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, 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, 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, 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 set_st_dev(file_stat->st_dev);
464 set_st_ino(file_stat->st_ino);
465 }
467 this->rtld_flags = rtld_flags;
468 }
470 static unsigned elfhash(const char* _name) {
471 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
472 unsigned h = 0, g;
474 while (*name) {
475 h = (h << 4) + *name++;
476 g = h & 0xf0000000;
477 h ^= g;
478 h ^= g >> 24;
479 }
480 return h;
481 }
483 static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi) {
484 unsigned elf_hash = elfhash(name);
485 ElfW(Sym)* s = nullptr;
487 /* "This element's presence in a shared object library alters the dynamic linker's
488 * symbol resolution algorithm for references within the library. Instead of starting
489 * a symbol search with the executable file, the dynamic linker starts from the shared
490 * object itself. If the shared object fails to supply the referenced symbol, the
491 * dynamic linker then searches the executable file and other shared objects as usual."
492 *
493 * http://www.sco.com/developers/gabi/2012-12-31/ch5.dynamic.html
494 *
495 * Note that this is unlikely since static linker avoids generating
496 * relocations for -Bsymbolic linked dynamic executables.
497 */
498 if (si->has_DT_SYMBOLIC) {
499 DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si->name, name);
500 s = soinfo_elf_lookup(si, elf_hash, name);
501 if (s != nullptr) {
502 *lsi = si;
503 }
504 }
506 if (s == nullptr && somain != nullptr) {
507 // 1. Look for it in the main executable unless we already did.
508 if (si != somain || !si->has_DT_SYMBOLIC) {
509 DEBUG("%s: looking up %s in executable %s",
510 si->name, name, somain->name);
511 s = soinfo_elf_lookup(somain, elf_hash, name);
512 if (s != nullptr) {
513 *lsi = somain;
514 }
515 }
517 // 2. Look for it in the ld_preloads
518 if (s == nullptr) {
519 for (int i = 0; g_ld_preloads[i] != NULL; i++) {
520 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
521 if (s != nullptr) {
522 *lsi = g_ld_preloads[i];
523 break;
524 }
525 }
526 }
527 }
529 /* Look for symbols in the local scope (the object who is
530 * searching). This happens with C++ templates on x86 for some
531 * reason.
532 *
533 * Notes on weak symbols:
534 * The ELF specs are ambiguous about treatment of weak definitions in
535 * dynamic linking. Some systems return the first definition found
536 * and some the first non-weak definition. This is system dependent.
537 * Here we return the first definition found for simplicity. */
539 if (s == nullptr && !si->has_DT_SYMBOLIC) {
540 DEBUG("%s: looking up %s in local scope", si->name, name);
541 s = soinfo_elf_lookup(si, elf_hash, name);
542 if (s != nullptr) {
543 *lsi = si;
544 }
545 }
547 if (s == nullptr) {
548 si->get_children().visit([&](soinfo* child) {
549 DEBUG("%s: looking up %s in %s", si->name, name, child->name);
550 s = soinfo_elf_lookup(child, elf_hash, name);
551 if (s != nullptr) {
552 *lsi = child;
553 return false;
554 }
555 return true;
556 });
557 }
559 if (s != nullptr) {
560 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
561 "found in %s, base = %p, load bias = %p",
562 si->name, name, reinterpret_cast<void*>(s->st_value),
563 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
564 reinterpret_cast<void*>((*lsi)->load_bias));
565 }
567 return s;
568 }
570 // Each size has it's own allocator.
571 template<size_t size>
572 class SizeBasedAllocator {
573 public:
574 static void* alloc() {
575 return allocator_.alloc();
576 }
578 static void free(void* ptr) {
579 allocator_.free(ptr);
580 }
582 private:
583 static LinkerBlockAllocator allocator_;
584 };
586 template<size_t size>
587 LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
589 template<typename T>
590 class TypeBasedAllocator {
591 public:
592 static T* alloc() {
593 return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
594 }
596 static void free(T* ptr) {
597 SizeBasedAllocator<sizeof(T)>::free(ptr);
598 }
599 };
601 class LoadTask {
602 public:
603 struct deleter_t {
604 void operator()(LoadTask* t) {
605 TypeBasedAllocator<LoadTask>::free(t);
606 }
607 };
609 typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
611 static deleter_t deleter;
613 static LoadTask* create(const char* name, soinfo* needed_by) {
614 LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
615 return new (ptr) LoadTask(name, needed_by);
616 }
618 const char* get_name() const {
619 return name_;
620 }
622 soinfo* get_needed_by() const {
623 return needed_by_;
624 }
625 private:
626 LoadTask(const char* name, soinfo* needed_by)
627 : name_(name), needed_by_(needed_by) {}
629 const char* name_;
630 soinfo* needed_by_;
632 DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
633 };
635 LoadTask::deleter_t LoadTask::deleter;
637 template <typename T>
638 using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
640 typedef linked_list_t<soinfo> SoinfoLinkedList;
641 typedef linked_list_t<const char> StringLinkedList;
642 typedef linked_list_t<LoadTask> LoadTaskList;
645 // This is used by dlsym(3). It performs symbol lookup only within the
646 // specified soinfo object and its dependencies in breadth first order.
647 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
648 SoinfoLinkedList visit_list;
649 SoinfoLinkedList visited;
651 visit_list.push_back(si);
652 soinfo* current_soinfo;
653 while ((current_soinfo = visit_list.pop_front()) != nullptr) {
654 if (visited.contains(current_soinfo)) {
655 continue;
656 }
658 ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name);
660 if (result != nullptr) {
661 *found = current_soinfo;
662 return result;
663 }
664 visited.push_back(current_soinfo);
666 current_soinfo->get_children().for_each([&](soinfo* child) {
667 visit_list.push_back(child);
668 });
669 }
671 return nullptr;
672 }
674 /* This is used by dlsym(3) to performs a global symbol lookup. If the
675 start value is null (for RTLD_DEFAULT), the search starts at the
676 beginning of the global solist. Otherwise the search starts at the
677 specified soinfo (for RTLD_NEXT).
678 */
679 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
680 unsigned elf_hash = elfhash(name);
682 if (start == nullptr) {
683 start = solist;
684 }
686 ElfW(Sym)* s = nullptr;
687 for (soinfo* si = start; (s == nullptr) && (si != nullptr); si = si->next) {
688 if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0) {
689 continue;
690 }
692 s = soinfo_elf_lookup(si, elf_hash, name);
693 if (s != nullptr) {
694 *found = si;
695 break;
696 }
697 }
699 if (s != nullptr) {
700 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
701 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
702 }
704 return s;
705 }
707 soinfo* find_containing_library(const void* p) {
708 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
709 for (soinfo* si = solist; si != nullptr; si = si->next) {
710 if (address >= si->base && address - si->base < si->size) {
711 return si;
712 }
713 }
714 return nullptr;
715 }
717 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
718 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
720 // Search the library's symbol table for any defined symbol which
721 // contains this address.
722 for (size_t i = 0; i < si->nchain; ++i) {
723 ElfW(Sym)* sym = &si->symtab[i];
724 if (sym->st_shndx != SHN_UNDEF &&
725 soaddr >= sym->st_value &&
726 soaddr < sym->st_value + sym->st_size) {
727 return sym;
728 }
729 }
731 return nullptr;
732 }
734 static int open_library_on_path(const char* name, const char* const paths[]) {
735 char buf[512];
736 for (size_t i = 0; paths[i] != nullptr; ++i) {
737 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
738 if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
739 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
740 continue;
741 }
742 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
743 if (fd != -1) {
744 return fd;
745 }
746 }
747 return -1;
748 }
750 static int open_library(const char* name) {
751 TRACE("[ opening %s ]", name);
753 // If the name contains a slash, we should attempt to open it directly and not search the paths.
754 if (strchr(name, '/') != nullptr) {
755 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
756 if (fd != -1) {
757 return fd;
758 }
759 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
760 #if defined(__LP64__)
761 return -1;
762 #endif
763 }
765 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
766 int fd = open_library_on_path(name, g_ld_library_paths);
767 if (fd == -1) {
768 fd = open_library_on_path(name, kDefaultLdPaths);
769 }
770 return fd;
771 }
773 template<typename F>
774 static void for_each_dt_needed(const soinfo* si, F action) {
775 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
776 if (d->d_tag == DT_NEEDED) {
777 action(si->get_string(d->d_un.d_val));
778 }
779 }
780 }
782 static soinfo* load_library(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
783 int fd = -1;
784 ScopedFd file_guard(-1);
786 if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
787 fd = extinfo->library_fd;
788 } else {
789 // Open the file.
790 fd = open_library(name);
791 if (fd == -1) {
792 DL_ERR("library \"%s\" not found", name);
793 return nullptr;
794 }
796 file_guard.reset(fd);
797 }
799 struct stat file_stat;
800 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
801 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno));
802 return nullptr;
803 }
805 // Check for symlink and other situations where
806 // file can have different names.
807 for (soinfo* si = solist; si != nullptr; si = si->next) {
808 if (si->get_st_dev() != 0 &&
809 si->get_st_ino() != 0 &&
810 si->get_st_dev() == file_stat.st_dev &&
811 si->get_st_ino() == file_stat.st_ino) {
812 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
813 return si;
814 }
815 }
817 if ((rtld_flags & RTLD_NOLOAD) != 0) {
818 DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
819 return nullptr;
820 }
822 // Read the ELF header and load the segments.
823 ElfReader elf_reader(name, fd);
824 if (!elf_reader.Load(extinfo)) {
825 return nullptr;
826 }
828 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat, rtld_flags);
829 if (si == nullptr) {
830 return nullptr;
831 }
832 si->base = elf_reader.load_start();
833 si->size = elf_reader.load_size();
834 si->load_bias = elf_reader.load_bias();
835 si->phnum = elf_reader.phdr_count();
836 si->phdr = elf_reader.loaded_phdr();
838 if (!si->PrelinkImage()) {
839 soinfo_free(si);
840 return nullptr;
841 }
843 for_each_dt_needed(si, [&] (const char* name) {
844 load_tasks.push_back(LoadTask::create(name, si));
845 });
847 return si;
848 }
850 static soinfo *find_loaded_library_by_name(const char* name) {
851 const char* search_name = SEARCH_NAME(name);
852 for (soinfo* si = solist; si != nullptr; si = si->next) {
853 if (!strcmp(search_name, si->name)) {
854 return si;
855 }
856 }
857 return nullptr;
858 }
860 static soinfo* find_library_internal(LoadTaskList& load_tasks, const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
862 soinfo* si = find_loaded_library_by_name(name);
864 // Library might still be loaded, the accurate detection
865 // of this fact is done by load_library.
866 if (si == nullptr) {
867 TRACE("[ '%s' has not been found by name. Trying harder...]", name);
868 si = load_library(load_tasks, name, rtld_flags, extinfo);
869 }
871 return si;
872 }
874 static void soinfo_unload(soinfo* si);
876 static bool is_recursive(soinfo* si, soinfo* parent) {
877 if (parent == nullptr) {
878 return false;
879 }
881 if (si == parent) {
882 DL_ERR("recursive link to \"%s\"", si->name);
883 return true;
884 }
886 return !parent->get_parents().visit([&](soinfo* grandparent) {
887 return !is_recursive(si, grandparent);
888 });
889 }
891 static bool find_libraries(const char* const library_names[], size_t library_names_size, soinfo* soinfos[],
892 soinfo* ld_preloads[], size_t ld_preloads_size, int rtld_flags, const android_dlextinfo* extinfo) {
893 // Step 0: prepare.
894 LoadTaskList load_tasks;
895 for (size_t i = 0; i < library_names_size; ++i) {
896 const char* name = library_names[i];
897 load_tasks.push_back(LoadTask::create(name, nullptr));
898 }
900 // Libraries added to this list in reverse order so that we can
901 // start linking from bottom-up - see step 2.
902 SoinfoLinkedList found_libs;
903 size_t soinfos_size = 0;
905 auto failure_guard = make_scope_guard([&]() {
906 // Housekeeping
907 load_tasks.for_each([] (LoadTask* t) {
908 LoadTask::deleter(t);
909 });
911 for (size_t i = 0; i<soinfos_size; ++i) {
912 soinfo_unload(soinfos[i]);
913 }
914 });
916 // Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
917 for (LoadTask::unique_ptr task(load_tasks.pop_front()); task.get() != nullptr; task.reset(load_tasks.pop_front())) {
918 soinfo* si = find_library_internal(load_tasks, task->get_name(), rtld_flags, extinfo);
919 if (si == nullptr) {
920 return false;
921 }
923 soinfo* needed_by = task->get_needed_by();
925 if (is_recursive(si, needed_by)) {
926 return false;
927 }
929 si->ref_count++;
930 if (needed_by != nullptr) {
931 needed_by->add_child(si);
932 }
933 found_libs.push_front(si);
935 // When ld_preloads is not null first
936 // ld_preloads_size libs are in fact ld_preloads.
937 if (ld_preloads != nullptr && soinfos_size < ld_preloads_size) {
938 ld_preloads[soinfos_size] = si;
939 }
941 if (soinfos_size<library_names_size) {
942 soinfos[soinfos_size++] = si;
943 }
944 }
946 // Step 2: link libraries.
947 soinfo* si;
948 while ((si = found_libs.pop_front()) != nullptr) {
949 if ((si->flags & FLAG_LINKED) == 0) {
950 if (!si->LinkImage(extinfo)) {
951 return false;
952 }
953 si->flags |= FLAG_LINKED;
954 }
955 }
957 // All is well - found_libs and load_tasks are empty at this point
958 // and all libs are successfully linked.
959 failure_guard.disable();
960 return true;
961 }
963 static soinfo* find_library(const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
964 if (name == nullptr) {
965 somain->ref_count++;
966 return somain;
967 }
969 soinfo* si;
971 if (!find_libraries(&name, 1, &si, nullptr, 0, rtld_flags, extinfo)) {
972 return nullptr;
973 }
975 return si;
976 }
978 static void soinfo_unload(soinfo* si) {
979 if (si->ref_count == 1) {
980 TRACE("unloading '%s'", si->name);
981 si->CallDestructors();
983 if (si->has_min_version(0)) {
984 soinfo* child = nullptr;
985 while ((child = si->get_children().pop_front()) != nullptr) {
986 TRACE("%s needs to unload %s", si->name, child->name);
987 soinfo_unload(child);
988 }
989 } else {
990 for_each_dt_needed(si, [&] (const char* library_name) {
991 TRACE("deprecated (old format of soinfo): %s needs to unload %s", si->name, library_name);
992 soinfo* needed = find_library(library_name, RTLD_NOLOAD, nullptr);
993 if (needed != nullptr) {
994 soinfo_unload(needed);
995 } else {
996 // Not found: for example if symlink was deleted between dlopen and dlclose
997 // Since we cannot really handle errors at this point - print and continue.
998 PRINT("warning: couldn't find %s needed by %s on unload.", library_name, si->name);
999 }
1000 });
1001 }
1003 notify_gdb_of_unload(si);
1004 si->ref_count = 0;
1005 soinfo_free(si);
1006 } else {
1007 si->ref_count--;
1008 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
1009 }
1010 }
1012 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
1013 // Use basic string manipulation calls to avoid snprintf.
1014 // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
1015 // When debug malloc is enabled, this call returns 0. This in turn causes
1016 // snprintf to do nothing, which causes libraries to fail to load.
1017 // See b/17302493 for further details.
1018 // Once the above bug is fixed, this code can be modified to use
1019 // snprintf again.
1020 size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
1021 if (buffer_size < required_len) {
1022 __libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: buffer len %zu, required len %zu",
1023 buffer_size, required_len);
1024 }
1025 char* end = stpcpy(buffer, kDefaultLdPaths[0]);
1026 *end = ':';
1027 strcpy(end + 1, kDefaultLdPaths[1]);
1028 }
1030 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
1031 if (!get_AT_SECURE()) {
1032 parse_LD_LIBRARY_PATH(ld_library_path);
1033 }
1034 }
1036 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
1037 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NOLOAD)) != 0) {
1038 DL_ERR("invalid flags to dlopen: %x", flags);
1039 return nullptr;
1040 }
1041 if (extinfo != nullptr && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) {
1042 DL_ERR("invalid extended flags to android_dlopen_ext: %" PRIx64, extinfo->flags);
1043 return nullptr;
1044 }
1045 protect_data(PROT_READ | PROT_WRITE);
1046 soinfo* si = find_library(name, flags, extinfo);
1047 if (si != nullptr) {
1048 si->CallConstructors();
1049 }
1050 protect_data(PROT_READ);
1051 return si;
1052 }
1054 void do_dlclose(soinfo* si) {
1055 protect_data(PROT_READ | PROT_WRITE);
1056 soinfo_unload(si);
1057 protect_data(PROT_READ);
1058 }
1060 static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
1061 typedef ElfW(Addr) (*ifunc_resolver_t)(void);
1062 ifunc_resolver_t ifunc_resolver = reinterpret_cast<ifunc_resolver_t>(resolver_addr);
1063 ElfW(Addr) ifunc_addr = ifunc_resolver();
1064 TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p", ifunc_resolver, reinterpret_cast<void*>(ifunc_addr));
1066 return ifunc_addr;
1067 }
1069 #if defined(USE_RELA)
1070 int soinfo::Relocate(ElfW(Rela)* rela, unsigned count) {
1071 for (size_t idx = 0; idx < count; ++idx, ++rela) {
1072 unsigned type = ELFW(R_TYPE)(rela->r_info);
1073 unsigned sym = ELFW(R_SYM)(rela->r_info);
1074 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + load_bias);
1075 ElfW(Addr) sym_addr = 0;
1076 const char* sym_name = nullptr;
1078 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1079 if (type == 0) { // R_*_NONE
1080 continue;
1081 }
1083 ElfW(Sym)* s = nullptr;
1084 soinfo* lsi = nullptr;
1086 if (sym != 0) {
1087 sym_name = get_string(symtab[sym].st_name);
1088 s = soinfo_do_lookup(this, sym_name, &lsi);
1089 if (s == nullptr) {
1090 // We only allow an undefined symbol if this is a weak reference...
1091 s = &symtab[sym];
1092 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1093 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1094 return -1;
1095 }
1097 /* IHI0044C AAELF 4.5.1.1:
1099 Libraries are not searched to resolve weak references.
1100 It is not an error for a weak reference to remain unsatisfied.
1102 During linking, the value of an undefined weak reference is:
1103 - Zero if the relocation type is absolute
1104 - The address of the place if the relocation is pc-relative
1105 - The address of nominal base address if the relocation
1106 type is base-relative.
1107 */
1109 switch (type) {
1110 #if defined(__aarch64__)
1111 case R_AARCH64_JUMP_SLOT:
1112 case R_AARCH64_GLOB_DAT:
1113 case R_AARCH64_ABS64:
1114 case R_AARCH64_ABS32:
1115 case R_AARCH64_ABS16:
1116 case R_AARCH64_RELATIVE:
1117 case R_AARCH64_IRELATIVE:
1118 /*
1119 * The sym_addr was initialized to be zero above, or the relocation
1120 * code below does not care about value of sym_addr.
1121 * No need to do anything.
1122 */
1123 break;
1124 #elif defined(__x86_64__)
1125 case R_X86_64_JUMP_SLOT:
1126 case R_X86_64_GLOB_DAT:
1127 case R_X86_64_32:
1128 case R_X86_64_64:
1129 case R_X86_64_RELATIVE:
1130 case R_X86_64_IRELATIVE:
1131 // No need to do anything.
1132 break;
1133 case R_X86_64_PC32:
1134 sym_addr = reloc;
1135 break;
1136 #endif
1137 default:
1138 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
1139 return -1;
1140 }
1141 } else {
1142 // We got a definition.
1143 sym_addr = lsi->resolve_symbol_address(s);
1144 }
1145 count_relocation(kRelocSymbol);
1146 }
1148 switch (type) {
1149 #if defined(__aarch64__)
1150 case R_AARCH64_JUMP_SLOT:
1151 count_relocation(kRelocAbsolute);
1152 MARK(rela->r_offset);
1153 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
1154 reloc, (sym_addr + rela->r_addend), sym_name);
1155 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1156 break;
1157 case R_AARCH64_GLOB_DAT:
1158 count_relocation(kRelocAbsolute);
1159 MARK(rela->r_offset);
1160 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
1161 reloc, (sym_addr + rela->r_addend), sym_name);
1162 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
1163 break;
1164 case R_AARCH64_ABS64:
1165 count_relocation(kRelocAbsolute);
1166 MARK(rela->r_offset);
1167 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
1168 reloc, (sym_addr + rela->r_addend), sym_name);
1169 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1170 break;
1171 case R_AARCH64_ABS32:
1172 count_relocation(kRelocAbsolute);
1173 MARK(rela->r_offset);
1174 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
1175 reloc, (sym_addr + rela->r_addend), sym_name);
1176 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1177 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1178 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1179 } else {
1180 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1181 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1182 static_cast<ElfW(Addr)>(INT32_MIN),
1183 static_cast<ElfW(Addr)>(UINT32_MAX));
1184 return -1;
1185 }
1186 break;
1187 case R_AARCH64_ABS16:
1188 count_relocation(kRelocAbsolute);
1189 MARK(rela->r_offset);
1190 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
1191 reloc, (sym_addr + rela->r_addend), sym_name);
1192 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
1193 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1194 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
1195 } else {
1196 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1197 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
1198 static_cast<ElfW(Addr)>(INT16_MIN),
1199 static_cast<ElfW(Addr)>(UINT16_MAX));
1200 return -1;
1201 }
1202 break;
1203 case R_AARCH64_PREL64:
1204 count_relocation(kRelocRelative);
1205 MARK(rela->r_offset);
1206 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
1207 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1208 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
1209 break;
1210 case R_AARCH64_PREL32:
1211 count_relocation(kRelocRelative);
1212 MARK(rela->r_offset);
1213 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
1214 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1215 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1216 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
1217 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
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) - rela->r_offset)),
1221 static_cast<ElfW(Addr)>(INT32_MIN),
1222 static_cast<ElfW(Addr)>(UINT32_MAX));
1223 return -1;
1224 }
1225 break;
1226 case R_AARCH64_PREL16:
1227 count_relocation(kRelocRelative);
1228 MARK(rela->r_offset);
1229 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
1230 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1231 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1232 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1233 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1234 } else {
1235 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1236 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1237 static_cast<ElfW(Addr)>(INT16_MIN),
1238 static_cast<ElfW(Addr)>(UINT16_MAX));
1239 return -1;
1240 }
1241 break;
1243 case R_AARCH64_RELATIVE:
1244 count_relocation(kRelocRelative);
1245 MARK(rela->r_offset);
1246 if (sym) {
1247 DL_ERR("odd RELATIVE form...");
1248 return -1;
1249 }
1250 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
1251 reloc, (base + rela->r_addend));
1252 *reinterpret_cast<ElfW(Addr)*>(reloc) = (base + rela->r_addend);
1253 break;
1255 case R_AARCH64_IRELATIVE:
1256 count_relocation(kRelocRelative);
1257 MARK(rela->r_offset);
1258 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1259 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1260 break;
1262 case R_AARCH64_COPY:
1263 /*
1264 * ET_EXEC is not supported so this should not happen.
1265 *
1266 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1267 *
1268 * Section 4.7.1.10 "Dynamic relocations"
1269 * R_AARCH64_COPY may only appear in executable objects where e_type is
1270 * set to ET_EXEC.
1271 */
1272 DL_ERR("%s R_AARCH64_COPY relocations are not supported", name);
1273 return -1;
1274 case R_AARCH64_TLS_TPREL64:
1275 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
1276 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1277 break;
1278 case R_AARCH64_TLS_DTPREL32:
1279 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
1280 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1281 break;
1282 #elif defined(__x86_64__)
1283 case R_X86_64_JUMP_SLOT:
1284 count_relocation(kRelocAbsolute);
1285 MARK(rela->r_offset);
1286 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1287 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1288 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1289 break;
1290 case R_X86_64_GLOB_DAT:
1291 count_relocation(kRelocAbsolute);
1292 MARK(rela->r_offset);
1293 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1294 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1295 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1296 break;
1297 case R_X86_64_RELATIVE:
1298 count_relocation(kRelocRelative);
1299 MARK(rela->r_offset);
1300 if (sym) {
1301 DL_ERR("odd RELATIVE form...");
1302 return -1;
1303 }
1304 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
1305 static_cast<size_t>(base));
1306 *reinterpret_cast<ElfW(Addr)*>(reloc) = base + rela->r_addend;
1307 break;
1308 case R_X86_64_IRELATIVE:
1309 count_relocation(kRelocRelative);
1310 MARK(rela->r_offset);
1311 TRACE_TYPE(RELO, "RELO IRELATIVE %16llx <- %16llx\n", reloc, (base + rela->r_addend));
1312 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + rela->r_addend);
1313 break;
1314 case R_X86_64_32:
1315 count_relocation(kRelocRelative);
1316 MARK(rela->r_offset);
1317 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1318 static_cast<size_t>(sym_addr), sym_name);
1319 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1320 break;
1321 case R_X86_64_64:
1322 count_relocation(kRelocRelative);
1323 MARK(rela->r_offset);
1324 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1325 static_cast<size_t>(sym_addr), sym_name);
1326 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1327 break;
1328 case R_X86_64_PC32:
1329 count_relocation(kRelocRelative);
1330 MARK(rela->r_offset);
1331 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
1332 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
1333 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
1334 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc;
1335 break;
1336 #endif
1338 default:
1339 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
1340 return -1;
1341 }
1342 }
1343 return 0;
1344 }
1346 #else // REL, not RELA.
1347 int soinfo::Relocate(ElfW(Rel)* rel, unsigned count) {
1348 for (size_t idx = 0; idx < count; ++idx, ++rel) {
1349 unsigned type = ELFW(R_TYPE)(rel->r_info);
1350 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
1351 unsigned sym = ELFW(R_SYM)(rel->r_info);
1352 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
1353 ElfW(Addr) sym_addr = 0;
1354 const char* sym_name = nullptr;
1356 DEBUG("Processing '%s' relocation at index %zd", name, idx);
1357 if (type == 0) { // R_*_NONE
1358 continue;
1359 }
1361 ElfW(Sym)* s = nullptr;
1362 soinfo* lsi = nullptr;
1364 if (sym != 0) {
1365 sym_name = get_string(symtab[sym].st_name);
1366 s = soinfo_do_lookup(this, sym_name, &lsi);
1367 if (s == nullptr) {
1368 // We only allow an undefined symbol if this is a weak reference...
1369 s = &symtab[sym];
1370 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1371 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, name);
1372 return -1;
1373 }
1375 /* IHI0044C AAELF 4.5.1.1:
1377 Libraries are not searched to resolve weak references.
1378 It is not an error for a weak reference to remain
1379 unsatisfied.
1381 During linking, the value of an undefined weak reference is:
1382 - Zero if the relocation type is absolute
1383 - The address of the place if the relocation is pc-relative
1384 - The address of nominal base address if the relocation
1385 type is base-relative.
1386 */
1388 switch (type) {
1389 #if defined(__arm__)
1390 case R_ARM_JUMP_SLOT:
1391 case R_ARM_GLOB_DAT:
1392 case R_ARM_ABS32:
1393 case R_ARM_RELATIVE: /* Don't care. */
1394 // sym_addr was initialized to be zero above or relocation
1395 // code below does not care about value of sym_addr.
1396 // No need to do anything.
1397 break;
1398 #elif defined(__i386__)
1399 case R_386_JMP_SLOT:
1400 case R_386_GLOB_DAT:
1401 case R_386_32:
1402 case R_386_RELATIVE: /* Don't care. */
1403 case R_386_IRELATIVE:
1404 // sym_addr was initialized to be zero above or relocation
1405 // code below does not care about value of sym_addr.
1406 // No need to do anything.
1407 break;
1408 case R_386_PC32:
1409 sym_addr = reloc;
1410 break;
1411 #endif
1413 #if defined(__arm__)
1414 case R_ARM_COPY:
1415 // Fall through. Can't really copy if weak symbol is not found at run-time.
1416 #endif
1417 default:
1418 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
1419 return -1;
1420 }
1421 } else {
1422 // We got a definition.
1423 sym_addr = lsi->resolve_symbol_address(s);
1424 }
1425 count_relocation(kRelocSymbol);
1426 }
1428 switch (type) {
1429 #if defined(__arm__)
1430 case R_ARM_JUMP_SLOT:
1431 count_relocation(kRelocAbsolute);
1432 MARK(rel->r_offset);
1433 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1434 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1435 break;
1436 case R_ARM_GLOB_DAT:
1437 count_relocation(kRelocAbsolute);
1438 MARK(rel->r_offset);
1439 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1440 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1441 break;
1442 case R_ARM_ABS32:
1443 count_relocation(kRelocAbsolute);
1444 MARK(rel->r_offset);
1445 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
1446 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1447 break;
1448 case R_ARM_REL32:
1449 count_relocation(kRelocRelative);
1450 MARK(rel->r_offset);
1451 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
1452 reloc, sym_addr, rel->r_offset, sym_name);
1453 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
1454 break;
1455 case R_ARM_COPY:
1456 /*
1457 * ET_EXEC is not supported so this should not happen.
1458 *
1459 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1460 *
1461 * Section 4.7.1.10 "Dynamic relocations"
1462 * R_ARM_COPY may only appear in executable objects where e_type is
1463 * set to ET_EXEC.
1464 */
1465 DL_ERR("%s R_ARM_COPY relocations are not supported", name);
1466 return -1;
1467 #elif defined(__i386__)
1468 case R_386_JMP_SLOT:
1469 count_relocation(kRelocAbsolute);
1470 MARK(rel->r_offset);
1471 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1472 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1473 break;
1474 case R_386_GLOB_DAT:
1475 count_relocation(kRelocAbsolute);
1476 MARK(rel->r_offset);
1477 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1478 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1479 break;
1480 case R_386_32:
1481 count_relocation(kRelocRelative);
1482 MARK(rel->r_offset);
1483 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
1484 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1485 break;
1486 case R_386_PC32:
1487 count_relocation(kRelocRelative);
1488 MARK(rel->r_offset);
1489 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
1490 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
1491 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
1492 break;
1493 #elif defined(__mips__)
1494 case R_MIPS_REL32:
1495 #if defined(__LP64__)
1496 // MIPS Elf64_Rel entries contain compound relocations
1497 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
1498 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
1499 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
1500 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
1501 type, (unsigned)ELF64_R_TYPE2(rel->r_info),
1502 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
1503 return -1;
1504 }
1505 #endif
1506 count_relocation(kRelocAbsolute);
1507 MARK(rel->r_offset);
1508 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
1509 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
1510 if (s) {
1511 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1512 } else {
1513 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1514 }
1515 break;
1516 #endif
1518 #if defined(__arm__)
1519 case R_ARM_RELATIVE:
1520 #elif defined(__i386__)
1521 case R_386_RELATIVE:
1522 #endif
1523 count_relocation(kRelocRelative);
1524 MARK(rel->r_offset);
1525 if (sym) {
1526 DL_ERR("odd RELATIVE form...");
1527 return -1;
1528 }
1529 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
1530 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1531 *reinterpret_cast<ElfW(Addr)*>(reloc) += base;
1532 break;
1533 #if defined(__i386__)
1534 case R_386_IRELATIVE:
1535 count_relocation(kRelocRelative);
1536 MARK(rel->r_offset);
1537 TRACE_TYPE(RELO, "RELO IRELATIVE %p <- %p", reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(base));
1538 *reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(base + *reinterpret_cast<ElfW(Addr)*>(reloc));
1539 break;
1540 #endif
1542 default:
1543 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
1544 return -1;
1545 }
1546 }
1547 return 0;
1548 }
1549 #endif
1551 #if defined(__mips__)
1552 static bool mips_relocate_got(soinfo* si) {
1553 ElfW(Addr)** got = si->plt_got;
1554 if (got == nullptr) {
1555 return true;
1556 }
1557 unsigned local_gotno = si->mips_local_gotno;
1558 unsigned gotsym = si->mips_gotsym;
1559 unsigned symtabno = si->mips_symtabno;
1560 ElfW(Sym)* symtab = si->symtab;
1562 // got[0] is the address of the lazy resolver function.
1563 // got[1] may be used for a GNU extension.
1564 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
1565 // FIXME: maybe this should be in a separate routine?
1566 if ((si->flags & FLAG_LINKER) == 0) {
1567 size_t g = 0;
1568 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
1569 if (reinterpret_cast<intptr_t>(got[g]) < 0) {
1570 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
1571 }
1572 // Relocate the local GOT entries.
1573 for (; g < local_gotno; g++) {
1574 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
1575 }
1576 }
1578 // Now for the global GOT entries...
1579 ElfW(Sym)* sym = symtab + gotsym;
1580 got = si->plt_got + local_gotno;
1581 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
1582 // This is an undefined reference... try to locate it.
1583 const char* sym_name = si->get_string(sym->st_name);
1584 soinfo* lsi = nullptr;
1585 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi);
1586 if (s == nullptr) {
1587 // We only allow an undefined symbol if this is a weak reference.
1588 s = &symtab[g];
1589 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1590 DL_ERR("cannot locate \"%s\"...", sym_name);
1591 return false;
1592 }
1593 *got = 0;
1594 } else {
1595 // FIXME: is this sufficient?
1596 // For reference see NetBSD link loader
1597 // 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
1598 *got = reinterpret_cast<ElfW(Addr)*>(lsi->resolve_symbol_address(s));
1599 }
1600 }
1601 return true;
1602 }
1603 #endif
1605 void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
1606 if (functions == nullptr) {
1607 return;
1608 }
1610 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
1612 int begin = reverse ? (count - 1) : 0;
1613 int end = reverse ? -1 : count;
1614 int step = reverse ? -1 : 1;
1616 for (int i = begin; i != end; i += step) {
1617 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
1618 CallFunction("function", functions[i]);
1619 }
1621 TRACE("[ Done calling %s for '%s' ]", array_name, name);
1622 }
1624 void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
1625 if (function == nullptr || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
1626 return;
1627 }
1629 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
1630 function();
1631 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
1633 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
1634 // are still writable. This happens with our debug malloc (see http://b/7941716).
1635 protect_data(PROT_READ | PROT_WRITE);
1636 }
1638 void soinfo::CallPreInitConstructors() {
1639 // DT_PREINIT_ARRAY functions are called before any other constructors for executables,
1640 // but ignored in a shared library.
1641 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
1642 }
1644 void soinfo::CallConstructors() {
1645 if (constructors_called) {
1646 return;
1647 }
1649 // We set constructors_called before actually calling the constructors, otherwise it doesn't
1650 // protect against recursive constructor calls. One simple example of constructor recursion
1651 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
1652 // 1. The program depends on libc, so libc's constructor is called here.
1653 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
1654 // 3. dlopen() calls the constructors on the newly created
1655 // soinfo for libc_malloc_debug_leak.so.
1656 // 4. The debug .so depends on libc, so CallConstructors is
1657 // called again with the libc soinfo. If it doesn't trigger the early-
1658 // out above, the libc constructor will be called again (recursively!).
1659 constructors_called = true;
1661 if ((flags & FLAG_EXE) == 0 && preinit_array != nullptr) {
1662 // The GNU dynamic linker silently ignores these, but we warn the developer.
1663 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
1664 name, preinit_array_count);
1665 }
1667 get_children().for_each([] (soinfo* si) {
1668 si->CallConstructors();
1669 });
1671 TRACE("\"%s\": calling constructors", name);
1673 // DT_INIT should be called before DT_INIT_ARRAY if both are present.
1674 CallFunction("DT_INIT", init_func);
1675 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
1676 }
1678 void soinfo::CallDestructors() {
1679 if (!constructors_called) {
1680 return;
1681 }
1682 TRACE("\"%s\": calling destructors", name);
1684 // DT_FINI_ARRAY must be parsed in reverse order.
1685 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
1687 // DT_FINI should be called after DT_FINI_ARRAY if both are present.
1688 CallFunction("DT_FINI", fini_func);
1690 // This is needed on second call to dlopen
1691 // after library has been unloaded with RTLD_NODELETE
1692 constructors_called = false;
1693 }
1695 void soinfo::add_child(soinfo* child) {
1696 if (has_min_version(0)) {
1697 child->parents.push_back(this);
1698 this->children.push_back(child);
1699 }
1700 }
1702 void soinfo::remove_all_links() {
1703 if (!has_min_version(0)) {
1704 return;
1705 }
1707 // 1. Untie connected soinfos from 'this'.
1708 children.for_each([&] (soinfo* child) {
1709 child->parents.remove_if([&] (const soinfo* parent) {
1710 return parent == this;
1711 });
1712 });
1714 parents.for_each([&] (soinfo* parent) {
1715 parent->children.remove_if([&] (const soinfo* child) {
1716 return child == this;
1717 });
1718 });
1720 // 2. Once everything untied - clear local lists.
1721 parents.clear();
1722 children.clear();
1723 }
1725 void soinfo::set_st_dev(dev_t dev) {
1726 if (has_min_version(0)) {
1727 st_dev = dev;
1728 }
1729 }
1731 void soinfo::set_st_ino(ino_t ino) {
1732 if (has_min_version(0)) {
1733 st_ino = ino;
1734 }
1735 }
1737 dev_t soinfo::get_st_dev() {
1738 if (has_min_version(0)) {
1739 return st_dev;
1740 }
1742 return 0;
1743 };
1745 ino_t soinfo::get_st_ino() {
1746 if (has_min_version(0)) {
1747 return st_ino;
1748 }
1750 return 0;
1751 }
1753 int soinfo::get_rtld_flags() {
1754 if (has_min_version(1)) {
1755 return rtld_flags;
1756 }
1758 return 0;
1759 }
1761 // This is a return on get_children()/get_parents() if
1762 // 'this->flags' does not have FLAG_NEW_SOINFO set.
1763 static soinfo::soinfo_list_t g_empty_list;
1765 soinfo::soinfo_list_t& soinfo::get_children() {
1766 if (has_min_version(0)) {
1767 return this->children;
1768 }
1770 return g_empty_list;
1771 }
1773 soinfo::soinfo_list_t& soinfo::get_parents() {
1774 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1775 return g_empty_list;
1776 }
1778 return this->parents;
1779 }
1781 ElfW(Addr) soinfo::resolve_symbol_address(ElfW(Sym)* s) {
1782 if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
1783 return call_ifunc_resolver(s->st_value + load_bias);
1784 }
1786 return static_cast<ElfW(Addr)>(s->st_value + load_bias);
1787 }
1789 const char* soinfo::get_string(ElfW(Word) index) const {
1790 if (has_min_version(1) && (index >= strtab_size)) {
1791 __libc_fatal("%s: strtab out of bounds error; STRSZ=%zd, name=%d", name, strtab_size, index);
1792 }
1794 return strtab + index;
1795 }
1797 /* Force any of the closed stdin, stdout and stderr to be associated with
1798 /dev/null. */
1799 static int nullify_closed_stdio() {
1800 int dev_null, i, status;
1801 int return_value = 0;
1803 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
1804 if (dev_null < 0) {
1805 DL_ERR("cannot open /dev/null: %s", strerror(errno));
1806 return -1;
1807 }
1808 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
1810 /* If any of the stdio file descriptors is valid and not associated
1811 with /dev/null, dup /dev/null to it. */
1812 for (i = 0; i < 3; i++) {
1813 /* If it is /dev/null already, we are done. */
1814 if (i == dev_null) {
1815 continue;
1816 }
1818 TRACE("[ Nullifying stdio file descriptor %d]", i);
1819 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
1821 /* If file is opened, we are good. */
1822 if (status != -1) {
1823 continue;
1824 }
1826 /* The only error we allow is that the file descriptor does not
1827 exist, in which case we dup /dev/null to it. */
1828 if (errno != EBADF) {
1829 DL_ERR("fcntl failed: %s", strerror(errno));
1830 return_value = -1;
1831 continue;
1832 }
1834 /* Try dupping /dev/null to this stdio file descriptor and
1835 repeat if there is a signal. Note that any errors in closing
1836 the stdio descriptor are lost. */
1837 status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
1838 if (status < 0) {
1839 DL_ERR("dup2 failed: %s", strerror(errno));
1840 return_value = -1;
1841 continue;
1842 }
1843 }
1845 /* If /dev/null is not one of the stdio file descriptors, close it. */
1846 if (dev_null > 2) {
1847 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
1848 status = TEMP_FAILURE_RETRY(close(dev_null));
1849 if (status == -1) {
1850 DL_ERR("close failed: %s", strerror(errno));
1851 return_value = -1;
1852 }
1853 }
1855 return return_value;
1856 }
1858 bool soinfo::PrelinkImage() {
1859 /* Extract dynamic section */
1860 ElfW(Word) dynamic_flags = 0;
1861 phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
1863 /* We can't log anything until the linker is relocated */
1864 bool relocating_linker = (flags & FLAG_LINKER) != 0;
1865 if (!relocating_linker) {
1866 INFO("[ linking %s ]", name);
1867 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags);
1868 }
1870 if (dynamic == nullptr) {
1871 if (!relocating_linker) {
1872 DL_ERR("missing PT_DYNAMIC in \"%s\"", name);
1873 }
1874 return false;
1875 } else {
1876 if (!relocating_linker) {
1877 DEBUG("dynamic = %p", dynamic);
1878 }
1879 }
1881 #if defined(__arm__)
1882 (void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
1883 &ARM_exidx, &ARM_exidx_count);
1884 #endif
1886 // Extract useful information from dynamic section.
1887 uint32_t needed_count = 0;
1888 for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
1889 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
1890 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1891 switch (d->d_tag) {
1892 case DT_SONAME:
1893 // TODO: glibc dynamic linker uses this name for
1894 // initial library lookup; consider doing the same here.
1895 break;
1896 case DT_HASH:
1897 nbucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
1898 nchain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
1899 bucket = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
1900 chain = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket * 4);
1901 break;
1902 case DT_STRTAB:
1903 strtab = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
1904 break;
1905 case DT_STRSZ:
1906 strtab_size = d->d_un.d_val;
1907 break;
1908 case DT_SYMTAB:
1909 symtab = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
1910 break;
1911 case DT_SYMENT:
1912 if (d->d_un.d_val != sizeof(ElfW(Sym))) {
1913 DL_ERR("invalid DT_SYMENT: %zd", static_cast<size_t>(d->d_un.d_val));
1914 return false;
1915 }
1916 break;
1917 #if !defined(__LP64__)
1918 case DT_PLTREL:
1919 if (d->d_un.d_val != DT_REL) {
1920 DL_ERR("unsupported DT_RELA in \"%s\"", name);
1921 return false;
1922 }
1923 break;
1924 #endif
1925 case DT_JMPREL:
1926 #if defined(USE_RELA)
1927 plt_rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
1928 #else
1929 plt_rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
1930 #endif
1931 break;
1932 case DT_PLTRELSZ:
1933 #if defined(USE_RELA)
1934 plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
1935 #else
1936 plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
1937 #endif
1938 break;
1939 case DT_PLTGOT:
1940 #if defined(__mips__)
1941 // Used by mips and mips64.
1942 plt_got = reinterpret_cast<ElfW(Addr)**>(load_bias + d->d_un.d_ptr);
1943 #endif
1944 // Ignore for other platforms... (because RTLD_LAZY is not supported)
1945 break;
1946 case DT_DEBUG:
1947 // Set the DT_DEBUG entry to the address of _r_debug for GDB
1948 // if the dynamic table is writable
1949 // FIXME: not working currently for N64
1950 // The flags for the LOAD and DYNAMIC program headers do not agree.
1951 // The LOAD section containing the dynamic table has been mapped as
1952 // read-only, but the DYNAMIC header claims it is writable.
1953 #if !(defined(__mips__) && defined(__LP64__))
1954 if ((dynamic_flags & PF_W) != 0) {
1955 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
1956 }
1957 break;
1958 #endif
1959 #if defined(USE_RELA)
1960 case DT_RELA:
1961 rela = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
1962 break;
1963 case DT_RELASZ:
1964 rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
1965 break;
1966 case DT_RELAENT:
1967 if (d->d_un.d_val != sizeof(ElfW(Rela))) {
1968 DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
1969 return false;
1970 }
1971 break;
1972 case DT_RELACOUNT:
1973 // ignored (see DT_RELCOUNT comments for details)
1974 break;
1975 case DT_REL:
1976 DL_ERR("unsupported DT_REL in \"%s\"", name);
1977 return false;
1978 case DT_RELSZ:
1979 DL_ERR("unsupported DT_RELSZ in \"%s\"", name);
1980 return false;
1981 #else
1982 case DT_REL:
1983 rel = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
1984 break;
1985 case DT_RELSZ:
1986 rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
1987 break;
1988 case DT_RELENT:
1989 if (d->d_un.d_val != sizeof(ElfW(Rel))) {
1990 DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
1991 return false;
1992 }
1993 break;
1994 case DT_RELCOUNT:
1995 // "Indicates that all RELATIVE relocations have been concatenated together,
1996 // and specifies the RELATIVE relocation count."
1997 //
1998 // TODO: Spec also mentions that this can be used to optimize relocation process;
1999 // Not currently used by bionic linker - ignored.
2000 break;
2001 case DT_RELA:
2002 DL_ERR("unsupported DT_RELA in \"%s\"", name);
2003 return false;
2004 #endif
2005 case DT_INIT:
2006 init_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2007 DEBUG("%s constructors (DT_INIT) found at %p", name, init_func);
2008 break;
2009 case DT_FINI:
2010 fini_func = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
2011 DEBUG("%s destructors (DT_FINI) found at %p", name, fini_func);
2012 break;
2013 case DT_INIT_ARRAY:
2014 init_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2015 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", name, init_array);
2016 break;
2017 case DT_INIT_ARRAYSZ:
2018 init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2019 break;
2020 case DT_FINI_ARRAY:
2021 fini_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2022 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", name, fini_array);
2023 break;
2024 case DT_FINI_ARRAYSZ:
2025 fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2026 break;
2027 case DT_PREINIT_ARRAY:
2028 preinit_array = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
2029 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", name, preinit_array);
2030 break;
2031 case DT_PREINIT_ARRAYSZ:
2032 preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
2033 break;
2034 case DT_TEXTREL:
2035 #if defined(__LP64__)
2036 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2037 return false;
2038 #else
2039 has_text_relocations = true;
2040 break;
2041 #endif
2042 case DT_SYMBOLIC:
2043 has_DT_SYMBOLIC = true;
2044 break;
2045 case DT_NEEDED:
2046 ++needed_count;
2047 break;
2048 case DT_FLAGS:
2049 if (d->d_un.d_val & DF_TEXTREL) {
2050 #if defined(__LP64__)
2051 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", name);
2052 return false;
2053 #else
2054 has_text_relocations = true;
2055 #endif
2056 }
2057 if (d->d_un.d_val & DF_SYMBOLIC) {
2058 has_DT_SYMBOLIC = true;
2059 }
2060 break;
2061 case DT_FLAGS_1:
2062 if ((d->d_un.d_val & DF_1_GLOBAL) != 0) {
2063 rtld_flags |= RTLD_GLOBAL;
2064 }
2065 // TODO: Implement other flags
2067 if ((d->d_un.d_val & ~(DF_1_NOW | DF_1_GLOBAL)) != 0) {
2068 DL_WARN("Unsupported flags DT_FLAGS_1=%p", reinterpret_cast<void*>(d->d_un.d_val));
2069 }
2070 break;
2071 #if defined(__mips__)
2072 case DT_MIPS_RLD_MAP:
2073 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
2074 {
2075 r_debug** dp = reinterpret_cast<r_debug**>(load_bias + d->d_un.d_ptr);
2076 *dp = &_r_debug;
2077 }
2078 break;
2079 case DT_MIPS_RLD_VERSION:
2080 case DT_MIPS_FLAGS:
2081 case DT_MIPS_BASE_ADDRESS:
2082 case DT_MIPS_UNREFEXTNO:
2083 break;
2085 case DT_MIPS_SYMTABNO:
2086 mips_symtabno = d->d_un.d_val;
2087 break;
2089 case DT_MIPS_LOCAL_GOTNO:
2090 mips_local_gotno = d->d_un.d_val;
2091 break;
2093 case DT_MIPS_GOTSYM:
2094 mips_gotsym = d->d_un.d_val;
2095 break;
2096 #endif
2098 default:
2099 if (!relocating_linker) {
2100 DL_WARN("%s: unused DT entry: type %p arg %p", name,
2101 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
2102 }
2103 break;
2104 }
2105 }
2107 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
2108 reinterpret_cast<void*>(base), strtab, symtab);
2110 // Sanity checks.
2111 if (relocating_linker && needed_count != 0) {
2112 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
2113 return false;
2114 }
2115 if (nbucket == 0) {
2116 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", name);
2117 return false;
2118 }
2119 if (strtab == 0) {
2120 DL_ERR("empty/missing DT_STRTAB in \"%s\"", name);
2121 return false;
2122 }
2123 if (symtab == 0) {
2124 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", name);
2125 return false;
2126 }
2127 return true;
2128 }
2130 bool soinfo::LinkImage(const android_dlextinfo* extinfo) {
2132 #if !defined(__LP64__)
2133 if (has_text_relocations) {
2134 // Make segments writable to allow text relocations to work properly. We will later call
2135 // phdr_table_protect_segments() after all of them are applied and all constructors are run.
2136 DL_WARN("%s has text relocations. This is wasting memory and prevents "
2137 "security hardening. Please fix.", name);
2138 if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
2139 DL_ERR("can't unprotect loadable segments for \"%s\": %s",
2140 name, strerror(errno));
2141 return false;
2142 }
2143 }
2144 #endif
2146 #if defined(USE_RELA)
2147 if (rela != nullptr) {
2148 DEBUG("[ relocating %s ]", name);
2149 if (Relocate(rela, rela_count)) {
2150 return false;
2151 }
2152 }
2153 if (plt_rela != nullptr) {
2154 DEBUG("[ relocating %s plt ]", name);
2155 if (Relocate(plt_rela, plt_rela_count)) {
2156 return false;
2157 }
2158 }
2159 #else
2160 if (rel != nullptr) {
2161 DEBUG("[ relocating %s ]", name);
2162 if (Relocate(rel, rel_count)) {
2163 return false;
2164 }
2165 }
2166 if (plt_rel != nullptr) {
2167 DEBUG("[ relocating %s plt ]", name);
2168 if (Relocate(plt_rel, plt_rel_count)) {
2169 return false;
2170 }
2171 }
2172 #endif
2174 #if defined(__mips__)
2175 if (!mips_relocate_got(this)) {
2176 return false;
2177 }
2178 #endif
2180 DEBUG("[ finished linking %s ]", name);
2182 #if !defined(__LP64__)
2183 if (has_text_relocations) {
2184 // All relocations are done, we can protect our segments back to read-only.
2185 if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
2186 DL_ERR("can't protect segments for \"%s\": %s",
2187 name, strerror(errno));
2188 return false;
2189 }
2190 }
2191 #endif
2193 /* We can also turn on GNU RELRO protection */
2194 if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
2195 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
2196 name, strerror(errno));
2197 return false;
2198 }
2200 /* Handle serializing/sharing the RELRO segment */
2201 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
2202 if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
2203 extinfo->relro_fd) < 0) {
2204 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
2205 name, strerror(errno));
2206 return false;
2207 }
2208 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
2209 if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
2210 extinfo->relro_fd) < 0) {
2211 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
2212 name, strerror(errno));
2213 return false;
2214 }
2215 }
2217 notify_gdb_of_load(this);
2218 return true;
2219 }
2221 /*
2222 * This function add vdso to internal dso list.
2223 * It helps to stack unwinding through signal handlers.
2224 * Also, it makes bionic more like glibc.
2225 */
2226 static void add_vdso(KernelArgumentBlock& args __unused) {
2227 #if defined(AT_SYSINFO_EHDR)
2228 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
2229 if (ehdr_vdso == nullptr) {
2230 return;
2231 }
2233 soinfo* si = soinfo_alloc("[vdso]", nullptr, 0);
2235 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
2236 si->phnum = ehdr_vdso->e_phnum;
2237 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
2238 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2239 si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
2241 si->PrelinkImage();
2242 si->LinkImage(nullptr);
2243 #endif
2244 }
2246 /*
2247 * This is linker soinfo for GDB. See details below.
2248 */
2249 #if defined(__LP64__)
2250 #define LINKER_PATH "/system/bin/linker64"
2251 #else
2252 #define LINKER_PATH "/system/bin/linker"
2253 #endif
2254 static soinfo linker_soinfo_for_gdb(LINKER_PATH, nullptr, 0);
2256 /* gdb expects the linker to be in the debug shared object list.
2257 * Without this, gdb has trouble locating the linker's ".text"
2258 * and ".plt" sections. Gdb could also potentially use this to
2259 * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
2260 * Don't use soinfo_alloc(), because the linker shouldn't
2261 * be on the soinfo list.
2262 */
2263 static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
2264 linker_soinfo_for_gdb.base = linker_base;
2266 /*
2267 * Set the dynamic field in the link map otherwise gdb will complain with
2268 * the following:
2269 * warning: .dynamic section for "/system/bin/linker" is not at the
2270 * expected address (wrong library or version mismatch?)
2271 */
2272 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
2273 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
2274 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
2275 &linker_soinfo_for_gdb.dynamic, nullptr);
2276 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
2277 }
2279 /*
2280 * This code is called after the linker has linked itself and
2281 * fixed it's own GOT. It is safe to make references to externs
2282 * and other non-local data at this point.
2283 */
2284 static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
2285 #if TIMING
2286 struct timeval t0, t1;
2287 gettimeofday(&t0, 0);
2288 #endif
2290 // Initialize environment functions, and get to the ELF aux vectors table.
2291 linker_env_init(args);
2293 // If this is a setuid/setgid program, close the security hole described in
2294 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2295 if (get_AT_SECURE()) {
2296 nullify_closed_stdio();
2297 }
2299 debuggerd_init();
2301 // Get a few environment variables.
2302 const char* LD_DEBUG = linker_env_get("LD_DEBUG");
2303 if (LD_DEBUG != nullptr) {
2304 g_ld_debug_verbosity = atoi(LD_DEBUG);
2305 }
2307 // Normally, these are cleaned by linker_env_init, but the test
2308 // doesn't cost us anything.
2309 const char* ldpath_env = nullptr;
2310 const char* ldpreload_env = nullptr;
2311 if (!get_AT_SECURE()) {
2312 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2313 ldpreload_env = linker_env_get("LD_PRELOAD");
2314 }
2316 INFO("[ android linker & debugger ]");
2318 soinfo* si = soinfo_alloc(args.argv[0], nullptr, RTLD_GLOBAL);
2319 if (si == nullptr) {
2320 exit(EXIT_FAILURE);
2321 }
2323 /* bootstrap the link map, the main exe always needs to be first */
2324 si->flags |= FLAG_EXE;
2325 link_map* map = &(si->link_map_head);
2327 map->l_addr = 0;
2328 map->l_name = args.argv[0];
2329 map->l_prev = nullptr;
2330 map->l_next = nullptr;
2332 _r_debug.r_map = map;
2333 r_debug_tail = map;
2335 init_linker_info_for_gdb(linker_base);
2337 // Extract information passed from the kernel.
2338 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
2339 si->phnum = args.getauxval(AT_PHNUM);
2340 si->entry = args.getauxval(AT_ENTRY);
2342 /* Compute the value of si->base. We can't rely on the fact that
2343 * the first entry is the PHDR because this will not be true
2344 * for certain executables (e.g. some in the NDK unit test suite)
2345 */
2346 si->base = 0;
2347 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2348 si->load_bias = 0;
2349 for (size_t i = 0; i < si->phnum; ++i) {
2350 if (si->phdr[i].p_type == PT_PHDR) {
2351 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
2352 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
2353 break;
2354 }
2355 }
2356 si->dynamic = nullptr;
2357 si->ref_count = 1;
2359 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
2360 if (elf_hdr->e_type != ET_DYN) {
2361 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
2362 exit(EXIT_FAILURE);
2363 }
2365 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
2366 parse_LD_LIBRARY_PATH(ldpath_env);
2367 parse_LD_PRELOAD(ldpreload_env);
2369 somain = si;
2371 si->PrelinkImage();
2373 // Load ld_preloads and dependencies.
2374 StringLinkedList needed_library_name_list;
2375 size_t needed_libraries_count = 0;
2376 size_t ld_preloads_count = 0;
2377 while (g_ld_preload_names[ld_preloads_count] != nullptr) {
2378 needed_library_name_list.push_back(g_ld_preload_names[ld_preloads_count++]);
2379 ++needed_libraries_count;
2380 }
2382 for_each_dt_needed(si, [&](const char* name) {
2383 needed_library_name_list.push_back(name);
2384 ++needed_libraries_count;
2385 });
2387 const char* needed_library_names[needed_libraries_count];
2388 soinfo* needed_library_si[needed_libraries_count];
2390 memset(needed_library_names, 0, sizeof(needed_library_names));
2391 needed_library_name_list.copy_to_array(needed_library_names, needed_libraries_count);
2393 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)) {
2394 __libc_format_fd(2, "CANNOT LINK EXECUTABLE DEPENDENCIES: %s\n", linker_get_error_buffer());
2395 exit(EXIT_FAILURE);
2396 }
2398 for (size_t i = 0; i<needed_libraries_count; ++i) {
2399 si->add_child(needed_library_si[i]);
2400 }
2402 if (!si->LinkImage(nullptr)) {
2403 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
2404 exit(EXIT_FAILURE);
2405 }
2407 add_vdso(args);
2409 si->CallPreInitConstructors();
2411 /* After the PrelinkImage, the si->load_bias is initialized.
2412 * For so lib, the map->l_addr will be updated in notify_gdb_of_load.
2413 * We need to update this value for so exe here. So Unwind_Backtrace
2414 * for some arch like x86 could work correctly within so exe.
2415 */
2416 map->l_addr = si->load_bias;
2417 si->CallConstructors();
2419 #if TIMING
2420 gettimeofday(&t1, nullptr);
2421 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
2422 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2423 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
2424 #endif
2425 #if STATS
2426 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
2427 linker_stats.count[kRelocAbsolute],
2428 linker_stats.count[kRelocRelative],
2429 linker_stats.count[kRelocCopy],
2430 linker_stats.count[kRelocSymbol]);
2431 #endif
2432 #if COUNT_PAGES
2433 {
2434 unsigned n;
2435 unsigned i;
2436 unsigned count = 0;
2437 for (n = 0; n < 4096; n++) {
2438 if (bitmask[n]) {
2439 unsigned x = bitmask[n];
2440 #if defined(__LP64__)
2441 for (i = 0; i < 32; i++) {
2442 #else
2443 for (i = 0; i < 8; i++) {
2444 #endif
2445 if (x & 1) {
2446 count++;
2447 }
2448 x >>= 1;
2449 }
2450 }
2451 }
2452 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
2453 }
2454 #endif
2456 #if TIMING || STATS || COUNT_PAGES
2457 fflush(stdout);
2458 #endif
2460 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry));
2461 return si->entry;
2462 }
2464 /* Compute the load-bias of an existing executable. This shall only
2465 * be used to compute the load bias of an executable or shared library
2466 * that was loaded by the kernel itself.
2467 *
2468 * Input:
2469 * elf -> address of ELF header, assumed to be at the start of the file.
2470 * Return:
2471 * load bias, i.e. add the value of any p_vaddr in the file to get
2472 * the corresponding address in memory.
2473 */
2474 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
2475 ElfW(Addr) offset = elf->e_phoff;
2476 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
2477 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
2479 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
2480 if (phdr->p_type == PT_LOAD) {
2481 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
2482 }
2483 }
2484 return 0;
2485 }
2487 extern "C" void _start();
2489 /*
2490 * This is the entry point for the linker, called from begin.S. This
2491 * method is responsible for fixing the linker's own relocations, and
2492 * then calling __linker_init_post_relocation().
2493 *
2494 * Because this method is called before the linker has fixed it's own
2495 * relocations, any attempt to reference an extern variable, extern
2496 * function, or other GOT reference will generate a segfault.
2497 */
2498 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
2499 KernelArgumentBlock args(raw_args);
2501 ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
2502 ElfW(Addr) entry_point = args.getauxval(AT_ENTRY);
2503 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
2504 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
2506 soinfo linker_so("[dynamic linker]", nullptr, 0);
2508 // If the linker is not acting as PT_INTERP entry_point is equal to
2509 // _start. Which means that the linker is running as an executable and
2510 // already linked by PT_INTERP.
2511 //
2512 // This happens when user tries to run 'adb shell /system/bin/linker'
2513 // see also https://code.google.com/p/android/issues/detail?id=63174
2514 if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) {
2515 __libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]);
2516 }
2518 linker_so.base = linker_addr;
2519 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
2520 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
2521 linker_so.dynamic = nullptr;
2522 linker_so.phdr = phdr;
2523 linker_so.phnum = elf_hdr->e_phnum;
2524 linker_so.flags |= FLAG_LINKER;
2526 if (!(linker_so.PrelinkImage() && linker_so.LinkImage(nullptr))) {
2527 // It would be nice to print an error message, but if the linker
2528 // can't link itself, there's no guarantee that we'll be able to
2529 // call write() (because it involves a GOT reference). We may as
2530 // well try though...
2531 const char* msg = "CANNOT LINK EXECUTABLE: ";
2532 write(2, msg, strlen(msg));
2533 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2534 write(2, "\n", 1);
2535 _exit(EXIT_FAILURE);
2536 }
2538 __libc_init_tls(args);
2540 // Initialize the linker's own global variables
2541 linker_so.CallConstructors();
2543 // Initialize static variables. Note that in order to
2544 // get correct libdl_info we need to call constructors
2545 // before get_libdl_info().
2546 solist = get_libdl_info();
2547 sonext = get_libdl_info();
2549 // We have successfully fixed our own relocations. It's safe to run
2550 // the main part of the linker now.
2551 args.abort_message_ptr = &g_abort_message;
2552 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
2554 protect_data(PROT_READ);
2556 // Return the address that the calling assembly stub should jump to.
2557 return start_address;
2558 }