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/atomics.h>
38 #include <sys/mman.h>
39 #include <sys/stat.h>
40 #include <unistd.h>
42 // Private C library headers.
43 #include "private/bionic_tls.h"
44 #include "private/KernelArgumentBlock.h"
45 #include "private/ScopedPthreadMutexLocker.h"
47 #include "linker.h"
48 #include "linker_debug.h"
49 #include "linker_environ.h"
50 #include "linker_phdr.h"
51 #include "linker_allocator.h"
53 /* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<<
54 *
55 * Do NOT use malloc() and friends or pthread_*() code here.
56 * Don't use printf() either; it's caused mysterious memory
57 * corruption in the past.
58 * The linker runs before we bring up libc and it's easiest
59 * to make sure it does not depend on any complex libc features
60 *
61 * open issues / todo:
62 *
63 * - cleaner error reporting
64 * - after linking, set as much stuff as possible to READONLY
65 * and NOEXEC
66 */
68 #if defined(__LP64__)
69 #define SEARCH_NAME(x) x
70 #else
71 // Nvidia drivers are relying on the bug:
72 // http://code.google.com/p/android/issues/detail?id=6670
73 // so we continue to use base-name lookup for lp32
74 static const char* get_base_name(const char* name) {
75 const char* bname = strrchr(name, '/');
76 return bname ? bname + 1 : name;
77 }
78 #define SEARCH_NAME(x) get_base_name(x)
79 #endif
81 static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo);
82 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
84 static LinkerAllocator<soinfo> g_soinfo_allocator;
85 static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator;
87 static soinfo* solist;
88 static soinfo* sonext;
89 static soinfo* somain; /* main process, always the one after libdl_info */
91 static const char* const kDefaultLdPaths[] = {
92 #if defined(__LP64__)
93 "/vendor/lib64",
94 "/system/lib64",
95 #else
96 "/vendor/lib",
97 "/system/lib",
98 #endif
99 NULL
100 };
102 #define LDPATH_BUFSIZE (LDPATH_MAX*64)
103 #define LDPATH_MAX 8
105 #define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64)
106 #define LDPRELOAD_MAX 8
108 static char g_ld_library_paths_buffer[LDPATH_BUFSIZE];
109 static const char* g_ld_library_paths[LDPATH_MAX + 1];
111 static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE];
112 static const char* g_ld_preload_names[LDPRELOAD_MAX + 1];
114 static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1];
116 __LIBC_HIDDEN__ int g_ld_debug_verbosity;
118 __LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd.
120 enum RelocationKind {
121 kRelocAbsolute = 0,
122 kRelocRelative,
123 kRelocCopy,
124 kRelocSymbol,
125 kRelocMax
126 };
128 #if STATS
129 struct linker_stats_t {
130 int count[kRelocMax];
131 };
133 static linker_stats_t linker_stats;
135 static void count_relocation(RelocationKind kind) {
136 ++linker_stats.count[kind];
137 }
138 #else
139 static void count_relocation(RelocationKind) {
140 }
141 #endif
143 #if COUNT_PAGES
144 static unsigned bitmask[4096];
145 #if defined(__LP64__)
146 #define MARK(offset) \
147 do { \
148 if ((((offset) >> 12) >> 5) < 4096) \
149 bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \
150 } while (0)
151 #else
152 #define MARK(offset) \
153 do { \
154 bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \
155 } while (0)
156 #endif
157 #else
158 #define MARK(x) do {} while (0)
159 #endif
161 // You shouldn't try to call memory-allocating functions in the dynamic linker.
162 // Guard against the most obvious ones.
163 #define DISALLOW_ALLOCATION(return_type, name, ...) \
164 return_type name __VA_ARGS__ \
165 { \
166 const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \
167 __libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \
168 write(2, msg, strlen(msg)); \
169 abort(); \
170 }
171 DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused));
172 DISALLOW_ALLOCATION(void, free, (void* u __unused));
173 DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused));
174 DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused));
176 static char tmp_err_buf[768];
177 static char __linker_dl_err_buf[768];
179 char* linker_get_error_buffer() {
180 return &__linker_dl_err_buf[0];
181 }
183 size_t linker_get_error_buffer_size() {
184 return sizeof(__linker_dl_err_buf);
185 }
187 /*
188 * This function is an empty stub where GDB locates a breakpoint to get notified
189 * about linker activity.
190 */
191 extern "C" void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity();
193 static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER;
194 static r_debug _r_debug = {1, NULL, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0};
195 static link_map* r_debug_tail = 0;
197 static void insert_soinfo_into_debug_map(soinfo* info) {
198 // Copy the necessary fields into the debug structure.
199 link_map* map = &(info->link_map_head);
200 map->l_addr = info->load_bias;
201 map->l_name = reinterpret_cast<char*>(info->name);
202 map->l_ld = info->dynamic;
204 /* Stick the new library at the end of the list.
205 * gdb tends to care more about libc than it does
206 * about leaf libraries, and ordering it this way
207 * reduces the back-and-forth over the wire.
208 */
209 if (r_debug_tail) {
210 r_debug_tail->l_next = map;
211 map->l_prev = r_debug_tail;
212 map->l_next = 0;
213 } else {
214 _r_debug.r_map = map;
215 map->l_prev = 0;
216 map->l_next = 0;
217 }
218 r_debug_tail = map;
219 }
221 static void remove_soinfo_from_debug_map(soinfo* info) {
222 link_map* map = &(info->link_map_head);
224 if (r_debug_tail == map) {
225 r_debug_tail = map->l_prev;
226 }
228 if (map->l_prev) {
229 map->l_prev->l_next = map->l_next;
230 }
231 if (map->l_next) {
232 map->l_next->l_prev = map->l_prev;
233 }
234 }
236 static void notify_gdb_of_load(soinfo* info) {
237 if (info->flags & FLAG_EXE) {
238 // GDB already knows about the main executable
239 return;
240 }
242 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
244 _r_debug.r_state = r_debug::RT_ADD;
245 rtld_db_dlactivity();
247 insert_soinfo_into_debug_map(info);
249 _r_debug.r_state = r_debug::RT_CONSISTENT;
250 rtld_db_dlactivity();
251 }
253 static void notify_gdb_of_unload(soinfo* info) {
254 if (info->flags & FLAG_EXE) {
255 // GDB already knows about the main executable
256 return;
257 }
259 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
261 _r_debug.r_state = r_debug::RT_DELETE;
262 rtld_db_dlactivity();
264 remove_soinfo_from_debug_map(info);
266 _r_debug.r_state = r_debug::RT_CONSISTENT;
267 rtld_db_dlactivity();
268 }
270 void notify_gdb_of_libraries() {
271 _r_debug.r_state = r_debug::RT_ADD;
272 rtld_db_dlactivity();
273 _r_debug.r_state = r_debug::RT_CONSISTENT;
274 rtld_db_dlactivity();
275 }
277 LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() {
278 return g_soinfo_links_allocator.alloc();
279 }
281 void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) {
282 g_soinfo_links_allocator.free(entry);
283 }
285 static void protect_data(int protection) {
286 g_soinfo_allocator.protect_all(protection);
287 g_soinfo_links_allocator.protect_all(protection);
288 }
290 static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) {
291 if (strlen(name) >= SOINFO_NAME_LEN) {
292 DL_ERR("library name \"%s\" too long", name);
293 return NULL;
294 }
296 soinfo* si = g_soinfo_allocator.alloc();
298 // Initialize the new element.
299 memset(si, 0, sizeof(soinfo));
300 strlcpy(si->name, name, sizeof(si->name));
301 si->flags = FLAG_NEW_SOINFO;
303 if (file_stat != NULL) {
304 si->set_st_dev(file_stat->st_dev);
305 si->set_st_ino(file_stat->st_ino);
306 }
308 sonext->next = si;
309 sonext = si;
311 TRACE("name %s: allocated soinfo @ %p", name, si);
312 return si;
313 }
315 static void soinfo_free(soinfo* si) {
316 if (si == NULL) {
317 return;
318 }
320 if (si->base != 0 && si->size != 0) {
321 munmap(reinterpret_cast<void*>(si->base), si->size);
322 }
324 soinfo *prev = NULL, *trav;
326 TRACE("name %s: freeing soinfo @ %p", si->name, si);
328 for (trav = solist; trav != NULL; trav = trav->next) {
329 if (trav == si)
330 break;
331 prev = trav;
332 }
333 if (trav == NULL) {
334 /* si was not in solist */
335 DL_ERR("name \"%s\" is not in solist!", si->name);
336 return;
337 }
339 // clear links to/from si
340 si->remove_all_links();
342 /* prev will never be NULL, because the first entry in solist is
343 always the static libdl_info.
344 */
345 prev->next = si->next;
346 if (si == sonext) {
347 sonext = prev;
348 }
350 g_soinfo_allocator.free(si);
351 }
354 static void parse_path(const char* path, const char* delimiters,
355 const char** array, char* buf, size_t buf_size, size_t max_count) {
356 if (path == NULL) {
357 return;
358 }
360 size_t len = strlcpy(buf, path, buf_size);
362 size_t i = 0;
363 char* buf_p = buf;
364 while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) {
365 if (*array[i] != '\0') {
366 ++i;
367 }
368 }
370 // Forget the last path if we had to truncate; this occurs if the 2nd to
371 // last char isn't '\0' (i.e. wasn't originally a delimiter).
372 if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') {
373 array[i - 1] = NULL;
374 } else {
375 array[i] = NULL;
376 }
377 }
379 static void parse_LD_LIBRARY_PATH(const char* path) {
380 parse_path(path, ":", g_ld_library_paths,
381 g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX);
382 }
384 static void parse_LD_PRELOAD(const char* path) {
385 // We have historically supported ':' as well as ' ' in LD_PRELOAD.
386 parse_path(path, " :", g_ld_preload_names,
387 g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX);
388 }
390 #if defined(__arm__)
392 /* For a given PC, find the .so that it belongs to.
393 * Returns the base address of the .ARM.exidx section
394 * for that .so, and the number of 8-byte entries
395 * in that section (via *pcount).
396 *
397 * Intended to be called by libc's __gnu_Unwind_Find_exidx().
398 *
399 * This function is exposed via dlfcn.cpp and libdl.so.
400 */
401 _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
402 unsigned addr = (unsigned)pc;
404 for (soinfo* si = solist; si != 0; si = si->next) {
405 if ((addr >= si->base) && (addr < (si->base + si->size))) {
406 *pcount = si->ARM_exidx_count;
407 return (_Unwind_Ptr)si->ARM_exidx;
408 }
409 }
410 *pcount = 0;
411 return NULL;
412 }
414 #endif
416 /* Here, we only have to provide a callback to iterate across all the
417 * loaded libraries. gcc_eh does the rest. */
418 int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
419 int rv = 0;
420 for (soinfo* si = solist; si != NULL; si = si->next) {
421 dl_phdr_info dl_info;
422 dl_info.dlpi_addr = si->link_map_head.l_addr;
423 dl_info.dlpi_name = si->link_map_head.l_name;
424 dl_info.dlpi_phdr = si->phdr;
425 dl_info.dlpi_phnum = si->phnum;
426 rv = cb(&dl_info, sizeof(dl_phdr_info), data);
427 if (rv != 0) {
428 break;
429 }
430 }
431 return rv;
432 }
434 static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) {
435 ElfW(Sym)* symtab = si->symtab;
436 const char* strtab = si->strtab;
438 TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd",
439 name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
441 for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) {
442 ElfW(Sym)* s = symtab + n;
443 if (strcmp(strtab + s->st_name, name)) continue;
445 /* only concern ourselves with global and weak symbol definitions */
446 switch (ELF_ST_BIND(s->st_info)) {
447 case STB_GLOBAL:
448 case STB_WEAK:
449 if (s->st_shndx == SHN_UNDEF) {
450 continue;
451 }
453 TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
454 name, si->name, reinterpret_cast<void*>(s->st_value),
455 static_cast<size_t>(s->st_size));
456 return s;
457 }
458 }
460 return NULL;
461 }
463 static unsigned elfhash(const char* _name) {
464 const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
465 unsigned h = 0, g;
467 while (*name) {
468 h = (h << 4) + *name++;
469 g = h & 0xf0000000;
470 h ^= g;
471 h ^= g >> 24;
472 }
473 return h;
474 }
476 static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) {
477 unsigned elf_hash = elfhash(name);
478 ElfW(Sym)* s = NULL;
480 if (si != NULL && somain != NULL) {
481 /*
482 * Local scope is executable scope. Just start looking into it right away
483 * for the shortcut.
484 */
486 if (si == somain) {
487 s = soinfo_elf_lookup(si, elf_hash, name);
488 if (s != NULL) {
489 *lsi = si;
490 goto done;
491 }
492 } else {
493 /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */
495 /*
496 * If this object was built with symbolic relocations disabled, the
497 * first place to look to resolve external references is the main
498 * executable.
499 */
501 if (!si->has_DT_SYMBOLIC) {
502 DEBUG("%s: looking up %s in executable %s",
503 si->name, name, somain->name);
504 s = soinfo_elf_lookup(somain, elf_hash, name);
505 if (s != NULL) {
506 *lsi = somain;
507 goto done;
508 }
509 }
511 /* Look for symbols in the local scope (the object who is
512 * searching). This happens with C++ templates on x86 for some
513 * reason.
514 *
515 * Notes on weak symbols:
516 * The ELF specs are ambiguous about treatment of weak definitions in
517 * dynamic linking. Some systems return the first definition found
518 * and some the first non-weak definition. This is system dependent.
519 * Here we return the first definition found for simplicity. */
521 s = soinfo_elf_lookup(si, elf_hash, name);
522 if (s != NULL) {
523 *lsi = si;
524 goto done;
525 }
527 /*
528 * If this object was built with -Bsymbolic and symbol is not found
529 * in the local scope, try to find the symbol in the main executable.
530 */
532 if (si->has_DT_SYMBOLIC) {
533 DEBUG("%s: looking up %s in executable %s after local scope",
534 si->name, name, somain->name);
535 s = soinfo_elf_lookup(somain, elf_hash, name);
536 if (s != NULL) {
537 *lsi = somain;
538 goto done;
539 }
540 }
541 }
542 }
544 /* Next, look for it in the preloads list */
545 for (int i = 0; g_ld_preloads[i] != NULL; i++) {
546 s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
547 if (s != NULL) {
548 *lsi = g_ld_preloads[i];
549 goto done;
550 }
551 }
553 for (int i = 0; needed[i] != NULL; i++) {
554 DEBUG("%s: looking up %s in %s",
555 si->name, name, needed[i]->name);
556 s = soinfo_elf_lookup(needed[i], elf_hash, name);
557 if (s != NULL) {
558 *lsi = needed[i];
559 goto done;
560 }
561 }
563 done:
564 if (s != NULL) {
565 TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
566 "found in %s, base = %p, load bias = %p",
567 si->name, name, reinterpret_cast<void*>(s->st_value),
568 (*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
569 reinterpret_cast<void*>((*lsi)->load_bias));
570 return s;
571 }
573 return NULL;
574 }
576 /* This is used by dlsym(3). It performs symbol lookup only within the
577 specified soinfo object and not in any of its dependencies.
579 TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says
580 that it should do a breadth first search through the dependency
581 tree. This agrees with the ELF spec (aka System V Application
582 Binary Interface) where in Chapter 5 it discuss resolving "Shared
583 Object Dependencies" in breadth first search order.
584 */
585 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) {
586 return soinfo_elf_lookup(si, elfhash(name), name);
587 }
589 /* This is used by dlsym(3) to performs a global symbol lookup. If the
590 start value is null (for RTLD_DEFAULT), the search starts at the
591 beginning of the global solist. Otherwise the search starts at the
592 specified soinfo (for RTLD_NEXT).
593 */
594 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
595 unsigned elf_hash = elfhash(name);
597 if (start == NULL) {
598 start = solist;
599 }
601 ElfW(Sym)* s = NULL;
602 for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) {
603 s = soinfo_elf_lookup(si, elf_hash, name);
604 if (s != NULL) {
605 *found = si;
606 break;
607 }
608 }
610 if (s != NULL) {
611 TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
612 name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
613 }
615 return s;
616 }
618 soinfo* find_containing_library(const void* p) {
619 ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
620 for (soinfo* si = solist; si != NULL; si = si->next) {
621 if (address >= si->base && address - si->base < si->size) {
622 return si;
623 }
624 }
625 return NULL;
626 }
628 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
629 ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
631 // Search the library's symbol table for any defined symbol which
632 // contains this address.
633 for (size_t i = 0; i < si->nchain; ++i) {
634 ElfW(Sym)* sym = &si->symtab[i];
635 if (sym->st_shndx != SHN_UNDEF &&
636 soaddr >= sym->st_value &&
637 soaddr < sym->st_value + sym->st_size) {
638 return sym;
639 }
640 }
642 return NULL;
643 }
645 static int open_library_on_path(const char* name, const char* const paths[]) {
646 char buf[512];
647 for (size_t i = 0; paths[i] != NULL; ++i) {
648 int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
649 if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
650 PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
651 continue;
652 }
653 int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
654 if (fd != -1) {
655 return fd;
656 }
657 }
658 return -1;
659 }
661 static int open_library(const char* name) {
662 TRACE("[ opening %s ]", name);
664 // If the name contains a slash, we should attempt to open it directly and not search the paths.
665 if (strchr(name, '/') != NULL) {
666 int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
667 if (fd != -1) {
668 return fd;
669 }
670 // ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
671 #if defined(__LP64__)
672 // TODO: uncomment this after bug b/7465467 is fixed.
673 // return -1;
674 #endif
675 }
677 // Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
678 int fd = open_library_on_path(name, g_ld_library_paths);
679 if (fd == -1) {
680 fd = open_library_on_path(name, kDefaultLdPaths);
681 }
682 return fd;
683 }
685 static soinfo* load_library(const char* name, const android_dlextinfo* extinfo) {
686 // Open the file.
687 int fd = open_library(name);
688 if (fd == -1) {
689 DL_ERR("library \"%s\" not found", name);
690 return NULL;
691 }
693 ElfReader elf_reader(name, fd);
695 struct stat file_stat;
696 if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
697 DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno));
698 return NULL;
699 }
701 // Check for symlink and other situations where
702 // file can have different names.
703 for (soinfo* si = solist; si != NULL; si = si->next) {
704 if (si->get_st_dev() != 0 &&
705 si->get_st_ino() != 0 &&
706 si->get_st_dev() == file_stat.st_dev &&
707 si->get_st_ino() == file_stat.st_ino) {
708 TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
709 return si;
710 }
711 }
713 // Read the ELF header and load the segments.
714 if (!elf_reader.Load(extinfo)) {
715 return NULL;
716 }
718 soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat);
719 if (si == NULL) {
720 return NULL;
721 }
722 si->base = elf_reader.load_start();
723 si->size = elf_reader.load_size();
724 si->load_bias = elf_reader.load_bias();
725 si->phnum = elf_reader.phdr_count();
726 si->phdr = elf_reader.loaded_phdr();
728 // At this point we know that whatever is loaded @ base is a valid ELF
729 // shared library whose segments are properly mapped in.
730 TRACE("[ find_library_internal base=%p size=%zu name='%s' ]",
731 reinterpret_cast<void*>(si->base), si->size, si->name);
733 if (!soinfo_link_image(si, extinfo)) {
734 soinfo_free(si);
735 return NULL;
736 }
738 return si;
739 }
741 static soinfo *find_loaded_library_by_name(const char* name) {
742 const char* search_name = SEARCH_NAME(name);
743 for (soinfo* si = solist; si != NULL; si = si->next) {
744 if (!strcmp(search_name, si->name)) {
745 return si;
746 }
747 }
748 return NULL;
749 }
751 static soinfo* find_library_internal(const char* name, const android_dlextinfo* extinfo) {
752 if (name == NULL) {
753 return somain;
754 }
756 soinfo* si = find_loaded_library_by_name(name);
757 if (si != NULL) {
758 if (si->flags & FLAG_LINKED) {
759 return si;
760 }
761 DL_ERR("OOPS: recursive link to \"%s\"", si->name);
762 return NULL;
763 }
765 TRACE("[ '%s' has not been loaded yet. Locating...]", name);
766 return load_library(name, extinfo);
767 }
769 static soinfo* find_library(const char* name, const android_dlextinfo* extinfo) {
770 soinfo* si = find_library_internal(name, extinfo);
771 if (si != NULL) {
772 si->ref_count++;
773 }
774 return si;
775 }
777 static int soinfo_unload(soinfo* si) {
778 if (si->ref_count == 1) {
779 TRACE("unloading '%s'", si->name);
780 si->CallDestructors();
782 if ((si->flags | FLAG_NEW_SOINFO) != 0) {
783 si->get_children().for_each([&] (soinfo* child) {
784 TRACE("%s needs to unload %s", si->name, child->name);
785 soinfo_unload(child);
786 });
787 } else {
788 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
789 if (d->d_tag == DT_NEEDED) {
790 const char* library_name = si->strtab + d->d_un.d_val;
791 TRACE("%s needs to unload %s", si->name, library_name);
792 soinfo_unload(find_loaded_library_by_name(library_name));
793 }
794 }
795 }
797 notify_gdb_of_unload(si);
798 si->ref_count = 0;
799 soinfo_free(si);
800 } else {
801 si->ref_count--;
802 TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
803 }
804 return 0;
805 }
807 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
808 snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]);
809 }
811 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
812 if (!get_AT_SECURE()) {
813 parse_LD_LIBRARY_PATH(ld_library_path);
814 }
815 }
817 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
818 if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL)) != 0) {
819 DL_ERR("invalid flags to dlopen: %x", flags);
820 return NULL;
821 }
822 if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) {
823 DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags);
824 return NULL;
825 }
826 protect_data(PROT_READ | PROT_WRITE);
827 soinfo* si = find_library(name, extinfo);
828 if (si != NULL) {
829 si->CallConstructors();
830 somain->add_child(si);
831 }
832 protect_data(PROT_READ);
833 return si;
834 }
836 int do_dlclose(soinfo* si) {
837 protect_data(PROT_READ | PROT_WRITE);
838 int result = soinfo_unload(si);
839 protect_data(PROT_READ);
840 return result;
841 }
843 #if defined(USE_RELA)
844 static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
845 ElfW(Sym)* s;
846 soinfo* lsi;
848 for (size_t idx = 0; idx < count; ++idx, ++rela) {
849 unsigned type = ELFW(R_TYPE)(rela->r_info);
850 unsigned sym = ELFW(R_SYM)(rela->r_info);
851 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias);
852 ElfW(Addr) sym_addr = 0;
853 const char* sym_name = NULL;
855 DEBUG("Processing '%s' relocation at index %zd", si->name, idx);
856 if (type == 0) { // R_*_NONE
857 continue;
858 }
859 if (sym != 0) {
860 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
861 s = soinfo_do_lookup(si, sym_name, &lsi, needed);
862 if (s == NULL) {
863 // We only allow an undefined symbol if this is a weak reference...
864 s = &si->symtab[sym];
865 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
866 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name);
867 return -1;
868 }
870 /* IHI0044C AAELF 4.5.1.1:
872 Libraries are not searched to resolve weak references.
873 It is not an error for a weak reference to remain unsatisfied.
875 During linking, the value of an undefined weak reference is:
876 - Zero if the relocation type is absolute
877 - The address of the place if the relocation is pc-relative
878 - The address of nominal base address if the relocation
879 type is base-relative.
880 */
882 switch (type) {
883 #if defined(__aarch64__)
884 case R_AARCH64_JUMP_SLOT:
885 case R_AARCH64_GLOB_DAT:
886 case R_AARCH64_ABS64:
887 case R_AARCH64_ABS32:
888 case R_AARCH64_ABS16:
889 case R_AARCH64_RELATIVE:
890 /*
891 * The sym_addr was initialized to be zero above, or the relocation
892 * code below does not care about value of sym_addr.
893 * No need to do anything.
894 */
895 break;
896 #elif defined(__x86_64__)
897 case R_X86_64_JUMP_SLOT:
898 case R_X86_64_GLOB_DAT:
899 case R_X86_64_32:
900 case R_X86_64_RELATIVE:
901 // No need to do anything.
902 break;
903 case R_X86_64_PC32:
904 sym_addr = reloc;
905 break;
906 #endif
907 default:
908 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
909 return -1;
910 }
911 } else {
912 // We got a definition.
913 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias);
914 }
915 count_relocation(kRelocSymbol);
916 } else {
917 s = NULL;
918 }
920 switch (type) {
921 #if defined(__aarch64__)
922 case R_AARCH64_JUMP_SLOT:
923 count_relocation(kRelocAbsolute);
924 MARK(rela->r_offset);
925 TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
926 reloc, (sym_addr + rela->r_addend), sym_name);
927 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
928 break;
929 case R_AARCH64_GLOB_DAT:
930 count_relocation(kRelocAbsolute);
931 MARK(rela->r_offset);
932 TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
933 reloc, (sym_addr + rela->r_addend), sym_name);
934 *reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
935 break;
936 case R_AARCH64_ABS64:
937 count_relocation(kRelocAbsolute);
938 MARK(rela->r_offset);
939 TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
940 reloc, (sym_addr + rela->r_addend), sym_name);
941 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
942 break;
943 case R_AARCH64_ABS32:
944 count_relocation(kRelocAbsolute);
945 MARK(rela->r_offset);
946 TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
947 reloc, (sym_addr + rela->r_addend), sym_name);
948 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
949 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
950 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
951 } else {
952 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
953 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
954 static_cast<ElfW(Addr)>(INT32_MIN),
955 static_cast<ElfW(Addr)>(UINT32_MAX));
956 return -1;
957 }
958 break;
959 case R_AARCH64_ABS16:
960 count_relocation(kRelocAbsolute);
961 MARK(rela->r_offset);
962 TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
963 reloc, (sym_addr + rela->r_addend), sym_name);
964 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
965 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
966 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
967 } else {
968 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
969 (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
970 static_cast<ElfW(Addr)>(INT16_MIN),
971 static_cast<ElfW(Addr)>(UINT16_MAX));
972 return -1;
973 }
974 break;
975 case R_AARCH64_PREL64:
976 count_relocation(kRelocRelative);
977 MARK(rela->r_offset);
978 TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
979 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
980 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
981 break;
982 case R_AARCH64_PREL32:
983 count_relocation(kRelocRelative);
984 MARK(rela->r_offset);
985 TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
986 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
987 if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
988 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
989 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
990 } else {
991 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
992 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
993 static_cast<ElfW(Addr)>(INT32_MIN),
994 static_cast<ElfW(Addr)>(UINT32_MAX));
995 return -1;
996 }
997 break;
998 case R_AARCH64_PREL16:
999 count_relocation(kRelocRelative);
1000 MARK(rela->r_offset);
1001 TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
1002 reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
1003 if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
1004 ((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
1005 *reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
1006 } else {
1007 DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
1008 (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
1009 static_cast<ElfW(Addr)>(INT16_MIN),
1010 static_cast<ElfW(Addr)>(UINT16_MAX));
1011 return -1;
1012 }
1013 break;
1015 case R_AARCH64_RELATIVE:
1016 count_relocation(kRelocRelative);
1017 MARK(rela->r_offset);
1018 if (sym) {
1019 DL_ERR("odd RELATIVE form...");
1020 return -1;
1021 }
1022 TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
1023 reloc, (si->base + rela->r_addend));
1024 *reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend);
1025 break;
1027 case R_AARCH64_COPY:
1028 /*
1029 * ET_EXEC is not supported so this should not happen.
1030 *
1031 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1032 *
1033 * Section 4.7.1.10 "Dynamic relocations"
1034 * R_AARCH64_COPY may only appear in executable objects where e_type is
1035 * set to ET_EXEC.
1036 */
1037 DL_ERR("%s R_AARCH64_COPY relocations are not supported", si->name);
1038 return -1;
1039 case R_AARCH64_TLS_TPREL64:
1040 TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
1041 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1042 break;
1043 case R_AARCH64_TLS_DTPREL32:
1044 TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
1045 reloc, (sym_addr + rela->r_addend), rela->r_offset);
1046 break;
1047 #elif defined(__x86_64__)
1048 case R_X86_64_JUMP_SLOT:
1049 count_relocation(kRelocAbsolute);
1050 MARK(rela->r_offset);
1051 TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1052 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1053 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1054 break;
1055 case R_X86_64_GLOB_DAT:
1056 count_relocation(kRelocAbsolute);
1057 MARK(rela->r_offset);
1058 TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
1059 static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
1060 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1061 break;
1062 case R_X86_64_RELATIVE:
1063 count_relocation(kRelocRelative);
1064 MARK(rela->r_offset);
1065 if (sym) {
1066 DL_ERR("odd RELATIVE form...");
1067 return -1;
1068 }
1069 TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
1070 static_cast<size_t>(si->base));
1071 *reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend;
1072 break;
1073 case R_X86_64_32:
1074 count_relocation(kRelocRelative);
1075 MARK(rela->r_offset);
1076 TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1077 static_cast<size_t>(sym_addr), sym_name);
1078 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1079 break;
1080 case R_X86_64_64:
1081 count_relocation(kRelocRelative);
1082 MARK(rela->r_offset);
1083 TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
1084 static_cast<size_t>(sym_addr), sym_name);
1085 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
1086 break;
1087 case R_X86_64_PC32:
1088 count_relocation(kRelocRelative);
1089 MARK(rela->r_offset);
1090 TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
1091 static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
1092 static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
1093 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend - reloc;
1094 break;
1095 #endif
1097 default:
1098 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
1099 return -1;
1100 }
1101 }
1102 return 0;
1103 }
1105 #else // REL, not RELA.
1107 static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) {
1108 ElfW(Sym)* s;
1109 soinfo* lsi;
1111 for (size_t idx = 0; idx < count; ++idx, ++rel) {
1112 unsigned type = ELFW(R_TYPE)(rel->r_info);
1113 // TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
1114 unsigned sym = ELFW(R_SYM)(rel->r_info);
1115 ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias);
1116 ElfW(Addr) sym_addr = 0;
1117 const char* sym_name = NULL;
1119 DEBUG("Processing '%s' relocation at index %zd", si->name, idx);
1120 if (type == 0) { // R_*_NONE
1121 continue;
1122 }
1123 if (sym != 0) {
1124 sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
1125 s = soinfo_do_lookup(si, sym_name, &lsi, needed);
1126 if (s == NULL) {
1127 // We only allow an undefined symbol if this is a weak reference...
1128 s = &si->symtab[sym];
1129 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1130 DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name);
1131 return -1;
1132 }
1134 /* IHI0044C AAELF 4.5.1.1:
1136 Libraries are not searched to resolve weak references.
1137 It is not an error for a weak reference to remain
1138 unsatisfied.
1140 During linking, the value of an undefined weak reference is:
1141 - Zero if the relocation type is absolute
1142 - The address of the place if the relocation is pc-relative
1143 - The address of nominal base address if the relocation
1144 type is base-relative.
1145 */
1147 switch (type) {
1148 #if defined(__arm__)
1149 case R_ARM_JUMP_SLOT:
1150 case R_ARM_GLOB_DAT:
1151 case R_ARM_ABS32:
1152 case R_ARM_RELATIVE: /* Don't care. */
1153 // sym_addr was initialized to be zero above or relocation
1154 // code below does not care about value of sym_addr.
1155 // No need to do anything.
1156 break;
1157 #elif defined(__i386__)
1158 case R_386_JMP_SLOT:
1159 case R_386_GLOB_DAT:
1160 case R_386_32:
1161 case R_386_RELATIVE: /* Don't care. */
1162 // sym_addr was initialized to be zero above or relocation
1163 // code below does not care about value of sym_addr.
1164 // No need to do anything.
1165 break;
1166 case R_386_PC32:
1167 sym_addr = reloc;
1168 break;
1169 #endif
1171 #if defined(__arm__)
1172 case R_ARM_COPY:
1173 // Fall through. Can't really copy if weak symbol is not found at run-time.
1174 #endif
1175 default:
1176 DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
1177 return -1;
1178 }
1179 } else {
1180 // We got a definition.
1181 sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias);
1182 }
1183 count_relocation(kRelocSymbol);
1184 } else {
1185 s = NULL;
1186 }
1188 switch (type) {
1189 #if defined(__arm__)
1190 case R_ARM_JUMP_SLOT:
1191 count_relocation(kRelocAbsolute);
1192 MARK(rel->r_offset);
1193 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1194 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1195 break;
1196 case R_ARM_GLOB_DAT:
1197 count_relocation(kRelocAbsolute);
1198 MARK(rel->r_offset);
1199 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1200 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1201 break;
1202 case R_ARM_ABS32:
1203 count_relocation(kRelocAbsolute);
1204 MARK(rel->r_offset);
1205 TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
1206 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1207 break;
1208 case R_ARM_REL32:
1209 count_relocation(kRelocRelative);
1210 MARK(rel->r_offset);
1211 TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
1212 reloc, sym_addr, rel->r_offset, sym_name);
1213 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
1214 break;
1215 case R_ARM_COPY:
1216 /*
1217 * ET_EXEC is not supported so this should not happen.
1218 *
1219 * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
1220 *
1221 * Section 4.7.1.10 "Dynamic relocations"
1222 * R_ARM_COPY may only appear in executable objects where e_type is
1223 * set to ET_EXEC.
1224 */
1225 DL_ERR("%s R_ARM_COPY relocations are not supported", si->name);
1226 return -1;
1227 #elif defined(__i386__)
1228 case R_386_JMP_SLOT:
1229 count_relocation(kRelocAbsolute);
1230 MARK(rel->r_offset);
1231 TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
1232 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1233 break;
1234 case R_386_GLOB_DAT:
1235 count_relocation(kRelocAbsolute);
1236 MARK(rel->r_offset);
1237 TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
1238 *reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
1239 break;
1240 case R_386_32:
1241 count_relocation(kRelocRelative);
1242 MARK(rel->r_offset);
1243 TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
1244 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1245 break;
1246 case R_386_PC32:
1247 count_relocation(kRelocRelative);
1248 MARK(rel->r_offset);
1249 TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
1250 reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
1251 *reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
1252 break;
1253 #elif defined(__mips__)
1254 case R_MIPS_REL32:
1255 #if defined(__LP64__)
1256 // MIPS Elf64_Rel entries contain compound relocations
1257 // We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
1258 if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
1259 ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
1260 DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
1261 type, (unsigned)ELF64_R_TYPE2(rel->r_info),
1262 (unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
1263 return -1;
1264 }
1265 #endif
1266 count_relocation(kRelocAbsolute);
1267 MARK(rel->r_offset);
1268 TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
1269 static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
1270 if (s) {
1271 *reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
1272 } else {
1273 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base;
1274 }
1275 break;
1276 #endif
1278 #if defined(__arm__)
1279 case R_ARM_RELATIVE:
1280 #elif defined(__i386__)
1281 case R_386_RELATIVE:
1282 #endif
1283 count_relocation(kRelocRelative);
1284 MARK(rel->r_offset);
1285 if (sym) {
1286 DL_ERR("odd RELATIVE form...");
1287 return -1;
1288 }
1289 TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
1290 reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base));
1291 *reinterpret_cast<ElfW(Addr)*>(reloc) += si->base;
1292 break;
1294 default:
1295 DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
1296 return -1;
1297 }
1298 }
1299 return 0;
1300 }
1301 #endif
1303 #if defined(__mips__)
1304 static bool mips_relocate_got(soinfo* si, soinfo* needed[]) {
1305 ElfW(Addr)** got = si->plt_got;
1306 if (got == NULL) {
1307 return true;
1308 }
1309 unsigned local_gotno = si->mips_local_gotno;
1310 unsigned gotsym = si->mips_gotsym;
1311 unsigned symtabno = si->mips_symtabno;
1312 ElfW(Sym)* symtab = si->symtab;
1314 // got[0] is the address of the lazy resolver function.
1315 // got[1] may be used for a GNU extension.
1316 // Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
1317 // FIXME: maybe this should be in a separate routine?
1318 if ((si->flags & FLAG_LINKER) == 0) {
1319 size_t g = 0;
1320 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
1321 if (reinterpret_cast<intptr_t>(got[g]) < 0) {
1322 got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
1323 }
1324 // Relocate the local GOT entries.
1325 for (; g < local_gotno; g++) {
1326 got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
1327 }
1328 }
1330 // Now for the global GOT entries...
1331 ElfW(Sym)* sym = symtab + gotsym;
1332 got = si->plt_got + local_gotno;
1333 for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
1334 // This is an undefined reference... try to locate it.
1335 const char* sym_name = si->strtab + sym->st_name;
1336 soinfo* lsi;
1337 ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed);
1338 if (s == NULL) {
1339 // We only allow an undefined symbol if this is a weak reference.
1340 s = &symtab[g];
1341 if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
1342 DL_ERR("cannot locate \"%s\"...", sym_name);
1343 return false;
1344 }
1345 *got = 0;
1346 } else {
1347 // FIXME: is this sufficient?
1348 // For reference see NetBSD link loader
1349 // 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
1350 *got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value);
1351 }
1352 }
1353 return true;
1354 }
1355 #endif
1357 void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
1358 if (functions == NULL) {
1359 return;
1360 }
1362 TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
1364 int begin = reverse ? (count - 1) : 0;
1365 int end = reverse ? -1 : count;
1366 int step = reverse ? -1 : 1;
1368 for (int i = begin; i != end; i += step) {
1369 TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
1370 CallFunction("function", functions[i]);
1371 }
1373 TRACE("[ Done calling %s for '%s' ]", array_name, name);
1374 }
1376 void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
1377 if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
1378 return;
1379 }
1381 TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
1382 function();
1383 TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
1385 // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
1386 // are still writable. This happens with our debug malloc (see http://b/7941716).
1387 protect_data(PROT_READ | PROT_WRITE);
1388 }
1390 void soinfo::CallPreInitConstructors() {
1391 // DT_PREINIT_ARRAY functions are called before any other constructors for executables,
1392 // but ignored in a shared library.
1393 CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
1394 }
1396 void soinfo::CallConstructors() {
1397 if (constructors_called) {
1398 return;
1399 }
1401 // We set constructors_called before actually calling the constructors, otherwise it doesn't
1402 // protect against recursive constructor calls. One simple example of constructor recursion
1403 // is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
1404 // 1. The program depends on libc, so libc's constructor is called here.
1405 // 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
1406 // 3. dlopen() calls the constructors on the newly created
1407 // soinfo for libc_malloc_debug_leak.so.
1408 // 4. The debug .so depends on libc, so CallConstructors is
1409 // called again with the libc soinfo. If it doesn't trigger the early-
1410 // out above, the libc constructor will be called again (recursively!).
1411 constructors_called = true;
1413 if ((flags & FLAG_EXE) == 0 && preinit_array != NULL) {
1414 // The GNU dynamic linker silently ignores these, but we warn the developer.
1415 PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
1416 name, preinit_array_count);
1417 }
1419 get_children().for_each([] (soinfo* si) {
1420 si->CallConstructors();
1421 });
1423 TRACE("\"%s\": calling constructors", name);
1425 // DT_INIT should be called before DT_INIT_ARRAY if both are present.
1426 CallFunction("DT_INIT", init_func);
1427 CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
1428 }
1430 void soinfo::CallDestructors() {
1431 TRACE("\"%s\": calling destructors", name);
1433 // DT_FINI_ARRAY must be parsed in reverse order.
1434 CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
1436 // DT_FINI should be called after DT_FINI_ARRAY if both are present.
1437 CallFunction("DT_FINI", fini_func);
1438 }
1440 void soinfo::add_child(soinfo* child) {
1441 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1442 return;
1443 }
1445 this->children.push_front(child);
1446 child->parents.push_front(this);
1447 }
1449 void soinfo::remove_all_links() {
1450 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1451 return;
1452 }
1454 // 1. Untie connected soinfos from 'this'.
1455 children.for_each([&] (soinfo* child) {
1456 child->parents.remove_if([&] (const soinfo* parent) {
1457 return parent == this;
1458 });
1459 });
1461 parents.for_each([&] (soinfo* parent) {
1462 parent->children.for_each([&] (const soinfo* child) {
1463 return child == this;
1464 });
1465 });
1467 // 2. Once everything untied - clear local lists.
1468 parents.clear();
1469 children.clear();
1470 }
1472 void soinfo::set_st_dev(dev_t dev) {
1473 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1474 return;
1475 }
1477 st_dev = dev;
1478 }
1480 void soinfo::set_st_ino(ino_t ino) {
1481 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1482 return;
1483 }
1485 st_ino = ino;
1486 }
1488 dev_t soinfo::get_st_dev() {
1489 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1490 return 0;
1491 }
1493 return st_dev;
1494 };
1496 ino_t soinfo::get_st_ino() {
1497 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1498 return 0;
1499 }
1501 return st_ino;
1502 }
1504 // This is a return on get_children() in case
1505 // 'this->flags' does not have FLAG_NEW_SOINFO set.
1506 static soinfo::soinfo_list_t g_empty_list;
1508 soinfo::soinfo_list_t& soinfo::get_children() {
1509 if ((this->flags & FLAG_NEW_SOINFO) == 0) {
1510 return g_empty_list;
1511 }
1513 return this->children;
1514 }
1516 /* Force any of the closed stdin, stdout and stderr to be associated with
1517 /dev/null. */
1518 static int nullify_closed_stdio() {
1519 int dev_null, i, status;
1520 int return_value = 0;
1522 dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
1523 if (dev_null < 0) {
1524 DL_ERR("cannot open /dev/null: %s", strerror(errno));
1525 return -1;
1526 }
1527 TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
1529 /* If any of the stdio file descriptors is valid and not associated
1530 with /dev/null, dup /dev/null to it. */
1531 for (i = 0; i < 3; i++) {
1532 /* If it is /dev/null already, we are done. */
1533 if (i == dev_null) {
1534 continue;
1535 }
1537 TRACE("[ Nullifying stdio file descriptor %d]", i);
1538 status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
1540 /* If file is opened, we are good. */
1541 if (status != -1) {
1542 continue;
1543 }
1545 /* The only error we allow is that the file descriptor does not
1546 exist, in which case we dup /dev/null to it. */
1547 if (errno != EBADF) {
1548 DL_ERR("fcntl failed: %s", strerror(errno));
1549 return_value = -1;
1550 continue;
1551 }
1553 /* Try dupping /dev/null to this stdio file descriptor and
1554 repeat if there is a signal. Note that any errors in closing
1555 the stdio descriptor are lost. */
1556 status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
1557 if (status < 0) {
1558 DL_ERR("dup2 failed: %s", strerror(errno));
1559 return_value = -1;
1560 continue;
1561 }
1562 }
1564 /* If /dev/null is not one of the stdio file descriptors, close it. */
1565 if (dev_null > 2) {
1566 TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
1567 status = TEMP_FAILURE_RETRY(close(dev_null));
1568 if (status == -1) {
1569 DL_ERR("close failed: %s", strerror(errno));
1570 return_value = -1;
1571 }
1572 }
1574 return return_value;
1575 }
1577 static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) {
1578 /* "base" might wrap around UINT32_MAX. */
1579 ElfW(Addr) base = si->load_bias;
1580 const ElfW(Phdr)* phdr = si->phdr;
1581 int phnum = si->phnum;
1582 bool relocating_linker = (si->flags & FLAG_LINKER) != 0;
1584 /* We can't debug anything until the linker is relocated */
1585 if (!relocating_linker) {
1586 INFO("[ linking %s ]", si->name);
1587 DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags);
1588 }
1590 /* Extract dynamic section */
1591 size_t dynamic_count;
1592 ElfW(Word) dynamic_flags;
1593 phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic,
1594 &dynamic_count, &dynamic_flags);
1595 if (si->dynamic == NULL) {
1596 if (!relocating_linker) {
1597 DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name);
1598 }
1599 return false;
1600 } else {
1601 if (!relocating_linker) {
1602 DEBUG("dynamic = %p", si->dynamic);
1603 }
1604 }
1606 #if defined(__arm__)
1607 (void) phdr_table_get_arm_exidx(phdr, phnum, base,
1608 &si->ARM_exidx, &si->ARM_exidx_count);
1609 #endif
1611 // Extract useful information from dynamic section.
1612 uint32_t needed_count = 0;
1613 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
1614 DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
1615 d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1616 switch (d->d_tag) {
1617 case DT_HASH:
1618 si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0];
1619 si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1];
1620 si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8);
1621 si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4);
1622 break;
1623 case DT_STRTAB:
1624 si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr);
1625 break;
1626 case DT_SYMTAB:
1627 si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr);
1628 break;
1629 #if !defined(__LP64__)
1630 case DT_PLTREL:
1631 if (d->d_un.d_val != DT_REL) {
1632 DL_ERR("unsupported DT_RELA in \"%s\"", si->name);
1633 return false;
1634 }
1635 break;
1636 #endif
1637 case DT_JMPREL:
1638 #if defined(USE_RELA)
1639 si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr);
1640 #else
1641 si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr);
1642 #endif
1643 break;
1644 case DT_PLTRELSZ:
1645 #if defined(USE_RELA)
1646 si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
1647 #else
1648 si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
1649 #endif
1650 break;
1651 #if defined(__mips__)
1652 case DT_PLTGOT:
1653 // Used by mips and mips64.
1654 si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr);
1655 break;
1656 #endif
1657 case DT_DEBUG:
1658 // Set the DT_DEBUG entry to the address of _r_debug for GDB
1659 // if the dynamic table is writable
1660 // FIXME: not working currently for N64
1661 // The flags for the LOAD and DYNAMIC program headers do not agree.
1662 // The LOAD section containng the dynamic table has been mapped as
1663 // read-only, but the DYNAMIC header claims it is writable.
1664 #if !(defined(__mips__) && defined(__LP64__))
1665 if ((dynamic_flags & PF_W) != 0) {
1666 d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
1667 }
1668 break;
1669 #endif
1670 #if defined(USE_RELA)
1671 case DT_RELA:
1672 si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr);
1673 break;
1674 case DT_RELASZ:
1675 si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
1676 break;
1677 case DT_REL:
1678 DL_ERR("unsupported DT_REL in \"%s\"", si->name);
1679 return false;
1680 case DT_RELSZ:
1681 DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name);
1682 return false;
1683 #else
1684 case DT_REL:
1685 si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr);
1686 break;
1687 case DT_RELSZ:
1688 si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
1689 break;
1690 case DT_RELA:
1691 DL_ERR("unsupported DT_RELA in \"%s\"", si->name);
1692 return false;
1693 #endif
1694 case DT_INIT:
1695 si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr);
1696 DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func);
1697 break;
1698 case DT_FINI:
1699 si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr);
1700 DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func);
1701 break;
1702 case DT_INIT_ARRAY:
1703 si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
1704 DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array);
1705 break;
1706 case DT_INIT_ARRAYSZ:
1707 si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
1708 break;
1709 case DT_FINI_ARRAY:
1710 si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
1711 DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array);
1712 break;
1713 case DT_FINI_ARRAYSZ:
1714 si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
1715 break;
1716 case DT_PREINIT_ARRAY:
1717 si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
1718 DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array);
1719 break;
1720 case DT_PREINIT_ARRAYSZ:
1721 si->preinit_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
1722 break;
1723 case DT_TEXTREL:
1724 #if defined(__LP64__)
1725 DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", si->name);
1726 return false;
1727 #else
1728 si->has_text_relocations = true;
1729 break;
1730 #endif
1731 case DT_SYMBOLIC:
1732 si->has_DT_SYMBOLIC = true;
1733 break;
1734 case DT_NEEDED:
1735 ++needed_count;
1736 break;
1737 case DT_FLAGS:
1738 if (d->d_un.d_val & DF_TEXTREL) {
1739 #if defined(__LP64__)
1740 DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", si->name);
1741 return false;
1742 #else
1743 si->has_text_relocations = true;
1744 #endif
1745 }
1746 if (d->d_un.d_val & DF_SYMBOLIC) {
1747 si->has_DT_SYMBOLIC = true;
1748 }
1749 break;
1750 #if defined(__mips__)
1751 case DT_STRSZ:
1752 case DT_SYMENT:
1753 case DT_RELENT:
1754 break;
1755 case DT_MIPS_RLD_MAP:
1756 // Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
1757 {
1758 r_debug** dp = reinterpret_cast<r_debug**>(base + d->d_un.d_ptr);
1759 *dp = &_r_debug;
1760 }
1761 break;
1762 case DT_MIPS_RLD_VERSION:
1763 case DT_MIPS_FLAGS:
1764 case DT_MIPS_BASE_ADDRESS:
1765 case DT_MIPS_UNREFEXTNO:
1766 break;
1768 case DT_MIPS_SYMTABNO:
1769 si->mips_symtabno = d->d_un.d_val;
1770 break;
1772 case DT_MIPS_LOCAL_GOTNO:
1773 si->mips_local_gotno = d->d_un.d_val;
1774 break;
1776 case DT_MIPS_GOTSYM:
1777 si->mips_gotsym = d->d_un.d_val;
1778 break;
1779 #endif
1781 default:
1782 DEBUG("Unused DT entry: type %p arg %p",
1783 reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
1784 break;
1785 }
1786 }
1788 DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
1789 reinterpret_cast<void*>(si->base), si->strtab, si->symtab);
1791 // Sanity checks.
1792 if (relocating_linker && needed_count != 0) {
1793 DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
1794 return false;
1795 }
1796 if (si->nbucket == 0) {
1797 DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name);
1798 return false;
1799 }
1800 if (si->strtab == 0) {
1801 DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name);
1802 return false;
1803 }
1804 if (si->symtab == 0) {
1805 DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name);
1806 return false;
1807 }
1809 // If this is the main executable, then load all of the libraries from LD_PRELOAD now.
1810 if (si->flags & FLAG_EXE) {
1811 memset(g_ld_preloads, 0, sizeof(g_ld_preloads));
1812 size_t preload_count = 0;
1813 for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) {
1814 soinfo* lsi = find_library(g_ld_preload_names[i], NULL);
1815 if (lsi != NULL) {
1816 g_ld_preloads[preload_count++] = lsi;
1817 } else {
1818 // As with glibc, failure to load an LD_PRELOAD library is just a warning.
1819 DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s",
1820 g_ld_preload_names[i], si->name, linker_get_error_buffer());
1821 }
1822 }
1823 }
1825 soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*)));
1826 soinfo** pneeded = needed;
1828 for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
1829 if (d->d_tag == DT_NEEDED) {
1830 const char* library_name = si->strtab + d->d_un.d_val;
1831 DEBUG("%s needs %s", si->name, library_name);
1832 soinfo* lsi = find_library(library_name, NULL);
1833 if (lsi == NULL) {
1834 strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf));
1835 DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s",
1836 library_name, si->name, tmp_err_buf);
1837 return false;
1838 }
1840 si->add_child(lsi);
1841 *pneeded++ = lsi;
1842 }
1843 }
1844 *pneeded = NULL;
1846 #if !defined(__LP64__)
1847 if (si->has_text_relocations) {
1848 // Make segments writable to allow text relocations to work properly. We will later call
1849 // phdr_table_protect_segments() after all of them are applied and all constructors are run.
1850 #if !defined(__i386__) // The platform itself has too many text relocations on x86.
1851 DL_WARN("%s has text relocations. This is wasting memory and prevents "
1852 "security hardening. Please fix.", si->name);
1853 #endif
1854 if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) {
1855 DL_ERR("can't unprotect loadable segments for \"%s\": %s",
1856 si->name, strerror(errno));
1857 return false;
1858 }
1859 }
1860 #endif
1862 #if defined(USE_RELA)
1863 if (si->plt_rela != NULL) {
1864 DEBUG("[ relocating %s plt ]\n", si->name);
1865 if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) {
1866 return false;
1867 }
1868 }
1869 if (si->rela != NULL) {
1870 DEBUG("[ relocating %s ]\n", si->name);
1871 if (soinfo_relocate(si, si->rela, si->rela_count, needed)) {
1872 return false;
1873 }
1874 }
1875 #else
1876 if (si->plt_rel != NULL) {
1877 DEBUG("[ relocating %s plt ]", si->name);
1878 if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) {
1879 return false;
1880 }
1881 }
1882 if (si->rel != NULL) {
1883 DEBUG("[ relocating %s ]", si->name);
1884 if (soinfo_relocate(si, si->rel, si->rel_count, needed)) {
1885 return false;
1886 }
1887 }
1888 #endif
1890 #if defined(__mips__)
1891 if (!mips_relocate_got(si, needed)) {
1892 return false;
1893 }
1894 #endif
1896 si->flags |= FLAG_LINKED;
1897 DEBUG("[ finished linking %s ]", si->name);
1899 #if !defined(__LP64__)
1900 if (si->has_text_relocations) {
1901 // All relocations are done, we can protect our segments back to read-only.
1902 if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) {
1903 DL_ERR("can't protect segments for \"%s\": %s",
1904 si->name, strerror(errno));
1905 return false;
1906 }
1907 }
1908 #endif
1910 /* We can also turn on GNU RELRO protection */
1911 if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) {
1912 DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
1913 si->name, strerror(errno));
1914 return false;
1915 }
1917 /* Handle serializing/sharing the RELRO segment */
1918 if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
1919 if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias,
1920 extinfo->relro_fd) < 0) {
1921 DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
1922 si->name, strerror(errno));
1923 return false;
1924 }
1925 } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
1926 if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias,
1927 extinfo->relro_fd) < 0) {
1928 DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
1929 si->name, strerror(errno));
1930 return false;
1931 }
1932 }
1934 notify_gdb_of_load(si);
1935 return true;
1936 }
1938 /*
1939 * This function add vdso to internal dso list.
1940 * It helps to stack unwinding through signal handlers.
1941 * Also, it makes bionic more like glibc.
1942 */
1943 static void add_vdso(KernelArgumentBlock& args __unused) {
1944 #if defined(AT_SYSINFO_EHDR)
1945 ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
1946 if (ehdr_vdso == NULL) {
1947 return;
1948 }
1950 soinfo* si = soinfo_alloc("[vdso]", NULL);
1952 si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
1953 si->phnum = ehdr_vdso->e_phnum;
1954 si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
1955 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
1956 si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
1958 soinfo_link_image(si, NULL);
1959 #endif
1960 }
1962 /*
1963 * This is linker soinfo for GDB. See details below.
1964 */
1965 static soinfo linker_soinfo_for_gdb;
1967 /* gdb expects the linker to be in the debug shared object list.
1968 * Without this, gdb has trouble locating the linker's ".text"
1969 * and ".plt" sections. Gdb could also potentially use this to
1970 * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
1971 * Don't use soinfo_alloc(), because the linker shouldn't
1972 * be on the soinfo list.
1973 */
1974 static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
1975 #if defined(__LP64__)
1976 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name));
1977 #else
1978 strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name));
1979 #endif
1980 linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO;
1981 linker_soinfo_for_gdb.base = linker_base;
1983 /*
1984 * Set the dynamic field in the link map otherwise gdb will complain with
1985 * the following:
1986 * warning: .dynamic section for "/system/bin/linker" is not at the
1987 * expected address (wrong library or version mismatch?)
1988 */
1989 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
1990 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
1991 phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
1992 &linker_soinfo_for_gdb.dynamic, NULL, NULL);
1993 insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
1994 }
1996 /*
1997 * This code is called after the linker has linked itself and
1998 * fixed it's own GOT. It is safe to make references to externs
1999 * and other non-local data at this point.
2000 */
2001 static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
2002 /* NOTE: we store the args pointer on a special location
2003 * of the temporary TLS area in order to pass it to
2004 * the C Library's runtime initializer.
2005 *
2006 * The initializer must clear the slot and reset the TLS
2007 * to point to a different location to ensure that no other
2008 * shared library constructor can access it.
2009 */
2010 __libc_init_tls(args);
2012 #if TIMING
2013 struct timeval t0, t1;
2014 gettimeofday(&t0, 0);
2015 #endif
2017 // Initialize environment functions, and get to the ELF aux vectors table.
2018 linker_env_init(args);
2020 // If this is a setuid/setgid program, close the security hole described in
2021 // ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2022 if (get_AT_SECURE()) {
2023 nullify_closed_stdio();
2024 }
2026 debuggerd_init();
2028 // Get a few environment variables.
2029 const char* LD_DEBUG = linker_env_get("LD_DEBUG");
2030 if (LD_DEBUG != NULL) {
2031 g_ld_debug_verbosity = atoi(LD_DEBUG);
2032 }
2034 // Normally, these are cleaned by linker_env_init, but the test
2035 // doesn't cost us anything.
2036 const char* ldpath_env = NULL;
2037 const char* ldpreload_env = NULL;
2038 if (!get_AT_SECURE()) {
2039 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2040 ldpreload_env = linker_env_get("LD_PRELOAD");
2041 }
2043 // Linker does not call constructors for its own
2044 // global variables so we need to initialize
2045 // the allocators explicitly.
2046 g_soinfo_allocator.init();
2047 g_soinfo_links_allocator.init();
2049 INFO("[ android linker & debugger ]");
2051 soinfo* si = soinfo_alloc(args.argv[0], NULL);
2052 if (si == NULL) {
2053 exit(EXIT_FAILURE);
2054 }
2056 /* bootstrap the link map, the main exe always needs to be first */
2057 si->flags |= FLAG_EXE;
2058 link_map* map = &(si->link_map_head);
2060 map->l_addr = 0;
2061 map->l_name = args.argv[0];
2062 map->l_prev = NULL;
2063 map->l_next = NULL;
2065 _r_debug.r_map = map;
2066 r_debug_tail = map;
2068 init_linker_info_for_gdb(linker_base);
2070 // Extract information passed from the kernel.
2071 si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
2072 si->phnum = args.getauxval(AT_PHNUM);
2073 si->entry = args.getauxval(AT_ENTRY);
2075 /* Compute the value of si->base. We can't rely on the fact that
2076 * the first entry is the PHDR because this will not be true
2077 * for certain executables (e.g. some in the NDK unit test suite)
2078 */
2079 si->base = 0;
2080 si->size = phdr_table_get_load_size(si->phdr, si->phnum);
2081 si->load_bias = 0;
2082 for (size_t i = 0; i < si->phnum; ++i) {
2083 if (si->phdr[i].p_type == PT_PHDR) {
2084 si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
2085 si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
2086 break;
2087 }
2088 }
2089 si->dynamic = NULL;
2090 si->ref_count = 1;
2092 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
2093 if (elf_hdr->e_type != ET_DYN) {
2094 __libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
2095 exit(EXIT_FAILURE);
2096 }
2098 // Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
2099 parse_LD_LIBRARY_PATH(ldpath_env);
2100 parse_LD_PRELOAD(ldpreload_env);
2102 somain = si;
2104 if (!soinfo_link_image(si, NULL)) {
2105 __libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
2106 exit(EXIT_FAILURE);
2107 }
2109 add_vdso(args);
2111 si->CallPreInitConstructors();
2113 for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) {
2114 g_ld_preloads[i]->CallConstructors();
2115 }
2117 /* After the link_image, the si->load_bias is initialized.
2118 * For so lib, the map->l_addr will be updated in notify_gdb_of_load.
2119 * We need to update this value for so exe here. So Unwind_Backtrace
2120 * for some arch like x86 could work correctly within so exe.
2121 */
2122 map->l_addr = si->load_bias;
2123 si->CallConstructors();
2125 #if TIMING
2126 gettimeofday(&t1, NULL);
2127 PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
2128 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2129 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
2130 #endif
2131 #if STATS
2132 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
2133 linker_stats.count[kRelocAbsolute],
2134 linker_stats.count[kRelocRelative],
2135 linker_stats.count[kRelocCopy],
2136 linker_stats.count[kRelocSymbol]);
2137 #endif
2138 #if COUNT_PAGES
2139 {
2140 unsigned n;
2141 unsigned i;
2142 unsigned count = 0;
2143 for (n = 0; n < 4096; n++) {
2144 if (bitmask[n]) {
2145 unsigned x = bitmask[n];
2146 #if defined(__LP64__)
2147 for (i = 0; i < 32; i++) {
2148 #else
2149 for (i = 0; i < 8; i++) {
2150 #endif
2151 if (x & 1) {
2152 count++;
2153 }
2154 x >>= 1;
2155 }
2156 }
2157 }
2158 PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
2159 }
2160 #endif
2162 #if TIMING || STATS || COUNT_PAGES
2163 fflush(stdout);
2164 #endif
2166 TRACE("[ Ready to execute '%s' @ %p ]", si->name, reinterpret_cast<void*>(si->entry));
2167 return si->entry;
2168 }
2170 /* Compute the load-bias of an existing executable. This shall only
2171 * be used to compute the load bias of an executable or shared library
2172 * that was loaded by the kernel itself.
2173 *
2174 * Input:
2175 * elf -> address of ELF header, assumed to be at the start of the file.
2176 * Return:
2177 * load bias, i.e. add the value of any p_vaddr in the file to get
2178 * the corresponding address in memory.
2179 */
2180 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
2181 ElfW(Addr) offset = elf->e_phoff;
2182 const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
2183 const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
2185 for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
2186 if (phdr->p_type == PT_LOAD) {
2187 return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
2188 }
2189 }
2190 return 0;
2191 }
2193 /*
2194 * This is the entry point for the linker, called from begin.S. This
2195 * method is responsible for fixing the linker's own relocations, and
2196 * then calling __linker_init_post_relocation().
2197 *
2198 * Because this method is called before the linker has fixed it's own
2199 * relocations, any attempt to reference an extern variable, extern
2200 * function, or other GOT reference will generate a segfault.
2201 */
2202 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
2203 // Initialize static variables.
2204 solist = get_libdl_info();
2205 sonext = get_libdl_info();
2207 KernelArgumentBlock args(raw_args);
2209 ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
2210 ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
2211 ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
2213 soinfo linker_so;
2214 memset(&linker_so, 0, sizeof(soinfo));
2216 strcpy(linker_so.name, "[dynamic linker]");
2217 linker_so.base = linker_addr;
2218 linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
2219 linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
2220 linker_so.dynamic = NULL;
2221 linker_so.phdr = phdr;
2222 linker_so.phnum = elf_hdr->e_phnum;
2223 linker_so.flags |= FLAG_LINKER;
2225 if (!soinfo_link_image(&linker_so, NULL)) {
2226 // It would be nice to print an error message, but if the linker
2227 // can't link itself, there's no guarantee that we'll be able to
2228 // call write() (because it involves a GOT reference). We may as
2229 // well try though...
2230 const char* msg = "CANNOT LINK EXECUTABLE: ";
2231 write(2, msg, strlen(msg));
2232 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2233 write(2, "\n", 1);
2234 _exit(EXIT_FAILURE);
2235 }
2237 // We have successfully fixed our own relocations. It's safe to run
2238 // the main part of the linker now.
2239 args.abort_message_ptr = &g_abort_message;
2240 ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
2242 protect_data(PROT_READ);
2244 // Return the address that the calling assembly stub should jump to.
2245 return start_address;
2246 }