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(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, const char* name, soinfo** lsi, const soinfo::soinfo_list_t& local_group) {
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 // 3. Look for it in the local group
531 if (s == nullptr) {
532 local_group.visit([&](soinfo* local_si) {
533 DEBUG("%s: looking up %s in %s (from local group)", si->name, name, local_si->name);
534 s = soinfo_elf_lookup(local_si, elf_hash, name);
535 if (s != nullptr) {
536 *lsi = local_si;
537 return false;
538 }
540 return true;
541 });
542 }
544 // 4. Look for it in this library (unless we already did it because of DT_SYMBOLIC)
545 if (s == nullptr && !si->has_DT_SYMBOLIC) {
546 DEBUG("%s: looking up %s in local scope", si->name, name);
547 s = soinfo_elf_lookup(si, elf_hash, name);
548 if (s != nullptr) {
549 *lsi = si;
550 }
551 }
553 // 5. Dependencies
554 if (s == nullptr) {
555 si->get_children().visit([&](soinfo* child) {
556 DEBUG("%s: looking up %s in %s", si->name, name, child->name);
557 s = soinfo_elf_lookup(child, elf_hash, name);
558 if (s != nullptr) {
559 *lsi = child;
560 return false;
561 }
562 return true;
563 });
564 }
566 if (s != nullptr) {
567 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
568 "found in %s, base = %p, load bias = %p",
569 si->name, name, reinterpret_cast<void*>(s->st_value),
570 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
571 reinterpret_cast<void*>((*lsi)->load_bias));
572 }
574 return s;
575 }
577 // Each size has it's own allocator.
578 template<size_t size>
579 class SizeBasedAllocator {
580 public:
581 static void* alloc() {
582 return allocator_.alloc();
583 }
585 static void free(void* ptr) {
586 allocator_.free(ptr);
587 }
589 private:
590 static LinkerBlockAllocator allocator_;
591 };
593 template<size_t size>
594 LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
596 template<typename T>
597 class TypeBasedAllocator {
598 public:
599 static T* alloc() {
600 return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
601 }
603 static void free(T* ptr) {
604 SizeBasedAllocator<sizeof(T)>::free(ptr);
605 }
606 };
608 class LoadTask {
609 public:
610 struct deleter_t {
611 void operator()(LoadTask* t) {
612 TypeBasedAllocator<LoadTask>::free(t);
613 }
614 };
616 typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
618 static deleter_t deleter;
620 static LoadTask* create(const char* name, soinfo* needed_by) {
621 LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
622 return new (ptr) LoadTask(name, needed_by);
623 }
625 const char* get_name() const {
626 return name_;
627 }
629 soinfo* get_needed_by() const {
630 return needed_by_;
631 }
632 private:
633 LoadTask(const char* name, soinfo* needed_by)
634 : name_(name), needed_by_(needed_by) {}
636 const char* name_;
637 soinfo* needed_by_;
639 DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
640 };
642 LoadTask::deleter_t LoadTask::deleter;
644 template <typename T>
645 using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
647 typedef linked_list_t<soinfo> SoinfoLinkedList;
648 typedef linked_list_t<const char> StringLinkedList;
649 typedef linked_list_t<LoadTask> LoadTaskList;
652 // This function walks down the tree of soinfo dependencies
653 // in breadth-first order and
654 // * calls action(soinfo* si) for each node, and
655 // * terminates walk if action returns false.
656 //
657 // walk_dependencies_tree returns false if walk was terminated
658 // by the action and true otherwise.
659 template<typename F>
660 static bool walk_dependencies_tree(soinfo* root_soinfos[], size_t root_soinfos_size, F action) {
661 SoinfoLinkedList visit_list;
662 SoinfoLinkedList visited;
664 for (size_t i = 0; i < root_soinfos_size; ++i) {
665 visit_list.push_back(root_soinfos[i]);
666 }
668 soinfo* si;
669 while ((si = visit_list.pop_front()) != nullptr) {
670 if (visited.contains(si)) {
671 continue;
672 }
674 if (!action(si)) {
675 return false;
676 }
678 visited.push_back(si);
680 si->get_children().for_each([&](soinfo* child) {
681 visit_list.push_back(child);
682 });
683 }
685 return true;
686 }
689 // This is used by dlsym(3). It performs symbol lookup only within the
690 // specified soinfo object and its dependencies in breadth first order.
691 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
692 ElfW(Sym)* result = nullptr;
693 uint32_t elf_hash = elfhash(name);
696 walk_dependencies_tree(&si, 1, [&](soinfo* current_soinfo) {
697 result = soinfo_elf_lookup(current_soinfo, elf_hash, name);
698 if (result != nullptr) {
699 *found = current_soinfo;
700 return false;
701 }
703 return true;
704 });
706 return result;
707 }
709 /* This is used by dlsym(3) to performs a global symbol lookup. If the
710 start value is null (for RTLD_DEFAULT), the search starts at the
711 beginning of the global solist. Otherwise the search starts at the
712 specified soinfo (for RTLD_NEXT).
713 */
714 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
715 unsigned elf_hash = elfhash(name);
717 if (start == nullptr) {
718 start = solist;
719 }
721 ElfW(Sym)* s = nullptr;
722 for (soinfo* si = start; (s == nullptr) && (si != nullptr); si = si->next) {
723 if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0) {
724 continue;
725 }
727 s = soinfo_elf_lookup(si, elf_hash, name);
728 if (s != nullptr) {
729 *found = si;
730 break;
731 }
732 }
734 if (s != nullptr) {
735 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
736 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
737 }
739 return s;
740 }
742 soinfo* find_containing_library(const void* p) {
743 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
744 for (soinfo* si = solist; si != nullptr; si = si->next) {
745 if (address >= si->base && address - si->base < si->size) {
746 return si;
747 }
748 }
749 return nullptr;
750 }
752 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
753 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
755 // Search the library's symbol table for any defined symbol which
756 // contains this address.
757 for (size_t i = 0; i < si->nchain; ++i) {
758 ElfW(Sym)* sym = &si->symtab[i];
759 if (sym->st_shndx != SHN_UNDEF &&
760 soaddr >= sym->st_value &&
761 soaddr < sym->st_value + sym->st_size) {
762 return sym;
763 }
764 }
766 return nullptr;
767 }
769 static int open_library_on_path(const char* name, const char* const paths[]) {
770 char buf[512];
771 for (size_t i = 0; paths[i] != nullptr; ++i) {
772 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
773 if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
774 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
775 continue;
776 }
777 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
778 if (fd != -1) {
779 return fd;
780 }
781 }
782 return -1;
783 }
785 static int open_library(const char* name) {
786 TRACE("[ opening %s ]", name);
788 // If the name contains a slash, we should attempt to open it directly and not search the paths.
789 if (strchr(name, '/') != nullptr) {
790 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
791 if (fd != -1) {
792 return fd;
793 }
794 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
795 #if defined(__LP64__)
796 return -1;
797 #endif
798 }
800 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
801 int fd = open_library_on_path(name, g_ld_library_paths);
802 if (fd == -1) {
803 fd = open_library_on_path(name, kDefaultLdPaths);
804 }
805 return fd;
806 }
808 template<typename F>
809 static void for_each_dt_needed(const soinfo* si, F action) {
810 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
811 if (d->d_tag == DT_NEEDED) {
812 action(si->get_string(d->d_un.d_val));
813 }
814 }
815 }
817 static soinfo* load_library(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
818 int fd = -1;
819 off64_t file_offset = 0;
820 ScopedFd file_guard(-1);
822 if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
823 fd = extinfo->library_fd;
824 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
825 file_offset = extinfo->library_fd_offset;
826 }
827 } else {
828 // Open the file.
829 fd = open_library(name);
830 if (fd == -1) {
831 DL_ERR("library \"%s\" not found", name);
832 return nullptr;
833 }
835 file_guard.reset(fd);
836 }
838 if ((file_offset % PAGE_SIZE) != 0) {
839 DL_ERR("file offset for the library \"%s\" is not page-aligned: %" PRId64, name, file_offset);
840 return nullptr;
841 }
843 struct stat file_stat;
844 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
845 DL_ERR("unable to stat file for the library \"%s\": %s", name, strerror(errno));
846 return nullptr;
847 }
849 // Check for symlink and other situations where
850 // file can have different names.
851 for (soinfo* si = solist; si != nullptr; si = si->next) {
852 if (si->get_st_dev() != 0 &&
853 si->get_st_ino() != 0 &&
854 si->get_st_dev() == file_stat.st_dev &&
855 si->get_st_ino() == file_stat.st_ino &&
856 si->get_file_offset() == file_offset) {
857 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
858 return si;
859 }
860 }
862 if ((rtld_flags & RTLD_NOLOAD) != 0) {
863 DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
864 return nullptr;
865 }
867 // Read the ELF header and load the segments.
868 ElfReader elf_reader(name, fd, file_offset);
869 if (!elf_reader.Load(extinfo)) {
870 return nullptr;
871 }
873 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat, file_offset, rtld_flags);
874 if (si == nullptr) {
875 return nullptr;
876 }
877 si->base = elf_reader.load_start();
878 si->size = elf_reader.load_size();
879 si->load_bias = elf_reader.load_bias();
880 si->phnum = elf_reader.phdr_count();
881 si->phdr = elf_reader.loaded_phdr();
883 if (!si->PrelinkImage()) {
884 soinfo_free(si);
885 return nullptr;
886 }
888 for_each_dt_needed(si, [&] (const char* name) {
889 load_tasks.push_back(LoadTask::create(name, si));
890 });
892 return si;
893 }
895 static soinfo *find_loaded_library_by_name(const char* name) {
896 const char* search_name = SEARCH_NAME(name);
897 for (soinfo* si = solist; si != nullptr; si = si->next) {
898 if (!strcmp(search_name, si->name)) {
899 return si;
900 }
901 }
902 return nullptr;
903 }
905 static soinfo* find_library_internal(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
907 soinfo* si = find_loaded_library_by_name(name);
909 // Library might still be loaded, the accurate detection
910 // of this fact is done by load_library.
911 if (si == nullptr) {
912 TRACE("[ '%s' has not been found by name. Trying harder...]", name);
913 si = load_library(load_tasks, name, rtld_flags, extinfo);
914 }
916 return si;
917 }
919 static void soinfo_unload(soinfo* si);
921 static bool is_recursive(soinfo* si, soinfo* parent) {
922 if (parent == nullptr) {
923 return false;
924 }
926 if (si == parent) {
927 DL_ERR("recursive link to \"%s\"", si->name);
928 return true;
929 }
931 return !parent->get_parents().visit([&](soinfo* grandparent) {
932 return !is_recursive(si, grandparent);
933 });
934 }
936 static bool find_libraries(soinfo* start_with, const char* const library_names[], size_t library_names_count, soinfo* soinfos[],
937 soinfo* ld_preloads[], size_t ld_preloads_count, int rtld_flags, const android_dlextinfo* extinfo) {
938 // Step 0: prepare.
939 LoadTaskList load_tasks;
940 for (size_t i = 0; i < library_names_count; ++i) {
941 const char* name = library_names[i];
942 load_tasks.push_back(LoadTask::create(name, start_with));
943 }
945 // If soinfos array is null allocate one on stack.
946 // The array is needed in case of failure; for example
947 // when library_names[] = {libone.so, libtwo.so} and libone.so
948 // is loaded correctly but libtwo.so failed for some reason.
949 // In this case libone.so should be unloaded on return.
950 // See also implementation of failure_guard below.
952 if (soinfos == nullptr) {
953 size_t soinfos_size = sizeof(soinfo*)*library_names_count;
954 soinfos = reinterpret_cast<soinfo**>(alloca(soinfos_size));
955 memset(soinfos, 0, soinfos_size);
956 }
958 // list of libraries to link - see step 2.
959 size_t soinfos_count = 0;
961 auto failure_guard = make_scope_guard([&]() {
962 // Housekeeping
963 load_tasks.for_each([] (LoadTask* t) {
964 LoadTask::deleter(t);
965 });
967 for (size_t i = 0; i<soinfos_count; ++i) {
968 soinfo_unload(soinfos[i]);
969 }
970 });
972 // Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
973 for (LoadTask::unique_ptr task(load_tasks.pop_front()); task.get() != nullptr; task.reset(load_tasks.pop_front())) {
974 soinfo* si = find_library_internal(load_tasks, task->get_name(), rtld_flags, extinfo);
975 if (si == nullptr) {
976 return false;
977 }
979 soinfo* needed_by = task->get_needed_by();
981 if (is_recursive(si, needed_by)) {
982 return false;
983 }
985 si->ref_count++;
986 if (needed_by != nullptr) {
987 needed_by->add_child(si);
988 }
990 // When ld_preloads is not null, the first
991 // ld_preloads_count libs are in fact ld_preloads.
992 if (ld_preloads != nullptr && soinfos_count < ld_preloads_count) {
993 ld_preloads[soinfos_count] = si;
994 }
996 if (soinfos_count < library_names_count) {
997 soinfos[soinfos_count++] = si;
998 }
999 }
1001 // Step 2: link libraries.
1002 soinfo::soinfo_list_t local_group;
1003 walk_dependencies_tree(
1004 start_with == nullptr ? soinfos : &start_with,
1005 start_with == nullptr ? soinfos_count : 1,
1006 [&] (soinfo* si) {
1007 local_group.push_back(si);
1008 return true;
1009 });
1011 bool linked = local_group.visit([&](soinfo* si) {
1012 if ((si->flags & FLAG_LINKED) == 0) {
1013 if (!si->LinkImage(local_group, extinfo)) {
1014 return false;
1015 }
1016 si->flags |= FLAG_LINKED;
1017 }
1019 return true;
1020 });
1022 if (linked) {
1023 failure_guard.disable();
1024 }
1026 return linked;
1027 }
1029 static soinfo* find_library(const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
1030 if (name == nullptr) {
1031 somain->ref_count++;
1032 return somain;
1033 }
1035 soinfo* si;
1037 if (!find_libraries(nullptr, &name, 1, &si, nullptr, 0, rtld_flags, extinfo)) {
1038 return nullptr;
1039 }
1041 return si;
1042 }
1044 static void soinfo_unload(soinfo* si) {
1045 if (!si->can_unload()) {
1046 TRACE("not unloading '%s' - the binary is flagged with NODELETE", si->name);
1047 return;
1048 }
1050 if (si->ref_count == 1) {
1051 TRACE("unloading '%s'", si->name);
1052 si->CallDestructors();
1054 if (si->has_min_version(0)) {
1055 soinfo* child = nullptr;
1056 while ((child = si->get_children().pop_front()) != nullptr) {
1057 TRACE("%s needs to unload %s", si->name, child->name);
1058 soinfo_unload(child);
1059 }
1060 } else {
1061 for_each_dt_needed(si, [&] (const char* library_name) {
1062 TRACE("deprecated (old format of soinfo): %s needs to unload %s", si->name, library_name);
1063 soinfo* needed = find_library(library_name, RTLD_NOLOAD, nullptr);
1064 if (needed != nullptr) {
1065 soinfo_unload(needed);
1066 } else {
1067 // Not found: for example if symlink was deleted between dlopen and dlclose
1068 // Since we cannot really handle errors at this point - print and continue.
1069 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name);
1070 }
1071 });
1072 }
1074 notify_gdb_of_unload(si);
1075 si->ref_count = 0;
1076 soinfo_free(si);
1077 } else {
1078 si->ref_count--;
1079 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
1080 }
1081 }
1083 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
1084 // Use basic string manipulation calls to avoid snprintf.
1085 // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
1086 // When debug malloc is enabled, this call returns 0. This in turn causes
1087 // snprintf to do nothing, which causes libraries to fail to load.
1088 // See b/17302493 for further details.
1089 // Once the above bug is fixed, this code can be modified to use
1090 // snprintf again.
1091 size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
1092 if (buffer_size < required_len) {
1093 __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu",
1094 buffer_size, required_len);
1095 }
1096 char* end = stpcpy(buffer, kDefaultLdPaths[0]);
1097 *end = ':';
1098 strcpy(end + 1, kDefaultLdPaths[1]);
1099 }
1101 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
1102 if (!get_AT_SECURE()) {
1103 parse_LD_LIBRARY_PATH(ld_library_path);
1104 }
1105 }
1107 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
1108 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
1109 DL_ERR("invalid flags to dlopen: %x", flags);
1110 return nullptr;
1111 }
1112 if (extinfo != nullptr) {
1113 if ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0) {
1114 DL_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
1115 return nullptr;
1116 }
1117 if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
1118 (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
1119 DL_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET without ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
1120 return nullptr;
1121 }
1122 }
1123 protect_data(PROT_READ | PROT_WRITE);
1124 soinfo* si = find_library(name, flags, extinfo);
1125 if (si != nullptr) {
1126 si->CallConstructors();
1127 }
1128 protect_data(PROT_READ);
1129 return si;
1130 }
1132 void do_dlclose(soinfo* si) {
1133 protect_data(PROT_READ | PROT_WRITE);
1134 soinfo_unload(si);
1135 protect_data(PROT_READ);
1136 }
1138 static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
1139 typedef ElfW(Addr) (*ifunc_resolver_t)(void);
1140 ifunc_resolver_t ifunc_resolver = reinterpret_cast<ifunc_resolver_t>(resolver_addr);
1141 ElfW(Addr) ifunc_addr = ifunc_resolver();
1142 TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p", ifunc_resolver, reinterpret_cast<void*>(ifunc_addr));
1144 return ifunc_addr;
1145 }
1147 #if defined(USE_RELA)
1148 int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& local_group) {
1149 for (size_t idx = 0; idx < count; ++idx, ++rela) {
1150 unsigned type = ELFW(R_TYPE)(rela->r_info);
1151 unsigned sym = ELFW(R_SYM)(rela->r_info);
1152 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + load_bias);
1153 ElfW(Addr) sym_addr = 0;
1154 const char* sym_name = nullptr;
1156 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1157 if (type == 0) { // R_*_NONE
1158 continue;
1159 }
1161 ElfW(Sym)* s = nullptr;
1162 soinfo* lsi = nullptr;
1164 if (sym != 0) {
1165 sym_name = get_string(symtab[sym].st_name);
1166 s = soinfo_do_lookup(this, sym_name, &lsi, local_group);
1167 if (s == nullptr) {
1168 // We only allow an undefined symbol if this is a weak reference...
1169 s = &symtab[sym];
1170 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1171 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1172 return -1;
1173 }
1175 /* IHI0044C AAELF 4.5.1.1:
1177 Libraries are not searched to resolve weak references.
1178 It is not an error for a weak reference to remain unsatisfied.
1180 During linking, the value of an undefined weak reference is:
1181 - Zero if the relocation type is absolute
1182 - The address of the place if the relocation is pc-relative
1183 - The address of nominal base address if the relocation
1184 type is base-relative.
1185 */
1187 switch (type) {
1188 #if defined(__aarch64__)
1189 case R_AARCH64_JUMP_SLOT:
1190 case R_AARCH64_GLOB_DAT:
1191 case R_AARCH64_ABS64:
1192 case R_AARCH64_ABS32:
1193 case R_AARCH64_ABS16:
1194 case R_AARCH64_RELATIVE:
1195 case R_AARCH64_IRELATIVE:
1196 /*
1197 * The sym_addr was initialized to be zero above, or the relocation
1198 * code below does not care about value of sym_addr.
1199 * No need to do anything.
1200 */
1201 break;
1202 #elif defined(__x86_64__)
1203 case R_X86_64_JUMP_SLOT:
1204 case R_X86_64_GLOB_DAT:
1205 case R_X86_64_32:
1206 case R_X86_64_64:
1207 case R_X86_64_RELATIVE:
1208 case R_X86_64_IRELATIVE:
1209 // No need to do anything.
1210 break;
1211 case R_X86_64_PC32:
1212 sym_addr = reloc;
1213 break;
1214 #endif
1215 default:
1216 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
1217 return -1;
1218 }
1219 } else {
1220 // We got a definition.
1221 sym_addr = lsi->resolve_symbol_address(s);
1222 }
1223 count_relocation(kRelocSymbol);
1224 }
1226 switch (type) {
1227 #if defined(__aarch64__)
1228 case R_AARCH64_JUMP_SLOT:
1229 count_relocation(kRelocAbsolute);
1230 MARK(rela->r_offset);
1231 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
1232 reloc, (sym_addr + rela->r_addend), sym_name);
1233 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1234 break;
1235 case R_AARCH64_GLOB_DAT:
1236 count_relocation(kRelocAbsolute);
1237 MARK(rela->r_offset);
1238 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
1239 reloc, (sym_addr + rela->r_addend), sym_name);
1240 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1241 break;
1242 case R_AARCH64_ABS64:
1243 count_relocation(kRelocAbsolute);
1244 MARK(rela->r_offset);
1245 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
1246 reloc, (sym_addr + rela->r_addend), sym_name);
1247 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1248 break;
1249 case R_AARCH64_ABS32:
1250 count_relocation(kRelocAbsolute);
1251 MARK(rela->r_offset);
1252 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
1253 reloc, (sym_addr + rela->r_addend), sym_name);
1254 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1255 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1256 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
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)),
1260 static_cast<ElfW(Addr)>(INT32_MIN),
1261 static_cast<ElfW(Addr)>(UINT32_MAX));
1262 return -1;
1263 }
1264 break;
1265 case R_AARCH64_ABS16:
1266 count_relocation(kRelocAbsolute);
1267 MARK(rela->r_offset);
1268 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
1269 reloc, (sym_addr + rela->r_addend), sym_name);
1270 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1271 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1272 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1273 } else {
1274 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1275 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1276 static_cast<ElfW(Addr)>(INT16_MIN),
1277 static_cast<ElfW(Addr)>(UINT16_MAX));
1278 return -1;
1279 }
1280 break;
1281 case R_AARCH64_PREL64:
1282 count_relocation(kRelocRelative);
1283 MARK(rela->r_offset);
1284 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
1285 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1286 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
1287 break;
1288 case R_AARCH64_PREL32:
1289 count_relocation(kRelocRelative);
1290 MARK(rela->r_offset);
1291 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
1292 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1293 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1294 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1295 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1296 } else {
1297 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1298 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1299 static_cast<ElfW(Addr)>(INT32_MIN),
1300 static_cast<ElfW(Addr)>(UINT32_MAX));
1301 return -1;
1302 }
1303 break;
1304 case R_AARCH64_PREL16:
1305 count_relocation(kRelocRelative);
1306 MARK(rela->r_offset);
1307 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
1308 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1309 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1310 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1311 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1312 } else {
1313 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1314 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1315 static_cast<ElfW(Addr)>(INT16_MIN),
1316 static_cast<ElfW(Addr)>(UINT16_MAX));
1317 return -1;
1318 }
1319 break;
1321 case R_AARCH64_RELATIVE:
1322 count_relocation(kRelocRelative);
1323 MARK(rela->r_offset);
1324 if (sym) {
1325 DL_ERR("odd RELATIVE form...");
1326 return -1;
1327 }
1328 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
1329 reloc, (base + rela->r_addend));
1330 *reinterpret_cast<ElfW(Addr)*>(reloc) = (base + rela->r_addend);
1331 break;
1333 case R_AARCH64_IRELATIVE:
1334 count_relocation(kRelocRelative);
1335 MARK(rela->r_offset);
1336 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1337 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1338 break;
1340 case R_AARCH64_COPY:
1341 /*
1342 * ET_EXEC is not supported so this should not happen.
1343 *
1344 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1345 *
1346 * Section 4.7.1.10 "Dynamic relocations"
1347 * R_AARCH64_COPY may only appear in executable objects where e_type is
1348 * set to ET_EXEC.
1349 */
1350 DL_ERR("%s R_AARCH64_COPY relocations are not supported", name);
1351 return -1;
1352 case R_AARCH64_TLS_TPREL64:
1353 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
1354 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1355 break;
1356 case R_AARCH64_TLS_DTPREL32:
1357 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
1358 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1359 break;
1360 #elif defined(__x86_64__)
1361 case R_X86_64_JUMP_SLOT:
1362 count_relocation(kRelocAbsolute);
1363 MARK(rela->r_offset);
1364 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1365 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1366 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1367 break;
1368 case R_X86_64_GLOB_DAT:
1369 count_relocation(kRelocAbsolute);
1370 MARK(rela->r_offset);
1371 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1372 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1373 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1374 break;
1375 case R_X86_64_RELATIVE:
1376 count_relocation(kRelocRelative);
1377 MARK(rela->r_offset);
1378 if (sym) {
1379 DL_ERR("odd RELATIVE form...");
1380 return -1;
1381 }
1382 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
1383 static_cast<size_t>(base));
1384 *reinterpret_cast<ElfW(Addr)*>(reloc) = base + rela->r_addend;
1385 break;
1386 case R_X86_64_IRELATIVE:
1387 count_relocation(kRelocRelative);
1388 MARK(rela->r_offset);
1389 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1390 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1391 break;
1392 case R_X86_64_32:
1393 count_relocation(kRelocRelative);
1394 MARK(rela->r_offset);
1395 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1396 static_cast<size_t>(sym_addr), sym_name);
1397 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1398 break;
1399 case R_X86_64_64:
1400 count_relocation(kRelocRelative);
1401 MARK(rela->r_offset);
1402 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1403 static_cast<size_t>(sym_addr), sym_name);
1404 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1405 break;
1406 case R_X86_64_PC32:
1407 count_relocation(kRelocRelative);
1408 MARK(rela->r_offset);
1409 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
1410 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
1411 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
1412 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc;
1413 break;
1414 #endif
1416 default:
1417 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
1418 return -1;
1419 }
1420 }
1421 return 0;
1422 }
1424 #else // REL, not RELA.
1425 int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& local_group) {
1426 for (size_t idx = 0; idx < count; ++idx, ++rel) {
1427 unsigned type = ELFW(R_TYPE)(rel->r_info);
1428 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
1429 unsigned sym = ELFW(R_SYM)(rel->r_info);
1430 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
1431 ElfW(Addr) sym_addr = 0;
1432 const char* sym_name = nullptr;
1434 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1435 if (type == 0) { // R_*_NONE
1436 continue;
1437 }
1439 ElfW(Sym)* s = nullptr;
1440 soinfo* lsi = nullptr;
1442 if (sym != 0) {
1443 sym_name = get_string(symtab[sym].st_name);
1444 s = soinfo_do_lookup(this, sym_name, &lsi, local_group);
1445 if (s == nullptr) {
1446 // We only allow an undefined symbol if this is a weak reference...
1447 s = &symtab[sym];
1448 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1449 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1450 return -1;
1451 }
1453 /* IHI0044C AAELF 4.5.1.1:
1455 Libraries are not searched to resolve weak references.
1456 It is not an error for a weak reference to remain
1457 unsatisfied.
1459 During linking, the value of an undefined weak reference is:
1460 - Zero if the relocation type is absolute
1461 - The address of the place if the relocation is pc-relative
1462 - The address of nominal base address if the relocation
1463 type is base-relative.
1464 */
1466 switch (type) {
1467 #if defined(__arm__)
1468 case R_ARM_JUMP_SLOT:
1469 case R_ARM_GLOB_DAT:
1470 case R_ARM_ABS32:
1471 case R_ARM_RELATIVE: /* Don't care. */
1472 // sym_addr was initialized to be zero above or relocation
1473 // code below does not care about value of sym_addr.
1474 // No need to do anything.
1475 break;
1476 #elif defined(__i386__)
1477 case R_386_JMP_SLOT:
1478 case R_386_GLOB_DAT:
1479 case R_386_32:
1480 case R_386_RELATIVE: /* Don't care. */
1481 case R_386_IRELATIVE:
1482 // sym_addr was initialized to be zero above or relocation
1483 // code below does not care about value of sym_addr.
1484 // No need to do anything.
1485 break;
1486 case R_386_PC32:
1487 sym_addr = reloc;
1488 break;
1489 #endif
1491 #if defined(__arm__)
1492 case R_ARM_COPY:
1493 // Fall through. Can't really copy if weak symbol is not found at run-time.
1494 #endif
1495 default:
1496 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
1497 return -1;
1498 }
1499 } else {
1500 // We got a definition.
1501 sym_addr = lsi->resolve_symbol_address(s);
1502 }
1503 count_relocation(kRelocSymbol);
1504 }
1506 switch (type) {
1507 #if defined(__arm__)
1508 case R_ARM_JUMP_SLOT:
1509 count_relocation(kRelocAbsolute);
1510 MARK(rel->r_offset);
1511 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1512 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1513 break;
1514 case R_ARM_GLOB_DAT:
1515 count_relocation(kRelocAbsolute);
1516 MARK(rel->r_offset);
1517 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1518 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1519 break;
1520 case R_ARM_ABS32:
1521 count_relocation(kRelocAbsolute);
1522 MARK(rel->r_offset);
1523 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
1524 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1525 break;
1526 case R_ARM_REL32:
1527 count_relocation(kRelocRelative);
1528 MARK(rel->r_offset);
1529 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
1530 reloc, sym_addr, rel->r_offset, sym_name);
1531 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
1532 break;
1533 case R_ARM_COPY:
1534 /*
1535 * ET_EXEC is not supported so this should not happen.
1536 *
1537 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1538 *
1539 * Section 4.7.1.10 "Dynamic relocations"
1540 * R_ARM_COPY may only appear in executable objects where e_type is
1541 * set to ET_EXEC.
1542 */
1543 DL_ERR("%s R_ARM_COPY relocations are not supported", name);
1544 return -1;
1545 #elif defined(__i386__)
1546 case R_386_JMP_SLOT:
1547 count_relocation(kRelocAbsolute);
1548 MARK(rel->r_offset);
1549 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1550 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1551 break;
1552 case R_386_GLOB_DAT:
1553 count_relocation(kRelocAbsolute);
1554 MARK(rel->r_offset);
1555 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1556 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1557 break;
1558 case R_386_32:
1559 count_relocation(kRelocRelative);
1560 MARK(rel->r_offset);
1561 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
1562 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1563 break;
1564 case R_386_PC32:
1565 count_relocation(kRelocRelative);
1566 MARK(rel->r_offset);
1567 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
1568 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
1569 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
1570 break;
1571 #elif defined(__mips__)
1572 case R_MIPS_REL32:
1573 #if defined(__LP64__)
1574 // MIPS Elf64_Rel entries contain compound relocations
1575 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
1576 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
1577 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
1578 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
1579 type, (unsigned)ELF64_R_TYPE2(rel->r_info),
1580 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
1581 return -1;
1582 }
1583 #endif
1584 count_relocation(kRelocAbsolute);
1585 MARK(rel->r_offset);
1586 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
1587 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
1588 if (s) {
1589 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1590 } else {
1591 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1592 }
1593 break;
1594 #endif
1596 #if defined(__arm__)
1597 case R_ARM_RELATIVE:
1598 #elif defined(__i386__)
1599 case R_386_RELATIVE:
1600 #endif
1601 count_relocation(kRelocRelative);
1602 MARK(rel->r_offset);
1603 if (sym) {
1604 DL_ERR("odd RELATIVE form...");
1605 return -1;
1606 }
1607 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
1608 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1609 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1610 break;
1611 #if defined(__i386__)
1612 case R_386_IRELATIVE:
1613 count_relocation(kRelocRelative);
1614 MARK(rel->r_offset);
1615 TRACE_TYPE(RELO, "RELO IRELATIVE %p <- %p", reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1616 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + *reinterpret_cast<ElfW(Addr)*>(reloc));
1617 break;
1618 #endif
1620 default:
1621 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
1622 return -1;
1623 }
1624 }
1625 return 0;
1626 }
1627 #endif
1629 #if defined(__mips__)
1630 static bool mips_relocate_got(soinfo* si, const soinfo::soinfo_list_t& local_group) {
1631 ElfW(Addr)** got = si->plt_got;
1632 if (got == nullptr) {
1633 return true;
1634 }
1635 unsigned local_gotno = si->mips_local_gotno;
1636 unsigned gotsym = si->mips_gotsym;
1637 unsigned symtabno = si->mips_symtabno;
1638 ElfW(Sym)* symtab = si->symtab;
1640 // got[0] is the address of the lazy resolver function.
1641 // got[1] may be used for a GNU extension.
1642 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
1643 // FIXME: maybe this should be in a separate routine?
1644 if ((si->flags & FLAG_LINKER) == 0) {
1645 size_t g = 0;
1646 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
1647 if (reinterpret_cast<intptr_t>(got[g]) < 0) {
1648 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
1649 }
1650 // Relocate the local GOT entries.
1651 for (; g < local_gotno; g++) {
1652 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
1653 }
1654 }
1656 // Now for the global GOT entries...
1657 ElfW(Sym)* sym = symtab + gotsym;
1658 got = si->plt_got + local_gotno;
1659 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
1660 // This is an undefined reference... try to locate it.
1661 const char* sym_name = si->get_string(sym->st_name);
1662 soinfo* lsi = nullptr;
1663 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, local_group);
1664 if (s == nullptr) {
1665 // We only allow an undefined symbol if this is a weak reference.
1666 s = &symtab[g];
1667 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1668 DL_ERR("cannot locate \"%s\"...", sym_name);
1669 return false;
1670 }
1671 *got = 0;
1672 } else {
1673 // FIXME: is this sufficient?
1674 // For reference see NetBSD link loader
1675 // 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
1676 *got = reinterpret_cast<ElfW(Addr)*>(lsi->resolve_symbol_address(s));
1677 }
1678 }
1679 return true;
1680 }
1681 #endif
1683 void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
1684 if (functions == nullptr) {
1685 return;
1686 }
1688 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
1690 int begin = reverse ? (count - 1) : 0;
1691 int end = reverse ? -1 : count;
1692 int step = reverse ? -1 : 1;
1694 for (int i = begin; i != end; i += step) {
1695 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
1696 CallFunction("function", functions[i]);
1697 }
1699 TRACE("[ Done calling %s for '%s' ]", array_name, name);
1700 }
1702 void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
1703 if (function == nullptr || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
1704 return;
1705 }
1707 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
1708 function();
1709 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
1711 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
1712 // are still writable. This happens with our debug malloc (see http://b/7941716).
1713 protect_data(PROT_READ | PROT_WRITE);
1714 }
1716 void soinfo::CallPreInitConstructors() {
1717 // DT_PREINIT_ARRAY functions are called before any other constructors for executables,
1718 // but ignored in a shared library.
1719 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
1720 }
1722 void soinfo::CallConstructors() {
1723 if (constructors_called) {
1724 return;
1725 }
1727 // We set constructors_called before actually calling the constructors, otherwise it doesn't
1728 // protect against recursive constructor calls. One simple example of constructor recursion
1729 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
1730 // 1. The program depends on libc, so libc's constructor is called here.
1731 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
1732 // 3. dlopen() calls the constructors on the newly created
1733 // soinfo for libc_malloc_debug_leak.so.
1734 // 4. The debug .so depends on libc, so CallConstructors is
1735 // called again with the libc soinfo. If it doesn't trigger the early-
1736 // out above, the libc constructor will be called again (recursively!).
1737 constructors_called = true;
1739 if ((flags & FLAG_EXE) == 0 && preinit_array != nullptr) {
1740 // The GNU dynamic linker silently ignores these, but we warn the developer.
1741 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
1742 name, preinit_array_count);
1743 }
1745 get_children().for_each([] (soinfo* si) {
1746 si->CallConstructors();
1747 });
1749 TRACE("\"%s\": calling constructors", name);
1751 // DT_INIT should be called before DT_INIT_ARRAY if both are present.
1752 CallFunction("DT_INIT", init_func);
1753 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
1754 }
1756 void soinfo::CallDestructors() {
1757 if (!constructors_called) {
1758 return;
1759 }
1760 TRACE("\"%s\": calling destructors", name);
1762 // DT_FINI_ARRAY must be parsed in reverse order.
1763 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
1765 // DT_FINI should be called after DT_FINI_ARRAY if both are present.
1766 CallFunction("DT_FINI", fini_func);
1768 // This is needed on second call to dlopen
1769 // after library has been unloaded with RTLD_NODELETE
1770 constructors_called = false;
1771 }
1773 void soinfo::add_child(soinfo* child) {
1774 if (has_min_version(0)) {
1775 child->parents.push_back(this);
1776 this->children.push_back(child);
1777 }
1778 }
1780 void soinfo::remove_all_links() {
1781 if (!has_min_version(0)) {
1782 return;
1783 }
1785 // 1. Untie connected soinfos from 'this'.
1786 children.for_each([&] (soinfo* child) {
1787 child->parents.remove_if([&] (const soinfo* parent) {
1788 return parent == this;
1789 });
1790 });
1792 parents.for_each([&] (soinfo* parent) {
1793 parent->children.remove_if([&] (const soinfo* child) {
1794 return child == this;
1795 });
1796 });
1798 // 2. Once everything untied - clear local lists.
1799 parents.clear();
1800 children.clear();
1801 }
1803 dev_t soinfo::get_st_dev() {
1804 if (has_min_version(0)) {
1805 return st_dev;
1806 }
1808 return 0;
1809 };
1811 ino_t soinfo::get_st_ino() {
1812 if (has_min_version(0)) {
1813 return st_ino;
1814 }
1816 return 0;
1817 }
1819 off64_t soinfo::get_file_offset() {
1820 if (has_min_version(1)) {
1821 return file_offset;
1822 }
1824 return 0;
1825 }
1827 int soinfo::get_rtld_flags() {
1828 if (has_min_version(1)) {
1829 return rtld_flags;
1830 }
1832 return 0;
1833 }
1835 // This is a return on get_children()/get_parents() if
1836 // 'this->flags' does not have FLAG_NEW_SOINFO set.
1837 static soinfo::soinfo_list_t g_empty_list;
1839 soinfo::soinfo_list_t& soinfo::get_children() {
1840 if (has_min_version(0)) {
1841 return this->children;
1842 }
1844 return g_empty_list;
1845 }
1847 soinfo::soinfo_list_t& soinfo::get_parents() {
1848 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1849 return g_empty_list;
1850 }
1852 return this->parents;
1853 }
1855 ElfW(Addr) soinfo::resolve_symbol_address(ElfW(Sym)* s) {
1856 if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
1857 return call_ifunc_resolver(s->st_value + load_bias);
1858 }
1860 return static_cast<ElfW(Addr)>(s->st_value + load_bias);
1861 }
1863 const char* soinfo::get_string(ElfW(Word) index) const {
1864 if (has_min_version(1) && (index >= strtab_size)) {
1865 __libc_fatal("%s: strtab out of bounds error; STRSZ=%zd, name=%d", name, strtab_size, index);
1866 }
1868 return strtab + index;
1869 }
1871 bool soinfo::can_unload() const {
1872 return (rtld_flags & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
1873 }
1874 /* Force any of the closed stdin, stdout and stderr to be associated with
1875 /dev/null. */
1876 static int nullify_closed_stdio() {
1877 int dev_null, i, status;
1878 int return_value = 0;
1880 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
1881 if (dev_null < 0) {
1882 DL_ERR("cannot open /dev/null: %s", strerror(errno));
1883 return -1;
1884 }
1885 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
1887 /* If any of the stdio file descriptors is valid and not associated
1888 with /dev/null, dup /dev/null to it. */
1889 for (i = 0; i < 3; i++) {
1890 /* If it is /dev/null already, we are done. */
1891 if (i == dev_null) {
1892 continue;
1893 }
1895 TRACE("[ Nullifying stdio file descriptor %d]", i);
1896 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
1898 /* If file is opened, we are good. */
1899 if (status != -1) {
1900 continue;
1901 }
1903 /* The only error we allow is that the file descriptor does not
1904 exist, in which case we dup /dev/null to it. */
1905 if (errno != EBADF) {
1906 DL_ERR("fcntl failed: %s", strerror(errno));
1907 return_value = -1;
1908 continue;
1909 }
1911 /* Try dupping /dev/null to this stdio file descriptor and
1912 repeat if there is a signal. Note that any errors in closing
1913 the stdio descriptor are lost. */
1914 status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
1915 if (status < 0) {
1916 DL_ERR("dup2 failed: %s", strerror(errno));
1917 return_value = -1;
1918 continue;
1919 }
1920 }
1922 /* If /dev/null is not one of the stdio file descriptors, close it. */
1923 if (dev_null > 2) {
1924 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
1925 status = TEMP_FAILURE_RETRY(close(dev_null));
1926 if (status == -1) {
1927 DL_ERR("close failed: %s", strerror(errno));
1928 return_value = -1;
1929 }
1930 }
1932 return return_value;
1933 }
1935 bool soinfo::PrelinkImage() {
1936 /* Extract dynamic section */
1937 ElfW(Word) dynamic_flags = 0;
1938 phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
1940 /* We can't log anything until the linker is relocated */
1941 bool relocating_linker = (flags & FLAG_LINKER) != 0;
1942 if (!relocating_linker) {
1943 INFO("[ linking %s ]", name);
1944 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags);
1945 }
1947 if (dynamic == nullptr) {
1948 if (!relocating_linker) {
1949 DL_ERR("missing PT_DYNAMIC in \"%s\"", name);
1950 }
1951 return false;
1952 } else {
1953 if (!relocating_linker) {
1954 DEBUG("dynamic = %p", dynamic);
1955 }
1956 }
1958 #if defined(__arm__)
1959 (void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
1960 &ARM_exidx, &ARM_exidx_count);
1961 #endif
1963 // Extract useful information from dynamic section.
1964 uint32_t needed_count = 0;
1965 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
1966 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
1967 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1968 switch (d->d_tag) {
1969 case DT_SONAME:
1970 // TODO: glibc dynamic linker uses this name for
1971 // initial library lookup; consider doing the same here.
1972 break;
1974 case DT_HASH:
1975 nbucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
1976 nchain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
1977 bucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
1978 chain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket * 4);
1979 break;
1981 case DT_STRTAB:
1982 strtab = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
1983 break;
1985 case DT_STRSZ:
1986 strtab_size = d->d_un.d_val;
1987 break;
1989 case DT_SYMTAB:
1990 symtab = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
1991 break;
1993 case DT_SYMENT:
1994 if (d->d_un.d_val != sizeof(ElfW(Sym))) {
1995 DL_ERR("invalid DT_SYMENT: %zd", static_cast<size_t>(d->d_un.d_val));
1996 return false;
1997 }
1998 break;
2000 case DT_PLTREL:
2001 #if defined(USE_RELA)
2002 if (d->d_un.d_val != DT_RELA) {
2003 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_RELA", name);
2004 return false;
2005 }
2006 #else
2007 if (d->d_un.d_val != DT_REL) {
2008 DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_REL", name);
2009 return false;
2010 }
2011 #endif
2012 break;
2014 case DT_JMPREL:
2015 #if defined(USE_RELA)
2016 plt_rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2017 #else
2018 plt_rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2019 #endif
2020 break;
2022 case DT_PLTRELSZ:
2023 #if defined(USE_RELA)
2024 plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
2025 #else
2026 plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
2027 #endif
2028 break;
2030 case DT_PLTGOT:
2031 #if defined(__mips__)
2032 // Used by mips and mips64.
2033 plt_got = reinterpret_cast<ElfW(Addr)**>(load_bias + d->d_un.d_ptr);
2034 #endif
2035 // Ignore for other platforms... (because RTLD_LAZY is not supported)
2036 break;
2038 case DT_DEBUG:
2039 // Set the DT_DEBUG entry to the address of _r_debug for GDB
2040 // if the dynamic table is writable
2041 // FIXME: not working currently for N64
2042 // The flags for the LOAD and DYNAMIC program headers do not agree.
2043 // The LOAD section containing the dynamic table has been mapped as
2044 // read-only, but the DYNAMIC header claims it is writable.
2045 #if !(defined(__mips__) && defined(__LP64__))
2046 if ((dynamic_flags & PF_W) != 0) {
2047 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
2048 }
2049 break;
2050 #endif
2051 #if defined(USE_RELA)
2052 case DT_RELA:
2053 rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2054 break;
2056 case DT_RELASZ:
2057 rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
2058 break;
2060 case DT_RELAENT:
2061 if (d->d_un.d_val != sizeof(ElfW(Rela))) {
2062 DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
2063 return false;
2064 }
2065 break;
2067 // ignored (see DT_RELCOUNT comments for details)
2068 case DT_RELACOUNT:
2069 break;
2071 case DT_REL:
2072 DL_ERR("unsupported DT_REL in \"%s\"", name);
2073 return false;
2075 case DT_RELSZ:
2076 DL_ERR("unsupported DT_RELSZ in \"%s\"", name);
2077 return false;
2078 #else
2079 case DT_REL:
2080 rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2081 break;
2083 case DT_RELSZ:
2084 rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
2085 break;
2087 case DT_RELENT:
2088 if (d->d_un.d_val != sizeof(ElfW(Rel))) {
2089 DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
2090 return false;
2091 }
2092 break;
2094 // "Indicates that all RELATIVE relocations have been concatenated together,
2095 // and specifies the RELATIVE relocation count."
2096 //
2097 // TODO: Spec also mentions that this can be used to optimize relocation process;
2098 // Not currently used by bionic linker - ignored.
2099 case DT_RELCOUNT:
2100 break;
2101 case DT_RELA:
2102 DL_ERR("unsupported DT_RELA in \"%s\"", name);
2103 return false;
2104 #endif
2105 case DT_INIT:
2106 init_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2107 DEBUG("%s constructors (DT_INIT) found at %p", name, init_func);
2108 break;
2110 case DT_FINI:
2111 fini_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2112 DEBUG("%s destructors (DT_FINI) found at %p", name, fini_func);
2113 break;
2115 case DT_INIT_ARRAY:
2116 init_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2117 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", name, init_array);
2118 break;
2120 case DT_INIT_ARRAYSZ:
2121 init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2122 break;
2124 case DT_FINI_ARRAY:
2125 fini_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2126 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", name, fini_array);
2127 break;
2129 case DT_FINI_ARRAYSZ:
2130 fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2131 break;
2133 case DT_PREINIT_ARRAY:
2134 preinit_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2135 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", name, preinit_array);
2136 break;
2138 case DT_PREINIT_ARRAYSZ:
2139 preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2140 break;
2142 case DT_TEXTREL:
2143 #if defined(__LP64__)
2144 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2145 return false;
2146 #else
2147 has_text_relocations = true;
2148 break;
2149 #endif
2151 case DT_SYMBOLIC:
2152 has_DT_SYMBOLIC = true;
2153 break;
2155 case DT_NEEDED:
2156 ++needed_count;
2157 break;
2159 case DT_FLAGS:
2160 if (d->d_un.d_val & DF_TEXTREL) {
2161 #if defined(__LP64__)
2162 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2163 return false;
2164 #else
2165 has_text_relocations = true;
2166 #endif
2167 }
2168 if (d->d_un.d_val & DF_SYMBOLIC) {
2169 has_DT_SYMBOLIC = true;
2170 }
2171 break;
2173 case DT_FLAGS_1:
2174 if ((d->d_un.d_val & DF_1_GLOBAL) != 0) {
2175 rtld_flags |= RTLD_GLOBAL;
2176 }
2178 if ((d->d_un.d_val & DF_1_NODELETE) != 0) {
2179 rtld_flags |= RTLD_NODELETE;
2180 }
2181 // TODO: Implement other flags
2183 if ((d->d_un.d_val & ~(DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE)) != 0) {
2184 DL_WARN("Unsupported flags DT_FLAGS_1=%p", reinterpret_cast<void*>(d->d_un.d_val));
2185 }
2186 break;
2187 #if defined(__mips__)
2188 case DT_MIPS_RLD_MAP:
2189 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
2190 {
2191 r_debug** dp = reinterpret_cast<r_debug**>(load_bias + d->d_un.d_ptr);
2192 *dp = &_r_debug;
2193 }
2194 break;
2196 case DT_MIPS_RLD_VERSION:
2197 case DT_MIPS_FLAGS:
2198 case DT_MIPS_BASE_ADDRESS:
2199 case DT_MIPS_UNREFEXTNO:
2200 break;
2202 case DT_MIPS_SYMTABNO:
2203 mips_symtabno = d->d_un.d_val;
2204 break;
2206 case DT_MIPS_LOCAL_GOTNO:
2207 mips_local_gotno = d->d_un.d_val;
2208 break;
2210 case DT_MIPS_GOTSYM:
2211 mips_gotsym = d->d_un.d_val;
2212 break;
2213 #endif
2214 // Ignored: "Its use has been superseded by the DF_BIND_NOW flag"
2215 case DT_BIND_NOW:
2216 break;
2218 // Ignore: bionic does not support symbol versioning...
2219 case DT_VERSYM:
2220 case DT_VERDEF:
2221 case DT_VERDEFNUM:
2222 break;
2224 default:
2225 if (!relocating_linker) {
2226 DL_WARN("%s: unused DT entry: type %p arg %p", name,
2227 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
2228 }
2229 break;
2230 }
2231 }
2233 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
2234 reinterpret_cast<void*>(base), strtab, symtab);
2236 // Sanity checks.
2237 if (relocating_linker && needed_count != 0) {
2238 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
2239 return false;
2240 }
2241 if (nbucket == 0) {
2242 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", name);
2243 return false;
2244 }
2245 if (strtab == 0) {
2246 DL_ERR("empty/missing DT_STRTAB in \"%s\"", name);
2247 return false;
2248 }
2249 if (symtab == 0) {
2250 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", name);
2251 return false;
2252 }
2253 return true;
2254 }
2256 bool soinfo::LinkImage(const soinfo_list_t& local_group, const android_dlextinfo* extinfo) {
2258 #if !defined(__LP64__)
2259 if (has_text_relocations) {
2260 // Make segments writable to allow text relocations to work properly. We will later call
2261 // phdr_table_protect_segments() after all of them are applied and all constructors are run.
2262 DL_WARN("%s has text relocations. This is wasting memory and prevents "
2263 "security hardening. Please fix.", name);
2264 if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
2265 DL_ERR("can't unprotect loadable segments for \"%s\": %s",
2266 name, strerror(errno));
2267 return false;
2268 }
2269 }
2270 #endif
2272 #if defined(USE_RELA)
2273 if (rela != nullptr) {
2274 DEBUG("[ relocating %s ]", name);
2275 if (Relocate(rela, rela_count, local_group)) {
2276 return false;
2277 }
2278 }
2279 if (plt_rela != nullptr) {
2280 DEBUG("[ relocating %s plt ]", name);
2281 if (Relocate(plt_rela, plt_rela_count, local_group)) {
2282 return false;
2283 }
2284 }
2285 #else
2286 if (rel != nullptr) {
2287 DEBUG("[ relocating %s ]", name);
2288 if (Relocate(rel, rel_count, local_group)) {
2289 return false;
2290 }
2291 }
2292 if (plt_rel != nullptr) {
2293 DEBUG("[ relocating %s plt ]", name);
2294 if (Relocate(plt_rel, plt_rel_count, local_group)) {
2295 return false;
2296 }
2297 }
2298 #endif
2300 #if defined(__mips__)
2301 if (!mips_relocate_got(this)) {
2302 return false;
2303 }
2304 #endif
2306 DEBUG("[ finished linking %s ]", name);
2308 #if !defined(__LP64__)
2309 if (has_text_relocations) {
2310 // All relocations are done, we can protect our segments back to read-only.
2311 if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
2312 DL_ERR("can't protect segments for \"%s\": %s",
2313 name, strerror(errno));
2314 return false;
2315 }
2316 }
2317 #endif
2319 /* We can also turn on GNU RELRO protection */
2320 if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
2321 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
2322 name, strerror(errno));
2323 return false;
2324 }
2326 /* Handle serializing/sharing the RELRO segment */
2327 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
2328 if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
2329 extinfo->relro_fd) < 0) {
2330 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
2331 name, strerror(errno));
2332 return false;
2333 }
2334 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
2335 if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
2336 extinfo->relro_fd) < 0) {
2337 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
2338 name, strerror(errno));
2339 return false;
2340 }
2341 }
2343 notify_gdb_of_load(this);
2344 return true;
2345 }
2347 /*
2348 * This function add vdso to internal dso list.
2349 * It helps to stack unwinding through signal handlers.
2350 * Also, it makes bionic more like glibc.
2351 */
2352 static void add_vdso(KernelArgumentBlock& args __unused) {
2353 #if defined(AT_SYSINFO_EHDR)
2354 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
2355 if (ehdr_vdso == nullptr) {
2356 return;
2357 }
2359 soinfo* si = soinfo_alloc("[vdso]", nullptr, 0, 0);
2361 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
2362 si->phnum = ehdr_vdso->e_phnum;
2363 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
2364 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2365 si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
2367 si->PrelinkImage();
2368 si->LinkImage(g_empty_list, nullptr);
2369 #endif
2370 }
2372 /*
2373 * This is linker soinfo for GDB. See details below.
2374 */
2375 #if defined(__LP64__)
2376 #define LINKER_PATH "/system/bin/linker64"
2377 #else
2378 #define LINKER_PATH "/system/bin/linker"
2379 #endif
2380 static soinfo linker_soinfo_for_gdb(LINKER_PATH, nullptr, 0, 0);
2382 /* gdb expects the linker to be in the debug shared object list.
2383 * Without this, gdb has trouble locating the linker's ".text"
2384 * and ".plt" sections. Gdb could also potentially use this to
2385 * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
2386 * Don't use soinfo_alloc(), because the linker shouldn't
2387 * be on the soinfo list.
2388 */
2389 static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
2390 linker_soinfo_for_gdb.base = linker_base;
2392 /*
2393 * Set the dynamic field in the link map otherwise gdb will complain with
2394 * the following:
2395 * warning: .dynamic section for "/system/bin/linker" is not at the
2396 * expected address (wrong library or version mismatch?)
2397 */
2398 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
2399 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
2400 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
2401 &linker_soinfo_for_gdb.dynamic, nullptr);
2402 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
2403 }
2405 /*
2406 * This code is called after the linker has linked itself and
2407 * fixed it's own GOT. It is safe to make references to externs
2408 * and other non-local data at this point.
2409 */
2410 static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
2411 #if TIMING
2412 struct timeval t0, t1;
2413 gettimeofday(&t0, 0);
2414 #endif
2416 // Initialize environment functions, and get to the ELF aux vectors table.
2417 linker_env_init(args);
2419 // If this is a setuid/setgid program, close the security hole described in
2420 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2421 if (get_AT_SECURE()) {
2422 nullify_closed_stdio();
2423 }
2425 debuggerd_init();
2427 // Get a few environment variables.
2428 const char* LD_DEBUG = linker_env_get("LD_DEBUG");
2429 if (LD_DEBUG != nullptr) {
2430 g_ld_debug_verbosity = atoi(LD_DEBUG);
2431 }
2433 // Normally, these are cleaned by linker_env_init, but the test
2434 // doesn't cost us anything.
2435 const char* ldpath_env = nullptr;
2436 const char* ldpreload_env = nullptr;
2437 if (!get_AT_SECURE()) {
2438 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2439 ldpreload_env = linker_env_get("LD_PRELOAD");
2440 }
2442 INFO("[ android linker & debugger ]");
2444 soinfo* si = soinfo_alloc(args.argv[0], nullptr, 0, RTLD_GLOBAL);
2445 if (si == nullptr) {
2446 exit(EXIT_FAILURE);
2447 }
2449 /* bootstrap the link map, the main exe always needs to be first */
2450 si->flags |= FLAG_EXE;
2451 link_map* map = &(si->link_map_head);
2453 map->l_addr = 0;
2454 map->l_name = args.argv[0];
2455 map->l_prev = nullptr;
2456 map->l_next = nullptr;
2458 _r_debug.r_map = map;
2459 r_debug_tail = map;
2461 init_linker_info_for_gdb(linker_base);
2463 // Extract information passed from the kernel.
2464 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
2465 si->phnum = args.getauxval(AT_PHNUM);
2466 si->entry = args.getauxval(AT_ENTRY);
2468 /* Compute the value of si->base. We can't rely on the fact that
2469 * the first entry is the PHDR because this will not be true
2470 * for certain executables (e.g. some in the NDK unit test suite)
2471 */
2472 si->base = 0;
2473 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2474 si->load_bias = 0;
2475 for (size_t i = 0; i < si->phnum; ++i) {
2476 if (si->phdr[i].p_type == PT_PHDR) {
2477 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
2478 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
2479 break;
2480 }
2481 }
2482 si->dynamic = nullptr;
2483 si->ref_count = 1;
2485 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
2486 if (elf_hdr->e_type != ET_DYN) {
2487 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
2488 exit(EXIT_FAILURE);
2489 }
2491 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
2492 parse_LD_LIBRARY_PATH(ldpath_env);
2493 parse_LD_PRELOAD(ldpreload_env);
2495 somain = si;
2497 si->PrelinkImage();
2499 // Load ld_preloads and dependencies.
2500 StringLinkedList needed_library_name_list;
2501 size_t needed_libraries_count = 0;
2502 size_t ld_preloads_count = 0;
2503 while (g_ld_preload_names[ld_preloads_count] != nullptr) {
2504 needed_library_name_list.push_back(g_ld_preload_names[ld_preloads_count++]);
2505 ++needed_libraries_count;
2506 }
2508 for_each_dt_needed(si, [&](const char* name) {
2509 needed_library_name_list.push_back(name);
2510 ++needed_libraries_count;
2511 });
2513 const char* needed_library_names[needed_libraries_count];
2515 memset(needed_library_names, 0, sizeof(needed_library_names));
2516 needed_library_name_list.copy_to_array(needed_library_names, needed_libraries_count);
2518 if (needed_libraries_count > 0 && !find_libraries(si, needed_library_names, needed_libraries_count, nullptr, g_ld_preloads, ld_preloads_count, RTLD_GLOBAL, nullptr)) {
2519 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
2520 exit(EXIT_FAILURE);
2521 }
2523 add_vdso(args);
2525 si->CallPreInitConstructors();
2527 /* After the PrelinkImage, the si->load_bias is initialized.
2528 * For so lib, the map->l_addr will be updated in notify_gdb_of_load.
2529 * We need to update this value for so exe here. So Unwind_Backtrace
2530 * for some arch like x86 could work correctly within so exe.
2531 */
2532 map->l_addr = si->load_bias;
2533 si->CallConstructors();
2535 #if TIMING
2536 gettimeofday(&t1, nullptr);
2537 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
2538 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2539 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
2540 #endif
2541 #if STATS
2542 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
2543 linker_stats.count[kRelocAbsolute],
2544 linker_stats.count[kRelocRelative],
2545 linker_stats.count[kRelocCopy],
2546 linker_stats.count[kRelocSymbol]);
2547 #endif
2548 #if COUNT_PAGES
2549 {
2550 unsigned n;
2551 unsigned i;
2552 unsigned count = 0;
2553 for (n = 0; n < 4096; n++) {
2554 if (bitmask[n]) {
2555 unsigned x = bitmask[n];
2556 #if defined(__LP64__)
2557 for (i = 0; i < 32; i++) {
2558 #else
2559 for (i = 0; i < 8; i++) {
2560 #endif
2561 if (x & 1) {
2562 count++;
2563 }
2564 x >>= 1;
2565 }
2566 }
2567 }
2568 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
2569 }
2570 #endif
2572 #if TIMING || STATS || COUNT_PAGES
2573 fflush(stdout);
2574 #endif
2576 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry));
2577 return si->entry;
2578 }
2580 /* Compute the load-bias of an existing executable. This shall only
2581 * be used to compute the load bias of an executable or shared library
2582 * that was loaded by the kernel itself.
2583 *
2584 * Input:
2585 * elf -> address of ELF header, assumed to be at the start of the file.
2586 * Return:
2587 * load bias, i.e. add the value of any p_vaddr in the file to get
2588 * the corresponding address in memory.
2589 */
2590 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
2591 ElfW(Addr) offset = elf->e_phoff;
2592 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
2593 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
2595 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
2596 if (phdr->p_type == PT_LOAD) {
2597 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
2598 }
2599 }
2600 return 0;
2601 }
2603 extern "C" void _start();
2605 /*
2606 * This is the entry point for the linker, called from begin.S. This
2607 * method is responsible for fixing the linker's own relocations, and
2608 * then calling __linker_init_post_relocation().
2609 *
2610 * Because this method is called before the linker has fixed it's own
2611 * relocations, any attempt to reference an extern variable, extern
2612 * function, or other GOT reference will generate a segfault.
2613 */
2614 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
2615 KernelArgumentBlock args(raw_args);
2617 ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
2618 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY);
2619 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
2620 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
2622 soinfo linker_so("[dynamic linker]", nullptr, 0, 0);
2624 // If the linker is not acting as PT_INTERP entry_point is equal to
2625 // _start. Which means that the linker is running as an executable and
2626 // already linked by PT_INTERP.
2627 //
2628 // This happens when user tries to run 'adb shell /system/bin/linker'
2629 // see also https://code.google.com/p/android/issues/detail?id=63174
2630 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) {
2631 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]);
2632 }
2634 linker_so.base = linker_addr;
2635 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
2636 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
2637 linker_so.dynamic = nullptr;
2638 linker_so.phdr = phdr;
2639 linker_so.phnum = elf_hdr->e_phnum;
2640 linker_so.flags |= FLAG_LINKER;
2642 if (!(linker_so.PrelinkImage() && linker_so.LinkImage(g_empty_list, nullptr))) {
2643 // It would be nice to print an error message, but if the linker
2644 // can't link itself, there's no guarantee that we'll be able to
2645 // call write() (because it involves a GOT reference). We may as
2646 // well try though...
2647 const char* msg = "CANNOT LINK EXECUTABLE: ";
2648 write(2, msg, strlen(msg));
2649 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2650 write(2, "\n", 1);
2651 _exit(EXIT_FAILURE);
2652 }
2654 __libc_init_tls(args);
2656 // Initialize the linker's own global variables
2657 linker_so.CallConstructors();
2659 // Initialize static variables. Note that in order to
2660 // get correct libdl_info we need to call constructors
2661 // before get_libdl_info().
2662 solist = get_libdl_info();
2663 sonext = get_libdl_info();
2665 // We have successfully fixed our own relocations. It's safe to run
2666 // the main part of the linker now.
2667 args.abort_message_ptr = &g_abort_message;
2668 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
2670 protect_data(PROT_READ);
2672 // Return the address that the calling assembly stub should jump to.
2673 return start_address;
2674 }