get_needed_by() const {
624 return needed_by_;
625 }
626 private:
627 LoadTask(const char* name, soinfo* needed_by)
628 : name_(name), needed_by_(needed_by) {}
630 const char* name_;
631 soinfo* needed_by_;
633 DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
634 };
636 LoadTask::deleter_t LoadTask::deleter;
638 template <typename T>
639 using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
641 typedef linked_list_t<soinfo> SoinfoLinkedList;
642 typedef linked_list_t<const char> StringLinkedList;
643 typedef linked_list_t<LoadTask> LoadTaskList;
646 // This is used by dlsym(3). It performs symbol lookup only within the
647 // specified soinfo object and its dependencies in breadth first order.
648 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
649 SoinfoLinkedList visit_list;
650 SoinfoLinkedList visited;
652 visit_list.push_back(si);
653 soinfo* current_soinfo;
654 while ((current_soinfo = visit_list.pop_front()) != nullptr) {
655 if (visited.contains(current_soinfo)) {
656 continue;
657 }
659 ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name);
661 if (result != nullptr) {
662 *found = current_soinfo;
663 return result;
664 }
665 visited.push_back(current_soinfo);
667 current_soinfo->get_children().for_each([&](soinfo* child) {
668 visit_list.push_back(child);
669 });
670 }
672 return nullptr;
673 }
675 /* This is used by dlsym(3) to performs a global symbol lookup. If the
676 start value is null (for RTLD_DEFAULT), the search starts at the
677 beginning of the global solist. Otherwise the search starts at the
678 specified soinfo (for RTLD_NEXT).
679 */
680 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
681 unsigned elf_hash = elfhash(name);
683 if (start == nullptr) {
684 start = solist;
685 }
687 ElfW(Sym)* s = nullptr;
688 for (soinfo* si = start; (s == nullptr) && (si != nullptr); si = si->next) {
689 if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0) {
690 continue;
691 }
693 s = soinfo_elf_lookup(si, elf_hash, name);
694 if (s != nullptr) {
695 *found = si;
696 break;
697 }
698 }
700 if (s != nullptr) {
701 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
702 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
703 }
705 return s;
706 }
708 soinfo* find_containing_library(const void* p) {
709 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
710 for (soinfo* si = solist; si != nullptr; si = si->next) {
711 if (address >= si->base && address - si->base < si->size) {
712 return si;
713 }
714 }
715 return nullptr;
716 }
718 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
719 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
721 // Search the library's symbol table for any defined symbol which
722 // contains this address.
723 for (size_t i = 0; i < si->nchain; ++i) {
724 ElfW(Sym)* sym = &si->symtab[i];
725 if (sym->st_shndx != SHN_UNDEF &&
726 soaddr >= sym->st_value &&
727 soaddr < sym->st_value + sym->st_size) {
728 return sym;
729 }
730 }
732 return nullptr;
733 }
735 static int open_library_on_path(const char* name, const char* const paths[]) {
736 char buf[512];
737 for (size_t i = 0; paths[i] != nullptr; ++i) {
738 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
739 if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
740 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
741 continue;
742 }
743 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
744 if (fd != -1) {
745 return fd;
746 }
747 }
748 return -1;
749 }
751 static int open_library(const char* name) {
752 TRACE("[ opening %s ]", name);
754 // If the name contains a slash, we should attempt to open it directly and not search the paths.
755 if (strchr(name, '/') != nullptr) {
756 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
757 if (fd != -1) {
758 return fd;
759 }
760 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
761 #if defined(__LP64__)
762 return -1;
763 #endif
764 }
766 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
767 int fd = open_library_on_path(name, g_ld_library_paths);
768 if (fd == -1) {
769 fd = open_library_on_path(name, kDefaultLdPaths);
770 }
771 return fd;
772 }
774 template<typename F>
775 static void for_each_dt_needed(const soinfo* si, F action) {
776 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
777 if (d->d_tag == DT_NEEDED) {
778 action(si->get_string(d->d_un.d_val));
779 }
780 }
781 }
783 static soinfo* load_library(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
784 int fd = -1;
785 off64_t file_offset = 0;
786 ScopedFd file_guard(-1);
788 if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
789 fd = extinfo->library_fd;
790 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_OFFSET) != 0) {
791 file_offset = extinfo->library_offset;
792 }
793 } else {
794 // Open the file.
795 fd = open_library(name);
796 if (fd == -1) {
797 DL_ERR("library \"%s\" not found", name);
798 return nullptr;
799 }
801 file_guard.reset(fd);
802 }
804 if ((file_offset % PAGE_SIZE) != 0) {
805 DL_ERR("file offset for the library %s is not page-aligned: %" PRId64, name, file_offset);
806 return nullptr;
807 }
809 struct stat file_stat;
810 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
811 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno));
812 return nullptr;
813 }
815 // Check for symlink and other situations where
816 // file can have different names.
817 for (soinfo* si = solist; si != nullptr; si = si->next) {
818 if (si->get_st_dev() != 0 &&
819 si->get_st_ino() != 0 &&
820 si->get_st_dev() == file_stat.st_dev &&
821 si->get_st_ino() == file_stat.st_ino &&
822 si->get_file_offset() == file_offset) {
823 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
824 return si;
825 }
826 }
828 if ((rtld_flags & RTLD_NOLOAD) != 0) {
829 DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
830 return nullptr;
831 }
833 // Read the ELF header and load the segments.
834 ElfReader elf_reader(name, fd, file_offset);
835 if (!elf_reader.Load(extinfo)) {
836 return nullptr;
837 }
839 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat, file_offset, rtld_flags);
840 if (si == nullptr) {
841 return nullptr;
842 }
843 si->base = elf_reader.load_start();
844 si->size = elf_reader.load_size();
845 si->load_bias = elf_reader.load_bias();
846 si->phnum = elf_reader.phdr_count();
847 si->phdr = elf_reader.loaded_phdr();
849 if (!si->PrelinkImage()) {
850 soinfo_free(si);
851 return nullptr;
852 }
854 for_each_dt_needed(si, [&] (const char* name) {
855 load_tasks.push_back(LoadTask::create(name, si));
856 });
858 return si;
859 }
861 static soinfo *find_loaded_library_by_name(const char* name) {
862 const char* search_name = SEARCH_NAME(name);
863 for (soinfo* si = solist; si != nullptr; si = si->next) {
864 if (!strcmp(search_name, si->name)) {
865 return si;
866 }
867 }
868 return nullptr;
869 }
871 static soinfo* find_library_internal(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
873 soinfo* si = find_loaded_library_by_name(name);
875 // Library might still be loaded, the accurate detection
876 // of this fact is done by load_library.
877 if (si == nullptr) {
878 TRACE("[ '%s' has not been found by name. Trying harder...]", name);
879 si = load_library(load_tasks, name, rtld_flags, extinfo);
880 }
882 return si;
883 }
885 static void soinfo_unload(soinfo* si);
887 static bool is_recursive(soinfo* si, soinfo* parent) {
888 if (parent == nullptr) {
889 return false;
890 }
892 if (si == parent) {
893 DL_ERR("recursive link to \"%s\"", si->name);
894 return true;
895 }
897 return !parent->get_parents().visit([&](soinfo* grandparent) {
898 return !is_recursive(si, grandparent);
899 });
900 }
902 static bool find_libraries(const char* const library_names[], size_t library_names_size, soinfo* soinfos[],
903 soinfo* ld_preloads[], size_t ld_preloads_size, int rtld_flags, const android_dlextinfo* extinfo) {
904 // Step 0: prepare.
905 LoadTaskList load_tasks;
906 for (size_t i = 0; i < library_names_size; ++i) {
907 const char* name = library_names[i];
908 load_tasks.push_back(LoadTask::create(name, nullptr));
909 }
911 // Libraries added to this list in reverse order so that we can
912 // start linking from bottom-up - see step 2.
913 SoinfoLinkedList found_libs;
914 size_t soinfos_size = 0;
916 auto failure_guard = make_scope_guard([&]() {
917 // Housekeeping
918 load_tasks.for_each([] (LoadTask* t) {
919 LoadTask::deleter(t);
920 });
922 for (size_t i = 0; i<soinfos_size; ++i) {
923 soinfo_unload(soinfos[i]);
924 }
925 });
927 // Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
928 for (LoadTask::unique_ptr task(load_tasks.pop_front()); task.get() != nullptr; task.reset(load_tasks.pop_front())) {
929 soinfo* si = find_library_internal(load_tasks, task->get_name(), rtld_flags, extinfo);
930 if (si == nullptr) {
931 return false;
932 }
934 soinfo* needed_by = task->get_needed_by();
936 if (is_recursive(si, needed_by)) {
937 return false;
938 }
940 si->ref_count++;
941 if (needed_by != nullptr) {
942 needed_by->add_child(si);
943 }
944 found_libs.push_front(si);
946 // When ld_preloads is not null first
947 // ld_preloads_size libs are in fact ld_preloads.
948 if (ld_preloads != nullptr && soinfos_size < ld_preloads_size) {
949 ld_preloads[soinfos_size] = si;
950 }
952 if (soinfos_size<library_names_size) {
953 soinfos[soinfos_size++] = si;
954 }
955 }
957 // Step 2: link libraries.
958 soinfo* si;
959 while ((si = found_libs.pop_front()) != nullptr) {
960 if ((si->flags & FLAG_LINKED) == 0) {
961 if (!si->LinkImage(extinfo)) {
962 return false;
963 }
964 si->flags |= FLAG_LINKED;
965 }
966 }
968 // All is well - found_libs and load_tasks are empty at this point
969 // and all libs are successfully linked.
970 failure_guard.disable();
971 return true;
972 }
974 static soinfo* find_library(const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
975 if (name == nullptr) {
976 somain->ref_count++;
977 return somain;
978 }
980 soinfo* si;
982 if (!find_libraries(&name, 1, &si, nullptr, 0, rtld_flags, extinfo)) {
983 return nullptr;
984 }
986 return si;
987 }
989 static void soinfo_unload(soinfo* si) {
990 if (!si->can_unload()) {
991 TRACE("not unloading '%s' - the binary is flagged with NODELETE", si->name);
992 return;
993 }
995 if (si->ref_count == 1) {
996 TRACE("unloading '%s'", si->name);
997 si->CallDestructors();
999 if (si->has_min_version(0)) {
1000 soinfo* child = nullptr;
1001 while ((child = si->get_children().pop_front()) != nullptr) {
1002 TRACE("%s needs to unload %s", si->name, child->name);
1003 soinfo_unload(child);
1004 }
1005 } else {
1006 for_each_dt_needed(si, [&] (const char* library_name) {
1007 TRACE("deprecated (old format of soinfo): %s needs to unload %s", si->name, library_name);
1008 soinfo* needed = find_library(library_name, RTLD_NOLOAD, nullptr);
1009 if (needed != nullptr) {
1010 soinfo_unload(needed);
1011 } else {
1012 // Not found: for example if symlink was deleted between dlopen and dlclose
1013 // Since we cannot really handle errors at this point - print and continue.
1014 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name);
1015 }
1016 });
1017 }
1019 notify_gdb_of_unload(si);
1020 si->ref_count = 0;
1021 soinfo_free(si);
1022 } else {
1023 si->ref_count--;
1024 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
1025 }
1026 }
1028 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
1029 // Use basic string manipulation calls to avoid snprintf.
1030 // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
1031 // When debug malloc is enabled, this call returns 0. This in turn causes
1032 // snprintf to do nothing, which causes libraries to fail to load.
1033 // See b/17302493 for further details.
1034 // Once the above bug is fixed, this code can be modified to use
1035 // snprintf again.
1036 size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
1037 if (buffer_size < required_len) {
1038 __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu",
1039 buffer_size, required_len);
1040 }
1041 char* end = stpcpy(buffer, kDefaultLdPaths[0]);
1042 *end = ':';
1043 strcpy(end + 1, kDefaultLdPaths[1]);
1044 }
1046 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
1047 if (!get_AT_SECURE()) {
1048 parse_LD_LIBRARY_PATH(ld_library_path);
1049 }
1050 }
1052 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
1053 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
1054 DL_ERR("invalid flags to dlopen: %x", flags);
1055 return nullptr;
1056 }
1057 if (extinfo != nullptr) {
1058 if ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0) {
1059 DL_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
1060 return nullptr;
1061 }
1062 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
1063 (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_OFFSET) != 0) {
1064 DL_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_OFFSET without ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
1065 return nullptr;
1066 }
1067 }
1068 protect_data(PROT_READ | PROT_WRITE);
1069 soinfo* si = find_library(name, flags, extinfo);
1070 if (si != nullptr) {
1071 si->CallConstructors();
1072 }
1073 protect_data(PROT_READ);
1074 return si;
1075 }
1077 void do_dlclose(soinfo* si) {
1078 protect_data(PROT_READ | PROT_WRITE);
1079 soinfo_unload(si);
1080 protect_data(PROT_READ);
1081 }
1083 static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
1084 typedef ElfW(Addr) (*ifunc_resolver_t)(void);
1085 ifunc_resolver_t ifunc_resolver = reinterpret_cast<ifunc_resolver_t>(resolver_addr);
1086 ElfW(Addr) ifunc_addr = ifunc_resolver();
1087 TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p", ifunc_resolver, reinterpret_cast<void*>(ifunc_addr));
1089 return ifunc_addr;
1090 }
1092 #if defined(USE_RELA)
1093 int soinfo::Relocate(ElfW(Rela)* rela, unsigned count) {
1094 for (size_t idx = 0; idx < count; ++idx, ++rela) {
1095 unsigned type = ELFW(R_TYPE)(rela->r_info);
1096 unsigned sym = ELFW(R_SYM)(rela->r_info);
1097 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + load_bias);
1098 ElfW(Addr) sym_addr = 0;
1099 const char* sym_name = nullptr;
1101 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1102 if (type == 0) { // R_*_NONE
1103 continue;
1104 }
1106 ElfW(Sym)* s = nullptr;
1107 soinfo* lsi = nullptr;
1109 if (sym != 0) {
1110 sym_name = get_string(symtab[sym].st_name);
1111 s = soinfo_do_lookup(this, sym_name, &lsi);
1112 if (s == nullptr) {
1113 // We only allow an undefined symbol if this is a weak reference...
1114 s = &symtab[sym];
1115 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1116 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1117 return -1;
1118 }
1120 /* IHI0044C AAELF 4.5.1.1:
1122 Libraries are not searched to resolve weak references.
1123 It is not an error for a weak reference to remain unsatisfied.
1125 During linking, the value of an undefined weak reference is:
1126 - Zero if the relocation type is absolute
1127 - The address of the place if the relocation is pc-relative
1128 - The address of nominal base address if the relocation
1129 type is base-relative.
1130 */
1132 switch (type) {
1133 #if defined(__aarch64__)
1134 case R_AARCH64_JUMP_SLOT:
1135 case R_AARCH64_GLOB_DAT:
1136 case R_AARCH64_ABS64:
1137 case R_AARCH64_ABS32:
1138 case R_AARCH64_ABS16:
1139 case R_AARCH64_RELATIVE:
1140 case R_AARCH64_IRELATIVE:
1141 /*
1142 * The sym_addr was initialized to be zero above, or the relocation
1143 * code below does not care about value of sym_addr.
1144 * No need to do anything.
1145 */
1146 break;
1147 #elif defined(__x86_64__)
1148 case R_X86_64_JUMP_SLOT:
1149 case R_X86_64_GLOB_DAT:
1150 case R_X86_64_32:
1151 case R_X86_64_64:
1152 case R_X86_64_RELATIVE:
1153 case R_X86_64_IRELATIVE:
1154 // No need to do anything.
1155 break;
1156 case R_X86_64_PC32:
1157 sym_addr = reloc;
1158 break;
1159 #endif
1160 default:
1161 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
1162 return -1;
1163 }
1164 } else {
1165 // We got a definition.
1166 sym_addr = lsi->resolve_symbol_address(s);
1167 }
1168 count_relocation(kRelocSymbol);
1169 }
1171 switch (type) {
1172 #if defined(__aarch64__)
1173 case R_AARCH64_JUMP_SLOT:
1174 count_relocation(kRelocAbsolute);
1175 MARK(rela->r_offset);
1176 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
1177 reloc, (sym_addr + rela->r_addend), sym_name);
1178 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1179 break;
1180 case R_AARCH64_GLOB_DAT:
1181 count_relocation(kRelocAbsolute);
1182 MARK(rela->r_offset);
1183 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
1184 reloc, (sym_addr + rela->r_addend), sym_name);
1185 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1186 break;
1187 case R_AARCH64_ABS64:
1188 count_relocation(kRelocAbsolute);
1189 MARK(rela->r_offset);
1190 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
1191 reloc, (sym_addr + rela->r_addend), sym_name);
1192 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1193 break;
1194 case R_AARCH64_ABS32:
1195 count_relocation(kRelocAbsolute);
1196 MARK(rela->r_offset);
1197 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
1198 reloc, (sym_addr + rela->r_addend), sym_name);
1199 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1200 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1201 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1202 } else {
1203 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1204 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1205 static_cast<ElfW(Addr)>(INT32_MIN),
1206 static_cast<ElfW(Addr)>(UINT32_MAX));
1207 return -1;
1208 }
1209 break;
1210 case R_AARCH64_ABS16:
1211 count_relocation(kRelocAbsolute);
1212 MARK(rela->r_offset);
1213 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
1214 reloc, (sym_addr + rela->r_addend), sym_name);
1215 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1216 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1217 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1218 } else {
1219 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1220 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1221 static_cast<ElfW(Addr)>(INT16_MIN),
1222 static_cast<ElfW(Addr)>(UINT16_MAX));
1223 return -1;
1224 }
1225 break;
1226 case R_AARCH64_PREL64:
1227 count_relocation(kRelocRelative);
1228 MARK(rela->r_offset);
1229 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
1230 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1231 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
1232 break;
1233 case R_AARCH64_PREL32:
1234 count_relocation(kRelocRelative);
1235 MARK(rela->r_offset);
1236 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
1237 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1238 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1239 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1240 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1241 } else {
1242 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1243 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1244 static_cast<ElfW(Addr)>(INT32_MIN),
1245 static_cast<ElfW(Addr)>(UINT32_MAX));
1246 return -1;
1247 }
1248 break;
1249 case R_AARCH64_PREL16:
1250 count_relocation(kRelocRelative);
1251 MARK(rela->r_offset);
1252 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
1253 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1254 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1255 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1256 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1257 } else {
1258 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1259 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1260 static_cast<ElfW(Addr)>(INT16_MIN),
1261 static_cast<ElfW(Addr)>(UINT16_MAX));
1262 return -1;
1263 }
1264 break;
1266 case R_AARCH64_RELATIVE:
1267 count_relocation(kRelocRelative);
1268 MARK(rela->r_offset);
1269 if (sym) {
1270 DL_ERR("odd RELATIVE form...");
1271 return -1;
1272 }
1273 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
1274 reloc, (base + rela->r_addend));
1275 *reinterpret_cast<ElfW(Addr)*>(reloc) = (base + rela->r_addend);
1276 break;
1278 case R_AARCH64_IRELATIVE:
1279 count_relocation(kRelocRelative);
1280 MARK(rela->r_offset);
1281 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1282 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1283 break;
1285 case R_AARCH64_COPY:
1286 /*
1287 * ET_EXEC is not supported so this should not happen.
1288 *
1289 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1290 *
1291 * Section 4.7.1.10 "Dynamic relocations"
1292 * R_AARCH64_COPY may only appear in executable objects where e_type is
1293 * set to ET_EXEC.
1294 */
1295 DL_ERR("%s R_AARCH64_COPY relocations are not supported", name);
1296 return -1;
1297 case R_AARCH64_TLS_TPREL64:
1298 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
1299 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1300 break;
1301 case R_AARCH64_TLS_DTPREL32:
1302 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
1303 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1304 break;
1305 #elif defined(__x86_64__)
1306 case R_X86_64_JUMP_SLOT:
1307 count_relocation(kRelocAbsolute);
1308 MARK(rela->r_offset);
1309 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1310 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1311 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1312 break;
1313 case R_X86_64_GLOB_DAT:
1314 count_relocation(kRelocAbsolute);
1315 MARK(rela->r_offset);
1316 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1317 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1318 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1319 break;
1320 case R_X86_64_RELATIVE:
1321 count_relocation(kRelocRelative);
1322 MARK(rela->r_offset);
1323 if (sym) {
1324 DL_ERR("odd RELATIVE form...");
1325 return -1;
1326 }
1327 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
1328 static_cast<size_t>(base));
1329 *reinterpret_cast<ElfW(Addr)*>(reloc) = base + rela->r_addend;
1330 break;
1331 case R_X86_64_IRELATIVE:
1332 count_relocation(kRelocRelative);
1333 MARK(rela->r_offset);
1334 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1335 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1336 break;
1337 case R_X86_64_32:
1338 count_relocation(kRelocRelative);
1339 MARK(rela->r_offset);
1340 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1341 static_cast<size_t>(sym_addr), sym_name);
1342 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1343 break;
1344 case R_X86_64_64:
1345 count_relocation(kRelocRelative);
1346 MARK(rela->r_offset);
1347 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1348 static_cast<size_t>(sym_addr), sym_name);
1349 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1350 break;
1351 case R_X86_64_PC32:
1352 count_relocation(kRelocRelative);
1353 MARK(rela->r_offset);
1354 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
1355 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
1356 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
1357 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc;
1358 break;
1359 #endif
1361 default:
1362 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
1363 return -1;
1364 }
1365 }
1366 return 0;
1367 }
1369 #else // REL, not RELA.
1370 int soinfo::Relocate(ElfW(Rel)* rel, unsigned count) {
1371 for (size_t idx = 0; idx < count; ++idx, ++rel) {
1372 unsigned type = ELFW(R_TYPE)(rel->r_info);
1373 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
1374 unsigned sym = ELFW(R_SYM)(rel->r_info);
1375 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
1376 ElfW(Addr) sym_addr = 0;
1377 const char* sym_name = nullptr;
1379 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1380 if (type == 0) { // R_*_NONE
1381 continue;
1382 }
1384 ElfW(Sym)* s = nullptr;
1385 soinfo* lsi = nullptr;
1387 if (sym != 0) {
1388 sym_name = get_string(symtab[sym].st_name);
1389 s = soinfo_do_lookup(this, sym_name, &lsi);
1390 if (s == nullptr) {
1391 // We only allow an undefined symbol if this is a weak reference...
1392 s = &symtab[sym];
1393 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1394 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1395 return -1;
1396 }
1398 /* IHI0044C AAELF 4.5.1.1:
1400 Libraries are not searched to resolve weak references.
1401 It is not an error for a weak reference to remain
1402 unsatisfied.
1404 During linking, the value of an undefined weak reference is:
1405 - Zero if the relocation type is absolute
1406 - The address of the place if the relocation is pc-relative
1407 - The address of nominal base address if the relocation
1408 type is base-relative.
1409 */
1411 switch (type) {
1412 #if defined(__arm__)
1413 case R_ARM_JUMP_SLOT:
1414 case R_ARM_GLOB_DAT:
1415 case R_ARM_ABS32:
1416 case R_ARM_RELATIVE: /* Don't care. */
1417 // sym_addr was initialized to be zero above or relocation
1418 // code below does not care about value of sym_addr.
1419 // No need to do anything.
1420 break;
1421 #elif defined(__i386__)
1422 case R_386_JMP_SLOT:
1423 case R_386_GLOB_DAT:
1424 case R_386_32:
1425 case R_386_RELATIVE: /* Don't care. */
1426 case R_386_IRELATIVE:
1427 // sym_addr was initialized to be zero above or relocation
1428 // code below does not care about value of sym_addr.
1429 // No need to do anything.
1430 break;
1431 case R_386_PC32:
1432 sym_addr = reloc;
1433 break;
1434 #endif
1436 #if defined(__arm__)
1437 case R_ARM_COPY:
1438 // Fall through. Can't really copy if weak symbol is not found at run-time.
1439 #endif
1440 default:
1441 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
1442 return -1;
1443 }
1444 } else {
1445 // We got a definition.
1446 sym_addr = lsi->resolve_symbol_address(s);
1447 }
1448 count_relocation(kRelocSymbol);
1449 }
1451 switch (type) {
1452 #if defined(__arm__)
1453 case R_ARM_JUMP_SLOT:
1454 count_relocation(kRelocAbsolute);
1455 MARK(rel->r_offset);
1456 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1457 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1458 break;
1459 case R_ARM_GLOB_DAT:
1460 count_relocation(kRelocAbsolute);
1461 MARK(rel->r_offset);
1462 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1463 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1464 break;
1465 case R_ARM_ABS32:
1466 count_relocation(kRelocAbsolute);
1467 MARK(rel->r_offset);
1468 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
1469 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1470 break;
1471 case R_ARM_REL32:
1472 count_relocation(kRelocRelative);
1473 MARK(rel->r_offset);
1474 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
1475 reloc, sym_addr, rel->r_offset, sym_name);
1476 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
1477 break;
1478 case R_ARM_COPY:
1479 /*
1480 * ET_EXEC is not supported so this should not happen.
1481 *
1482 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1483 *
1484 * Section 4.7.1.10 "Dynamic relocations"
1485 * R_ARM_COPY may only appear in executable objects where e_type is
1486 * set to ET_EXEC.
1487 */
1488 DL_ERR("%s R_ARM_COPY relocations are not supported", name);
1489 return -1;
1490 #elif defined(__i386__)
1491 case R_386_JMP_SLOT:
1492 count_relocation(kRelocAbsolute);
1493 MARK(rel->r_offset);
1494 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1495 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1496 break;
1497 case R_386_GLOB_DAT:
1498 count_relocation(kRelocAbsolute);
1499 MARK(rel->r_offset);
1500 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1501 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1502 break;
1503 case R_386_32:
1504 count_relocation(kRelocRelative);
1505 MARK(rel->r_offset);
1506 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
1507 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1508 break;
1509 case R_386_PC32:
1510 count_relocation(kRelocRelative);
1511 MARK(rel->r_offset);
1512 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
1513 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
1514 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
1515 break;
1516 #elif defined(__mips__)
1517 case R_MIPS_REL32:
1518 #if defined(__LP64__)
1519 // MIPS Elf64_Rel entries contain compound relocations
1520 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
1521 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
1522 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
1523 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
1524 type, (unsigned)ELF64_R_TYPE2(rel->r_info),
1525 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
1526 return -1;
1527 }
1528 #endif
1529 count_relocation(kRelocAbsolute);
1530 MARK(rel->r_offset);
1531 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
1532 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
1533 if (s) {
1534 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1535 } else {
1536 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1537 }
1538 break;
1539 #endif
1541 #if defined(__arm__)
1542 case R_ARM_RELATIVE:
1543 #elif defined(__i386__)
1544 case R_386_RELATIVE:
1545 #endif
1546 count_relocation(kRelocRelative);
1547 MARK(rel->r_offset);
1548 if (sym) {
1549 DL_ERR("odd RELATIVE form...");
1550 return -1;
1551 }
1552 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
1553 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1554 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1555 break;
1556 #if defined(__i386__)
1557 case R_386_IRELATIVE:
1558 count_relocation(kRelocRelative);
1559 MARK(rel->r_offset);
1560 TRACE_TYPE(RELO, "RELO IRELATIVE %p <- %p", reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1561 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + *reinterpret_cast<ElfW(Addr)*>(reloc));
1562 break;
1563 #endif
1565 default:
1566 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
1567 return -1;
1568 }
1569 }
1570 return 0;
1571 }
1572 #endif
1574 #if defined(__mips__)
1575 static bool mips_relocate_got(soinfo* si) {
1576 ElfW(Addr)** got = si->plt_got;
1577 if (got == nullptr) {
1578 return true;
1579 }
1580 unsigned local_gotno = si->mips_local_gotno;
1581 unsigned gotsym = si->mips_gotsym;
1582 unsigned symtabno = si->mips_symtabno;
1583 ElfW(Sym)* symtab = si->symtab;
1585 // got[0] is the address of the lazy resolver function.
1586 // got[1] may be used for a GNU extension.
1587 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
1588 // FIXME: maybe this should be in a separate routine?
1589 if ((si->flags & FLAG_LINKER) == 0) {
1590 size_t g = 0;
1591 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
1592 if (reinterpret_cast<intptr_t>(got[g]) < 0) {
1593 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
1594 }
1595 // Relocate the local GOT entries.
1596 for (; g < local_gotno; g++) {
1597 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
1598 }
1599 }
1601 // Now for the global GOT entries...
1602 ElfW(Sym)* sym = symtab + gotsym;
1603 got = si->plt_got + local_gotno;
1604 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
1605 // This is an undefined reference... try to locate it.
1606 const char* sym_name = si->get_string(sym->st_name);
1607 soinfo* lsi = nullptr;
1608 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi);
1609 if (s == nullptr) {
1610 // We only allow an undefined symbol if this is a weak reference.
1611 s = &symtab[g];
1612 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1613 DL_ERR("cannot locate \"%s\"...", sym_name);
1614 return false;
1615 }
1616 *got = 0;
1617 } else {
1618 // FIXME: is this sufficient?
1619 // For reference see NetBSD link loader
1620 // 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
1621 *got = reinterpret_cast<ElfW(Addr)*>(lsi->resolve_symbol_address(s));
1622 }
1623 }
1624 return true;
1625 }
1626 #endif
1628 void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
1629 if (functions == nullptr) {
1630 return;
1631 }
1633 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
1635 int begin = reverse ? (count - 1) : 0;
1636 int end = reverse ? -1 : count;
1637 int step = reverse ? -1 : 1;
1639 for (int i = begin; i != end; i += step) {
1640 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
1641 CallFunction("function", functions[i]);
1642 }
1644 TRACE("[ Done calling %s for '%s' ]", array_name, name);
1645 }
1647 void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
1648 if (function == nullptr || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
1649 return;
1650 }
1652 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
1653 function();
1654 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
1656 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
1657 // are still writable. This happens with our debug malloc (see http://b/7941716).
1658 protect_data(PROT_READ | PROT_WRITE);
1659 }
1661 void soinfo::CallPreInitConstructors() {
1662 // DT_PREINIT_ARRAY functions are called before any other constructors for executables,
1663 // but ignored in a shared library.
1664 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
1665 }
1667 void soinfo::CallConstructors() {
1668 if (constructors_called) {
1669 return;
1670 }
1672 // We set constructors_called before actually calling the constructors, otherwise it doesn't
1673 // protect against recursive constructor calls. One simple example of constructor recursion
1674 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
1675 // 1. The program depends on libc, so libc's constructor is called here.
1676 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
1677 // 3. dlopen() calls the constructors on the newly created
1678 // soinfo for libc_malloc_debug_leak.so.
1679 // 4. The debug .so depends on libc, so CallConstructors is
1680 // called again with the libc soinfo. If it doesn't trigger the early-
1681 // out above, the libc constructor will be called again (recursively!).
1682 constructors_called = true;
1684 if ((flags & FLAG_EXE) == 0 && preinit_array != nullptr) {
1685 // The GNU dynamic linker silently ignores these, but we warn the developer.
1686 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
1687 name, preinit_array_count);
1688 }
1690 get_children().for_each([] (soinfo* si) {
1691 si->CallConstructors();
1692 });
1694 TRACE("\"%s\": calling constructors", name);
1696 // DT_INIT should be called before DT_INIT_ARRAY if both are present.
1697 CallFunction("DT_INIT", init_func);
1698 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
1699 }
1701 void soinfo::CallDestructors() {
1702 if (!constructors_called) {
1703 return;
1704 }
1705 TRACE("\"%s\": calling destructors", name);
1707 // DT_FINI_ARRAY must be parsed in reverse order.
1708 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
1710 // DT_FINI should be called after DT_FINI_ARRAY if both are present.
1711 CallFunction("DT_FINI", fini_func);
1713 // This is needed on second call to dlopen
1714 // after library has been unloaded with RTLD_NODELETE
1715 constructors_called = false;
1716 }
1718 void soinfo::add_child(soinfo* child) {
1719 if (has_min_version(0)) {
1720 child->parents.push_back(this);
1721 this->children.push_back(child);
1722 }
1723 }
1725 void soinfo::remove_all_links() {
1726 if (!has_min_version(0)) {
1727 return;
1728 }
1730 // 1. Untie connected soinfos from 'this'.
1731 children.for_each([&] (soinfo* child) {
1732 child->parents.remove_if([&] (const soinfo* parent) {
1733 return parent == this;
1734 });
1735 });
1737 parents.for_each([&] (soinfo* parent) {
1738 parent->children.remove_if([&] (const soinfo* child) {
1739 return child == this;
1740 });
1741 });
1743 // 2. Once everything untied - clear local lists.
1744 parents.clear();
1745 children.clear();
1746 }
1748 dev_t soinfo::get_st_dev() {
1749 if (has_min_version(0)) {
1750 return st_dev;
1751 }
1753 return 0;
1754 };
1756 ino_t soinfo::get_st_ino() {
1757 if (has_min_version(0)) {
1758 return st_ino;
1759 }
1761 return 0;
1762 }
1764 off64_t soinfo::get_file_offset() {
1765 if (has_min_version(1)) {
1766 return file_offset;
1767 }
1769 return 0;
1770 }
1772 int soinfo::get_rtld_flags() {
1773 if (has_min_version(1)) {
1774 return rtld_flags;
1775 }
1777 return 0;
1778 }
1780 // This is a return on get_children()/get_parents() if
1781 // 'this->flags' does not have FLAG_NEW_SOINFO set.
1782 static soinfo::soinfo_list_t g_empty_list;
1784 soinfo::soinfo_list_t& soinfo::get_children() {
1785 if (has_min_version(0)) {
1786 return this->children;
1787 }
1789 return g_empty_list;
1790 }
1792 soinfo::soinfo_list_t& soinfo::get_parents() {
1793 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1794 return g_empty_list;
1795 }
1797 return this->parents;
1798 }
1800 ElfW(Addr) soinfo::resolve_symbol_address(ElfW(Sym)* s) {
1801 if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
1802 return call_ifunc_resolver(s->st_value + load_bias);
1803 }
1805 return static_cast<ElfW(Addr)>(s->st_value + load_bias);
1806 }
1808 const char* soinfo::get_string(ElfW(Word) index) const {
1809 if (has_min_version(1) && (index >= strtab_size)) {
1810 __libc_fatal("%s: strtab out of bounds error; STRSZ=%zd, name=%d", name, strtab_size, index);
1811 }
1813 return strtab + index;
1814 }
1816 bool soinfo::can_unload() const {
1817 return (rtld_flags & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
1818 }
1819 /* Force any of the closed stdin, stdout and stderr to be associated with
1820 /dev/null. */
1821 static int nullify_closed_stdio() {
1822 int dev_null, i, status;
1823 int return_value = 0;
1825 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
1826 if (dev_null < 0) {
1827 DL_ERR("cannot open /dev/null: %s", strerror(errno));
1828 return -1;
1829 }
1830 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
1832 /* If any of the stdio file descriptors is valid and not associated
1833 with /dev/null, dup /dev/null to it. */
1834 for (i = 0; i < 3; i++) {
1835 /* If it is /dev/null already, we are done. */
1836 if (i == dev_null) {
1837 continue;
1838 }
1840 TRACE("[ Nullifying stdio file descriptor %d]", i);
1841 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
1843 /* If file is opened, we are good. */
1844 if (status != -1) {
1845 continue;
1846 }
1848 /* The only error we allow is that the file descriptor does not
1849 exist, in which case we dup /dev/null to it. */
1850 if (errno != EBADF) {
1851 DL_ERR("fcntl failed: %s", strerror(errno));
1852 return_value = -1;
1853 continue;
1854 }
1856 /* Try dupping /dev/null to this stdio file descriptor and
1857 repeat if there is a signal. Note that any errors in closing
1858 the stdio descriptor are lost. */
1859 status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
1860 if (status < 0) {
1861 DL_ERR("dup2 failed: %s", strerror(errno));
1862 return_value = -1;
1863 continue;
1864 }
1865 }
1867 /* If /dev/null is not one of the stdio file descriptors, close it. */
1868 if (dev_null > 2) {
1869 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
1870 status = TEMP_FAILURE_RETRY(close(dev_null));
1871 if (status == -1) {
1872 DL_ERR("close failed: %s", strerror(errno));
1873 return_value = -1;
1874 }
1875 }
1877 return return_value;
1878 }
1880 bool soinfo::PrelinkImage() {
1881 /* Extract dynamic section */
1882 ElfW(Word) dynamic_flags = 0;
1883 phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
1885 /* We can't log anything until the linker is relocated */
1886 bool relocating_linker = (flags & FLAG_LINKER) != 0;
1887 if (!relocating_linker) {
1888 INFO("[ linking %s ]", name);
1889 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags);
1890 }
1892 if (dynamic == nullptr) {
1893 if (!relocating_linker) {
1894 DL_ERR("missing PT_DYNAMIC in \"%s\"", name);
1895 }
1896 return false;
1897 } else {
1898 if (!relocating_linker) {
1899 DEBUG("dynamic = %p", dynamic);
1900 }
1901 }
1903 #if defined(__arm__)
1904 (void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
1905 &ARM_exidx, &ARM_exidx_count);
1906 #endif
1908 // Extract useful information from dynamic section.
1909 uint32_t needed_count = 0;
1910 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
1911 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
1912 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1913 switch (d->d_tag) {
1914 case DT_SONAME:
1915 // TODO: glibc dynamic linker uses this name for
1916 // initial library lookup; consider doing the same here.
1917 break;
1919 case DT_HASH:
1920 nbucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
1921 nchain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
1922 bucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
1923 chain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket * 4);
1924 break;
1926 case DT_STRTAB:
1927 strtab = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
1928 break;
1930 case DT_STRSZ:
1931 strtab_size = d->d_un.d_val;
1932 break;
1934 case DT_SYMTAB:
1935 symtab = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
1936 break;
1938 case DT_SYMENT:
1939 if (d->d_un.d_val != sizeof(ElfW(Sym))) {
1940 DL_ERR("invalid DT_SYMENT: %zd", static_cast<size_t>(d->d_un.d_val));
1941 return false;
1942 }
1943 break;
1945 case DT_PLTREL:
1946 #if defined(USE_RELA)
1947 if (d->d_un.d_val != DT_RELA) {
1948 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_RELA", name);
1949 return false;
1950 }
1951 #else
1952 if (d->d_un.d_val != DT_REL) {
1953 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_REL", name);
1954 return false;
1955 }
1956 #endif
1957 break;
1959 case DT_JMPREL:
1960 #if defined(USE_RELA)
1961 plt_rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
1962 #else
1963 plt_rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
1964 #endif
1965 break;
1967 case DT_PLTRELSZ:
1968 #if defined(USE_RELA)
1969 plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
1970 #else
1971 plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
1972 #endif
1973 break;
1975 case DT_PLTGOT:
1976 #if defined(__mips__)
1977 // Used by mips and mips64.
1978 plt_got = reinterpret_cast<ElfW(Addr)**>(load_bias + d->d_un.d_ptr);
1979 #endif
1980 // Ignore for other platforms... (because RTLD_LAZY is not supported)
1981 break;
1983 case DT_DEBUG:
1984 // Set the DT_DEBUG entry to the address of _r_debug for GDB
1985 // if the dynamic table is writable
1986 // FIXME: not working currently for N64
1987 // The flags for the LOAD and DYNAMIC program headers do not agree.
1988 // The LOAD section containing the dynamic table has been mapped as
1989 // read-only, but the DYNAMIC header claims it is writable.
1990 #if !(defined(__mips__) && defined(__LP64__))
1991 if ((dynamic_flags & PF_W) != 0) {
1992 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
1993 }
1994 break;
1995 #endif
1996 #if defined(USE_RELA)
1997 case DT_RELA:
1998 rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
1999 break;
2001 case DT_RELASZ:
2002 rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
2003 break;
2005 case DT_RELAENT:
2006 if (d->d_un.d_val != sizeof(ElfW(Rela))) {
2007 DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
2008 return false;
2009 }
2010 break;
2012 // ignored (see DT_RELCOUNT comments for details)
2013 case DT_RELACOUNT:
2014 break;
2016 case DT_REL:
2017 DL_ERR("unsupported DT_REL in \"%s\"", name);
2018 return false;
2020 case DT_RELSZ:
2021 DL_ERR("unsupported DT_RELSZ in \"%s\"", name);
2022 return false;
2023 #else
2024 case DT_REL:
2025 rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2026 break;
2028 case DT_RELSZ:
2029 rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
2030 break;
2032 case DT_RELENT:
2033 if (d->d_un.d_val != sizeof(ElfW(Rel))) {
2034 DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
2035 return false;
2036 }
2037 break;
2039 // "Indicates that all RELATIVE relocations have been concatenated together,
2040 // and specifies the RELATIVE relocation count."
2041 //
2042 // TODO: Spec also mentions that this can be used to optimize relocation process;
2043 // Not currently used by bionic linker - ignored.
2044 case DT_RELCOUNT:
2045 break;
2046 case DT_RELA:
2047 DL_ERR("unsupported DT_RELA in \"%s\"", name);
2048 return false;
2049 #endif
2050 case DT_INIT:
2051 init_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2052 DEBUG("%s constructors (DT_INIT) found at %p", name, init_func);
2053 break;
2055 case DT_FINI:
2056 fini_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2057 DEBUG("%s destructors (DT_FINI) found at %p", name, fini_func);
2058 break;
2060 case DT_INIT_ARRAY:
2061 init_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2062 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", name, init_array);
2063 break;
2065 case DT_INIT_ARRAYSZ:
2066 init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2067 break;
2069 case DT_FINI_ARRAY:
2070 fini_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2071 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", name, fini_array);
2072 break;
2074 case DT_FINI_ARRAYSZ:
2075 fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2076 break;
2078 case DT_PREINIT_ARRAY:
2079 preinit_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2080 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", name, preinit_array);
2081 break;
2083 case DT_PREINIT_ARRAYSZ:
2084 preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2085 break;
2087 case DT_TEXTREL:
2088 #if defined(__LP64__)
2089 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2090 return false;
2091 #else
2092 has_text_relocations = true;
2093 break;
2094 #endif
2096 case DT_SYMBOLIC:
2097 has_DT_SYMBOLIC = true;
2098 break;
2100 case DT_NEEDED:
2101 ++needed_count;
2102 break;
2104 case DT_FLAGS:
2105 if (d->d_un.d_val & DF_TEXTREL) {
2106 #if defined(__LP64__)
2107 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2108 return false;
2109 #else
2110 has_text_relocations = true;
2111 #endif
2112 }
2113 if (d->d_un.d_val & DF_SYMBOLIC) {
2114 has_DT_SYMBOLIC = true;
2115 }
2116 break;
2118 case DT_FLAGS_1:
2119 if ((d->d_un.d_val & DF_1_GLOBAL) != 0) {
2120 rtld_flags |= RTLD_GLOBAL;
2121 }
2123 if ((d->d_un.d_val & DF_1_NODELETE) != 0) {
2124 rtld_flags |= RTLD_NODELETE;
2125 }
2126 // TODO: Implement other flags
2128 if ((d->d_un.d_val & ~(DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE)) != 0) {
2129 DL_WARN("Unsupported flags DT_FLAGS_1=%p", reinterpret_cast<void*>(d->d_un.d_val));
2130 }
2131 break;
2132 #if defined(__mips__)
2133 case DT_MIPS_RLD_MAP:
2134 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
2135 {
2136 r_debug** dp = reinterpret_cast<r_debug**>(load_bias + d->d_un.d_ptr);
2137 *dp = &_r_debug;
2138 }
2139 break;
2141 case DT_MIPS_RLD_VERSION:
2142 case DT_MIPS_FLAGS:
2143 case DT_MIPS_BASE_ADDRESS:
2144 case DT_MIPS_UNREFEXTNO:
2145 break;
2147 case DT_MIPS_SYMTABNO:
2148 mips_symtabno = d->d_un.d_val;
2149 break;
2151 case DT_MIPS_LOCAL_GOTNO:
2152 mips_local_gotno = d->d_un.d_val;
2153 break;
2155 case DT_MIPS_GOTSYM:
2156 mips_gotsym = d->d_un.d_val;
2157 break;
2158 #endif
2159 // Ignored: "Its use has been superseded by the DF_BIND_NOW flag"
2160 case DT_BIND_NOW:
2161 break;
2163 // Ignore: bionic does not support symbol versioning...
2164 case DT_VERSYM:
2165 case DT_VERDEF:
2166 case DT_VERDEFNUM:
2167 break;
2169 default:
2170 if (!relocating_linker) {
2171 DL_WARN("%s: unused DT entry: type %p arg %p", name,
2172 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
2173 }
2174 break;
2175 }
2176 }
2178 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
2179 reinterpret_cast<void*>(base), strtab, symtab);
2181 // Sanity checks.
2182 if (relocating_linker && needed_count != 0) {
2183 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
2184 return false;
2185 }
2186 if (nbucket == 0) {
2187 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", name);
2188 return false;
2189 }
2190 if (strtab == 0) {
2191 DL_ERR("empty/missing DT_STRTAB in \"%s\"", name);
2192 return false;
2193 }
2194 if (symtab == 0) {
2195 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", name);
2196 return false;
2197 }
2198 return true;
2199 }
2201 bool soinfo::LinkImage(const android_dlextinfo* extinfo) {
2203 #if !defined(__LP64__)
2204 if (has_text_relocations) {
2205 // Make segments writable to allow text relocations to work properly. We will later call
2206 // phdr_table_protect_segments() after all of them are applied and all constructors are run.
2207 DL_WARN("%s has text relocations. This is wasting memory and prevents "
2208 "security hardening. Please fix.", name);
2209 if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
2210 DL_ERR("can't unprotect loadable segments for \"%s\": %s",
2211 name, strerror(errno));
2212 return false;
2213 }
2214 }
2215 #endif
2217 #if defined(USE_RELA)
2218 if (rela != nullptr) {
2219 DEBUG("[ relocating %s ]", name);
2220 if (Relocate(rela, rela_count)) {
2221 return false;
2222 }
2223 }
2224 if (plt_rela != nullptr) {
2225 DEBUG("[ relocating %s plt ]", name);
2226 if (Relocate(plt_rela, plt_rela_count)) {
2227 return false;
2228 }
2229 }
2230 #else
2231 if (rel != nullptr) {
2232 DEBUG("[ relocating %s ]", name);
2233 if (Relocate(rel, rel_count)) {
2234 return false;
2235 }
2236 }
2237 if (plt_rel != nullptr) {
2238 DEBUG("[ relocating %s plt ]", name);
2239 if (Relocate(plt_rel, plt_rel_count)) {
2240 return false;
2241 }
2242 }
2243 #endif
2245 #if defined(__mips__)
2246 if (!mips_relocate_got(this)) {
2247 return false;
2248 }
2249 #endif
2251 DEBUG("[ finished linking %s ]", name);
2253 #if !defined(__LP64__)
2254 if (has_text_relocations) {
2255 // All relocations are done, we can protect our segments back to read-only.
2256 if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
2257 DL_ERR("can't protect segments for \"%s\": %s",
2258 name, strerror(errno));
2259 return false;
2260 }
2261 }
2262 #endif
2264 /* We can also turn on GNU RELRO protection */
2265 if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
2266 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
2267 name, strerror(errno));
2268 return false;
2269 }
2271 /* Handle serializing/sharing the RELRO segment */
2272 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
2273 if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
2274 extinfo->relro_fd) < 0) {
2275 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
2276 name, strerror(errno));
2277 return false;
2278 }
2279 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
2280 if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
2281 extinfo->relro_fd) < 0) {
2282 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
2283 name, strerror(errno));
2284 return false;
2285 }
2286 }
2288 notify_gdb_of_load(this);
2289 return true;
2290 }
2292 /*
2293 * This function add vdso to internal dso list.
2294 * It helps to stack unwinding through signal handlers.
2295 * Also, it makes bionic more like glibc.
2296 */
2297 static void add_vdso(KernelArgumentBlock& args __unused) {
2298 #if defined(AT_SYSINFO_EHDR)
2299 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
2300 if (ehdr_vdso == nullptr) {
2301 return;
2302 }
2304 soinfo* si = soinfo_alloc("[vdso]", nullptr, 0, 0);
2306 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
2307 si->phnum = ehdr_vdso->e_phnum;
2308 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
2309 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2310 si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
2312 si->PrelinkImage();
2313 si->LinkImage(nullptr);
2314 #endif
2315 }
2317 /*
2318 * This is linker soinfo for GDB. See details below.
2319 */
2320 #if defined(__LP64__)
2321 #define LINKER_PATH "/system/bin/linker64"
2322 #else
2323 #define LINKER_PATH "/system/bin/linker"
2324 #endif
2325 static soinfo linker_soinfo_for_gdb(LINKER_PATH, nullptr, 0, 0);
2327 /* gdb expects the linker to be in the debug shared object list.
2328 * Without this, gdb has trouble locating the linker's ".text"
2329 * and ".plt" sections. Gdb could also potentially use this to
2330 * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
2331 * Don't use soinfo_alloc(), because the linker shouldn't
2332 * be on the soinfo list.
2333 */
2334 static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
2335 linker_soinfo_for_gdb.base = linker_base;
2337 /*
2338 * Set the dynamic field in the link map otherwise gdb will complain with
2339 * the following:
2340 * warning: .dynamic section for "/system/bin/linker" is not at the
2341 * expected address (wrong library or version mismatch?)
2342 */
2343 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
2344 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
2345 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
2346 &linker_soinfo_for_gdb.dynamic, nullptr);
2347 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
2348 }
2350 /*
2351 * This code is called after the linker has linked itself and
2352 * fixed it's own GOT. It is safe to make references to externs
2353 * and other non-local data at this point.
2354 */
2355 static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
2356 #if TIMING
2357 struct timeval t0, t1;
2358 gettimeofday(&t0, 0);
2359 #endif
2361 // Initialize environment functions, and get to the ELF aux vectors table.
2362 linker_env_init(args);
2364 // If this is a setuid/setgid program, close the security hole described in
2365 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2366 if (get_AT_SECURE()) {
2367 nullify_closed_stdio();
2368 }
2370 debuggerd_init();
2372 // Get a few environment variables.
2373 const char* LD_DEBUG = linker_env_get("LD_DEBUG");
2374 if (LD_DEBUG != nullptr) {
2375 g_ld_debug_verbosity = atoi(LD_DEBUG);
2376 }
2378 // Normally, these are cleaned by linker_env_init, but the test
2379 // doesn't cost us anything.
2380 const char* ldpath_env = nullptr;
2381 const char* ldpreload_env = nullptr;
2382 if (!get_AT_SECURE()) {
2383 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2384 ldpreload_env = linker_env_get("LD_PRELOAD");
2385 }
2387 INFO("[ android linker & debugger ]");
2389 soinfo* si = soinfo_alloc(args.argv[0], nullptr, 0, RTLD_GLOBAL);
2390 if (si == nullptr) {
2391 exit(EXIT_FAILURE);
2392 }
2394 /* bootstrap the link map, the main exe always needs to be first */
2395 si->flags |= FLAG_EXE;
2396 link_map* map = &(si->link_map_head);
2398 map->l_addr = 0;
2399 map->l_name = args.argv[0];
2400 map->l_prev = nullptr;
2401 map->l_next = nullptr;
2403 _r_debug.r_map = map;
2404 r_debug_tail = map;
2406 init_linker_info_for_gdb(linker_base);
2408 // Extract information passed from the kernel.
2409 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
2410 si->phnum = args.getauxval(AT_PHNUM);
2411 si->entry = args.getauxval(AT_ENTRY);
2413 /* Compute the value of si->base. We can't rely on the fact that
2414 * the first entry is the PHDR because this will not be true
2415 * for certain executables (e.g. some in the NDK unit test suite)
2416 */
2417 si->base = 0;
2418 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2419 si->load_bias = 0;
2420 for (size_t i = 0; i < si->phnum; ++i) {
2421 if (si->phdr[i].p_type == PT_PHDR) {
2422 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
2423 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
2424 break;
2425 }
2426 }
2427 si->dynamic = nullptr;
2428 si->ref_count = 1;
2430 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
2431 if (elf_hdr->e_type != ET_DYN) {
2432 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
2433 exit(EXIT_FAILURE);
2434 }
2436 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
2437 parse_LD_LIBRARY_PATH(ldpath_env);
2438 parse_LD_PRELOAD(ldpreload_env);
2440 somain = si;
2442 si->PrelinkImage();
2444 // Load ld_preloads and dependencies.
2445 StringLinkedList needed_library_name_list;
2446 size_t needed_libraries_count = 0;
2447 size_t ld_preloads_count = 0;
2448 while (g_ld_preload_names[ld_preloads_count] != nullptr) {
2449 needed_library_name_list.push_back(g_ld_preload_names[ld_preloads_count++]);
2450 ++needed_libraries_count;
2451 }
2453 for_each_dt_needed(si, [&](const char* name) {
2454 needed_library_name_list.push_back(name);
2455 ++needed_libraries_count;
2456 });
2458 const char* needed_library_names[needed_libraries_count];
2459 soinfo* needed_library_si[needed_libraries_count];
2461 memset(needed_library_names, 0, sizeof(needed_library_names));
2462 needed_library_name_list.copy_to_array(needed_library_names, needed_libraries_count);
2464 if (needed_libraries_count > 0 && !find_libraries(needed_library_names, needed_libraries_count, needed_library_si, g_ld_preloads, ld_preloads_count, RTLD_GLOBAL, nullptr)) {
2465 __libc_format_fd(2, "CANNOT LINK EXECUTABLE DEPENDENCIES: %s\n", linker_get_error_buffer());
2466 exit(EXIT_FAILURE);
2467 }
2469 for (size_t i = 0; i<needed_libraries_count; ++i) {
2470 si->add_child(needed_library_si[i]);
2471 }
2473 if (!si->LinkImage(nullptr)) {
2474 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
2475 exit(EXIT_FAILURE);
2476 }
2478 add_vdso(args);
2480 si->CallPreInitConstructors();
2482 /* After the PrelinkImage, the si->load_bias is initialized.
2483 * For so lib, the map->l_addr will be updated in notify_gdb_of_load.
2484 * We need to update this value for so exe here. So Unwind_Backtrace
2485 * for some arch like x86 could work correctly within so exe.
2486 */
2487 map->l_addr = si->load_bias;
2488 si->CallConstructors();
2490 #if TIMING
2491 gettimeofday(&t1, nullptr);
2492 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
2493 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2494 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
2495 #endif
2496 #if STATS
2497 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
2498 linker_stats.count[kRelocAbsolute],
2499 linker_stats.count[kRelocRelative],
2500 linker_stats.count[kRelocCopy],
2501 linker_stats.count[kRelocSymbol]);
2502 #endif
2503 #if COUNT_PAGES
2504 {
2505 unsigned n;
2506 unsigned i;
2507 unsigned count = 0;
2508 for (n = 0; n < 4096; n++) {
2509 if (bitmask[n]) {
2510 unsigned x = bitmask[n];
2511 #if defined(__LP64__)
2512 for (i = 0; i < 32; i++) {
2513 #else
2514 for (i = 0; i < 8; i++) {
2515 #endif
2516 if (x & 1) {
2517 count++;
2518 }
2519 x >>= 1;
2520 }
2521 }
2522 }
2523 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
2524 }
2525 #endif
2527 #if TIMING || STATS || COUNT_PAGES
2528 fflush(stdout);
2529 #endif
2531 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry));
2532 return si->entry;
2533 }
2535 /* Compute the load-bias of an existing executable. This shall only
2536 * be used to compute the load bias of an executable or shared library
2537 * that was loaded by the kernel itself.
2538 *
2539 * Input:
2540 * elf -> address of ELF header, assumed to be at the start of the file.
2541 * Return:
2542 * load bias, i.e. add the value of any p_vaddr in the file to get
2543 * the corresponding address in memory.
2544 */
2545 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
2546 ElfW(Addr) offset = elf->e_phoff;
2547 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
2548 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
2550 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
2551 if (phdr->p_type == PT_LOAD) {
2552 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
2553 }
2554 }
2555 return 0;
2556 }
2558 extern "C" void _start();
2560 /*
2561 * This is the entry point for the linker, called from begin.S. This
2562 * method is responsible for fixing the linker's own relocations, and
2563 * then calling __linker_init_post_relocation().
2564 *
2565 * Because this method is called before the linker has fixed it's own
2566 * relocations, any attempt to reference an extern variable, extern
2567 * function, or other GOT reference will generate a segfault.
2568 */
2569 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
2570 KernelArgumentBlock args(raw_args);
2572 ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
2573 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY);
2574 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
2575 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
2577 soinfo linker_so("[dynamic linker]", nullptr, 0, 0);
2579 // If the linker is not acting as PT_INTERP entry_point is equal to
2580 // _start. Which means that the linker is running as an executable and
2581 // already linked by PT_INTERP.
2582 //
2583 // This happens when user tries to run 'adb shell /system/bin/linker'
2584 // see also https://code.google.com/p/android/issues/detail?id=63174
2585 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) {
2586 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]);
2587 }
2589 linker_so.base = linker_addr;
2590 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
2591 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
2592 linker_so.dynamic = nullptr;
2593 linker_so.phdr = phdr;
2594 linker_so.phnum = elf_hdr->e_phnum;
2595 linker_so.flags |= FLAG_LINKER;
2597 if (!(linker_so.PrelinkImage() && linker_so.LinkImage(nullptr))) {
2598 // It would be nice to print an error message, but if the linker
2599 // can't link itself, there's no guarantee that we'll be able to
2600 // call write() (because it involves a GOT reference). We may as
2601 // well try though...
2602 const char* msg = "CANNOT LINK EXECUTABLE: ";
2603 write(2, msg, strlen(msg));
2604 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2605 write(2, "\n", 1);
2606 _exit(EXIT_FAILURE);
2607 }
2609 __libc_init_tls(args);
2611 // Initialize the linker's own global variables
2612 linker_so.CallConstructors();
2614 // Initialize static variables. Note that in order to
2615 // get correct libdl_info we need to call constructors
2616 // before get_libdl_info().
2617 solist = get_libdl_info();
2618 sonext = get_libdl_info();
2620 // We have successfully fixed our own relocations. It's safe to run
2621 // the main part of the linker now.
2622 args.abort_message_ptr = &g_abort_message;
2623 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
2625 protect_data(PROT_READ);
2627 // Return the address that the calling assembly stub should jump to.
2628 return start_address;
2629 }