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 */
28
29 #include <linux/auxvec.h>
30
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <unistd.h>
35 #include <fcntl.h>
36 #include <errno.h>
37 #include <dlfcn.h>
38 #include <sys/stat.h>
39
40 #include <pthread.h>
41
42 #include <sys/mman.h>
43
44 #include <sys/atomics.h>
45
46 /* special private C library header - see Android.mk */
47 #include <bionic_tls.h>
48
49 #include "linker.h"
50 #include "linker_debug.h"
51 #include "linker_environ.h"
52 #include "linker_format.h"
53
54 #define ALLOW_SYMBOLS_FROM_MAIN 1
55 #define SO_MAX 128
56
57 /* Assume average path length of 64 and max 8 paths */
58 #define LDPATH_BUFSIZE 512
59 #define LDPATH_MAX 8
60
61 #define LDPRELOAD_BUFSIZE 512
62 #define LDPRELOAD_MAX 8
63
64 /* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<<
65 *
66 * Do NOT use malloc() and friends or pthread_*() code here.
67 * Don't use printf() either; it's caused mysterious memory
68 * corruption in the past.
69 * The linker runs before we bring up libc and it's easiest
70 * to make sure it does not depend on any complex libc features
71 *
72 * open issues / todo:
73 *
74 * - are we doing everything we should for ARM_COPY relocations?
75 * - cleaner error reporting
76 * - after linking, set as much stuff as possible to READONLY
77 * and NOEXEC
78 * - linker hardcodes PAGE_SIZE and PAGE_MASK because the kernel
79 * headers provide versions that are negative...
80 * - allocate space for soinfo structs dynamically instead of
81 * having a hard limit (64)
82 */
83
84
85 static int link_image(soinfo *si, unsigned wr_offset);
86
87 static int socount = 0;
88 static soinfo sopool[SO_MAX];
89 static soinfo *freelist = NULL;
90 static soinfo *solist = &libdl_info;
91 static soinfo *sonext = &libdl_info;
92 #if ALLOW_SYMBOLS_FROM_MAIN
93 static soinfo *somain; /* main process, always the one after libdl_info */
94 #endif
95
96
validate_soinfo(soinfo * si)97 static inline int validate_soinfo(soinfo *si)
98 {
99 return (si >= sopool && si < sopool + SO_MAX) ||
100 si == &libdl_info;
101 }
102
103 static char ldpaths_buf[LDPATH_BUFSIZE];
104 static const char *ldpaths[LDPATH_MAX + 1];
105
106 static char ldpreloads_buf[LDPRELOAD_BUFSIZE];
107 static const char *ldpreload_names[LDPRELOAD_MAX + 1];
108
109 static soinfo *preloads[LDPRELOAD_MAX + 1];
110
111 int debug_verbosity;
112 static int pid;
113
114 /* This boolean is set if the program being loaded is setuid */
115 static int program_is_setuid;
116
117 #if STATS
118 struct _link_stats linker_stats;
119 #endif
120
121 #if COUNT_PAGES
122 unsigned bitmask[4096];
123 #endif
124
125 #ifndef PT_ARM_EXIDX
126 #define PT_ARM_EXIDX 0x70000001 /* .ARM.exidx segment */
127 #endif
128
129 #define HOODLUM(name, ret, ...) \
130 ret name __VA_ARGS__ \
131 { \
132 char errstr[] = "ERROR: " #name " called from the dynamic linker!\n"; \
133 write(2, errstr, sizeof(errstr)); \
134 abort(); \
135 }
136 HOODLUM(malloc, void *, (size_t size));
137 HOODLUM(free, void, (void *ptr));
138 HOODLUM(realloc, void *, (void *ptr, size_t size));
139 HOODLUM(calloc, void *, (size_t cnt, size_t size));
140
141 static char tmp_err_buf[768];
142 static char __linker_dl_err_buf[768];
143 #define DL_ERR(fmt, x...) \
144 do { \
145 format_buffer(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), \
146 "%s[%d]: " fmt, __func__, __LINE__, ##x); \
147 ERROR(fmt "\n", ##x); \
148 } while(0)
149
linker_get_error(void)150 const char *linker_get_error(void)
151 {
152 return (const char *)&__linker_dl_err_buf[0];
153 }
154
155 /*
156 * This function is an empty stub where GDB locates a breakpoint to get notified
157 * about linker activity.
158 */
159 extern void __attribute__((noinline)) rtld_db_dlactivity(void);
160
161 static struct r_debug _r_debug = {1, NULL, &rtld_db_dlactivity,
162 RT_CONSISTENT, 0};
163 static struct link_map *r_debug_tail = 0;
164
165 static pthread_mutex_t _r_debug_lock = PTHREAD_MUTEX_INITIALIZER;
166
insert_soinfo_into_debug_map(soinfo * info)167 static void insert_soinfo_into_debug_map(soinfo * info)
168 {
169 struct link_map * map;
170
171 /* Copy the necessary fields into the debug structure.
172 */
173 map = &(info->linkmap);
174 map->l_addr = info->base;
175 map->l_name = (char*) info->name;
176 map->l_ld = (uintptr_t)info->dynamic;
177
178 /* Stick the new library at the end of the list.
179 * gdb tends to care more about libc than it does
180 * about leaf libraries, and ordering it this way
181 * reduces the back-and-forth over the wire.
182 */
183 if (r_debug_tail) {
184 r_debug_tail->l_next = map;
185 map->l_prev = r_debug_tail;
186 map->l_next = 0;
187 } else {
188 _r_debug.r_map = map;
189 map->l_prev = 0;
190 map->l_next = 0;
191 }
192 r_debug_tail = map;
193 }
194
remove_soinfo_from_debug_map(soinfo * info)195 static void remove_soinfo_from_debug_map(soinfo * info)
196 {
197 struct link_map * map = &(info->linkmap);
198
199 if (r_debug_tail == map)
200 r_debug_tail = map->l_prev;
201
202 if (map->l_prev) map->l_prev->l_next = map->l_next;
203 if (map->l_next) map->l_next->l_prev = map->l_prev;
204 }
205
notify_gdb_of_load(soinfo * info)206 void notify_gdb_of_load(soinfo * info)
207 {
208 if (info->flags & FLAG_EXE) {
209 // GDB already knows about the main executable
210 return;
211 }
212
213 pthread_mutex_lock(&_r_debug_lock);
214
215 _r_debug.r_state = RT_ADD;
216 rtld_db_dlactivity();
217
218 insert_soinfo_into_debug_map(info);
219
220 _r_debug.r_state = RT_CONSISTENT;
221 rtld_db_dlactivity();
222
223 pthread_mutex_unlock(&_r_debug_lock);
224 }
225
notify_gdb_of_unload(soinfo * info)226 void notify_gdb_of_unload(soinfo * info)
227 {
228 if (info->flags & FLAG_EXE) {
229 // GDB already knows about the main executable
230 return;
231 }
232
233 pthread_mutex_lock(&_r_debug_lock);
234
235 _r_debug.r_state = RT_DELETE;
236 rtld_db_dlactivity();
237
238 remove_soinfo_from_debug_map(info);
239
240 _r_debug.r_state = RT_CONSISTENT;
241 rtld_db_dlactivity();
242
243 pthread_mutex_unlock(&_r_debug_lock);
244 }
245
notify_gdb_of_libraries()246 void notify_gdb_of_libraries()
247 {
248 _r_debug.r_state = RT_ADD;
249 rtld_db_dlactivity();
250 _r_debug.r_state = RT_CONSISTENT;
251 rtld_db_dlactivity();
252 }
253
alloc_info(const char * name)254 static soinfo *alloc_info(const char *name)
255 {
256 soinfo *si;
257
258 if(strlen(name) >= SOINFO_NAME_LEN) {
259 DL_ERR("%5d library name %s too long", pid, name);
260 return NULL;
261 }
262
263 /* The freelist is populated when we call free_info(), which in turn is
264 done only by dlclose(), which is not likely to be used.
265 */
266 if (!freelist) {
267 if(socount == SO_MAX) {
268 DL_ERR("%5d too many libraries when loading %s", pid, name);
269 return NULL;
270 }
271 freelist = sopool + socount++;
272 freelist->next = NULL;
273 }
274
275 si = freelist;
276 freelist = freelist->next;
277
278 /* Make sure we get a clean block of soinfo */
279 memset(si, 0, sizeof(soinfo));
280 strlcpy((char*) si->name, name, sizeof(si->name));
281 sonext->next = si;
282 si->next = NULL;
283 si->refcount = 0;
284 sonext = si;
285
286 TRACE("%5d name %s: allocated soinfo @ %p\n", pid, name, si);
287 return si;
288 }
289
free_info(soinfo * si)290 static void free_info(soinfo *si)
291 {
292 soinfo *prev = NULL, *trav;
293
294 TRACE("%5d name %s: freeing soinfo @ %p\n", pid, si->name, si);
295
296 for(trav = solist; trav != NULL; trav = trav->next){
297 if (trav == si)
298 break;
299 prev = trav;
300 }
301 if (trav == NULL) {
302 /* si was not ni solist */
303 DL_ERR("%5d name %s is not in solist!", pid, si->name);
304 return;
305 }
306
307 /* prev will never be NULL, because the first entry in solist is
308 always the static libdl_info.
309 */
310 prev->next = si->next;
311 if (si == sonext) sonext = prev;
312 si->next = freelist;
313 freelist = si;
314 }
315
316 #ifndef LINKER_TEXT_BASE
317 #error "linker's makefile must define LINKER_TEXT_BASE"
318 #endif
319 #ifndef LINKER_AREA_SIZE
320 #error "linker's makefile must define LINKER_AREA_SIZE"
321 #endif
322 #define LINKER_BASE ((LINKER_TEXT_BASE) & 0xfff00000)
323 #define LINKER_TOP (LINKER_BASE + (LINKER_AREA_SIZE))
324
addr_to_name(unsigned addr)325 const char *addr_to_name(unsigned addr)
326 {
327 soinfo *si;
328
329 for(si = solist; si != 0; si = si->next){
330 if((addr >= si->base) && (addr < (si->base + si->size))) {
331 return si->name;
332 }
333 }
334
335 if((addr >= LINKER_BASE) && (addr < LINKER_TOP)){
336 return "linker";
337 }
338
339 return "";
340 }
341
342 /* For a given PC, find the .so that it belongs to.
343 * Returns the base address of the .ARM.exidx section
344 * for that .so, and the number of 8-byte entries
345 * in that section (via *pcount).
346 *
347 * Intended to be called by libc's __gnu_Unwind_Find_exidx().
348 *
349 * This function is exposed via dlfcn.c and libdl.so.
350 */
351 #ifdef ANDROID_ARM_LINKER
dl_unwind_find_exidx(_Unwind_Ptr pc,int * pcount)352 _Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount)
353 {
354 soinfo *si;
355 unsigned addr = (unsigned)pc;
356
357 if ((addr < LINKER_BASE) || (addr >= LINKER_TOP)) {
358 for (si = solist; si != 0; si = si->next){
359 if ((addr >= si->base) && (addr < (si->base + si->size))) {
360 *pcount = si->ARM_exidx_count;
361 return (_Unwind_Ptr)(si->base + (unsigned long)si->ARM_exidx);
362 }
363 }
364 }
365 *pcount = 0;
366 return NULL;
367 }
368 #elif defined(ANDROID_X86_LINKER) || defined(ANDROID_SH_LINKER)
369 /* Here, we only have to provide a callback to iterate across all the
370 * loaded libraries. gcc_eh does the rest. */
371 int
dl_iterate_phdr(int (* cb)(struct dl_phdr_info * info,size_t size,void * data),void * data)372 dl_iterate_phdr(int (*cb)(struct dl_phdr_info *info, size_t size, void *data),
373 void *data)
374 {
375 soinfo *si;
376 struct dl_phdr_info dl_info;
377 int rv = 0;
378
379 for (si = solist; si != NULL; si = si->next) {
380 dl_info.dlpi_addr = si->linkmap.l_addr;
381 dl_info.dlpi_name = si->linkmap.l_name;
382 dl_info.dlpi_phdr = si->phdr;
383 dl_info.dlpi_phnum = si->phnum;
384 rv = cb(&dl_info, sizeof (struct dl_phdr_info), data);
385 if (rv != 0)
386 break;
387 }
388 return rv;
389 }
390 #endif
391
_elf_lookup(soinfo * si,unsigned hash,const char * name)392 static Elf32_Sym *_elf_lookup(soinfo *si, unsigned hash, const char *name)
393 {
394 Elf32_Sym *s;
395 Elf32_Sym *symtab = si->symtab;
396 const char *strtab = si->strtab;
397 unsigned n;
398
399 TRACE_TYPE(LOOKUP, "%5d SEARCH %s in %s@0x%08x %08x %d\n", pid,
400 name, si->name, si->base, hash, hash % si->nbucket);
401 n = hash % si->nbucket;
402
403 for(n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]){
404 s = symtab + n;
405 if(strcmp(strtab + s->st_name, name)) continue;
406
407 /* only concern ourselves with global and weak symbol definitions */
408 switch(ELF32_ST_BIND(s->st_info)){
409 case STB_GLOBAL:
410 case STB_WEAK:
411 /* no section == undefined */
412 if(s->st_shndx == 0) continue;
413
414 TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", pid,
415 name, si->name, s->st_value, s->st_size);
416 return s;
417 }
418 }
419
420 return NULL;
421 }
422
elfhash(const char * _name)423 static unsigned elfhash(const char *_name)
424 {
425 const unsigned char *name = (const unsigned char *) _name;
426 unsigned h = 0, g;
427
428 while(*name) {
429 h = (h << 4) + *name++;
430 g = h & 0xf0000000;
431 h ^= g;
432 h ^= g >> 24;
433 }
434 return h;
435 }
436
437 static Elf32_Sym *
_do_lookup(soinfo * si,const char * name,unsigned * base)438 _do_lookup(soinfo *si, const char *name, unsigned *base)
439 {
440 unsigned elf_hash = elfhash(name);
441 Elf32_Sym *s;
442 unsigned *d;
443 soinfo *lsi = si;
444 int i;
445
446 /* Look for symbols in the local scope first (the object who is
447 * searching). This happens with C++ templates on i386 for some
448 * reason.
449 *
450 * Notes on weak symbols:
451 * The ELF specs are ambigious about treatment of weak definitions in
452 * dynamic linking. Some systems return the first definition found
453 * and some the first non-weak definition. This is system dependent.
454 * Here we return the first definition found for simplicity. */
455 s = _elf_lookup(si, elf_hash, name);
456 if(s != NULL)
457 goto done;
458
459 /* Next, look for it in the preloads list */
460 for(i = 0; preloads[i] != NULL; i++) {
461 lsi = preloads[i];
462 s = _elf_lookup(lsi, elf_hash, name);
463 if(s != NULL)
464 goto done;
465 }
466
467 for(d = si->dynamic; *d; d += 2) {
468 if(d[0] == DT_NEEDED){
469 lsi = (soinfo *)d[1];
470 if (!validate_soinfo(lsi)) {
471 DL_ERR("%5d bad DT_NEEDED pointer in %s",
472 pid, si->name);
473 return NULL;
474 }
475
476 DEBUG("%5d %s: looking up %s in %s\n",
477 pid, si->name, name, lsi->name);
478 s = _elf_lookup(lsi, elf_hash, name);
479 if ((s != NULL) && (s->st_shndx != SHN_UNDEF))
480 goto done;
481 }
482 }
483
484 #if ALLOW_SYMBOLS_FROM_MAIN
485 /* If we are resolving relocations while dlopen()ing a library, it's OK for
486 * the library to resolve a symbol that's defined in the executable itself,
487 * although this is rare and is generally a bad idea.
488 */
489 if (somain) {
490 lsi = somain;
491 DEBUG("%5d %s: looking up %s in executable %s\n",
492 pid, si->name, name, lsi->name);
493 s = _elf_lookup(lsi, elf_hash, name);
494 }
495 #endif
496
497 done:
498 if(s != NULL) {
499 TRACE_TYPE(LOOKUP, "%5d si %s sym %s s->st_value = 0x%08x, "
500 "found in %s, base = 0x%08x\n",
501 pid, si->name, name, s->st_value, lsi->name, lsi->base);
502 *base = lsi->base;
503 return s;
504 }
505
506 return NULL;
507 }
508
509 /* This is used by dl_sym(). It performs symbol lookup only within the
510 specified soinfo object and not in any of its dependencies.
511 */
lookup_in_library(soinfo * si,const char * name)512 Elf32_Sym *lookup_in_library(soinfo *si, const char *name)
513 {
514 return _elf_lookup(si, elfhash(name), name);
515 }
516
517 /* This is used by dl_sym(). It performs a global symbol lookup.
518 */
lookup(const char * name,soinfo ** found,soinfo * start)519 Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start)
520 {
521 unsigned elf_hash = elfhash(name);
522 Elf32_Sym *s = NULL;
523 soinfo *si;
524
525 if(start == NULL) {
526 start = solist;
527 }
528
529 for(si = start; (s == NULL) && (si != NULL); si = si->next)
530 {
531 if(si->flags & FLAG_ERROR)
532 continue;
533 s = _elf_lookup(si, elf_hash, name);
534 if (s != NULL) {
535 *found = si;
536 break;
537 }
538 }
539
540 if(s != NULL) {
541 TRACE_TYPE(LOOKUP, "%5d %s s->st_value = 0x%08x, "
542 "si->base = 0x%08x\n", pid, name, s->st_value, si->base);
543 return s;
544 }
545
546 return NULL;
547 }
548
find_containing_library(const void * addr)549 soinfo *find_containing_library(const void *addr)
550 {
551 soinfo *si;
552
553 for(si = solist; si != NULL; si = si->next)
554 {
555 if((unsigned)addr >= si->base && (unsigned)addr - si->base < si->size) {
556 return si;
557 }
558 }
559
560 return NULL;
561 }
562
find_containing_symbol(const void * addr,soinfo * si)563 Elf32_Sym *find_containing_symbol(const void *addr, soinfo *si)
564 {
565 unsigned int i;
566 unsigned soaddr = (unsigned)addr - si->base;
567
568 /* Search the library's symbol table for any defined symbol which
569 * contains this address */
570 for(i=0; i<si->nchain; i++) {
571 Elf32_Sym *sym = &si->symtab[i];
572
573 if(sym->st_shndx != SHN_UNDEF &&
574 soaddr >= sym->st_value &&
575 soaddr < sym->st_value + sym->st_size) {
576 return sym;
577 }
578 }
579
580 return NULL;
581 }
582
583 #if 0
584 static void dump(soinfo *si)
585 {
586 Elf32_Sym *s = si->symtab;
587 unsigned n;
588
589 for(n = 0; n < si->nchain; n++) {
590 TRACE("%5d %04d> %08x: %02x %04x %08x %08x %s\n", pid, n, s,
591 s->st_info, s->st_shndx, s->st_value, s->st_size,
592 si->strtab + s->st_name);
593 s++;
594 }
595 }
596 #endif
597
598 static const char *sopaths[] = {
599 "/vendor/lib",
600 "/system/lib",
601 0
602 };
603
_open_lib(const char * name)604 static int _open_lib(const char *name)
605 {
606 int fd;
607 struct stat filestat;
608
609 if ((stat(name, &filestat) >= 0) && S_ISREG(filestat.st_mode)) {
610 if ((fd = open(name, O_RDONLY)) >= 0)
611 return fd;
612 }
613
614 return -1;
615 }
616
open_library(const char * name)617 static int open_library(const char *name)
618 {
619 int fd;
620 char buf[512];
621 const char **path;
622 int n;
623
624 TRACE("[ %5d opening %s ]\n", pid, name);
625
626 if(name == 0) return -1;
627 if(strlen(name) > 256) return -1;
628
629 if ((name[0] == '/') && ((fd = _open_lib(name)) >= 0))
630 return fd;
631
632 for (path = ldpaths; *path; path++) {
633 n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name);
634 if (n < 0 || n >= (int)sizeof(buf)) {
635 WARN("Ignoring very long library path: %s/%s\n", *path, name);
636 continue;
637 }
638 if ((fd = _open_lib(buf)) >= 0)
639 return fd;
640 }
641 for (path = sopaths; *path; path++) {
642 n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name);
643 if (n < 0 || n >= (int)sizeof(buf)) {
644 WARN("Ignoring very long library path: %s/%s\n", *path, name);
645 continue;
646 }
647 if ((fd = _open_lib(buf)) >= 0)
648 return fd;
649 }
650
651 return -1;
652 }
653
654 /* temporary space for holding the first page of the shared lib
655 * which contains the elf header (with the pht). */
656 static unsigned char __header[PAGE_SIZE];
657
658 typedef struct {
659 long mmap_addr;
660 char tag[4]; /* 'P', 'R', 'E', ' ' */
661 } prelink_info_t;
662
663 /* Returns the requested base address if the library is prelinked,
664 * and 0 otherwise. */
665 static unsigned long
is_prelinked(int fd,const char * name)666 is_prelinked(int fd, const char *name)
667 {
668 off_t sz;
669 prelink_info_t info;
670
671 sz = lseek(fd, -sizeof(prelink_info_t), SEEK_END);
672 if (sz < 0) {
673 DL_ERR("lseek() failed!");
674 return 0;
675 }
676
677 if (read(fd, &info, sizeof(info)) != sizeof(info)) {
678 WARN("Could not read prelink_info_t structure for `%s`\n", name);
679 return 0;
680 }
681
682 if (strncmp(info.tag, "PRE ", 4)) {
683 WARN("`%s` is not a prelinked library\n", name);
684 return 0;
685 }
686
687 return (unsigned long)info.mmap_addr;
688 }
689
690 /* verify_elf_object
691 * Verifies if the object @ base is a valid ELF object
692 *
693 * Args:
694 *
695 * Returns:
696 * 0 on success
697 * -1 if no valid ELF object is found @ base.
698 */
699 static int
verify_elf_object(void * base,const char * name)700 verify_elf_object(void *base, const char *name)
701 {
702 Elf32_Ehdr *hdr = (Elf32_Ehdr *) base;
703
704 if (hdr->e_ident[EI_MAG0] != ELFMAG0) return -1;
705 if (hdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
706 if (hdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
707 if (hdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
708
709 /* TODO: Should we verify anything else in the header? */
710
711 return 0;
712 }
713
714
715 /* get_lib_extents
716 * Retrieves the base (*base) address where the ELF object should be
717 * mapped and its overall memory size (*total_sz).
718 *
719 * Args:
720 * fd: Opened file descriptor for the library
721 * name: The name of the library
722 * _hdr: Pointer to the header page of the library
723 * total_sz: Total size of the memory that should be allocated for
724 * this library
725 *
726 * Returns:
727 * -1 if there was an error while trying to get the lib extents.
728 * The possible reasons are:
729 * - Could not determine if the library was prelinked.
730 * - The library provided is not a valid ELF object
731 * 0 if the library did not request a specific base offset (normal
732 * for non-prelinked libs)
733 * > 0 if the library requests a specific address to be mapped to.
734 * This indicates a pre-linked library.
735 */
736 static unsigned
get_lib_extents(int fd,const char * name,void * __hdr,unsigned * total_sz)737 get_lib_extents(int fd, const char *name, void *__hdr, unsigned *total_sz)
738 {
739 unsigned req_base;
740 unsigned min_vaddr = 0xffffffff;
741 unsigned max_vaddr = 0;
742 unsigned char *_hdr = (unsigned char *)__hdr;
743 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)_hdr;
744 Elf32_Phdr *phdr;
745 int cnt;
746
747 TRACE("[ %5d Computing extents for '%s'. ]\n", pid, name);
748 if (verify_elf_object(_hdr, name) < 0) {
749 DL_ERR("%5d - %s is not a valid ELF object", pid, name);
750 return (unsigned)-1;
751 }
752
753 req_base = (unsigned) is_prelinked(fd, name);
754 if (req_base == (unsigned)-1)
755 return -1;
756 else if (req_base != 0) {
757 TRACE("[ %5d - Prelinked library '%s' requesting base @ 0x%08x ]\n",
758 pid, name, req_base);
759 } else {
760 TRACE("[ %5d - Non-prelinked library '%s' found. ]\n", pid, name);
761 }
762
763 phdr = (Elf32_Phdr *)(_hdr + ehdr->e_phoff);
764
765 /* find the min/max p_vaddrs from all the PT_LOAD segments so we can
766 * get the range. */
767 for (cnt = 0; cnt < ehdr->e_phnum; ++cnt, ++phdr) {
768 if (phdr->p_type == PT_LOAD) {
769 if ((phdr->p_vaddr + phdr->p_memsz) > max_vaddr)
770 max_vaddr = phdr->p_vaddr + phdr->p_memsz;
771 if (phdr->p_vaddr < min_vaddr)
772 min_vaddr = phdr->p_vaddr;
773 }
774 }
775
776 if ((min_vaddr == 0xffffffff) && (max_vaddr == 0)) {
777 DL_ERR("%5d - No loadable segments found in %s.", pid, name);
778 return (unsigned)-1;
779 }
780
781 /* truncate min_vaddr down to page boundary */
782 min_vaddr &= ~PAGE_MASK;
783
784 /* round max_vaddr up to the next page */
785 max_vaddr = (max_vaddr + PAGE_SIZE - 1) & ~PAGE_MASK;
786
787 *total_sz = (max_vaddr - min_vaddr);
788 return (unsigned)req_base;
789 }
790
791 /* alloc_mem_region
792 *
793 * This function reserves a chunk of memory to be used for mapping in
794 * the shared library. We reserve the entire memory region here, and
795 * then the rest of the linker will relocate the individual loadable
796 * segments into the correct locations within this memory range.
797 *
798 * Args:
799 * si->base: The requested base of the allocation. If 0, a sane one will be
800 * chosen in the range LIBBASE <= base < LIBLAST.
801 * si->size: The size of the allocation.
802 *
803 * Returns:
804 * -1 on failure, and 0 on success. On success, si->base will contain
805 * the virtual address at which the library will be mapped.
806 */
807
reserve_mem_region(soinfo * si)808 static int reserve_mem_region(soinfo *si)
809 {
810 void *base = mmap((void *)si->base, si->size, PROT_READ | PROT_EXEC,
811 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
812 if (base == MAP_FAILED) {
813 DL_ERR("%5d can NOT map (%sprelinked) library '%s' at 0x%08x "
814 "as requested, will try general pool: %d (%s)",
815 pid, (si->base ? "" : "non-"), si->name, si->base,
816 errno, strerror(errno));
817 return -1;
818 } else if (base != (void *)si->base) {
819 DL_ERR("OOPS: %5d %sprelinked library '%s' mapped at 0x%08x, "
820 "not at 0x%08x", pid, (si->base ? "" : "non-"),
821 si->name, (unsigned)base, si->base);
822 munmap(base, si->size);
823 return -1;
824 }
825 return 0;
826 }
827
828 static int
alloc_mem_region(soinfo * si)829 alloc_mem_region(soinfo *si)
830 {
831 if (si->base) {
832 /* Attempt to mmap a prelinked library. */
833 return reserve_mem_region(si);
834 }
835
836 /* This is not a prelinked library, so we use the kernel's default
837 allocator.
838 */
839
840 void *base = mmap(NULL, si->size, PROT_READ | PROT_EXEC,
841 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
842 if (base == MAP_FAILED) {
843 DL_ERR("%5d mmap of library '%s' failed: %d (%s)\n",
844 pid, si->name,
845 errno, strerror(errno));
846 goto err;
847 }
848 si->base = (unsigned) base;
849 PRINT("%5d mapped library '%s' to %08x via kernel allocator.\n",
850 pid, si->name, si->base);
851 return 0;
852
853 err:
854 DL_ERR("OOPS: %5d cannot map library '%s'. no vspace available.",
855 pid, si->name);
856 return -1;
857 }
858
859 #define MAYBE_MAP_FLAG(x,from,to) (((x) & (from)) ? (to) : 0)
860 #define PFLAGS_TO_PROT(x) (MAYBE_MAP_FLAG((x), PF_X, PROT_EXEC) | \
861 MAYBE_MAP_FLAG((x), PF_R, PROT_READ) | \
862 MAYBE_MAP_FLAG((x), PF_W, PROT_WRITE))
863 /* load_segments
864 *
865 * This function loads all the loadable (PT_LOAD) segments into memory
866 * at their appropriate memory offsets off the base address.
867 *
868 * Args:
869 * fd: Open file descriptor to the library to load.
870 * header: Pointer to a header page that contains the ELF header.
871 * This is needed since we haven't mapped in the real file yet.
872 * si: ptr to soinfo struct describing the shared object.
873 *
874 * Returns:
875 * 0 on success, -1 on failure.
876 */
877 static int
load_segments(int fd,void * header,soinfo * si)878 load_segments(int fd, void *header, soinfo *si)
879 {
880 Elf32_Ehdr *ehdr = (Elf32_Ehdr *)header;
881 Elf32_Phdr *phdr = (Elf32_Phdr *)((unsigned char *)header + ehdr->e_phoff);
882 unsigned char *base = (unsigned char *)si->base;
883 int cnt;
884 unsigned len;
885 unsigned char *tmp;
886 unsigned char *pbase;
887 unsigned char *extra_base;
888 unsigned extra_len;
889 unsigned total_sz = 0;
890
891 si->wrprotect_start = 0xffffffff;
892 si->wrprotect_end = 0;
893
894 TRACE("[ %5d - Begin loading segments for '%s' @ 0x%08x ]\n",
895 pid, si->name, (unsigned)si->base);
896 /* Now go through all the PT_LOAD segments and map them into memory
897 * at the appropriate locations. */
898 for (cnt = 0; cnt < ehdr->e_phnum; ++cnt, ++phdr) {
899 if (phdr->p_type == PT_LOAD) {
900 DEBUG_DUMP_PHDR(phdr, "PT_LOAD", pid);
901 /* we want to map in the segment on a page boundary */
902 tmp = base + (phdr->p_vaddr & (~PAGE_MASK));
903 /* add the # of bytes we masked off above to the total length. */
904 len = phdr->p_filesz + (phdr->p_vaddr & PAGE_MASK);
905
906 TRACE("[ %d - Trying to load segment from '%s' @ 0x%08x "
907 "(0x%08x). p_vaddr=0x%08x p_offset=0x%08x ]\n", pid, si->name,
908 (unsigned)tmp, len, phdr->p_vaddr, phdr->p_offset);
909 pbase = mmap(tmp, len, PFLAGS_TO_PROT(phdr->p_flags),
910 MAP_PRIVATE | MAP_FIXED, fd,
911 phdr->p_offset & (~PAGE_MASK));
912 if (pbase == MAP_FAILED) {
913 DL_ERR("%d failed to map segment from '%s' @ 0x%08x (0x%08x). "
914 "p_vaddr=0x%08x p_offset=0x%08x", pid, si->name,
915 (unsigned)tmp, len, phdr->p_vaddr, phdr->p_offset);
916 goto fail;
917 }
918
919 /* If 'len' didn't end on page boundary, and it's a writable
920 * segment, zero-fill the rest. */
921 if ((len & PAGE_MASK) && (phdr->p_flags & PF_W))
922 memset((void *)(pbase + len), 0, PAGE_SIZE - (len & PAGE_MASK));
923
924 /* Check to see if we need to extend the map for this segment to
925 * cover the diff between filesz and memsz (i.e. for bss).
926 *
927 * base _+---------------------+ page boundary
928 * . .
929 * | |
930 * . .
931 * pbase _+---------------------+ page boundary
932 * | |
933 * . .
934 * base + p_vaddr _| |
935 * . \ \ .
936 * . | filesz | .
937 * pbase + len _| / | |
938 * <0 pad> . . .
939 * extra_base _+------------|--------+ page boundary
940 * / . . .
941 * | . . .
942 * | +------------|--------+ page boundary
943 * extra_len-> | | | |
944 * | . | memsz .
945 * | . | .
946 * \ _| / |
947 * . .
948 * | |
949 * _+---------------------+ page boundary
950 */
951 tmp = (unsigned char *)(((unsigned)pbase + len + PAGE_SIZE - 1) &
952 (~PAGE_MASK));
953 if (tmp < (base + phdr->p_vaddr + phdr->p_memsz)) {
954 extra_len = base + phdr->p_vaddr + phdr->p_memsz - tmp;
955 TRACE("[ %5d - Need to extend segment from '%s' @ 0x%08x "
956 "(0x%08x) ]\n", pid, si->name, (unsigned)tmp, extra_len);
957 /* map in the extra page(s) as anonymous into the range.
958 * This is probably not necessary as we already mapped in
959 * the entire region previously, but we just want to be
960 * sure. This will also set the right flags on the region
961 * (though we can probably accomplish the same thing with
962 * mprotect).
963 */
964 extra_base = mmap((void *)tmp, extra_len,
965 PFLAGS_TO_PROT(phdr->p_flags),
966 MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS,
967 -1, 0);
968 if (extra_base == MAP_FAILED) {
969 DL_ERR("[ %5d - failed to extend segment from '%s' @ 0x%08x"
970 " (0x%08x) ]", pid, si->name, (unsigned)tmp,
971 extra_len);
972 goto fail;
973 }
974 /* TODO: Check if we need to memset-0 this region.
975 * Anonymous mappings are zero-filled copy-on-writes, so we
976 * shouldn't need to. */
977 TRACE("[ %5d - Segment from '%s' extended @ 0x%08x "
978 "(0x%08x)\n", pid, si->name, (unsigned)extra_base,
979 extra_len);
980 }
981 /* set the len here to show the full extent of the segment we
982 * just loaded, mostly for debugging */
983 len = (((unsigned)base + phdr->p_vaddr + phdr->p_memsz +
984 PAGE_SIZE - 1) & (~PAGE_MASK)) - (unsigned)pbase;
985 TRACE("[ %5d - Successfully loaded segment from '%s' @ 0x%08x "
986 "(0x%08x). p_vaddr=0x%08x p_offset=0x%08x\n", pid, si->name,
987 (unsigned)pbase, len, phdr->p_vaddr, phdr->p_offset);
988 total_sz += len;
989 /* Make the section writable just in case we'll have to write to
990 * it during relocation (i.e. text segment). However, we will
991 * remember what range of addresses should be write protected.
992 *
993 */
994 if (!(phdr->p_flags & PF_W)) {
995 if ((unsigned)pbase < si->wrprotect_start)
996 si->wrprotect_start = (unsigned)pbase;
997 if (((unsigned)pbase + len) > si->wrprotect_end)
998 si->wrprotect_end = (unsigned)pbase + len;
999 mprotect(pbase, len,
1000 PFLAGS_TO_PROT(phdr->p_flags) | PROT_WRITE);
1001 }
1002 } else if (phdr->p_type == PT_DYNAMIC) {
1003 DEBUG_DUMP_PHDR(phdr, "PT_DYNAMIC", pid);
1004 /* this segment contains the dynamic linking information */
1005 si->dynamic = (unsigned *)(base + phdr->p_vaddr);
1006 } else {
1007 #ifdef ANDROID_ARM_LINKER
1008 if (phdr->p_type == PT_ARM_EXIDX) {
1009 DEBUG_DUMP_PHDR(phdr, "PT_ARM_EXIDX", pid);
1010 /* exidx entries (used for stack unwinding) are 8 bytes each.
1011 */
1012 si->ARM_exidx = (unsigned *)phdr->p_vaddr;
1013 si->ARM_exidx_count = phdr->p_memsz / 8;
1014 }
1015 #endif
1016 }
1017
1018 }
1019
1020 /* Sanity check */
1021 if (total_sz > si->size) {
1022 DL_ERR("%5d - Total length (0x%08x) of mapped segments from '%s' is "
1023 "greater than what was allocated (0x%08x). THIS IS BAD!",
1024 pid, total_sz, si->name, si->size);
1025 goto fail;
1026 }
1027
1028 TRACE("[ %5d - Finish loading segments for '%s' @ 0x%08x. "
1029 "Total memory footprint: 0x%08x bytes ]\n", pid, si->name,
1030 (unsigned)si->base, si->size);
1031 return 0;
1032
1033 fail:
1034 /* We can just blindly unmap the entire region even though some things
1035 * were mapped in originally with anonymous and others could have been
1036 * been mapped in from the file before we failed. The kernel will unmap
1037 * all the pages in the range, irrespective of how they got there.
1038 */
1039 munmap((void *)si->base, si->size);
1040 si->flags |= FLAG_ERROR;
1041 return -1;
1042 }
1043
1044 /* TODO: Implement this to take care of the fact that Android ARM
1045 * ELF objects shove everything into a single loadable segment that has the
1046 * write bit set. wr_offset is then used to set non-(data|bss) pages to be
1047 * non-writable.
1048 */
1049 #if 0
1050 static unsigned
1051 get_wr_offset(int fd, const char *name, Elf32_Ehdr *ehdr)
1052 {
1053 Elf32_Shdr *shdr_start;
1054 Elf32_Shdr *shdr;
1055 int shdr_sz = ehdr->e_shnum * sizeof(Elf32_Shdr);
1056 int cnt;
1057 unsigned wr_offset = 0xffffffff;
1058
1059 shdr_start = mmap(0, shdr_sz, PROT_READ, MAP_PRIVATE, fd,
1060 ehdr->e_shoff & (~PAGE_MASK));
1061 if (shdr_start == MAP_FAILED) {
1062 WARN("%5d - Could not read section header info from '%s'. Will not "
1063 "not be able to determine write-protect offset.\n", pid, name);
1064 return (unsigned)-1;
1065 }
1066
1067 for(cnt = 0, shdr = shdr_start; cnt < ehdr->e_shnum; ++cnt, ++shdr) {
1068 if ((shdr->sh_type != SHT_NULL) && (shdr->sh_flags & SHF_WRITE) &&
1069 (shdr->sh_addr < wr_offset)) {
1070 wr_offset = shdr->sh_addr;
1071 }
1072 }
1073
1074 munmap(shdr_start, shdr_sz);
1075 return wr_offset;
1076 }
1077 #endif
1078
1079 static soinfo *
load_library(const char * name)1080 load_library(const char *name)
1081 {
1082 int fd = open_library(name);
1083 int cnt;
1084 unsigned ext_sz;
1085 unsigned req_base;
1086 const char *bname;
1087 soinfo *si = NULL;
1088 Elf32_Ehdr *hdr;
1089
1090 if(fd == -1) {
1091 DL_ERR("Library '%s' not found", name);
1092 return NULL;
1093 }
1094
1095 /* We have to read the ELF header to figure out what to do with this image
1096 */
1097 if (lseek(fd, 0, SEEK_SET) < 0) {
1098 DL_ERR("lseek() failed!");
1099 goto fail;
1100 }
1101
1102 if ((cnt = read(fd, &__header[0], PAGE_SIZE)) < 0) {
1103 DL_ERR("read() failed!");
1104 goto fail;
1105 }
1106
1107 /* Parse the ELF header and get the size of the memory footprint for
1108 * the library */
1109 req_base = get_lib_extents(fd, name, &__header[0], &ext_sz);
1110 if (req_base == (unsigned)-1)
1111 goto fail;
1112 TRACE("[ %5d - '%s' (%s) wants base=0x%08x sz=0x%08x ]\n", pid, name,
1113 (req_base ? "prelinked" : "not pre-linked"), req_base, ext_sz);
1114
1115 /* Now configure the soinfo struct where we'll store all of our data
1116 * for the ELF object. If the loading fails, we waste the entry, but
1117 * same thing would happen if we failed during linking. Configuring the
1118 * soinfo struct here is a lot more convenient.
1119 */
1120 bname = strrchr(name, '/');
1121 si = alloc_info(bname ? bname + 1 : name);
1122 if (si == NULL)
1123 goto fail;
1124
1125 /* Carve out a chunk of memory where we will map in the individual
1126 * segments */
1127 si->base = req_base;
1128 si->size = ext_sz;
1129 si->flags = 0;
1130 si->entry = 0;
1131 si->dynamic = (unsigned *)-1;
1132 if (alloc_mem_region(si) < 0)
1133 goto fail;
1134
1135 TRACE("[ %5d allocated memory for %s @ %p (0x%08x) ]\n",
1136 pid, name, (void *)si->base, (unsigned) ext_sz);
1137
1138 /* Now actually load the library's segments into right places in memory */
1139 if (load_segments(fd, &__header[0], si) < 0) {
1140 goto fail;
1141 }
1142
1143 /* this might not be right. Technically, we don't even need this info
1144 * once we go through 'load_segments'. */
1145 hdr = (Elf32_Ehdr *)si->base;
1146 si->phdr = (Elf32_Phdr *)((unsigned char *)si->base + hdr->e_phoff);
1147 si->phnum = hdr->e_phnum;
1148 /**/
1149
1150 close(fd);
1151 return si;
1152
1153 fail:
1154 if (si) free_info(si);
1155 close(fd);
1156 return NULL;
1157 }
1158
1159 static soinfo *
init_library(soinfo * si)1160 init_library(soinfo *si)
1161 {
1162 unsigned wr_offset = 0xffffffff;
1163
1164 /* At this point we know that whatever is loaded @ base is a valid ELF
1165 * shared library whose segments are properly mapped in. */
1166 TRACE("[ %5d init_library base=0x%08x sz=0x%08x name='%s') ]\n",
1167 pid, si->base, si->size, si->name);
1168
1169 if(link_image(si, wr_offset)) {
1170 /* We failed to link. However, we can only restore libbase
1171 ** if no additional libraries have moved it since we updated it.
1172 */
1173 munmap((void *)si->base, si->size);
1174 return NULL;
1175 }
1176
1177 return si;
1178 }
1179
find_library(const char * name)1180 soinfo *find_library(const char *name)
1181 {
1182 soinfo *si;
1183 const char *bname;
1184
1185 #if ALLOW_SYMBOLS_FROM_MAIN
1186 if (name == NULL)
1187 return somain;
1188 #else
1189 if (name == NULL)
1190 return NULL;
1191 #endif
1192
1193 bname = strrchr(name, '/');
1194 bname = bname ? bname + 1 : name;
1195
1196 for(si = solist; si != 0; si = si->next){
1197 if(!strcmp(bname, si->name)) {
1198 if(si->flags & FLAG_ERROR) {
1199 DL_ERR("%5d '%s' failed to load previously", pid, bname);
1200 return NULL;
1201 }
1202 if(si->flags & FLAG_LINKED) return si;
1203 DL_ERR("OOPS: %5d recursive link to '%s'", pid, si->name);
1204 return NULL;
1205 }
1206 }
1207
1208 TRACE("[ %5d '%s' has not been loaded yet. Locating...]\n", pid, name);
1209 si = load_library(name);
1210 if(si == NULL)
1211 return NULL;
1212 return init_library(si);
1213 }
1214
1215 /* TODO:
1216 * notify gdb of unload
1217 * for non-prelinked libraries, find a way to decrement libbase
1218 */
1219 static void call_destructors(soinfo *si);
unload_library(soinfo * si)1220 unsigned unload_library(soinfo *si)
1221 {
1222 unsigned *d;
1223 if (si->refcount == 1) {
1224 TRACE("%5d unloading '%s'\n", pid, si->name);
1225 call_destructors(si);
1226
1227 for(d = si->dynamic; *d; d += 2) {
1228 if(d[0] == DT_NEEDED){
1229 soinfo *lsi = (soinfo *)d[1];
1230 d[1] = 0;
1231 if (validate_soinfo(lsi)) {
1232 TRACE("%5d %s needs to unload %s\n", pid,
1233 si->name, lsi->name);
1234 unload_library(lsi);
1235 }
1236 else
1237 DL_ERR("%5d %s: could not unload dependent library",
1238 pid, si->name);
1239 }
1240 }
1241
1242 munmap((char *)si->base, si->size);
1243 notify_gdb_of_unload(si);
1244 free_info(si);
1245 si->refcount = 0;
1246 }
1247 else {
1248 si->refcount--;
1249 PRINT("%5d not unloading '%s', decrementing refcount to %d\n",
1250 pid, si->name, si->refcount);
1251 }
1252 return si->refcount;
1253 }
1254
1255 /* TODO: don't use unsigned for addrs below. It works, but is not
1256 * ideal. They should probably be either uint32_t, Elf32_Addr, or unsigned
1257 * long.
1258 */
reloc_library(soinfo * si,Elf32_Rel * rel,unsigned count)1259 static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count)
1260 {
1261 Elf32_Sym *symtab = si->symtab;
1262 const char *strtab = si->strtab;
1263 Elf32_Sym *s;
1264 unsigned base;
1265 Elf32_Rel *start = rel;
1266 unsigned idx;
1267
1268 for (idx = 0; idx < count; ++idx) {
1269 unsigned type = ELF32_R_TYPE(rel->r_info);
1270 unsigned sym = ELF32_R_SYM(rel->r_info);
1271 unsigned reloc = (unsigned)(rel->r_offset + si->base);
1272 unsigned sym_addr = 0;
1273 char *sym_name = NULL;
1274
1275 DEBUG("%5d Processing '%s' relocation at index %d\n", pid,
1276 si->name, idx);
1277 if(sym != 0) {
1278 sym_name = (char *)(strtab + symtab[sym].st_name);
1279 s = _do_lookup(si, sym_name, &base);
1280 if(s == NULL) {
1281 /* We only allow an undefined symbol if this is a weak
1282 reference.. */
1283 s = &symtab[sym];
1284 if (ELF32_ST_BIND(s->st_info) != STB_WEAK) {
1285 DL_ERR("%5d cannot locate '%s'...\n", pid, sym_name);
1286 return -1;
1287 }
1288
1289 /* IHI0044C AAELF 4.5.1.1:
1290
1291 Libraries are not searched to resolve weak references.
1292 It is not an error for a weak reference to remain
1293 unsatisfied.
1294
1295 During linking, the value of an undefined weak reference is:
1296 - Zero if the relocation type is absolute
1297 - The address of the place if the relocation is pc-relative
1298 - The address of nominial base address if the relocation
1299 type is base-relative.
1300 */
1301
1302 switch (type) {
1303 #if defined(ANDROID_ARM_LINKER)
1304 case R_ARM_JUMP_SLOT:
1305 case R_ARM_GLOB_DAT:
1306 case R_ARM_ABS32:
1307 case R_ARM_RELATIVE: /* Don't care. */
1308 case R_ARM_NONE: /* Don't care. */
1309 #elif defined(ANDROID_X86_LINKER)
1310 case R_386_JUMP_SLOT:
1311 case R_386_GLOB_DAT:
1312 case R_386_32:
1313 case R_386_RELATIVE: /* Dont' care. */
1314 #endif /* ANDROID_*_LINKER */
1315 /* sym_addr was initialized to be zero above or relocation
1316 code below does not care about value of sym_addr.
1317 No need to do anything. */
1318 break;
1319
1320 #if defined(ANDROID_X86_LINKER)
1321 case R_386_PC32:
1322 sym_addr = reloc;
1323 break;
1324 #endif /* ANDROID_X86_LINKER */
1325
1326 #if defined(ANDROID_ARM_LINKER)
1327 case R_ARM_COPY:
1328 /* Fall through. Can't really copy if weak symbol is
1329 not found in run-time. */
1330 #endif /* ANDROID_ARM_LINKER */
1331 default:
1332 DL_ERR("%5d unknown weak reloc type %d @ %p (%d)\n",
1333 pid, type, rel, (int) (rel - start));
1334 return -1;
1335 }
1336 } else {
1337 /* We got a definition. */
1338 #if 0
1339 if((base == 0) && (si->base != 0)){
1340 /* linking from libraries to main image is bad */
1341 DL_ERR("%5d cannot locate '%s'...",
1342 pid, strtab + symtab[sym].st_name);
1343 return -1;
1344 }
1345 #endif
1346 sym_addr = (unsigned)(s->st_value + base);
1347 }
1348 COUNT_RELOC(RELOC_SYMBOL);
1349 } else {
1350 s = NULL;
1351 }
1352
1353 /* TODO: This is ugly. Split up the relocations by arch into
1354 * different files.
1355 */
1356 switch(type){
1357 #if defined(ANDROID_ARM_LINKER)
1358 case R_ARM_JUMP_SLOT:
1359 COUNT_RELOC(RELOC_ABSOLUTE);
1360 MARK(rel->r_offset);
1361 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid,
1362 reloc, sym_addr, sym_name);
1363 *((unsigned*)reloc) = sym_addr;
1364 break;
1365 case R_ARM_GLOB_DAT:
1366 COUNT_RELOC(RELOC_ABSOLUTE);
1367 MARK(rel->r_offset);
1368 TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", pid,
1369 reloc, sym_addr, sym_name);
1370 *((unsigned*)reloc) = sym_addr;
1371 break;
1372 case R_ARM_ABS32:
1373 COUNT_RELOC(RELOC_ABSOLUTE);
1374 MARK(rel->r_offset);
1375 TRACE_TYPE(RELO, "%5d RELO ABS %08x <- %08x %s\n", pid,
1376 reloc, sym_addr, sym_name);
1377 *((unsigned*)reloc) += sym_addr;
1378 break;
1379 case R_ARM_REL32:
1380 COUNT_RELOC(RELOC_RELATIVE);
1381 MARK(rel->r_offset);
1382 TRACE_TYPE(RELO, "%5d RELO REL32 %08x <- %08x - %08x %s\n", pid,
1383 reloc, sym_addr, rel->r_offset, sym_name);
1384 *((unsigned*)reloc) += sym_addr - rel->r_offset;
1385 break;
1386 #elif defined(ANDROID_X86_LINKER)
1387 case R_386_JUMP_SLOT:
1388 COUNT_RELOC(RELOC_ABSOLUTE);
1389 MARK(rel->r_offset);
1390 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid,
1391 reloc, sym_addr, sym_name);
1392 *((unsigned*)reloc) = sym_addr;
1393 break;
1394 case R_386_GLOB_DAT:
1395 COUNT_RELOC(RELOC_ABSOLUTE);
1396 MARK(rel->r_offset);
1397 TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", pid,
1398 reloc, sym_addr, sym_name);
1399 *((unsigned*)reloc) = sym_addr;
1400 break;
1401 #endif /* ANDROID_*_LINKER */
1402
1403 #if defined(ANDROID_ARM_LINKER)
1404 case R_ARM_RELATIVE:
1405 #elif defined(ANDROID_X86_LINKER)
1406 case R_386_RELATIVE:
1407 #endif /* ANDROID_*_LINKER */
1408 COUNT_RELOC(RELOC_RELATIVE);
1409 MARK(rel->r_offset);
1410 if(sym){
1411 DL_ERR("%5d odd RELATIVE form...", pid);
1412 return -1;
1413 }
1414 TRACE_TYPE(RELO, "%5d RELO RELATIVE %08x <- +%08x\n", pid,
1415 reloc, si->base);
1416 *((unsigned*)reloc) += si->base;
1417 break;
1418
1419 #if defined(ANDROID_X86_LINKER)
1420 case R_386_32:
1421 COUNT_RELOC(RELOC_RELATIVE);
1422 MARK(rel->r_offset);
1423
1424 TRACE_TYPE(RELO, "%5d RELO R_386_32 %08x <- +%08x %s\n", pid,
1425 reloc, sym_addr, sym_name);
1426 *((unsigned *)reloc) += (unsigned)sym_addr;
1427 break;
1428
1429 case R_386_PC32:
1430 COUNT_RELOC(RELOC_RELATIVE);
1431 MARK(rel->r_offset);
1432 TRACE_TYPE(RELO, "%5d RELO R_386_PC32 %08x <- "
1433 "+%08x (%08x - %08x) %s\n", pid, reloc,
1434 (sym_addr - reloc), sym_addr, reloc, sym_name);
1435 *((unsigned *)reloc) += (unsigned)(sym_addr - reloc);
1436 break;
1437 #endif /* ANDROID_X86_LINKER */
1438
1439 #ifdef ANDROID_ARM_LINKER
1440 case R_ARM_COPY:
1441 COUNT_RELOC(RELOC_COPY);
1442 MARK(rel->r_offset);
1443 TRACE_TYPE(RELO, "%5d RELO %08x <- %d @ %08x %s\n", pid,
1444 reloc, s->st_size, sym_addr, sym_name);
1445 memcpy((void*)reloc, (void*)sym_addr, s->st_size);
1446 break;
1447 case R_ARM_NONE:
1448 break;
1449 #endif /* ANDROID_ARM_LINKER */
1450
1451 default:
1452 DL_ERR("%5d unknown reloc type %d @ %p (%d)",
1453 pid, type, rel, (int) (rel - start));
1454 return -1;
1455 }
1456 rel++;
1457 }
1458 return 0;
1459 }
1460
1461 #if defined(ANDROID_SH_LINKER)
reloc_library_a(soinfo * si,Elf32_Rela * rela,unsigned count)1462 static int reloc_library_a(soinfo *si, Elf32_Rela *rela, unsigned count)
1463 {
1464 Elf32_Sym *symtab = si->symtab;
1465 const char *strtab = si->strtab;
1466 Elf32_Sym *s;
1467 unsigned base;
1468 Elf32_Rela *start = rela;
1469 unsigned idx;
1470
1471 for (idx = 0; idx < count; ++idx) {
1472 unsigned type = ELF32_R_TYPE(rela->r_info);
1473 unsigned sym = ELF32_R_SYM(rela->r_info);
1474 unsigned reloc = (unsigned)(rela->r_offset + si->base);
1475 unsigned sym_addr = 0;
1476 char *sym_name = NULL;
1477
1478 DEBUG("%5d Processing '%s' relocation at index %d\n", pid,
1479 si->name, idx);
1480 if(sym != 0) {
1481 sym_name = (char *)(strtab + symtab[sym].st_name);
1482 s = _do_lookup(si, sym_name, &base);
1483 if(s == 0) {
1484 DL_ERR("%5d cannot locate '%s'...", pid, sym_name);
1485 return -1;
1486 }
1487 #if 0
1488 if((base == 0) && (si->base != 0)){
1489 /* linking from libraries to main image is bad */
1490 DL_ERR("%5d cannot locate '%s'...",
1491 pid, strtab + symtab[sym].st_name);
1492 return -1;
1493 }
1494 #endif
1495 if ((s->st_shndx == SHN_UNDEF) && (s->st_value != 0)) {
1496 DL_ERR("%5d In '%s', shndx=%d && value=0x%08x. We do not "
1497 "handle this yet", pid, si->name, s->st_shndx,
1498 s->st_value);
1499 return -1;
1500 }
1501 sym_addr = (unsigned)(s->st_value + base);
1502 COUNT_RELOC(RELOC_SYMBOL);
1503 } else {
1504 s = 0;
1505 }
1506
1507 /* TODO: This is ugly. Split up the relocations by arch into
1508 * different files.
1509 */
1510 switch(type){
1511 case R_SH_JUMP_SLOT:
1512 COUNT_RELOC(RELOC_ABSOLUTE);
1513 MARK(rela->r_offset);
1514 TRACE_TYPE(RELO, "%5d RELO JMP_SLOT %08x <- %08x %s\n", pid,
1515 reloc, sym_addr, sym_name);
1516 *((unsigned*)reloc) = sym_addr;
1517 break;
1518 case R_SH_GLOB_DAT:
1519 COUNT_RELOC(RELOC_ABSOLUTE);
1520 MARK(rela->r_offset);
1521 TRACE_TYPE(RELO, "%5d RELO GLOB_DAT %08x <- %08x %s\n", pid,
1522 reloc, sym_addr, sym_name);
1523 *((unsigned*)reloc) = sym_addr;
1524 break;
1525 case R_SH_DIR32:
1526 COUNT_RELOC(RELOC_ABSOLUTE);
1527 MARK(rela->r_offset);
1528 TRACE_TYPE(RELO, "%5d RELO DIR32 %08x <- %08x %s\n", pid,
1529 reloc, sym_addr, sym_name);
1530 *((unsigned*)reloc) += sym_addr;
1531 break;
1532 case R_SH_RELATIVE:
1533 COUNT_RELOC(RELOC_RELATIVE);
1534 MARK(rela->r_offset);
1535 if(sym){
1536 DL_ERR("%5d odd RELATIVE form...", pid);
1537 return -1;
1538 }
1539 TRACE_TYPE(RELO, "%5d RELO RELATIVE %08x <- +%08x\n", pid,
1540 reloc, si->base);
1541 *((unsigned*)reloc) += si->base;
1542 break;
1543
1544 default:
1545 DL_ERR("%5d unknown reloc type %d @ %p (%d)",
1546 pid, type, rela, (int) (rela - start));
1547 return -1;
1548 }
1549 rela++;
1550 }
1551 return 0;
1552 }
1553 #endif /* ANDROID_SH_LINKER */
1554
1555
1556 /* Please read the "Initialization and Termination functions" functions.
1557 * of the linker design note in bionic/linker/README.TXT to understand
1558 * what the following code is doing.
1559 *
1560 * The important things to remember are:
1561 *
1562 * DT_PREINIT_ARRAY must be called first for executables, and should
1563 * not appear in shared libraries.
1564 *
1565 * DT_INIT should be called before DT_INIT_ARRAY if both are present
1566 *
1567 * DT_FINI should be called after DT_FINI_ARRAY if both are present
1568 *
1569 * DT_FINI_ARRAY must be parsed in reverse order.
1570 */
1571
call_array(unsigned * ctor,int count,int reverse)1572 static void call_array(unsigned *ctor, int count, int reverse)
1573 {
1574 int n, inc = 1;
1575
1576 if (reverse) {
1577 ctor += (count-1);
1578 inc = -1;
1579 }
1580
1581 for(n = count; n > 0; n--) {
1582 TRACE("[ %5d Looking at %s *0x%08x == 0x%08x ]\n", pid,
1583 reverse ? "dtor" : "ctor",
1584 (unsigned)ctor, (unsigned)*ctor);
1585 void (*func)() = (void (*)()) *ctor;
1586 ctor += inc;
1587 if(((int) func == 0) || ((int) func == -1)) continue;
1588 TRACE("[ %5d Calling func @ 0x%08x ]\n", pid, (unsigned)func);
1589 func();
1590 }
1591 }
1592
call_constructors(soinfo * si)1593 static void call_constructors(soinfo *si)
1594 {
1595 if (si->flags & FLAG_EXE) {
1596 TRACE("[ %5d Calling preinit_array @ 0x%08x [%d] for '%s' ]\n",
1597 pid, (unsigned)si->preinit_array, si->preinit_array_count,
1598 si->name);
1599 call_array(si->preinit_array, si->preinit_array_count, 0);
1600 TRACE("[ %5d Done calling preinit_array for '%s' ]\n", pid, si->name);
1601 } else {
1602 if (si->preinit_array) {
1603 DL_ERR("%5d Shared library '%s' has a preinit_array table @ 0x%08x."
1604 " This is INVALID.", pid, si->name,
1605 (unsigned)si->preinit_array);
1606 }
1607 }
1608
1609 if (si->init_func) {
1610 TRACE("[ %5d Calling init_func @ 0x%08x for '%s' ]\n", pid,
1611 (unsigned)si->init_func, si->name);
1612 si->init_func();
1613 TRACE("[ %5d Done calling init_func for '%s' ]\n", pid, si->name);
1614 }
1615
1616 if (si->init_array) {
1617 TRACE("[ %5d Calling init_array @ 0x%08x [%d] for '%s' ]\n", pid,
1618 (unsigned)si->init_array, si->init_array_count, si->name);
1619 call_array(si->init_array, si->init_array_count, 0);
1620 TRACE("[ %5d Done calling init_array for '%s' ]\n", pid, si->name);
1621 }
1622 }
1623
1624
call_destructors(soinfo * si)1625 static void call_destructors(soinfo *si)
1626 {
1627 if (si->fini_array) {
1628 TRACE("[ %5d Calling fini_array @ 0x%08x [%d] for '%s' ]\n", pid,
1629 (unsigned)si->fini_array, si->fini_array_count, si->name);
1630 call_array(si->fini_array, si->fini_array_count, 1);
1631 TRACE("[ %5d Done calling fini_array for '%s' ]\n", pid, si->name);
1632 }
1633
1634 if (si->fini_func) {
1635 TRACE("[ %5d Calling fini_func @ 0x%08x for '%s' ]\n", pid,
1636 (unsigned)si->fini_func, si->name);
1637 si->fini_func();
1638 TRACE("[ %5d Done calling fini_func for '%s' ]\n", pid, si->name);
1639 }
1640 }
1641
1642 /* Force any of the closed stdin, stdout and stderr to be associated with
1643 /dev/null. */
nullify_closed_stdio(void)1644 static int nullify_closed_stdio (void)
1645 {
1646 int dev_null, i, status;
1647 int return_value = 0;
1648
1649 dev_null = open("/dev/null", O_RDWR);
1650 if (dev_null < 0) {
1651 DL_ERR("Cannot open /dev/null.");
1652 return -1;
1653 }
1654 TRACE("[ %5d Opened /dev/null file-descriptor=%d]\n", pid, dev_null);
1655
1656 /* If any of the stdio file descriptors is valid and not associated
1657 with /dev/null, dup /dev/null to it. */
1658 for (i = 0; i < 3; i++) {
1659 /* If it is /dev/null already, we are done. */
1660 if (i == dev_null)
1661 continue;
1662
1663 TRACE("[ %5d Nullifying stdio file descriptor %d]\n", pid, i);
1664 /* The man page of fcntl does not say that fcntl(..,F_GETFL)
1665 can be interrupted but we do this just to be safe. */
1666 do {
1667 status = fcntl(i, F_GETFL);
1668 } while (status < 0 && errno == EINTR);
1669
1670 /* If file is openned, we are good. */
1671 if (status >= 0)
1672 continue;
1673
1674 /* The only error we allow is that the file descriptor does not
1675 exist, in which case we dup /dev/null to it. */
1676 if (errno != EBADF) {
1677 DL_ERR("nullify_stdio: unhandled error %s", strerror(errno));
1678 return_value = -1;
1679 continue;
1680 }
1681
1682 /* Try dupping /dev/null to this stdio file descriptor and
1683 repeat if there is a signal. Note that any errors in closing
1684 the stdio descriptor are lost. */
1685 do {
1686 status = dup2(dev_null, i);
1687 } while (status < 0 && errno == EINTR);
1688
1689 if (status < 0) {
1690 DL_ERR("nullify_stdio: dup2 error %s", strerror(errno));
1691 return_value = -1;
1692 continue;
1693 }
1694 }
1695
1696 /* If /dev/null is not one of the stdio file descriptors, close it. */
1697 if (dev_null > 2) {
1698 TRACE("[ %5d Closing /dev/null file-descriptor=%d]\n", pid, dev_null);
1699 do {
1700 status = close(dev_null);
1701 } while (status < 0 && errno == EINTR);
1702
1703 if (status < 0) {
1704 DL_ERR("nullify_stdio: close error %s", strerror(errno));
1705 return_value = -1;
1706 }
1707 }
1708
1709 return return_value;
1710 }
1711
link_image(soinfo * si,unsigned wr_offset)1712 static int link_image(soinfo *si, unsigned wr_offset)
1713 {
1714 unsigned *d;
1715 Elf32_Phdr *phdr = si->phdr;
1716 int phnum = si->phnum;
1717
1718 INFO("[ %5d linking %s ]\n", pid, si->name);
1719 DEBUG("%5d si->base = 0x%08x si->flags = 0x%08x\n", pid,
1720 si->base, si->flags);
1721
1722 if (si->flags & FLAG_EXE) {
1723 /* Locate the needed program segments (DYNAMIC/ARM_EXIDX) for
1724 * linkage info if this is the executable. If this was a
1725 * dynamic lib, that would have been done at load time.
1726 *
1727 * TODO: It's unfortunate that small pieces of this are
1728 * repeated from the load_library routine. Refactor this just
1729 * slightly to reuse these bits.
1730 */
1731 si->size = 0;
1732 for(; phnum > 0; --phnum, ++phdr) {
1733 #ifdef ANDROID_ARM_LINKER
1734 if(phdr->p_type == PT_ARM_EXIDX) {
1735 /* exidx entries (used for stack unwinding) are 8 bytes each.
1736 */
1737 si->ARM_exidx = (unsigned *)phdr->p_vaddr;
1738 si->ARM_exidx_count = phdr->p_memsz / 8;
1739 }
1740 #endif
1741 if (phdr->p_type == PT_LOAD) {
1742 /* For the executable, we use the si->size field only in
1743 dl_unwind_find_exidx(), so the meaning of si->size
1744 is not the size of the executable; it is the last
1745 virtual address of the loadable part of the executable;
1746 since si->base == 0 for an executable, we use the
1747 range [0, si->size) to determine whether a PC value
1748 falls within the executable section. Of course, if
1749 a value is below phdr->p_vaddr, it's not in the
1750 executable section, but a) we shouldn't be asking for
1751 such a value anyway, and b) if we have to provide
1752 an EXIDX for such a value, then the executable's
1753 EXIDX is probably the better choice.
1754 */
1755 DEBUG_DUMP_PHDR(phdr, "PT_LOAD", pid);
1756 if (phdr->p_vaddr + phdr->p_memsz > si->size)
1757 si->size = phdr->p_vaddr + phdr->p_memsz;
1758 /* try to remember what range of addresses should be write
1759 * protected */
1760 if (!(phdr->p_flags & PF_W)) {
1761 unsigned _end;
1762
1763 if (phdr->p_vaddr < si->wrprotect_start)
1764 si->wrprotect_start = phdr->p_vaddr;
1765 _end = (((phdr->p_vaddr + phdr->p_memsz + PAGE_SIZE - 1) &
1766 (~PAGE_MASK)));
1767 if (_end > si->wrprotect_end)
1768 si->wrprotect_end = _end;
1769 }
1770 } else if (phdr->p_type == PT_DYNAMIC) {
1771 if (si->dynamic != (unsigned *)-1) {
1772 DL_ERR("%5d multiple PT_DYNAMIC segments found in '%s'. "
1773 "Segment at 0x%08x, previously one found at 0x%08x",
1774 pid, si->name, si->base + phdr->p_vaddr,
1775 (unsigned)si->dynamic);
1776 goto fail;
1777 }
1778 DEBUG_DUMP_PHDR(phdr, "PT_DYNAMIC", pid);
1779 si->dynamic = (unsigned *) (si->base + phdr->p_vaddr);
1780 }
1781 }
1782 }
1783
1784 if (si->dynamic == (unsigned *)-1) {
1785 DL_ERR("%5d missing PT_DYNAMIC?!", pid);
1786 goto fail;
1787 }
1788
1789 DEBUG("%5d dynamic = %p\n", pid, si->dynamic);
1790
1791 /* extract useful information from dynamic section */
1792 for(d = si->dynamic; *d; d++){
1793 DEBUG("%5d d = %p, d[0] = 0x%08x d[1] = 0x%08x\n", pid, d, d[0], d[1]);
1794 switch(*d++){
1795 case DT_HASH:
1796 si->nbucket = ((unsigned *) (si->base + *d))[0];
1797 si->nchain = ((unsigned *) (si->base + *d))[1];
1798 si->bucket = (unsigned *) (si->base + *d + 8);
1799 si->chain = (unsigned *) (si->base + *d + 8 + si->nbucket * 4);
1800 break;
1801 case DT_STRTAB:
1802 si->strtab = (const char *) (si->base + *d);
1803 break;
1804 case DT_SYMTAB:
1805 si->symtab = (Elf32_Sym *) (si->base + *d);
1806 break;
1807 #if !defined(ANDROID_SH_LINKER)
1808 case DT_PLTREL:
1809 if(*d != DT_REL) {
1810 DL_ERR("DT_RELA not supported");
1811 goto fail;
1812 }
1813 break;
1814 #endif
1815 #ifdef ANDROID_SH_LINKER
1816 case DT_JMPREL:
1817 si->plt_rela = (Elf32_Rela*) (si->base + *d);
1818 break;
1819 case DT_PLTRELSZ:
1820 si->plt_rela_count = *d / sizeof(Elf32_Rela);
1821 break;
1822 #else
1823 case DT_JMPREL:
1824 si->plt_rel = (Elf32_Rel*) (si->base + *d);
1825 break;
1826 case DT_PLTRELSZ:
1827 si->plt_rel_count = *d / 8;
1828 break;
1829 #endif
1830 case DT_REL:
1831 si->rel = (Elf32_Rel*) (si->base + *d);
1832 break;
1833 case DT_RELSZ:
1834 si->rel_count = *d / 8;
1835 break;
1836 #ifdef ANDROID_SH_LINKER
1837 case DT_RELASZ:
1838 si->rela_count = *d / sizeof(Elf32_Rela);
1839 break;
1840 #endif
1841 case DT_PLTGOT:
1842 /* Save this in case we decide to do lazy binding. We don't yet. */
1843 si->plt_got = (unsigned *)(si->base + *d);
1844 break;
1845 case DT_DEBUG:
1846 // Set the DT_DEBUG entry to the addres of _r_debug for GDB
1847 *d = (int) &_r_debug;
1848 break;
1849 #ifdef ANDROID_SH_LINKER
1850 case DT_RELA:
1851 si->rela = (Elf32_Rela *) (si->base + *d);
1852 break;
1853 #else
1854 case DT_RELA:
1855 DL_ERR("%5d DT_RELA not supported", pid);
1856 goto fail;
1857 #endif
1858 case DT_INIT:
1859 si->init_func = (void (*)(void))(si->base + *d);
1860 DEBUG("%5d %s constructors (init func) found at %p\n",
1861 pid, si->name, si->init_func);
1862 break;
1863 case DT_FINI:
1864 si->fini_func = (void (*)(void))(si->base + *d);
1865 DEBUG("%5d %s destructors (fini func) found at %p\n",
1866 pid, si->name, si->fini_func);
1867 break;
1868 case DT_INIT_ARRAY:
1869 si->init_array = (unsigned *)(si->base + *d);
1870 DEBUG("%5d %s constructors (init_array) found at %p\n",
1871 pid, si->name, si->init_array);
1872 break;
1873 case DT_INIT_ARRAYSZ:
1874 si->init_array_count = ((unsigned)*d) / sizeof(Elf32_Addr);
1875 break;
1876 case DT_FINI_ARRAY:
1877 si->fini_array = (unsigned *)(si->base + *d);
1878 DEBUG("%5d %s destructors (fini_array) found at %p\n",
1879 pid, si->name, si->fini_array);
1880 break;
1881 case DT_FINI_ARRAYSZ:
1882 si->fini_array_count = ((unsigned)*d) / sizeof(Elf32_Addr);
1883 break;
1884 case DT_PREINIT_ARRAY:
1885 si->preinit_array = (unsigned *)(si->base + *d);
1886 DEBUG("%5d %s constructors (preinit_array) found at %p\n",
1887 pid, si->name, si->preinit_array);
1888 break;
1889 case DT_PREINIT_ARRAYSZ:
1890 si->preinit_array_count = ((unsigned)*d) / sizeof(Elf32_Addr);
1891 break;
1892 case DT_TEXTREL:
1893 /* TODO: make use of this. */
1894 /* this means that we might have to write into where the text
1895 * segment was loaded during relocation... Do something with
1896 * it.
1897 */
1898 DEBUG("%5d Text segment should be writable during relocation.\n",
1899 pid);
1900 break;
1901 }
1902 }
1903
1904 DEBUG("%5d si->base = 0x%08x, si->strtab = %p, si->symtab = %p\n",
1905 pid, si->base, si->strtab, si->symtab);
1906
1907 if((si->strtab == 0) || (si->symtab == 0)) {
1908 DL_ERR("%5d missing essential tables", pid);
1909 goto fail;
1910 }
1911
1912 /* if this is the main executable, then load all of the preloads now */
1913 if(si->flags & FLAG_EXE) {
1914 int i;
1915 memset(preloads, 0, sizeof(preloads));
1916 for(i = 0; ldpreload_names[i] != NULL; i++) {
1917 soinfo *lsi = find_library(ldpreload_names[i]);
1918 if(lsi == 0) {
1919 strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf));
1920 DL_ERR("%5d could not load needed library '%s' for '%s' (%s)",
1921 pid, ldpreload_names[i], si->name, tmp_err_buf);
1922 goto fail;
1923 }
1924 lsi->refcount++;
1925 preloads[i] = lsi;
1926 }
1927 }
1928
1929 for(d = si->dynamic; *d; d += 2) {
1930 if(d[0] == DT_NEEDED){
1931 DEBUG("%5d %s needs %s\n", pid, si->name, si->strtab + d[1]);
1932 soinfo *lsi = find_library(si->strtab + d[1]);
1933 if(lsi == 0) {
1934 strlcpy(tmp_err_buf, linker_get_error(), sizeof(tmp_err_buf));
1935 DL_ERR("%5d could not load needed library '%s' for '%s' (%s)",
1936 pid, si->strtab + d[1], si->name, tmp_err_buf);
1937 goto fail;
1938 }
1939 /* Save the soinfo of the loaded DT_NEEDED library in the payload
1940 of the DT_NEEDED entry itself, so that we can retrieve the
1941 soinfo directly later from the dynamic segment. This is a hack,
1942 but it allows us to map from DT_NEEDED to soinfo efficiently
1943 later on when we resolve relocations, trying to look up a symgol
1944 with dlsym().
1945 */
1946 d[1] = (unsigned)lsi;
1947 lsi->refcount++;
1948 }
1949 }
1950
1951 if(si->plt_rel) {
1952 DEBUG("[ %5d relocating %s plt ]\n", pid, si->name );
1953 if(reloc_library(si, si->plt_rel, si->plt_rel_count))
1954 goto fail;
1955 }
1956 if(si->rel) {
1957 DEBUG("[ %5d relocating %s ]\n", pid, si->name );
1958 if(reloc_library(si, si->rel, si->rel_count))
1959 goto fail;
1960 }
1961
1962 #ifdef ANDROID_SH_LINKER
1963 if(si->plt_rela) {
1964 DEBUG("[ %5d relocating %s plt ]\n", pid, si->name );
1965 if(reloc_library_a(si, si->plt_rela, si->plt_rela_count))
1966 goto fail;
1967 }
1968 if(si->rela) {
1969 DEBUG("[ %5d relocating %s ]\n", pid, si->name );
1970 if(reloc_library_a(si, si->rela, si->rela_count))
1971 goto fail;
1972 }
1973 #endif /* ANDROID_SH_LINKER */
1974
1975 si->flags |= FLAG_LINKED;
1976 DEBUG("[ %5d finished linking %s ]\n", pid, si->name);
1977
1978 #if 0
1979 /* This is the way that the old dynamic linker did protection of
1980 * non-writable areas. It would scan section headers and find where
1981 * .text ended (rather where .data/.bss began) and assume that this is
1982 * the upper range of the non-writable area. This is too coarse,
1983 * and is kept here for reference until we fully move away from single
1984 * segment elf objects. See the code in get_wr_offset (also #if'd 0)
1985 * that made this possible.
1986 */
1987 if(wr_offset < 0xffffffff){
1988 mprotect((void*) si->base, wr_offset, PROT_READ | PROT_EXEC);
1989 }
1990 #else
1991 /* TODO: Verify that this does the right thing in all cases, as it
1992 * presently probably does not. It is possible that an ELF image will
1993 * come with multiple read-only segments. What we ought to do is scan
1994 * the program headers again and mprotect all the read-only segments.
1995 * To prevent re-scanning the program header, we would have to build a
1996 * list of loadable segments in si, and then scan that instead. */
1997 if (si->wrprotect_start != 0xffffffff && si->wrprotect_end != 0) {
1998 mprotect((void *)si->wrprotect_start,
1999 si->wrprotect_end - si->wrprotect_start,
2000 PROT_READ | PROT_EXEC);
2001 }
2002 #endif
2003
2004 /* If this is a SET?ID program, dup /dev/null to opened stdin,
2005 stdout and stderr to close a security hole described in:
2006
2007 ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
2008
2009 */
2010 if (program_is_setuid)
2011 nullify_closed_stdio ();
2012 notify_gdb_of_load(si);
2013 call_constructors(si);
2014 return 0;
2015
2016 fail:
2017 ERROR("failed to link %s\n", si->name);
2018 si->flags |= FLAG_ERROR;
2019 return -1;
2020 }
2021
parse_library_path(const char * path,char * delim)2022 static void parse_library_path(const char *path, char *delim)
2023 {
2024 size_t len;
2025 char *ldpaths_bufp = ldpaths_buf;
2026 int i = 0;
2027
2028 len = strlcpy(ldpaths_buf, path, sizeof(ldpaths_buf));
2029
2030 while (i < LDPATH_MAX && (ldpaths[i] = strsep(&ldpaths_bufp, delim))) {
2031 if (*ldpaths[i] != '\0')
2032 ++i;
2033 }
2034
2035 /* Forget the last path if we had to truncate; this occurs if the 2nd to
2036 * last char isn't '\0' (i.e. not originally a delim). */
2037 if (i > 0 && len >= sizeof(ldpaths_buf) &&
2038 ldpaths_buf[sizeof(ldpaths_buf) - 2] != '\0') {
2039 ldpaths[i - 1] = NULL;
2040 } else {
2041 ldpaths[i] = NULL;
2042 }
2043 }
2044
parse_preloads(const char * path,char * delim)2045 static void parse_preloads(const char *path, char *delim)
2046 {
2047 size_t len;
2048 char *ldpreloads_bufp = ldpreloads_buf;
2049 int i = 0;
2050
2051 len = strlcpy(ldpreloads_buf, path, sizeof(ldpreloads_buf));
2052
2053 while (i < LDPRELOAD_MAX && (ldpreload_names[i] = strsep(&ldpreloads_bufp, delim))) {
2054 if (*ldpreload_names[i] != '\0') {
2055 ++i;
2056 }
2057 }
2058
2059 /* Forget the last path if we had to truncate; this occurs if the 2nd to
2060 * last char isn't '\0' (i.e. not originally a delim). */
2061 if (i > 0 && len >= sizeof(ldpreloads_buf) &&
2062 ldpreloads_buf[sizeof(ldpreloads_buf) - 2] != '\0') {
2063 ldpreload_names[i - 1] = NULL;
2064 } else {
2065 ldpreload_names[i] = NULL;
2066 }
2067 }
2068
main(int argc,char ** argv)2069 int main(int argc, char **argv)
2070 {
2071 return 0;
2072 }
2073
2074 #define ANDROID_TLS_SLOTS BIONIC_TLS_SLOTS
2075
2076 static void * __tls_area[ANDROID_TLS_SLOTS];
2077
__linker_init(unsigned ** elfdata)2078 unsigned __linker_init(unsigned **elfdata)
2079 {
2080 static soinfo linker_soinfo;
2081
2082 int argc = (int) *elfdata;
2083 char **argv = (char**) (elfdata + 1);
2084 unsigned *vecs = (unsigned*) (argv + argc + 1);
2085 soinfo *si;
2086 struct link_map * map;
2087 const char *ldpath_env = NULL;
2088 const char *ldpreload_env = NULL;
2089
2090 /* Setup a temporary TLS area that is used to get a working
2091 * errno for system calls.
2092 */
2093 __set_tls(__tls_area);
2094
2095 pid = getpid();
2096
2097 #if TIMING
2098 struct timeval t0, t1;
2099 gettimeofday(&t0, 0);
2100 #endif
2101
2102 /* NOTE: we store the elfdata pointer on a special location
2103 * of the temporary TLS area in order to pass it to
2104 * the C Library's runtime initializer.
2105 *
2106 * The initializer must clear the slot and reset the TLS
2107 * to point to a different location to ensure that no other
2108 * shared library constructor can access it.
2109 */
2110 __tls_area[TLS_SLOT_BIONIC_PREINIT] = elfdata;
2111
2112 /* Are we setuid? */
2113 program_is_setuid = (getuid() != geteuid()) || (getgid() != getegid());
2114
2115 /* Initialize environment functions, and get to the ELF aux vectors table */
2116 vecs = linker_env_init(vecs);
2117
2118 /* Sanitize environment if we're loading a setuid program */
2119 if (program_is_setuid)
2120 linker_env_secure();
2121
2122 debugger_init();
2123
2124 /* Get a few environment variables */
2125 {
2126 const char* env;
2127 env = linker_env_get("DEBUG"); /* XXX: TODO: Change to LD_DEBUG */
2128 if (env)
2129 debug_verbosity = atoi(env);
2130
2131 /* Normally, these are cleaned by linker_env_secure, but the test
2132 * against program_is_setuid doesn't cost us anything */
2133 if (!program_is_setuid) {
2134 ldpath_env = linker_env_get("LD_LIBRARY_PATH");
2135 ldpreload_env = linker_env_get("LD_PRELOAD");
2136 }
2137 }
2138
2139 INFO("[ android linker & debugger ]\n");
2140 DEBUG("%5d elfdata @ 0x%08x\n", pid, (unsigned)elfdata);
2141
2142 si = alloc_info(argv[0]);
2143 if(si == 0) {
2144 exit(-1);
2145 }
2146
2147 /* bootstrap the link map, the main exe always needs to be first */
2148 si->flags |= FLAG_EXE;
2149 map = &(si->linkmap);
2150
2151 map->l_addr = 0;
2152 map->l_name = argv[0];
2153 map->l_prev = NULL;
2154 map->l_next = NULL;
2155
2156 _r_debug.r_map = map;
2157 r_debug_tail = map;
2158
2159 /* gdb expects the linker to be in the debug shared object list,
2160 * and we need to make sure that the reported load address is zero.
2161 * Without this, gdb gets the wrong idea of where rtld_db_dlactivity()
2162 * is. Don't use alloc_info(), because the linker shouldn't
2163 * be on the soinfo list.
2164 */
2165 strlcpy((char*) linker_soinfo.name, "/system/bin/linker", sizeof linker_soinfo.name);
2166 linker_soinfo.flags = 0;
2167 linker_soinfo.base = 0; // This is the important part; must be zero.
2168 insert_soinfo_into_debug_map(&linker_soinfo);
2169
2170 /* extract information passed from the kernel */
2171 while(vecs[0] != 0){
2172 switch(vecs[0]){
2173 case AT_PHDR:
2174 si->phdr = (Elf32_Phdr*) vecs[1];
2175 break;
2176 case AT_PHNUM:
2177 si->phnum = (int) vecs[1];
2178 break;
2179 case AT_ENTRY:
2180 si->entry = vecs[1];
2181 break;
2182 }
2183 vecs += 2;
2184 }
2185
2186 si->base = 0;
2187 si->dynamic = (unsigned *)-1;
2188 si->wrprotect_start = 0xffffffff;
2189 si->wrprotect_end = 0;
2190 si->refcount = 1;
2191
2192 /* Use LD_LIBRARY_PATH if we aren't setuid/setgid */
2193 if (ldpath_env)
2194 parse_library_path(ldpath_env, ":");
2195
2196 if (ldpreload_env) {
2197 parse_preloads(ldpreload_env, " :");
2198 }
2199
2200 if(link_image(si, 0)) {
2201 char errmsg[] = "CANNOT LINK EXECUTABLE\n";
2202 write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
2203 write(2, errmsg, sizeof(errmsg));
2204 exit(-1);
2205 }
2206
2207 #if ALLOW_SYMBOLS_FROM_MAIN
2208 /* Set somain after we've loaded all the libraries in order to prevent
2209 * linking of symbols back to the main image, which is not set up at that
2210 * point yet.
2211 */
2212 somain = si;
2213 #endif
2214
2215 #if TIMING
2216 gettimeofday(&t1,NULL);
2217 PRINT("LINKER TIME: %s: %d microseconds\n", argv[0], (int) (
2218 (((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
2219 (((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)
2220 ));
2221 #endif
2222 #if STATS
2223 PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol\n", argv[0],
2224 linker_stats.reloc[RELOC_ABSOLUTE],
2225 linker_stats.reloc[RELOC_RELATIVE],
2226 linker_stats.reloc[RELOC_COPY],
2227 linker_stats.reloc[RELOC_SYMBOL]);
2228 #endif
2229 #if COUNT_PAGES
2230 {
2231 unsigned n;
2232 unsigned i;
2233 unsigned count = 0;
2234 for(n = 0; n < 4096; n++){
2235 if(bitmask[n]){
2236 unsigned x = bitmask[n];
2237 for(i = 0; i < 8; i++){
2238 if(x & 1) count++;
2239 x >>= 1;
2240 }
2241 }
2242 }
2243 PRINT("PAGES MODIFIED: %s: %d (%dKB)\n", argv[0], count, count * 4);
2244 }
2245 #endif
2246
2247 #if TIMING || STATS || COUNT_PAGES
2248 fflush(stdout);
2249 #endif
2250
2251 TRACE("[ %5d Ready to execute '%s' @ 0x%08x ]\n", pid, si->name,
2252 si->entry);
2253 return si->entry;
2254 }
2255