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1 /*
2  * Copyright (C) 2008 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 <android/api-level.h>
30 #include <assert.h>
31 #include <errno.h>
32 #include <fcntl.h>
33 #include <inttypes.h>
34 #include <pthread.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <string.h>
38 #include <sys/auxv.h>
39 #include <sys/mman.h>
40 #include <sys/param.h>
41 #include <sys/vfs.h>
42 #include <unistd.h>
43 
44 #include <iterator>
45 #include <new>
46 #include <string>
47 #include <unordered_map>
48 #include <vector>
49 
50 #include <android-base/properties.h>
51 #include <android-base/scopeguard.h>
52 #include <async_safe/log.h>
53 #include <bionic/pthread_internal.h>
54 
55 // Private C library headers.
56 
57 #include "linker.h"
58 #include "linker_block_allocator.h"
59 #include "linker_cfi.h"
60 #include "linker_config.h"
61 #include "linker_gdb_support.h"
62 #include "linker_globals.h"
63 #include "linker_debug.h"
64 #include "linker_dlwarning.h"
65 #include "linker_main.h"
66 #include "linker_namespaces.h"
67 #include "linker_sleb128.h"
68 #include "linker_phdr.h"
69 #include "linker_relocate.h"
70 #include "linker_tls.h"
71 #include "linker_translate_path.h"
72 #include "linker_utils.h"
73 
74 #include "android-base/macros.h"
75 #include "android-base/stringprintf.h"
76 #include "android-base/strings.h"
77 #include "private/bionic_asm_note.h"
78 #include "private/bionic_call_ifunc_resolver.h"
79 #include "private/bionic_globals.h"
80 #include "ziparchive/zip_archive.h"
81 
82 static std::unordered_map<void*, size_t> g_dso_handle_counters;
83 
84 static bool g_anonymous_namespace_set = false;
85 static android_namespace_t* g_anonymous_namespace = &g_default_namespace;
86 static std::unordered_map<std::string, android_namespace_t*> g_exported_namespaces;
87 
88 static LinkerTypeAllocator<soinfo> g_soinfo_allocator;
89 static LinkerTypeAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator;
90 
91 static LinkerTypeAllocator<android_namespace_t> g_namespace_allocator;
92 static LinkerTypeAllocator<LinkedListEntry<android_namespace_t>> g_namespace_list_allocator;
93 
94 static uint64_t g_module_load_counter = 0;
95 static uint64_t g_module_unload_counter = 0;
96 
97 static const char* const kLdConfigArchFilePath = "/system/etc/ld.config." ABI_STRING ".txt";
98 
99 static const char* const kLdConfigFilePath = "/system/etc/ld.config.txt";
100 static const char* const kLdConfigVndkLiteFilePath = "/system/etc/ld.config.vndk_lite.txt";
101 
102 static const char* const kLdGeneratedConfigFilePath = "/linkerconfig/ld.config.txt";
103 
104 #if defined(__LP64__)
105 static const char* const kSystemLibDir        = "/system/lib64";
106 static const char* const kOdmLibDir           = "/odm/lib64";
107 static const char* const kVendorLibDir        = "/vendor/lib64";
108 static const char* const kAsanSystemLibDir    = "/data/asan/system/lib64";
109 static const char* const kAsanOdmLibDir       = "/data/asan/odm/lib64";
110 static const char* const kAsanVendorLibDir    = "/data/asan/vendor/lib64";
111 #else
112 static const char* const kSystemLibDir        = "/system/lib";
113 static const char* const kOdmLibDir           = "/odm/lib";
114 static const char* const kVendorLibDir        = "/vendor/lib";
115 static const char* const kAsanSystemLibDir    = "/data/asan/system/lib";
116 static const char* const kAsanOdmLibDir       = "/data/asan/odm/lib";
117 static const char* const kAsanVendorLibDir    = "/data/asan/vendor/lib";
118 #endif
119 
120 static const char* const kAsanLibDirPrefix = "/data/asan";
121 
122 static const char* const kDefaultLdPaths[] = {
123   kSystemLibDir,
124   kOdmLibDir,
125   kVendorLibDir,
126   nullptr
127 };
128 
129 static const char* const kAsanDefaultLdPaths[] = {
130   kAsanSystemLibDir,
131   kSystemLibDir,
132   kAsanOdmLibDir,
133   kOdmLibDir,
134   kAsanVendorLibDir,
135   kVendorLibDir,
136   nullptr
137 };
138 
139 #if defined(__aarch64__)
140 static const char* const kHwasanSystemLibDir  = "/system/lib64/hwasan";
141 static const char* const kHwasanOdmLibDir     = "/odm/lib64/hwasan";
142 static const char* const kHwasanVendorLibDir  = "/vendor/lib64/hwasan";
143 
144 // HWASan is only supported on aarch64.
145 static const char* const kHwsanDefaultLdPaths[] = {
146   kHwasanSystemLibDir,
147   kSystemLibDir,
148   kHwasanOdmLibDir,
149   kOdmLibDir,
150   kHwasanVendorLibDir,
151   kVendorLibDir,
152   nullptr
153 };
154 
155 // Is HWASAN enabled?
156 static bool g_is_hwasan = false;
157 #else
158 static const char* const kHwsanDefaultLdPaths[] = {
159   kSystemLibDir,
160   kOdmLibDir,
161   kVendorLibDir,
162   nullptr
163 };
164 
165 // Never any HWASan. Help the compiler remove the code we don't need.
166 constexpr bool g_is_hwasan = false;
167 #endif
168 
169 // Is ASAN enabled?
170 static bool g_is_asan = false;
171 
172 static CFIShadowWriter g_cfi_shadow;
173 
get_cfi_shadow()174 CFIShadowWriter* get_cfi_shadow() {
175   return &g_cfi_shadow;
176 }
177 
is_system_library(const std::string & realpath)178 static bool is_system_library(const std::string& realpath) {
179   for (const auto& dir : g_default_namespace.get_default_library_paths()) {
180     if (file_is_in_dir(realpath, dir)) {
181       return true;
182     }
183   }
184   return false;
185 }
186 
187 // Checks if the file exists and not a directory.
file_exists(const char * path)188 static bool file_exists(const char* path) {
189   struct stat s;
190 
191   if (stat(path, &s) != 0) {
192     return false;
193   }
194 
195   return S_ISREG(s.st_mode);
196 }
197 
resolve_soname(const std::string & name)198 static std::string resolve_soname(const std::string& name) {
199   // We assume that soname equals to basename here
200 
201   // TODO(dimitry): consider having honest absolute-path -> soname resolution
202   // note that since we might end up refusing to load this library because
203   // it is not in shared libs list we need to get the soname without actually loading
204   // the library.
205   //
206   // On the other hand there are several places where we already assume that
207   // soname == basename in particular for any not-loaded library mentioned
208   // in DT_NEEDED list.
209   return basename(name.c_str());
210 }
211 
maybe_accessible_via_namespace_links(android_namespace_t * ns,const char * name)212 static bool maybe_accessible_via_namespace_links(android_namespace_t* ns, const char* name) {
213   std::string soname = resolve_soname(name);
214   for (auto& ns_link : ns->linked_namespaces()) {
215     if (ns_link.is_accessible(soname.c_str())) {
216       return true;
217     }
218   }
219 
220   return false;
221 }
222 
223 // TODO(dimitry): The exempt-list is a workaround for http://b/26394120 ---
224 // gradually remove libraries from this list until it is gone.
is_exempt_lib(android_namespace_t * ns,const char * name,const soinfo * needed_by)225 static bool is_exempt_lib(android_namespace_t* ns, const char* name, const soinfo* needed_by) {
226   static const char* const kLibraryExemptList[] = {
227     "libandroid_runtime.so",
228     "libbinder.so",
229     "libcrypto.so",
230     "libcutils.so",
231     "libexpat.so",
232     "libgui.so",
233     "libmedia.so",
234     "libnativehelper.so",
235     "libssl.so",
236     "libstagefright.so",
237     "libsqlite.so",
238     "libui.so",
239     "libutils.so",
240     nullptr
241   };
242 
243   // If you're targeting N, you don't get the exempt-list.
244   if (get_application_target_sdk_version() >= 24) {
245     return false;
246   }
247 
248   // if the library needed by a system library - implicitly assume it
249   // is exempt unless it is in the list of shared libraries for one or
250   // more linked namespaces
251   if (needed_by != nullptr && is_system_library(needed_by->get_realpath())) {
252     return !maybe_accessible_via_namespace_links(ns, name);
253   }
254 
255   // if this is an absolute path - make sure it points to /system/lib(64)
256   if (name[0] == '/' && dirname(name) == kSystemLibDir) {
257     // and reduce the path to basename
258     name = basename(name);
259   }
260 
261   for (size_t i = 0; kLibraryExemptList[i] != nullptr; ++i) {
262     if (strcmp(name, kLibraryExemptList[i]) == 0) {
263       return true;
264     }
265   }
266 
267   return false;
268 }
269 // END OF WORKAROUND
270 
271 static std::vector<std::string> g_ld_preload_names;
272 
notify_gdb_of_load(soinfo * info)273 static void notify_gdb_of_load(soinfo* info) {
274   if (info->is_linker() || info->is_main_executable()) {
275     // gdb already knows about the linker and the main executable.
276     return;
277   }
278 
279   link_map* map = &(info->link_map_head);
280 
281   map->l_addr = info->load_bias;
282   // link_map l_name field is not const.
283   map->l_name = const_cast<char*>(info->get_realpath());
284   map->l_ld = info->dynamic;
285 
286   CHECK(map->l_name != nullptr);
287   CHECK(map->l_name[0] != '\0');
288 
289   notify_gdb_of_load(map);
290 }
291 
notify_gdb_of_unload(soinfo * info)292 static void notify_gdb_of_unload(soinfo* info) {
293   notify_gdb_of_unload(&(info->link_map_head));
294 }
295 
alloc()296 LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() {
297   return g_soinfo_links_allocator.alloc();
298 }
299 
free(LinkedListEntry<soinfo> * entry)300 void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) {
301   g_soinfo_links_allocator.free(entry);
302 }
303 
alloc()304 LinkedListEntry<android_namespace_t>* NamespaceListAllocator::alloc() {
305   return g_namespace_list_allocator.alloc();
306 }
307 
free(LinkedListEntry<android_namespace_t> * entry)308 void NamespaceListAllocator::free(LinkedListEntry<android_namespace_t>* entry) {
309   g_namespace_list_allocator.free(entry);
310 }
311 
soinfo_alloc(android_namespace_t * ns,const char * name,const struct stat * file_stat,off64_t file_offset,uint32_t rtld_flags)312 soinfo* soinfo_alloc(android_namespace_t* ns, const char* name,
313                      const struct stat* file_stat, off64_t file_offset,
314                      uint32_t rtld_flags) {
315   if (strlen(name) >= PATH_MAX) {
316     async_safe_fatal("library name \"%s\" too long", name);
317   }
318 
319   TRACE("name %s: allocating soinfo for ns=%p", name, ns);
320 
321   soinfo* si = new (g_soinfo_allocator.alloc()) soinfo(ns, name, file_stat,
322                                                        file_offset, rtld_flags);
323 
324   solist_add_soinfo(si);
325 
326   si->generate_handle();
327   ns->add_soinfo(si);
328 
329   TRACE("name %s: allocated soinfo @ %p", name, si);
330   return si;
331 }
332 
soinfo_free(soinfo * si)333 static void soinfo_free(soinfo* si) {
334   if (si == nullptr) {
335     return;
336   }
337 
338   if (si->base != 0 && si->size != 0) {
339     if (!si->is_mapped_by_caller()) {
340       munmap(reinterpret_cast<void*>(si->base), si->size);
341     } else {
342       // remap the region as PROT_NONE, MAP_ANONYMOUS | MAP_NORESERVE
343       mmap(reinterpret_cast<void*>(si->base), si->size, PROT_NONE,
344            MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
345     }
346   }
347 
348   if (si->has_min_version(6) && si->get_gap_size()) {
349     munmap(reinterpret_cast<void*>(si->get_gap_start()), si->get_gap_size());
350   }
351 
352   TRACE("name %s: freeing soinfo @ %p", si->get_realpath(), si);
353 
354   if (!solist_remove_soinfo(si)) {
355     async_safe_fatal("soinfo=%p is not in soinfo_list (double unload?)", si);
356   }
357 
358   // clear links to/from si
359   si->remove_all_links();
360 
361   si->~soinfo();
362   g_soinfo_allocator.free(si);
363 }
364 
parse_path(const char * path,const char * delimiters,std::vector<std::string> * resolved_paths)365 static void parse_path(const char* path, const char* delimiters,
366                        std::vector<std::string>* resolved_paths) {
367   std::vector<std::string> paths;
368   split_path(path, delimiters, &paths);
369   resolve_paths(paths, resolved_paths);
370 }
371 
parse_LD_LIBRARY_PATH(const char * path)372 static void parse_LD_LIBRARY_PATH(const char* path) {
373   std::vector<std::string> ld_libary_paths;
374   parse_path(path, ":", &ld_libary_paths);
375   g_default_namespace.set_ld_library_paths(std::move(ld_libary_paths));
376 }
377 
realpath_fd(int fd,std::string * realpath)378 static bool realpath_fd(int fd, std::string* realpath) {
379   // proc_self_fd needs to be large enough to hold "/proc/self/fd/" plus an
380   // integer, plus the NULL terminator.
381   char proc_self_fd[32];
382   // We want to statically allocate this large buffer so that we don't grow
383   // the stack by too much.
384   static char buf[PATH_MAX];
385 
386   async_safe_format_buffer(proc_self_fd, sizeof(proc_self_fd), "/proc/self/fd/%d", fd);
387   auto length = readlink(proc_self_fd, buf, sizeof(buf));
388   if (length == -1) {
389     if (!is_first_stage_init()) {
390       PRINT("readlink(\"%s\") failed: %s [fd=%d]", proc_self_fd, strerror(errno), fd);
391     }
392     return false;
393   }
394 
395   realpath->assign(buf, length);
396   return true;
397 }
398 
399 // Returns the address of the current thread's copy of a TLS module. If the current thread doesn't
400 // have a copy yet, allocate one on-demand if should_alloc is true, and return nullptr otherwise.
get_tls_block_for_this_thread(const soinfo_tls * si_tls,bool should_alloc)401 static inline void* get_tls_block_for_this_thread(const soinfo_tls* si_tls, bool should_alloc) {
402   const TlsModule& tls_mod = get_tls_module(si_tls->module_id);
403   if (tls_mod.static_offset != SIZE_MAX) {
404     const StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
405     char* static_tls = reinterpret_cast<char*>(__get_bionic_tcb()) - layout.offset_bionic_tcb();
406     return static_tls + tls_mod.static_offset;
407   } else if (should_alloc) {
408     const TlsIndex ti { si_tls->module_id, static_cast<size_t>(0 - TLS_DTV_OFFSET) };
409     return TLS_GET_ADDR(&ti);
410   } else {
411     TlsDtv* dtv = __get_tcb_dtv(__get_bionic_tcb());
412     if (dtv->generation < tls_mod.first_generation) return nullptr;
413     return dtv->modules[__tls_module_id_to_idx(si_tls->module_id)];
414   }
415 }
416 
417 #if defined(__arm__)
418 
419 // For a given PC, find the .so that it belongs to.
420 // Returns the base address of the .ARM.exidx section
421 // for that .so, and the number of 8-byte entries
422 // in that section (via *pcount).
423 //
424 // Intended to be called by libc's __gnu_Unwind_Find_exidx().
do_dl_unwind_find_exidx(_Unwind_Ptr pc,int * pcount)425 _Unwind_Ptr do_dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
426   if (soinfo* si = find_containing_library(reinterpret_cast<void*>(pc))) {
427     *pcount = si->ARM_exidx_count;
428     return reinterpret_cast<_Unwind_Ptr>(si->ARM_exidx);
429   }
430   *pcount = 0;
431   return 0;
432 }
433 
434 #endif
435 
436 // Here, we only have to provide a callback to iterate across all the
437 // loaded libraries. gcc_eh does the rest.
do_dl_iterate_phdr(int (* cb)(dl_phdr_info * info,size_t size,void * data),void * data)438 int do_dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
439   int rv = 0;
440   for (soinfo* si = solist_get_head(); si != nullptr; si = si->next) {
441     dl_phdr_info dl_info;
442     dl_info.dlpi_addr = si->link_map_head.l_addr;
443     dl_info.dlpi_name = si->link_map_head.l_name;
444     dl_info.dlpi_phdr = si->phdr;
445     dl_info.dlpi_phnum = si->phnum;
446     dl_info.dlpi_adds = g_module_load_counter;
447     dl_info.dlpi_subs = g_module_unload_counter;
448     if (soinfo_tls* tls_module = si->get_tls()) {
449       dl_info.dlpi_tls_modid = tls_module->module_id;
450       dl_info.dlpi_tls_data = get_tls_block_for_this_thread(tls_module, /*should_alloc=*/false);
451     } else {
452       dl_info.dlpi_tls_modid = 0;
453       dl_info.dlpi_tls_data = nullptr;
454     }
455 
456     rv = cb(&dl_info, sizeof(dl_phdr_info), data);
457     if (rv != 0) {
458       break;
459     }
460   }
461   return rv;
462 }
463 
ProtectedDataGuard()464 ProtectedDataGuard::ProtectedDataGuard() {
465   if (ref_count_++ == 0) {
466     protect_data(PROT_READ | PROT_WRITE);
467   }
468 
469   if (ref_count_ == 0) { // overflow
470     async_safe_fatal("Too many nested calls to dlopen()");
471   }
472 }
473 
~ProtectedDataGuard()474 ProtectedDataGuard::~ProtectedDataGuard() {
475   if (--ref_count_ == 0) {
476     protect_data(PROT_READ);
477   }
478 }
479 
protect_data(int protection)480 void ProtectedDataGuard::protect_data(int protection) {
481   g_soinfo_allocator.protect_all(protection);
482   g_soinfo_links_allocator.protect_all(protection);
483   g_namespace_allocator.protect_all(protection);
484   g_namespace_list_allocator.protect_all(protection);
485 }
486 
487 size_t ProtectedDataGuard::ref_count_ = 0;
488 
489 // Each size has it's own allocator.
490 template<size_t size>
491 class SizeBasedAllocator {
492  public:
alloc()493   static void* alloc() {
494     return allocator_.alloc();
495   }
496 
free(void * ptr)497   static void free(void* ptr) {
498     allocator_.free(ptr);
499   }
500 
purge()501   static void purge() {
502     allocator_.purge();
503   }
504 
505  private:
506   static LinkerBlockAllocator allocator_;
507 };
508 
509 template<size_t size>
510 LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
511 
512 template<typename T>
513 class TypeBasedAllocator {
514  public:
alloc()515   static T* alloc() {
516     return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
517   }
518 
free(T * ptr)519   static void free(T* ptr) {
520     SizeBasedAllocator<sizeof(T)>::free(ptr);
521   }
522 
purge()523   static void purge() {
524     SizeBasedAllocator<sizeof(T)>::purge();
525   }
526 };
527 
528 class LoadTask {
529  public:
530   struct deleter_t {
operator ()LoadTask::deleter_t531     void operator()(LoadTask* t) {
532       t->~LoadTask();
533       TypeBasedAllocator<LoadTask>::free(t);
534     }
535   };
536 
537   static deleter_t deleter;
538 
539   // needed_by is NULL iff dlopen is called from memory that isn't part of any known soinfo.
create(const char * _Nonnull name,soinfo * _Nullable needed_by,android_namespace_t * _Nonnull start_from,std::unordered_map<const soinfo *,ElfReader> * _Nonnull readers_map)540   static LoadTask* create(const char* _Nonnull name, soinfo* _Nullable needed_by,
541                           android_namespace_t* _Nonnull start_from,
542                           std::unordered_map<const soinfo*, ElfReader>* _Nonnull readers_map) {
543     LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
544     return new (ptr) LoadTask(name, needed_by, start_from, readers_map);
545   }
546 
get_name() const547   const char* get_name() const {
548     return name_;
549   }
550 
get_needed_by() const551   soinfo* get_needed_by() const {
552     return needed_by_;
553   }
554 
get_soinfo() const555   soinfo* get_soinfo() const {
556     return si_;
557   }
558 
set_soinfo(soinfo * si)559   void set_soinfo(soinfo* si) {
560     si_ = si;
561   }
562 
get_file_offset() const563   off64_t get_file_offset() const {
564     return file_offset_;
565   }
566 
set_file_offset(off64_t offset)567   void set_file_offset(off64_t offset) {
568     file_offset_ = offset;
569   }
570 
get_fd() const571   int get_fd() const {
572     return fd_;
573   }
574 
set_fd(int fd,bool assume_ownership)575   void set_fd(int fd, bool assume_ownership) {
576     if (fd_ != -1 && close_fd_) {
577       close(fd_);
578     }
579     fd_ = fd;
580     close_fd_ = assume_ownership;
581   }
582 
get_extinfo() const583   const android_dlextinfo* get_extinfo() const {
584     return extinfo_;
585   }
586 
set_extinfo(const android_dlextinfo * extinfo)587   void set_extinfo(const android_dlextinfo* extinfo) {
588     extinfo_ = extinfo;
589   }
590 
is_dt_needed() const591   bool is_dt_needed() const {
592     return is_dt_needed_;
593   }
594 
set_dt_needed(bool is_dt_needed)595   void set_dt_needed(bool is_dt_needed) {
596     is_dt_needed_ = is_dt_needed;
597   }
598 
599   // returns the namespace from where we need to start loading this.
get_start_from() const600   const android_namespace_t* get_start_from() const {
601     return start_from_;
602   }
603 
remove_cached_elf_reader()604   void remove_cached_elf_reader() {
605     CHECK(si_ != nullptr);
606     (*elf_readers_map_).erase(si_);
607   }
608 
get_elf_reader() const609   const ElfReader& get_elf_reader() const {
610     CHECK(si_ != nullptr);
611     return (*elf_readers_map_)[si_];
612   }
613 
get_elf_reader()614   ElfReader& get_elf_reader() {
615     CHECK(si_ != nullptr);
616     return (*elf_readers_map_)[si_];
617   }
618 
get_readers_map()619   std::unordered_map<const soinfo*, ElfReader>* get_readers_map() {
620     return elf_readers_map_;
621   }
622 
read(const char * realpath,off64_t file_size)623   bool read(const char* realpath, off64_t file_size) {
624     ElfReader& elf_reader = get_elf_reader();
625     return elf_reader.Read(realpath, fd_, file_offset_, file_size);
626   }
627 
load(address_space_params * address_space)628   bool load(address_space_params* address_space) {
629     ElfReader& elf_reader = get_elf_reader();
630     if (!elf_reader.Load(address_space)) {
631       return false;
632     }
633 
634     si_->base = elf_reader.load_start();
635     si_->size = elf_reader.load_size();
636     si_->set_mapped_by_caller(elf_reader.is_mapped_by_caller());
637     si_->load_bias = elf_reader.load_bias();
638     si_->phnum = elf_reader.phdr_count();
639     si_->phdr = elf_reader.loaded_phdr();
640     si_->set_gap_start(elf_reader.gap_start());
641     si_->set_gap_size(elf_reader.gap_size());
642     si_->set_should_pad_segments(elf_reader.should_pad_segments());
643 
644     return true;
645   }
646 
647  private:
LoadTask(const char * name,soinfo * needed_by,android_namespace_t * start_from,std::unordered_map<const soinfo *,ElfReader> * readers_map)648   LoadTask(const char* name,
649            soinfo* needed_by,
650            android_namespace_t* start_from,
651            std::unordered_map<const soinfo*, ElfReader>* readers_map)
652     : name_(name), needed_by_(needed_by), si_(nullptr),
653       fd_(-1), close_fd_(false), file_offset_(0), elf_readers_map_(readers_map),
654       is_dt_needed_(false), start_from_(start_from) {}
655 
~LoadTask()656   ~LoadTask() {
657     if (fd_ != -1 && close_fd_) {
658       close(fd_);
659     }
660   }
661 
662   const char* name_;
663   soinfo* needed_by_;
664   soinfo* si_;
665   const android_dlextinfo* extinfo_;
666   int fd_;
667   bool close_fd_;
668   off64_t file_offset_;
669   std::unordered_map<const soinfo*, ElfReader>* elf_readers_map_;
670   // TODO(dimitry): needed by workaround for http://b/26394120 (the exempt-list)
671   bool is_dt_needed_;
672   // END OF WORKAROUND
673   const android_namespace_t* const start_from_;
674 
675   DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
676 };
677 
678 LoadTask::deleter_t LoadTask::deleter;
679 
680 template <typename T>
681 using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
682 
683 typedef linked_list_t<soinfo> SoinfoLinkedList;
684 typedef linked_list_t<const char> StringLinkedList;
685 typedef std::vector<LoadTask*> LoadTaskList;
686 
687 enum walk_action_result_t : uint32_t {
688   kWalkStop = 0,
689   kWalkContinue = 1,
690   kWalkSkip = 2
691 };
692 
693 // This function walks down the tree of soinfo dependencies
694 // in breadth-first order and
695 //   * calls action(soinfo* si) for each node, and
696 //   * terminates walk if action returns kWalkStop
697 //   * skips children of the node if action
698 //     return kWalkSkip
699 //
700 // walk_dependencies_tree returns false if walk was terminated
701 // by the action and true otherwise.
702 template<typename F>
walk_dependencies_tree(soinfo * root_soinfo,F action)703 static bool walk_dependencies_tree(soinfo* root_soinfo, F action) {
704   SoinfoLinkedList visit_list;
705   SoinfoLinkedList visited;
706 
707   visit_list.push_back(root_soinfo);
708 
709   soinfo* si;
710   while ((si = visit_list.pop_front()) != nullptr) {
711     if (visited.contains(si)) {
712       continue;
713     }
714 
715     walk_action_result_t result = action(si);
716 
717     if (result == kWalkStop) {
718       return false;
719     }
720 
721     visited.push_back(si);
722 
723     if (result != kWalkSkip) {
724       si->get_children().for_each([&](soinfo* child) {
725         visit_list.push_back(child);
726       });
727     }
728   }
729 
730   return true;
731 }
732 
733 
ElfW(Sym)734 static const ElfW(Sym)* dlsym_handle_lookup_impl(android_namespace_t* ns,
735                                                  soinfo* root,
736                                                  soinfo* skip_until,
737                                                  soinfo** found,
738                                                  SymbolName& symbol_name,
739                                                  const version_info* vi) {
740   const ElfW(Sym)* result = nullptr;
741   bool skip_lookup = skip_until != nullptr;
742 
743   walk_dependencies_tree(root, [&](soinfo* current_soinfo) {
744     if (skip_lookup) {
745       skip_lookup = current_soinfo != skip_until;
746       return kWalkContinue;
747     }
748 
749     if (!ns->is_accessible(current_soinfo)) {
750       return kWalkSkip;
751     }
752 
753     result = current_soinfo->find_symbol_by_name(symbol_name, vi);
754     if (result != nullptr) {
755       *found = current_soinfo;
756       return kWalkStop;
757     }
758 
759     return kWalkContinue;
760   });
761 
762   return result;
763 }
764 
765 /* This is used by dlsym(3) to performs a global symbol lookup. If the
766    start value is null (for RTLD_DEFAULT), the search starts at the
767    beginning of the global solist. Otherwise the search starts at the
768    specified soinfo (for RTLD_NEXT).
769  */
ElfW(Sym)770 static const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns,
771                                             const char* name,
772                                             const version_info* vi,
773                                             soinfo** found,
774                                             soinfo* caller,
775                                             void* handle) {
776   SymbolName symbol_name(name);
777 
778   auto& soinfo_list = ns->soinfo_list();
779   auto start = soinfo_list.begin();
780 
781   if (handle == RTLD_NEXT) {
782     if (caller == nullptr) {
783       return nullptr;
784     } else {
785       auto it = soinfo_list.find(caller);
786       CHECK (it != soinfo_list.end());
787       start = ++it;
788     }
789   }
790 
791   const ElfW(Sym)* s = nullptr;
792   for (auto it = start, end = soinfo_list.end(); it != end; ++it) {
793     soinfo* si = *it;
794     // Do not skip RTLD_LOCAL libraries in dlsym(RTLD_DEFAULT, ...)
795     // if the library is opened by application with target api level < M.
796     // See http://b/21565766
797     if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0 && si->get_target_sdk_version() >= 23) {
798       continue;
799     }
800 
801     s = si->find_symbol_by_name(symbol_name, vi);
802     if (s != nullptr) {
803       *found = si;
804       break;
805     }
806   }
807 
808   // If not found - use dlsym_handle_lookup_impl for caller's local_group
809   if (s == nullptr && caller != nullptr) {
810     soinfo* local_group_root = caller->get_local_group_root();
811 
812     return dlsym_handle_lookup_impl(local_group_root->get_primary_namespace(),
813                                     local_group_root,
814                                     (handle == RTLD_NEXT) ? caller : nullptr,
815                                     found,
816                                     symbol_name,
817                                     vi);
818   }
819 
820   if (s != nullptr) {
821     TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
822                name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
823   }
824 
825   return s;
826 }
827 
828 // This is used by dlsym(3).  It performs symbol lookup only within the
829 // specified soinfo object and its dependencies in breadth first order.
ElfW(Sym)830 static const ElfW(Sym)* dlsym_handle_lookup(soinfo* si,
831                                             soinfo** found,
832                                             const char* name,
833                                             const version_info* vi) {
834   // According to man dlopen(3) and posix docs in the case when si is handle
835   // of the main executable we need to search not only in the executable and its
836   // dependencies but also in all libraries loaded with RTLD_GLOBAL.
837   //
838   // Since RTLD_GLOBAL is always set for the main executable and all dt_needed shared
839   // libraries and they are loaded in breath-first (correct) order we can just execute
840   // dlsym(RTLD_DEFAULT, ...); instead of doing two stage lookup.
841   if (si == solist_get_somain()) {
842     return dlsym_linear_lookup(&g_default_namespace, name, vi, found, nullptr, RTLD_DEFAULT);
843   }
844 
845   SymbolName symbol_name(name);
846   // note that the namespace is not the namespace associated with caller_addr
847   // we use ns associated with root si intentionally here. Using caller_ns
848   // causes problems when user uses dlopen_ext to open a library in the separate
849   // namespace and then calls dlsym() on the handle.
850   return dlsym_handle_lookup_impl(si->get_primary_namespace(), si, nullptr, found, symbol_name, vi);
851 }
852 
find_containing_library(const void * p)853 soinfo* find_containing_library(const void* p) {
854   // Addresses within a library may be tagged if they point to globals. Untag
855   // them so that the bounds check succeeds.
856   ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(untag_address(p));
857   for (soinfo* si = solist_get_head(); si != nullptr; si = si->next) {
858     if (address < si->base || address - si->base >= si->size) {
859       continue;
860     }
861     ElfW(Addr) vaddr = address - si->load_bias;
862     for (size_t i = 0; i != si->phnum; ++i) {
863       const ElfW(Phdr)* phdr = &si->phdr[i];
864       if (phdr->p_type != PT_LOAD) {
865         continue;
866       }
867       if (vaddr >= phdr->p_vaddr && vaddr < phdr->p_vaddr + phdr->p_memsz) {
868         return si;
869       }
870     }
871   }
872   return nullptr;
873 }
874 
875 class ZipArchiveCache {
876  public:
ZipArchiveCache()877   ZipArchiveCache() {}
878   ~ZipArchiveCache();
879 
880   bool get_or_open(const char* zip_path, ZipArchiveHandle* handle);
881  private:
882   DISALLOW_COPY_AND_ASSIGN(ZipArchiveCache);
883 
884   std::unordered_map<std::string, ZipArchiveHandle> cache_;
885 };
886 
get_or_open(const char * zip_path,ZipArchiveHandle * handle)887 bool ZipArchiveCache::get_or_open(const char* zip_path, ZipArchiveHandle* handle) {
888   std::string key(zip_path);
889 
890   auto it = cache_.find(key);
891   if (it != cache_.end()) {
892     *handle = it->second;
893     return true;
894   }
895 
896   int fd = TEMP_FAILURE_RETRY(open(zip_path, O_RDONLY | O_CLOEXEC));
897   if (fd == -1) {
898     return false;
899   }
900 
901   if (OpenArchiveFd(fd, "", handle) != 0) {
902     // invalid zip-file (?)
903     CloseArchive(*handle);
904     return false;
905   }
906 
907   cache_[key] = *handle;
908   return true;
909 }
910 
~ZipArchiveCache()911 ZipArchiveCache::~ZipArchiveCache() {
912   for (const auto& it : cache_) {
913     CloseArchive(it.second);
914   }
915 }
916 
open_library_in_zipfile(ZipArchiveCache * zip_archive_cache,const char * const input_path,off64_t * file_offset,std::string * realpath)917 static int open_library_in_zipfile(ZipArchiveCache* zip_archive_cache,
918                                    const char* const input_path,
919                                    off64_t* file_offset, std::string* realpath) {
920   std::string normalized_path;
921   if (!normalize_path(input_path, &normalized_path)) {
922     return -1;
923   }
924 
925   const char* const path = normalized_path.c_str();
926   TRACE("Trying zip file open from path \"%s\" -> normalized \"%s\"", input_path, path);
927 
928   // Treat an '!/' separator inside a path as the separator between the name
929   // of the zip file on disk and the subdirectory to search within it.
930   // For example, if path is "foo.zip!/bar/bas/x.so", then we search for
931   // "bar/bas/x.so" within "foo.zip".
932   const char* const separator = strstr(path, kZipFileSeparator);
933   if (separator == nullptr) {
934     return -1;
935   }
936 
937   char buf[512];
938   if (strlcpy(buf, path, sizeof(buf)) >= sizeof(buf)) {
939     PRINT("Warning: ignoring very long library path: %s", path);
940     return -1;
941   }
942 
943   buf[separator - path] = '\0';
944 
945   const char* zip_path = buf;
946   const char* file_path = &buf[separator - path + 2];
947   int fd = TEMP_FAILURE_RETRY(open(zip_path, O_RDONLY | O_CLOEXEC));
948   if (fd == -1) {
949     return -1;
950   }
951 
952   ZipArchiveHandle handle;
953   if (!zip_archive_cache->get_or_open(zip_path, &handle)) {
954     // invalid zip-file (?)
955     close(fd);
956     return -1;
957   }
958 
959   ZipEntry entry;
960 
961   if (FindEntry(handle, file_path, &entry) != 0) {
962     // Entry was not found.
963     close(fd);
964     return -1;
965   }
966 
967   // Check if it is properly stored
968   if (entry.method != kCompressStored || (entry.offset % page_size()) != 0) {
969     close(fd);
970     return -1;
971   }
972 
973   *file_offset = entry.offset;
974 
975   if (realpath_fd(fd, realpath)) {
976     *realpath += separator;
977   } else {
978     if (!is_first_stage_init()) {
979       PRINT("warning: unable to get realpath for the library \"%s\". Will use given path.",
980             normalized_path.c_str());
981     }
982     *realpath = normalized_path;
983   }
984 
985   return fd;
986 }
987 
format_path(char * buf,size_t buf_size,const char * path,const char * name)988 static bool format_path(char* buf, size_t buf_size, const char* path, const char* name) {
989   int n = async_safe_format_buffer(buf, buf_size, "%s/%s", path, name);
990   if (n < 0 || n >= static_cast<int>(buf_size)) {
991     PRINT("Warning: ignoring very long library path: %s/%s", path, name);
992     return false;
993   }
994 
995   return true;
996 }
997 
open_library_at_path(ZipArchiveCache * zip_archive_cache,const char * path,off64_t * file_offset,std::string * realpath)998 static int open_library_at_path(ZipArchiveCache* zip_archive_cache,
999                                 const char* path, off64_t* file_offset,
1000                                 std::string* realpath) {
1001   int fd = -1;
1002   if (strstr(path, kZipFileSeparator) != nullptr) {
1003     fd = open_library_in_zipfile(zip_archive_cache, path, file_offset, realpath);
1004   }
1005 
1006   if (fd == -1) {
1007     fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC));
1008     if (fd != -1) {
1009       *file_offset = 0;
1010       if (!realpath_fd(fd, realpath)) {
1011         if (!is_first_stage_init()) {
1012           PRINT("warning: unable to get realpath for the library \"%s\". Will use given path.",
1013                 path);
1014         }
1015         *realpath = path;
1016       }
1017     }
1018   }
1019 
1020   return fd;
1021 }
1022 
open_library_on_paths(ZipArchiveCache * zip_archive_cache,const char * name,off64_t * file_offset,const std::vector<std::string> & paths,std::string * realpath)1023 static int open_library_on_paths(ZipArchiveCache* zip_archive_cache,
1024                                  const char* name, off64_t* file_offset,
1025                                  const std::vector<std::string>& paths,
1026                                  std::string* realpath) {
1027   for (const auto& path : paths) {
1028     char buf[512];
1029     if (!format_path(buf, sizeof(buf), path.c_str(), name)) {
1030       continue;
1031     }
1032 
1033     int fd = open_library_at_path(zip_archive_cache, buf, file_offset, realpath);
1034     if (fd != -1) {
1035       return fd;
1036     }
1037   }
1038 
1039   return -1;
1040 }
1041 
open_library(android_namespace_t * ns,ZipArchiveCache * zip_archive_cache,const char * name,soinfo * needed_by,off64_t * file_offset,std::string * realpath)1042 static int open_library(android_namespace_t* ns,
1043                         ZipArchiveCache* zip_archive_cache,
1044                         const char* name, soinfo *needed_by,
1045                         off64_t* file_offset, std::string* realpath) {
1046   TRACE("[ opening %s from namespace %s ]", name, ns->get_name());
1047 
1048   // If the name contains a slash, we should attempt to open it directly and not search the paths.
1049   if (strchr(name, '/') != nullptr) {
1050     return open_library_at_path(zip_archive_cache, name, file_offset, realpath);
1051   }
1052 
1053   // LD_LIBRARY_PATH has the highest priority. We don't have to check accessibility when searching
1054   // the namespace's path lists, because anything found on a namespace path list should always be
1055   // accessible.
1056   int fd = open_library_on_paths(zip_archive_cache, name, file_offset, ns->get_ld_library_paths(), realpath);
1057 
1058   // Try the DT_RUNPATH, and verify that the library is accessible.
1059   if (fd == -1 && needed_by != nullptr) {
1060     fd = open_library_on_paths(zip_archive_cache, name, file_offset, needed_by->get_dt_runpath(), realpath);
1061     if (fd != -1 && !ns->is_accessible(*realpath)) {
1062       close(fd);
1063       fd = -1;
1064     }
1065   }
1066 
1067   // Finally search the namespace's main search path list.
1068   if (fd == -1) {
1069     fd = open_library_on_paths(zip_archive_cache, name, file_offset, ns->get_default_library_paths(), realpath);
1070   }
1071 
1072   return fd;
1073 }
1074 
open_executable(const char * path,off64_t * file_offset,std::string * realpath)1075 int open_executable(const char* path, off64_t* file_offset, std::string* realpath) {
1076   ZipArchiveCache zip_archive_cache;
1077   return open_library_at_path(&zip_archive_cache, path, file_offset, realpath);
1078 }
1079 
fix_dt_needed(const char * dt_needed,const char * sopath __unused)1080 const char* fix_dt_needed(const char* dt_needed, const char* sopath __unused) {
1081 #if !defined(__LP64__)
1082   // Work around incorrect DT_NEEDED entries for old apps: http://b/21364029
1083   int app_target_api_level = get_application_target_sdk_version();
1084   if (app_target_api_level < 23) {
1085     const char* bname = basename(dt_needed);
1086     if (bname != dt_needed) {
1087       DL_WARN_documented_change(23,
1088                                 "invalid-dt_needed-entries-enforced-for-api-level-23",
1089                                 "library \"%s\" has invalid DT_NEEDED entry \"%s\"",
1090                                 sopath, dt_needed, app_target_api_level);
1091       add_dlwarning(sopath, "invalid DT_NEEDED entry",  dt_needed);
1092     }
1093 
1094     return bname;
1095   }
1096 #endif
1097   return dt_needed;
1098 }
1099 
1100 template<typename F>
for_each_dt_needed(const ElfReader & elf_reader,F action)1101 static void for_each_dt_needed(const ElfReader& elf_reader, F action) {
1102   for (const ElfW(Dyn)* d = elf_reader.dynamic(); d->d_tag != DT_NULL; ++d) {
1103     if (d->d_tag == DT_NEEDED) {
1104       action(fix_dt_needed(elf_reader.get_string(d->d_un.d_val), elf_reader.name()));
1105     }
1106   }
1107 }
1108 
find_loaded_library_by_inode(android_namespace_t * ns,const struct stat & file_stat,off64_t file_offset,bool search_linked_namespaces,soinfo ** candidate)1109 static bool find_loaded_library_by_inode(android_namespace_t* ns,
1110                                          const struct stat& file_stat,
1111                                          off64_t file_offset,
1112                                          bool search_linked_namespaces,
1113                                          soinfo** candidate) {
1114   if (file_stat.st_dev == 0 || file_stat.st_ino == 0) {
1115     *candidate = nullptr;
1116     return false;
1117   }
1118 
1119   auto predicate = [&](soinfo* si) {
1120     return si->get_st_ino() == file_stat.st_ino &&
1121            si->get_st_dev() == file_stat.st_dev &&
1122            si->get_file_offset() == file_offset;
1123   };
1124 
1125   *candidate = ns->soinfo_list().find_if(predicate);
1126 
1127   if (*candidate == nullptr && search_linked_namespaces) {
1128     for (auto& link : ns->linked_namespaces()) {
1129       android_namespace_t* linked_ns = link.linked_namespace();
1130       soinfo* si = linked_ns->soinfo_list().find_if(predicate);
1131 
1132       if (si != nullptr && link.is_accessible(si->get_soname())) {
1133         *candidate = si;
1134         return true;
1135       }
1136     }
1137   }
1138 
1139   return *candidate != nullptr;
1140 }
1141 
find_loaded_library_by_realpath(android_namespace_t * ns,const char * realpath,bool search_linked_namespaces,soinfo ** candidate)1142 static bool find_loaded_library_by_realpath(android_namespace_t* ns, const char* realpath,
1143                                             bool search_linked_namespaces, soinfo** candidate) {
1144   auto predicate = [&](soinfo* si) { return strcmp(realpath, si->get_realpath()) == 0; };
1145 
1146   *candidate = ns->soinfo_list().find_if(predicate);
1147 
1148   if (*candidate == nullptr && search_linked_namespaces) {
1149     for (auto& link : ns->linked_namespaces()) {
1150       android_namespace_t* linked_ns = link.linked_namespace();
1151       soinfo* si = linked_ns->soinfo_list().find_if(predicate);
1152 
1153       if (si != nullptr && link.is_accessible(si->get_soname())) {
1154         *candidate = si;
1155         return true;
1156       }
1157     }
1158   }
1159 
1160   return *candidate != nullptr;
1161 }
1162 
load_library(android_namespace_t * ns,LoadTask * task,LoadTaskList * load_tasks,int rtld_flags,const std::string & realpath,bool search_linked_namespaces)1163 static bool load_library(android_namespace_t* ns,
1164                          LoadTask* task,
1165                          LoadTaskList* load_tasks,
1166                          int rtld_flags,
1167                          const std::string& realpath,
1168                          bool search_linked_namespaces) {
1169   off64_t file_offset = task->get_file_offset();
1170   const char* name = task->get_name();
1171   const android_dlextinfo* extinfo = task->get_extinfo();
1172 
1173   LD_LOG(kLogDlopen,
1174          "load_library(ns=%s, task=%s, flags=0x%x, realpath=%s, search_linked_namespaces=%d)",
1175          ns->get_name(), name, rtld_flags, realpath.c_str(), search_linked_namespaces);
1176 
1177   if ((file_offset % page_size()) != 0) {
1178     DL_OPEN_ERR("file offset for the library \"%s\" is not page-aligned: %" PRId64, name, file_offset);
1179     return false;
1180   }
1181   if (file_offset < 0) {
1182     DL_OPEN_ERR("file offset for the library \"%s\" is negative: %" PRId64, name, file_offset);
1183     return false;
1184   }
1185 
1186   struct stat file_stat;
1187   if (TEMP_FAILURE_RETRY(fstat(task->get_fd(), &file_stat)) != 0) {
1188     DL_OPEN_ERR("unable to stat file for the library \"%s\": %s", name, strerror(errno));
1189     return false;
1190   }
1191   if (file_offset >= file_stat.st_size) {
1192     DL_OPEN_ERR("file offset for the library \"%s\" >= file size: %" PRId64 " >= %" PRId64,
1193         name, file_offset, file_stat.st_size);
1194     return false;
1195   }
1196 
1197   // Check for symlink and other situations where
1198   // file can have different names, unless ANDROID_DLEXT_FORCE_LOAD is set
1199   if (extinfo == nullptr || (extinfo->flags & ANDROID_DLEXT_FORCE_LOAD) == 0) {
1200     soinfo* si = nullptr;
1201     if (find_loaded_library_by_inode(ns, file_stat, file_offset, search_linked_namespaces, &si)) {
1202       LD_LOG(kLogDlopen,
1203              "load_library(ns=%s, task=%s): Already loaded under different name/path \"%s\" - "
1204              "will return existing soinfo",
1205              ns->get_name(), name, si->get_realpath());
1206       task->set_soinfo(si);
1207       return true;
1208     }
1209   }
1210 
1211   if ((rtld_flags & RTLD_NOLOAD) != 0) {
1212     DL_OPEN_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
1213     return false;
1214   }
1215 
1216   struct statfs fs_stat;
1217   if (TEMP_FAILURE_RETRY(fstatfs(task->get_fd(), &fs_stat)) != 0) {
1218     DL_OPEN_ERR("unable to fstatfs file for the library \"%s\": %s", name, strerror(errno));
1219     return false;
1220   }
1221 
1222   // do not check accessibility using realpath if fd is located on tmpfs
1223   // this enables use of memfd_create() for apps
1224   if ((fs_stat.f_type != TMPFS_MAGIC) && (!ns->is_accessible(realpath))) {
1225     // TODO(dimitry): workaround for http://b/26394120 - the exempt-list
1226 
1227     const soinfo* needed_by = task->is_dt_needed() ? task->get_needed_by() : nullptr;
1228     if (is_exempt_lib(ns, name, needed_by)) {
1229       // print warning only if needed by non-system library
1230       if (needed_by == nullptr || !is_system_library(needed_by->get_realpath())) {
1231         const soinfo* needed_or_dlopened_by = task->get_needed_by();
1232         const char* sopath = needed_or_dlopened_by == nullptr ? "(unknown)" :
1233                                                       needed_or_dlopened_by->get_realpath();
1234         DL_WARN_documented_change(24,
1235                                   "private-api-enforced-for-api-level-24",
1236                                   "library \"%s\" (\"%s\") needed or dlopened by \"%s\" "
1237                                   "is not accessible by namespace \"%s\"",
1238                                   name, realpath.c_str(), sopath, ns->get_name());
1239         add_dlwarning(sopath, "unauthorized access to",  name);
1240       }
1241     } else {
1242       // do not load libraries if they are not accessible for the specified namespace.
1243       const char* needed_or_dlopened_by = task->get_needed_by() == nullptr ?
1244                                           "(unknown)" :
1245                                           task->get_needed_by()->get_realpath();
1246 
1247       DL_OPEN_ERR("library \"%s\" needed or dlopened by \"%s\" is not accessible for the namespace \"%s\"",
1248              name, needed_or_dlopened_by, ns->get_name());
1249 
1250       // do not print this if a library is in the list of shared libraries for linked namespaces
1251       if (!maybe_accessible_via_namespace_links(ns, name)) {
1252         PRINT("library \"%s\" (\"%s\") needed or dlopened by \"%s\" is not accessible for the"
1253               " namespace: [name=\"%s\", ld_library_paths=\"%s\", default_library_paths=\"%s\","
1254               " permitted_paths=\"%s\"]",
1255               name, realpath.c_str(),
1256               needed_or_dlopened_by,
1257               ns->get_name(),
1258               android::base::Join(ns->get_ld_library_paths(), ':').c_str(),
1259               android::base::Join(ns->get_default_library_paths(), ':').c_str(),
1260               android::base::Join(ns->get_permitted_paths(), ':').c_str());
1261       }
1262       return false;
1263     }
1264   }
1265 
1266   soinfo* si = soinfo_alloc(ns, realpath.c_str(), &file_stat, file_offset, rtld_flags);
1267 
1268   task->set_soinfo(si);
1269 
1270   // Read the ELF header and some of the segments.
1271   if (!task->read(realpath.c_str(), file_stat.st_size)) {
1272     task->remove_cached_elf_reader();
1273     task->set_soinfo(nullptr);
1274     soinfo_free(si);
1275     return false;
1276   }
1277 
1278   // Find and set DT_RUNPATH, DT_SONAME, and DT_FLAGS_1.
1279   // Note that these field values are temporary and are
1280   // going to be overwritten on soinfo::prelink_image
1281   // with values from PT_LOAD segments.
1282   const ElfReader& elf_reader = task->get_elf_reader();
1283   for (const ElfW(Dyn)* d = elf_reader.dynamic(); d->d_tag != DT_NULL; ++d) {
1284     if (d->d_tag == DT_RUNPATH) {
1285       si->set_dt_runpath(elf_reader.get_string(d->d_un.d_val));
1286     }
1287     if (d->d_tag == DT_SONAME) {
1288       si->set_soname(elf_reader.get_string(d->d_un.d_val));
1289     }
1290     // We need to identify a DF_1_GLOBAL library early so we can link it to namespaces.
1291     if (d->d_tag == DT_FLAGS_1) {
1292       si->set_dt_flags_1(d->d_un.d_val);
1293     }
1294   }
1295 
1296 #if !defined(__ANDROID__)
1297   // Bionic on the host currently uses some Android prebuilts, which don't set
1298   // DT_RUNPATH with any relative paths, so they can't find their dependencies.
1299   // b/118058804
1300   if (si->get_dt_runpath().empty()) {
1301     si->set_dt_runpath("$ORIGIN/../lib64:$ORIGIN/lib64");
1302   }
1303 #endif
1304 
1305   for_each_dt_needed(task->get_elf_reader(), [&](const char* name) {
1306     LD_LOG(kLogDlopen, "load_library(ns=%s, task=%s): Adding DT_NEEDED task: %s",
1307            ns->get_name(), task->get_name(), name);
1308     load_tasks->push_back(LoadTask::create(name, si, ns, task->get_readers_map()));
1309   });
1310 
1311   return true;
1312 }
1313 
load_library(android_namespace_t * ns,LoadTask * task,ZipArchiveCache * zip_archive_cache,LoadTaskList * load_tasks,int rtld_flags,bool search_linked_namespaces)1314 static bool load_library(android_namespace_t* ns,
1315                          LoadTask* task,
1316                          ZipArchiveCache* zip_archive_cache,
1317                          LoadTaskList* load_tasks,
1318                          int rtld_flags,
1319                          bool search_linked_namespaces) {
1320   const char* name = task->get_name();
1321   soinfo* needed_by = task->get_needed_by();
1322   const android_dlextinfo* extinfo = task->get_extinfo();
1323 
1324   if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
1325     off64_t file_offset = 0;
1326     if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
1327       file_offset = extinfo->library_fd_offset;
1328     }
1329 
1330     std::string realpath;
1331     if (!realpath_fd(extinfo->library_fd, &realpath)) {
1332       if (!is_first_stage_init()) {
1333         PRINT(
1334             "warning: unable to get realpath for the library \"%s\" by extinfo->library_fd. "
1335             "Will use given name.",
1336             name);
1337       }
1338       realpath = name;
1339     }
1340 
1341     task->set_fd(extinfo->library_fd, false);
1342     task->set_file_offset(file_offset);
1343     return load_library(ns, task, load_tasks, rtld_flags, realpath, search_linked_namespaces);
1344   }
1345 
1346   LD_LOG(kLogDlopen,
1347          "load_library(ns=%s, task=%s, flags=0x%x, search_linked_namespaces=%d): calling "
1348          "open_library",
1349          ns->get_name(), name, rtld_flags, search_linked_namespaces);
1350 
1351   // Open the file.
1352   off64_t file_offset;
1353   std::string realpath;
1354   int fd = open_library(ns, zip_archive_cache, name, needed_by, &file_offset, &realpath);
1355   if (fd == -1) {
1356     if (task->is_dt_needed()) {
1357       if (needed_by->is_main_executable()) {
1358         DL_OPEN_ERR("library \"%s\" not found: needed by main executable", name);
1359       } else {
1360         DL_OPEN_ERR("library \"%s\" not found: needed by %s in namespace %s", name,
1361                     needed_by->get_realpath(), task->get_start_from()->get_name());
1362       }
1363     } else {
1364       DL_OPEN_ERR("library \"%s\" not found", name);
1365     }
1366     return false;
1367   }
1368 
1369   task->set_fd(fd, true);
1370   task->set_file_offset(file_offset);
1371 
1372   return load_library(ns, task, load_tasks, rtld_flags, realpath, search_linked_namespaces);
1373 }
1374 
find_loaded_library_by_soname(android_namespace_t * ns,const char * name,soinfo ** candidate)1375 static bool find_loaded_library_by_soname(android_namespace_t* ns,
1376                                           const char* name,
1377                                           soinfo** candidate) {
1378   return !ns->soinfo_list().visit([&](soinfo* si) {
1379     if (strcmp(name, si->get_soname()) == 0) {
1380       *candidate = si;
1381       return false;
1382     }
1383 
1384     return true;
1385   });
1386 }
1387 
1388 // Returns true if library was found and false otherwise
find_loaded_library_by_soname(android_namespace_t * ns,const char * name,bool search_linked_namespaces,soinfo ** candidate)1389 static bool find_loaded_library_by_soname(android_namespace_t* ns,
1390                                          const char* name,
1391                                          bool search_linked_namespaces,
1392                                          soinfo** candidate) {
1393   *candidate = nullptr;
1394 
1395   // Ignore filename with path.
1396   if (strchr(name, '/') != nullptr) {
1397     return false;
1398   }
1399 
1400   bool found = find_loaded_library_by_soname(ns, name, candidate);
1401 
1402   if (!found && search_linked_namespaces) {
1403     // if a library was not found - look into linked namespaces
1404     for (auto& link : ns->linked_namespaces()) {
1405       if (!link.is_accessible(name)) {
1406         continue;
1407       }
1408 
1409       android_namespace_t* linked_ns = link.linked_namespace();
1410 
1411       if (find_loaded_library_by_soname(linked_ns, name, candidate)) {
1412         return true;
1413       }
1414     }
1415   }
1416 
1417   return found;
1418 }
1419 
find_library_in_linked_namespace(const android_namespace_link_t & namespace_link,LoadTask * task)1420 static bool find_library_in_linked_namespace(const android_namespace_link_t& namespace_link,
1421                                              LoadTask* task) {
1422   android_namespace_t* ns = namespace_link.linked_namespace();
1423 
1424   soinfo* candidate;
1425   bool loaded = false;
1426 
1427   std::string soname;
1428   if (find_loaded_library_by_soname(ns, task->get_name(), false, &candidate)) {
1429     loaded = true;
1430     soname = candidate->get_soname();
1431   } else {
1432     soname = resolve_soname(task->get_name());
1433   }
1434 
1435   if (!namespace_link.is_accessible(soname.c_str())) {
1436     // the library is not accessible via namespace_link
1437     LD_LOG(kLogDlopen,
1438            "find_library_in_linked_namespace(ns=%s, task=%s): Not accessible (soname=%s)",
1439            ns->get_name(), task->get_name(), soname.c_str());
1440     return false;
1441   }
1442 
1443   // if library is already loaded - return it
1444   if (loaded) {
1445     LD_LOG(kLogDlopen, "find_library_in_linked_namespace(ns=%s, task=%s): Already loaded",
1446            ns->get_name(), task->get_name());
1447     task->set_soinfo(candidate);
1448     return true;
1449   }
1450 
1451   // returning true with empty soinfo means that the library is okay to be
1452   // loaded in the namespace but has not yet been loaded there before.
1453   LD_LOG(kLogDlopen, "find_library_in_linked_namespace(ns=%s, task=%s): Ok to load", ns->get_name(),
1454          task->get_name());
1455   task->set_soinfo(nullptr);
1456   return true;
1457 }
1458 
find_library_internal(android_namespace_t * ns,LoadTask * task,ZipArchiveCache * zip_archive_cache,LoadTaskList * load_tasks,int rtld_flags)1459 static bool find_library_internal(android_namespace_t* ns,
1460                                   LoadTask* task,
1461                                   ZipArchiveCache* zip_archive_cache,
1462                                   LoadTaskList* load_tasks,
1463                                   int rtld_flags) {
1464   soinfo* candidate;
1465 
1466   if (find_loaded_library_by_soname(ns, task->get_name(), true /* search_linked_namespaces */,
1467                                     &candidate)) {
1468     LD_LOG(kLogDlopen,
1469            "find_library_internal(ns=%s, task=%s): Already loaded (by soname): %s",
1470            ns->get_name(), task->get_name(), candidate->get_realpath());
1471     task->set_soinfo(candidate);
1472     return true;
1473   }
1474 
1475   // Library might still be loaded, the accurate detection
1476   // of this fact is done by load_library.
1477   TRACE("[ \"%s\" find_loaded_library_by_soname failed (*candidate=%s@%p). Trying harder... ]",
1478         task->get_name(), candidate == nullptr ? "n/a" : candidate->get_realpath(), candidate);
1479 
1480   if (load_library(ns, task, zip_archive_cache, load_tasks, rtld_flags,
1481                    true /* search_linked_namespaces */)) {
1482     return true;
1483   }
1484 
1485   // TODO(dimitry): workaround for http://b/26394120 (the exempt-list)
1486   if (ns->is_exempt_list_enabled() && is_exempt_lib(ns, task->get_name(), task->get_needed_by())) {
1487     // For the libs in the exempt-list, switch to the default namespace and then
1488     // try the load again from there. The library could be loaded from the
1489     // default namespace or from another namespace (e.g. runtime) that is linked
1490     // from the default namespace.
1491     LD_LOG(kLogDlopen,
1492            "find_library_internal(ns=%s, task=%s): Exempt system library - trying namespace %s",
1493            ns->get_name(), task->get_name(), g_default_namespace.get_name());
1494     ns = &g_default_namespace;
1495     if (load_library(ns, task, zip_archive_cache, load_tasks, rtld_flags,
1496                      true /* search_linked_namespaces */)) {
1497       return true;
1498     }
1499   }
1500   // END OF WORKAROUND
1501 
1502   // if a library was not found - look into linked namespaces
1503   // preserve current dlerror in the case it fails.
1504   DlErrorRestorer dlerror_restorer;
1505   LD_LOG(kLogDlopen, "find_library_internal(ns=%s, task=%s): Trying %zu linked namespaces",
1506          ns->get_name(), task->get_name(), ns->linked_namespaces().size());
1507   for (auto& linked_namespace : ns->linked_namespaces()) {
1508     if (find_library_in_linked_namespace(linked_namespace, task)) {
1509       // Library is already loaded.
1510       if (task->get_soinfo() != nullptr) {
1511         // n.b. This code path runs when find_library_in_linked_namespace found an already-loaded
1512         // library by soname. That should only be possible with a exempt-list lookup, where we
1513         // switch the namespace, because otherwise, find_library_in_linked_namespace is duplicating
1514         // the soname scan done in this function's first call to find_loaded_library_by_soname.
1515         return true;
1516       }
1517 
1518       if (load_library(linked_namespace.linked_namespace(), task, zip_archive_cache, load_tasks,
1519                        rtld_flags, false /* search_linked_namespaces */)) {
1520         LD_LOG(kLogDlopen, "find_library_internal(ns=%s, task=%s): Found in linked namespace %s",
1521                ns->get_name(), task->get_name(), linked_namespace.linked_namespace()->get_name());
1522         return true;
1523       }
1524     }
1525   }
1526 
1527   return false;
1528 }
1529 
1530 static void soinfo_unload(soinfo* si);
1531 
shuffle(std::vector<LoadTask * > * v)1532 static void shuffle(std::vector<LoadTask*>* v) {
1533   if (is_first_stage_init()) {
1534     // arc4random* is not available in first stage init because /dev/random
1535     // hasn't yet been created.
1536     return;
1537   }
1538   for (size_t i = 0, size = v->size(); i < size; ++i) {
1539     size_t n = size - i;
1540     size_t r = arc4random_uniform(n);
1541     std::swap((*v)[n-1], (*v)[r]);
1542   }
1543 }
1544 
1545 // add_as_children - add first-level loaded libraries (i.e. library_names[], but
1546 // not their transitive dependencies) as children of the start_with library.
1547 // This is false when find_libraries is called for dlopen(), when newly loaded
1548 // libraries must form a disjoint tree.
find_libraries(android_namespace_t * ns,soinfo * start_with,const char * const library_names[],size_t library_names_count,soinfo * soinfos[],std::vector<soinfo * > * ld_preloads,size_t ld_preloads_count,int rtld_flags,const android_dlextinfo * extinfo,bool add_as_children,std::vector<android_namespace_t * > * namespaces)1549 bool find_libraries(android_namespace_t* ns,
1550                     soinfo* start_with,
1551                     const char* const library_names[],
1552                     size_t library_names_count,
1553                     soinfo* soinfos[],
1554                     std::vector<soinfo*>* ld_preloads,
1555                     size_t ld_preloads_count,
1556                     int rtld_flags,
1557                     const android_dlextinfo* extinfo,
1558                     bool add_as_children,
1559                     std::vector<android_namespace_t*>* namespaces) {
1560   // Step 0: prepare.
1561   std::unordered_map<const soinfo*, ElfReader> readers_map;
1562   LoadTaskList load_tasks;
1563 
1564   for (size_t i = 0; i < library_names_count; ++i) {
1565     const char* name = library_names[i];
1566     load_tasks.push_back(LoadTask::create(name, start_with, ns, &readers_map));
1567   }
1568 
1569   // If soinfos array is null allocate one on stack.
1570   // The array is needed in case of failure; for example
1571   // when library_names[] = {libone.so, libtwo.so} and libone.so
1572   // is loaded correctly but libtwo.so failed for some reason.
1573   // In this case libone.so should be unloaded on return.
1574   // See also implementation of failure_guard below.
1575 
1576   if (soinfos == nullptr) {
1577     size_t soinfos_size = sizeof(soinfo*)*library_names_count;
1578     soinfos = reinterpret_cast<soinfo**>(alloca(soinfos_size));
1579     memset(soinfos, 0, soinfos_size);
1580   }
1581 
1582   // list of libraries to link - see step 2.
1583   size_t soinfos_count = 0;
1584 
1585   auto scope_guard = android::base::make_scope_guard([&]() {
1586     for (LoadTask* t : load_tasks) {
1587       LoadTask::deleter(t);
1588     }
1589   });
1590 
1591   ZipArchiveCache zip_archive_cache;
1592   soinfo_list_t new_global_group_members;
1593 
1594   // Step 1: expand the list of load_tasks to include
1595   // all DT_NEEDED libraries (do not load them just yet)
1596   for (size_t i = 0; i<load_tasks.size(); ++i) {
1597     LoadTask* task = load_tasks[i];
1598     soinfo* needed_by = task->get_needed_by();
1599 
1600     bool is_dt_needed = needed_by != nullptr && (needed_by != start_with || add_as_children);
1601     task->set_extinfo(is_dt_needed ? nullptr : extinfo);
1602     task->set_dt_needed(is_dt_needed);
1603 
1604     // Note: start from the namespace that is stored in the LoadTask. This namespace
1605     // is different from the current namespace when the LoadTask is for a transitive
1606     // dependency and the lib that created the LoadTask is not found in the
1607     // current namespace but in one of the linked namespaces.
1608     android_namespace_t* start_ns = const_cast<android_namespace_t*>(task->get_start_from());
1609 
1610     LD_LOG(kLogDlopen, "find_library_internal(ns=%s@%p): task=%s, is_dt_needed=%d",
1611            start_ns->get_name(), start_ns, task->get_name(), is_dt_needed);
1612 
1613     if (!find_library_internal(start_ns, task, &zip_archive_cache, &load_tasks, rtld_flags)) {
1614       return false;
1615     }
1616 
1617     soinfo* si = task->get_soinfo();
1618 
1619     if (is_dt_needed) {
1620       needed_by->add_child(si);
1621     }
1622 
1623     // When ld_preloads is not null, the first
1624     // ld_preloads_count libs are in fact ld_preloads.
1625     bool is_ld_preload = false;
1626     if (ld_preloads != nullptr && soinfos_count < ld_preloads_count) {
1627       ld_preloads->push_back(si);
1628       is_ld_preload = true;
1629     }
1630 
1631     if (soinfos_count < library_names_count) {
1632       soinfos[soinfos_count++] = si;
1633     }
1634 
1635     // Add the new global group members to all initial namespaces. Do this secondary namespace setup
1636     // at the same time that libraries are added to their primary namespace so that the order of
1637     // global group members is the same in the every namespace. Only add a library to a namespace
1638     // once, even if it appears multiple times in the dependency graph.
1639     if (is_ld_preload || (si->get_dt_flags_1() & DF_1_GLOBAL) != 0) {
1640       if (!si->is_linked() && namespaces != nullptr && !new_global_group_members.contains(si)) {
1641         new_global_group_members.push_back(si);
1642         for (auto linked_ns : *namespaces) {
1643           if (si->get_primary_namespace() != linked_ns) {
1644             linked_ns->add_soinfo(si);
1645             si->add_secondary_namespace(linked_ns);
1646           }
1647         }
1648       }
1649     }
1650   }
1651 
1652   // Step 2: Load libraries in random order (see b/24047022)
1653   LoadTaskList load_list;
1654   for (auto&& task : load_tasks) {
1655     soinfo* si = task->get_soinfo();
1656     auto pred = [&](const LoadTask* t) {
1657       return t->get_soinfo() == si;
1658     };
1659 
1660     if (!si->is_linked() &&
1661         std::find_if(load_list.begin(), load_list.end(), pred) == load_list.end() ) {
1662       load_list.push_back(task);
1663     }
1664   }
1665   bool reserved_address_recursive = false;
1666   if (extinfo) {
1667     reserved_address_recursive = extinfo->flags & ANDROID_DLEXT_RESERVED_ADDRESS_RECURSIVE;
1668   }
1669   if (!reserved_address_recursive) {
1670     // Shuffle the load order in the normal case, but not if we are loading all
1671     // the libraries to a reserved address range.
1672     shuffle(&load_list);
1673   }
1674 
1675   // Set up address space parameters.
1676   address_space_params extinfo_params, default_params;
1677   size_t relro_fd_offset = 0;
1678   if (extinfo) {
1679     if (extinfo->flags & ANDROID_DLEXT_RESERVED_ADDRESS) {
1680       extinfo_params.start_addr = extinfo->reserved_addr;
1681       extinfo_params.reserved_size = extinfo->reserved_size;
1682       extinfo_params.must_use_address = true;
1683     } else if (extinfo->flags & ANDROID_DLEXT_RESERVED_ADDRESS_HINT) {
1684       extinfo_params.start_addr = extinfo->reserved_addr;
1685       extinfo_params.reserved_size = extinfo->reserved_size;
1686     }
1687   }
1688 
1689   for (auto&& task : load_list) {
1690     address_space_params* address_space =
1691         (reserved_address_recursive || !task->is_dt_needed()) ? &extinfo_params : &default_params;
1692     if (!task->load(address_space)) {
1693       return false;
1694     }
1695   }
1696 
1697   // Step 3: pre-link all DT_NEEDED libraries in breadth first order.
1698   bool any_memtag_stack = false;
1699   for (auto&& task : load_tasks) {
1700     soinfo* si = task->get_soinfo();
1701     if (!si->is_linked() && !si->prelink_image()) {
1702       return false;
1703     }
1704     // si->memtag_stack() needs to be called after si->prelink_image() which populates
1705     // the dynamic section.
1706     if (si->has_min_version(7) && si->memtag_stack()) {
1707       any_memtag_stack = true;
1708       LD_LOG(kLogDlopen,
1709              "... load_library requesting stack MTE for: realpath=\"%s\", soname=\"%s\"",
1710              si->get_realpath(), si->get_soname());
1711     }
1712     register_soinfo_tls(si);
1713   }
1714   if (any_memtag_stack) {
1715     if (auto* cb = __libc_shared_globals()->memtag_stack_dlopen_callback) {
1716       cb();
1717     } else {
1718       // find_library is used by the initial linking step, so we communicate that we
1719       // want memtag_stack enabled to __libc_init_mte.
1720       __libc_shared_globals()->initial_memtag_stack = true;
1721     }
1722   }
1723 
1724   // Step 4: Construct the global group. DF_1_GLOBAL bit is force set for LD_PRELOADed libs because
1725   // they must be added to the global group. Note: The DF_1_GLOBAL bit for a library is normally set
1726   // in step 3.
1727   if (ld_preloads != nullptr) {
1728     for (auto&& si : *ld_preloads) {
1729       si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
1730     }
1731   }
1732 
1733   // Step 5: Collect roots of local_groups.
1734   // Whenever needed_by->si link crosses a namespace boundary it forms its own local_group.
1735   // Here we collect new roots to link them separately later on. Note that we need to avoid
1736   // collecting duplicates. Also the order is important. They need to be linked in the same
1737   // BFS order we link individual libraries.
1738   std::vector<soinfo*> local_group_roots;
1739   if (start_with != nullptr && add_as_children) {
1740     local_group_roots.push_back(start_with);
1741   } else {
1742     CHECK(soinfos_count == 1);
1743     local_group_roots.push_back(soinfos[0]);
1744   }
1745 
1746   for (auto&& task : load_tasks) {
1747     soinfo* si = task->get_soinfo();
1748     soinfo* needed_by = task->get_needed_by();
1749     bool is_dt_needed = needed_by != nullptr && (needed_by != start_with || add_as_children);
1750     android_namespace_t* needed_by_ns =
1751         is_dt_needed ? needed_by->get_primary_namespace() : ns;
1752 
1753     if (!si->is_linked() && si->get_primary_namespace() != needed_by_ns) {
1754       auto it = std::find(local_group_roots.begin(), local_group_roots.end(), si);
1755       LD_LOG(kLogDlopen,
1756              "Crossing namespace boundary (si=%s@%p, si_ns=%s@%p, needed_by=%s@%p, ns=%s@%p, needed_by_ns=%s@%p) adding to local_group_roots: %s",
1757              si->get_realpath(),
1758              si,
1759              si->get_primary_namespace()->get_name(),
1760              si->get_primary_namespace(),
1761              needed_by == nullptr ? "(nullptr)" : needed_by->get_realpath(),
1762              needed_by,
1763              ns->get_name(),
1764              ns,
1765              needed_by_ns->get_name(),
1766              needed_by_ns,
1767              it == local_group_roots.end() ? "yes" : "no");
1768 
1769       if (it == local_group_roots.end()) {
1770         local_group_roots.push_back(si);
1771       }
1772     }
1773   }
1774 
1775   // Step 6: Link all local groups
1776   for (auto root : local_group_roots) {
1777     soinfo_list_t local_group;
1778     android_namespace_t* local_group_ns = root->get_primary_namespace();
1779 
1780     walk_dependencies_tree(root,
1781       [&] (soinfo* si) {
1782         if (local_group_ns->is_accessible(si)) {
1783           local_group.push_back(si);
1784           return kWalkContinue;
1785         } else {
1786           return kWalkSkip;
1787         }
1788       });
1789 
1790     soinfo_list_t global_group = local_group_ns->get_global_group();
1791     SymbolLookupList lookup_list(global_group, local_group);
1792     soinfo* local_group_root = local_group.front();
1793 
1794     bool linked = local_group.visit([&](soinfo* si) {
1795       // Even though local group may contain accessible soinfos from other namespaces
1796       // we should avoid linking them (because if they are not linked -> they
1797       // are in the local_group_roots and will be linked later).
1798       if (!si->is_linked() && si->get_primary_namespace() == local_group_ns) {
1799         const android_dlextinfo* link_extinfo = nullptr;
1800         if (si == soinfos[0] || reserved_address_recursive) {
1801           // Only forward extinfo for the first library unless the recursive
1802           // flag is set.
1803           link_extinfo = extinfo;
1804         }
1805         if (__libc_shared_globals()->load_hook) {
1806           __libc_shared_globals()->load_hook(si->load_bias, si->phdr, si->phnum);
1807         }
1808         lookup_list.set_dt_symbolic_lib(si->has_DT_SYMBOLIC ? si : nullptr);
1809         if (!si->link_image(lookup_list, local_group_root, link_extinfo, &relro_fd_offset) ||
1810             !get_cfi_shadow()->AfterLoad(si, solist_get_head())) {
1811           return false;
1812         }
1813       }
1814 
1815       return true;
1816     });
1817 
1818     if (!linked) {
1819       return false;
1820     }
1821   }
1822 
1823   // Step 7: Mark all load_tasks as linked and increment refcounts
1824   // for references between load_groups (at this point it does not matter if
1825   // referenced load_groups were loaded by previous dlopen or as part of this
1826   // one on step 6)
1827   if (start_with != nullptr && add_as_children) {
1828     start_with->set_linked();
1829   }
1830 
1831   for (auto&& task : load_tasks) {
1832     soinfo* si = task->get_soinfo();
1833     si->set_linked();
1834   }
1835 
1836   for (auto&& task : load_tasks) {
1837     soinfo* si = task->get_soinfo();
1838     soinfo* needed_by = task->get_needed_by();
1839     if (needed_by != nullptr &&
1840         needed_by != start_with &&
1841         needed_by->get_local_group_root() != si->get_local_group_root()) {
1842       si->increment_ref_count();
1843     }
1844   }
1845 
1846 
1847   return true;
1848 }
1849 
find_library(android_namespace_t * ns,const char * name,int rtld_flags,const android_dlextinfo * extinfo,soinfo * needed_by)1850 static soinfo* find_library(android_namespace_t* ns,
1851                             const char* name, int rtld_flags,
1852                             const android_dlextinfo* extinfo,
1853                             soinfo* needed_by) {
1854   soinfo* si = nullptr;
1855 
1856   if (name == nullptr) {
1857     si = solist_get_somain();
1858   } else if (!find_libraries(ns,
1859                              needed_by,
1860                              &name,
1861                              1,
1862                              &si,
1863                              nullptr,
1864                              0,
1865                              rtld_flags,
1866                              extinfo,
1867                              false /* add_as_children */)) {
1868     if (si != nullptr) {
1869       soinfo_unload(si);
1870     }
1871     return nullptr;
1872   }
1873 
1874   si->increment_ref_count();
1875 
1876   return si;
1877 }
1878 
soinfo_unload_impl(soinfo * root)1879 static void soinfo_unload_impl(soinfo* root) {
1880   ScopedTrace trace((std::string("unload ") + root->get_realpath()).c_str());
1881   bool is_linked = root->is_linked();
1882 
1883   if (!root->can_unload()) {
1884     LD_LOG(kLogDlopen,
1885            "... dlclose(root=\"%s\"@%p) ... not unloading - the load group is flagged with NODELETE",
1886            root->get_realpath(),
1887            root);
1888     return;
1889   }
1890 
1891 
1892   soinfo_list_t unload_list;
1893   unload_list.push_back(root);
1894 
1895   soinfo_list_t local_unload_list;
1896   soinfo_list_t external_unload_list;
1897   soinfo* si = nullptr;
1898 
1899   while ((si = unload_list.pop_front()) != nullptr) {
1900     if (local_unload_list.contains(si)) {
1901       continue;
1902     }
1903 
1904     local_unload_list.push_back(si);
1905 
1906     if (si->has_min_version(0)) {
1907       soinfo* child = nullptr;
1908       while ((child = si->get_children().pop_front()) != nullptr) {
1909         TRACE("%s@%p needs to unload %s@%p", si->get_realpath(), si,
1910             child->get_realpath(), child);
1911 
1912         child->get_parents().remove(si);
1913 
1914         if (local_unload_list.contains(child)) {
1915           continue;
1916         } else if (child->is_linked() && child->get_local_group_root() != root) {
1917           external_unload_list.push_back(child);
1918         } else if (child->get_parents().empty()) {
1919           unload_list.push_back(child);
1920         }
1921       }
1922     } else {
1923       async_safe_fatal("soinfo for \"%s\"@%p has no version", si->get_realpath(), si);
1924     }
1925   }
1926 
1927   local_unload_list.for_each([](soinfo* si) {
1928     LD_LOG(kLogDlopen,
1929            "... dlclose: calling destructors for \"%s\"@%p ... ",
1930            si->get_realpath(),
1931            si);
1932     si->call_destructors();
1933     LD_LOG(kLogDlopen,
1934            "... dlclose: calling destructors for \"%s\"@%p ... done",
1935            si->get_realpath(),
1936            si);
1937   });
1938 
1939   while ((si = local_unload_list.pop_front()) != nullptr) {
1940     LD_LOG(kLogDlopen,
1941            "... dlclose: unloading \"%s\"@%p ...",
1942            si->get_realpath(),
1943            si);
1944     ++g_module_unload_counter;
1945     notify_gdb_of_unload(si);
1946     unregister_soinfo_tls(si);
1947     if (__libc_shared_globals()->unload_hook) {
1948       __libc_shared_globals()->unload_hook(si->load_bias, si->phdr, si->phnum);
1949     }
1950     get_cfi_shadow()->BeforeUnload(si);
1951     soinfo_free(si);
1952   }
1953 
1954   if (is_linked) {
1955     while ((si = external_unload_list.pop_front()) != nullptr) {
1956       LD_LOG(kLogDlopen,
1957              "... dlclose: unloading external reference \"%s\"@%p ...",
1958              si->get_realpath(),
1959              si);
1960       soinfo_unload(si);
1961     }
1962   } else {
1963       LD_LOG(kLogDlopen,
1964              "... dlclose: unload_si was not linked - not unloading external references ...");
1965   }
1966 }
1967 
soinfo_unload(soinfo * unload_si)1968 static void soinfo_unload(soinfo* unload_si) {
1969   // Note that the library can be loaded but not linked;
1970   // in which case there is no root but we still need
1971   // to walk the tree and unload soinfos involved.
1972   //
1973   // This happens on unsuccessful dlopen, when one of
1974   // the DT_NEEDED libraries could not be linked/found.
1975   bool is_linked = unload_si->is_linked();
1976   soinfo* root = is_linked ? unload_si->get_local_group_root() : unload_si;
1977 
1978   LD_LOG(kLogDlopen,
1979          "... dlclose(realpath=\"%s\"@%p) ... load group root is \"%s\"@%p",
1980          unload_si->get_realpath(),
1981          unload_si,
1982          root->get_realpath(),
1983          root);
1984 
1985 
1986   size_t ref_count = is_linked ? root->decrement_ref_count() : 0;
1987   if (ref_count > 0) {
1988     LD_LOG(kLogDlopen,
1989            "... dlclose(root=\"%s\"@%p) ... not unloading - decrementing ref_count to %zd",
1990            root->get_realpath(),
1991            root,
1992            ref_count);
1993     return;
1994   }
1995 
1996   soinfo_unload_impl(root);
1997 }
1998 
increment_dso_handle_reference_counter(void * dso_handle)1999 void increment_dso_handle_reference_counter(void* dso_handle) {
2000   if (dso_handle == nullptr) {
2001     return;
2002   }
2003 
2004   auto it = g_dso_handle_counters.find(dso_handle);
2005   if (it != g_dso_handle_counters.end()) {
2006     CHECK(++it->second != 0);
2007   } else {
2008     soinfo* si = find_containing_library(dso_handle);
2009     if (si != nullptr) {
2010       ProtectedDataGuard guard;
2011       si->increment_ref_count();
2012     } else {
2013       async_safe_fatal(
2014           "increment_dso_handle_reference_counter: Couldn't find soinfo by dso_handle=%p",
2015           dso_handle);
2016     }
2017     g_dso_handle_counters[dso_handle] = 1U;
2018   }
2019 }
2020 
decrement_dso_handle_reference_counter(void * dso_handle)2021 void decrement_dso_handle_reference_counter(void* dso_handle) {
2022   if (dso_handle == nullptr) {
2023     return;
2024   }
2025 
2026   auto it = g_dso_handle_counters.find(dso_handle);
2027   CHECK(it != g_dso_handle_counters.end());
2028   CHECK(it->second != 0);
2029 
2030   if (--it->second == 0) {
2031     soinfo* si = find_containing_library(dso_handle);
2032     if (si != nullptr) {
2033       ProtectedDataGuard guard;
2034       soinfo_unload(si);
2035     } else {
2036       async_safe_fatal(
2037           "decrement_dso_handle_reference_counter: Couldn't find soinfo by dso_handle=%p",
2038           dso_handle);
2039     }
2040     g_dso_handle_counters.erase(it);
2041   }
2042 }
2043 
symbol_display_name(const char * sym_name,const char * sym_ver)2044 static std::string symbol_display_name(const char* sym_name, const char* sym_ver) {
2045   if (sym_ver == nullptr) {
2046     return sym_name;
2047   }
2048 
2049   return std::string(sym_name) + ", version " + sym_ver;
2050 }
2051 
get_caller_namespace(soinfo * caller)2052 static android_namespace_t* get_caller_namespace(soinfo* caller) {
2053   return caller != nullptr ? caller->get_primary_namespace() : g_anonymous_namespace;
2054 }
2055 
do_android_get_LD_LIBRARY_PATH(char * buffer,size_t buffer_size)2056 void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
2057   // Use basic string manipulation calls to avoid snprintf.
2058   // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
2059   // When debug malloc is enabled, this call returns 0. This in turn causes
2060   // snprintf to do nothing, which causes libraries to fail to load.
2061   // See b/17302493 for further details.
2062   // Once the above bug is fixed, this code can be modified to use
2063   // snprintf again.
2064   const auto& default_ld_paths = g_default_namespace.get_default_library_paths();
2065 
2066   size_t required_size = 0;
2067   for (const auto& path : default_ld_paths) {
2068     required_size += path.size() + 1;
2069   }
2070 
2071   if (buffer_size < required_size) {
2072     async_safe_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: "
2073                      "buffer len %zu, required len %zu", buffer_size, required_size);
2074   }
2075 
2076   char* end = buffer;
2077   for (size_t i = 0; i < default_ld_paths.size(); ++i) {
2078     if (i > 0) *end++ = ':';
2079     end = stpcpy(end, default_ld_paths[i].c_str());
2080   }
2081 }
2082 
do_android_update_LD_LIBRARY_PATH(const char * ld_library_path)2083 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
2084   parse_LD_LIBRARY_PATH(ld_library_path);
2085 }
2086 
android_dlextinfo_to_string(const android_dlextinfo * info)2087 static std::string android_dlextinfo_to_string(const android_dlextinfo* info) {
2088   if (info == nullptr) {
2089     return "(null)";
2090   }
2091 
2092   return android::base::StringPrintf("[flags=0x%" PRIx64 ","
2093                                      " reserved_addr=%p,"
2094                                      " reserved_size=0x%zx,"
2095                                      " relro_fd=%d,"
2096                                      " library_fd=%d,"
2097                                      " library_fd_offset=0x%" PRIx64 ","
2098                                      " library_namespace=%s@%p]",
2099                                      info->flags,
2100                                      info->reserved_addr,
2101                                      info->reserved_size,
2102                                      info->relro_fd,
2103                                      info->library_fd,
2104                                      info->library_fd_offset,
2105                                      (info->flags & ANDROID_DLEXT_USE_NAMESPACE) != 0 ?
2106                                         (info->library_namespace != nullptr ?
2107                                           info->library_namespace->get_name() : "(null)") : "(n/a)",
2108                                      (info->flags & ANDROID_DLEXT_USE_NAMESPACE) != 0 ?
2109                                         info->library_namespace : nullptr);
2110 }
2111 
do_dlopen(const char * name,int flags,const android_dlextinfo * extinfo,const void * caller_addr)2112 void* do_dlopen(const char* name, int flags,
2113                 const android_dlextinfo* extinfo,
2114                 const void* caller_addr) {
2115   std::string trace_prefix = std::string("dlopen: ") + (name == nullptr ? "(nullptr)" : name);
2116   ScopedTrace trace(trace_prefix.c_str());
2117   ScopedTrace loading_trace((trace_prefix + " - loading and linking").c_str());
2118   soinfo* const caller = find_containing_library(caller_addr);
2119   android_namespace_t* ns = get_caller_namespace(caller);
2120 
2121   LD_LOG(kLogDlopen,
2122          "dlopen(name=\"%s\", flags=0x%x, extinfo=%s, caller=\"%s\", caller_ns=%s@%p, targetSdkVersion=%i) ...",
2123          name,
2124          flags,
2125          android_dlextinfo_to_string(extinfo).c_str(),
2126          caller == nullptr ? "(null)" : caller->get_realpath(),
2127          ns == nullptr ? "(null)" : ns->get_name(),
2128          ns,
2129          get_application_target_sdk_version());
2130 
2131   auto purge_guard = android::base::make_scope_guard([&]() { purge_unused_memory(); });
2132 
2133   auto failure_guard = android::base::make_scope_guard(
2134       [&]() { LD_LOG(kLogDlopen, "... dlopen failed: %s", linker_get_error_buffer()); });
2135 
2136   if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
2137     DL_OPEN_ERR("invalid flags to dlopen: %x", flags);
2138     return nullptr;
2139   }
2140 
2141   if (extinfo != nullptr) {
2142     if ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0) {
2143       DL_OPEN_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
2144       return nullptr;
2145     }
2146 
2147     if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
2148         (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
2149       DL_OPEN_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET without "
2150           "ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
2151       return nullptr;
2152     }
2153 
2154     if ((extinfo->flags & ANDROID_DLEXT_USE_NAMESPACE) != 0) {
2155       if (extinfo->library_namespace == nullptr) {
2156         DL_OPEN_ERR("ANDROID_DLEXT_USE_NAMESPACE is set but extinfo->library_namespace is null");
2157         return nullptr;
2158       }
2159       ns = extinfo->library_namespace;
2160     }
2161   }
2162 
2163   // Workaround for dlopen(/system/lib/<soname>) when .so is in /apex. http://b/121248172
2164   // The workaround works only when targetSdkVersion < Q.
2165   std::string name_to_apex;
2166   if (translateSystemPathToApexPath(name, &name_to_apex)) {
2167     const char* new_name = name_to_apex.c_str();
2168     LD_LOG(kLogDlopen, "dlopen considering translation from %s to APEX path %s",
2169            name,
2170            new_name);
2171     // Some APEXs could be optionally disabled. Only translate the path
2172     // when the old file is absent and the new file exists.
2173     // TODO(b/124218500): Re-enable it once app compat issue is resolved
2174     /*
2175     if (file_exists(name)) {
2176       LD_LOG(kLogDlopen, "dlopen %s exists, not translating", name);
2177     } else
2178     */
2179     if (!file_exists(new_name)) {
2180       LD_LOG(kLogDlopen, "dlopen %s does not exist, not translating",
2181              new_name);
2182     } else {
2183       LD_LOG(kLogDlopen, "dlopen translation accepted: using %s", new_name);
2184       name = new_name;
2185     }
2186   }
2187   // End Workaround for dlopen(/system/lib/<soname>) when .so is in /apex.
2188 
2189   std::string translated_name_holder;
2190 
2191   assert(!g_is_hwasan || !g_is_asan);
2192   const char* translated_name = name;
2193   if (g_is_asan && translated_name != nullptr && translated_name[0] == '/') {
2194     char original_path[PATH_MAX];
2195     if (realpath(name, original_path) != nullptr) {
2196       translated_name_holder = std::string(kAsanLibDirPrefix) + original_path;
2197       if (file_exists(translated_name_holder.c_str())) {
2198         soinfo* si = nullptr;
2199         if (find_loaded_library_by_realpath(ns, original_path, true, &si)) {
2200           PRINT("linker_asan dlopen NOT translating \"%s\" -> \"%s\": library already loaded", name,
2201                 translated_name_holder.c_str());
2202         } else {
2203           PRINT("linker_asan dlopen translating \"%s\" -> \"%s\"", name, translated_name);
2204           translated_name = translated_name_holder.c_str();
2205         }
2206       }
2207     }
2208   } else if (g_is_hwasan && translated_name != nullptr && translated_name[0] == '/') {
2209     char original_path[PATH_MAX];
2210     if (realpath(name, original_path) != nullptr) {
2211       // Keep this the same as CreateHwasanPath in system/linkerconfig/modules/namespace.cc.
2212       std::string path(original_path);
2213       auto slash = path.rfind('/');
2214       if (slash != std::string::npos || slash != path.size() - 1) {
2215         translated_name_holder = path.substr(0, slash) + "/hwasan" + path.substr(slash);
2216       }
2217       if (!translated_name_holder.empty() && file_exists(translated_name_holder.c_str())) {
2218         soinfo* si = nullptr;
2219         if (find_loaded_library_by_realpath(ns, original_path, true, &si)) {
2220           PRINT("linker_hwasan dlopen NOT translating \"%s\" -> \"%s\": library already loaded", name,
2221                 translated_name_holder.c_str());
2222         } else {
2223           PRINT("linker_hwasan dlopen translating \"%s\" -> \"%s\"", name, translated_name);
2224           translated_name = translated_name_holder.c_str();
2225         }
2226       }
2227     }
2228   }
2229   ProtectedDataGuard guard;
2230   soinfo* si = find_library(ns, translated_name, flags, extinfo, caller);
2231   loading_trace.End();
2232 
2233   if (si != nullptr) {
2234     void* handle = si->to_handle();
2235     LD_LOG(kLogDlopen,
2236            "... dlopen calling constructors: realpath=\"%s\", soname=\"%s\", handle=%p",
2237            si->get_realpath(), si->get_soname(), handle);
2238     si->call_constructors();
2239     failure_guard.Disable();
2240     LD_LOG(kLogDlopen,
2241            "... dlopen successful: realpath=\"%s\", soname=\"%s\", handle=%p",
2242            si->get_realpath(), si->get_soname(), handle);
2243     return handle;
2244   }
2245 
2246   return nullptr;
2247 }
2248 
do_dladdr(const void * addr,Dl_info * info)2249 int do_dladdr(const void* addr, Dl_info* info) {
2250   // Determine if this address can be found in any library currently mapped.
2251   soinfo* si = find_containing_library(addr);
2252   if (si == nullptr) {
2253     return 0;
2254   }
2255 
2256   memset(info, 0, sizeof(Dl_info));
2257 
2258   info->dli_fname = si->get_realpath();
2259   // Address at which the shared object is loaded.
2260   info->dli_fbase = reinterpret_cast<void*>(si->base);
2261 
2262   // Determine if any symbol in the library contains the specified address.
2263   ElfW(Sym)* sym = si->find_symbol_by_address(addr);
2264   if (sym != nullptr) {
2265     info->dli_sname = si->get_string(sym->st_name);
2266     info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));
2267   }
2268 
2269   return 1;
2270 }
2271 
soinfo_from_handle(void * handle)2272 static soinfo* soinfo_from_handle(void* handle) {
2273   if ((reinterpret_cast<uintptr_t>(handle) & 1) != 0) {
2274     auto it = g_soinfo_handles_map.find(reinterpret_cast<uintptr_t>(handle));
2275     if (it == g_soinfo_handles_map.end()) {
2276       return nullptr;
2277     } else {
2278       return it->second;
2279     }
2280   }
2281 
2282   return static_cast<soinfo*>(handle);
2283 }
2284 
do_dlsym(void * handle,const char * sym_name,const char * sym_ver,const void * caller_addr,void ** symbol)2285 bool do_dlsym(void* handle,
2286               const char* sym_name,
2287               const char* sym_ver,
2288               const void* caller_addr,
2289               void** symbol) {
2290   ScopedTrace trace("dlsym");
2291 #if !defined(__LP64__)
2292   if (handle == nullptr) {
2293     DL_SYM_ERR("dlsym failed: library handle is null");
2294     return false;
2295   }
2296 #endif
2297 
2298   soinfo* found = nullptr;
2299   const ElfW(Sym)* sym = nullptr;
2300   soinfo* caller = find_containing_library(caller_addr);
2301   android_namespace_t* ns = get_caller_namespace(caller);
2302   soinfo* si = nullptr;
2303   if (handle != RTLD_DEFAULT && handle != RTLD_NEXT) {
2304     si = soinfo_from_handle(handle);
2305   }
2306 
2307   LD_LOG(kLogDlsym,
2308          "dlsym(handle=%p(\"%s\"), sym_name=\"%s\", sym_ver=\"%s\", caller=\"%s\", caller_ns=%s@%p) ...",
2309          handle,
2310          si != nullptr ? si->get_realpath() : "n/a",
2311          sym_name,
2312          sym_ver,
2313          caller == nullptr ? "(null)" : caller->get_realpath(),
2314          ns == nullptr ? "(null)" : ns->get_name(),
2315          ns);
2316 
2317   auto failure_guard = android::base::make_scope_guard(
2318       [&]() { LD_LOG(kLogDlsym, "... dlsym failed: %s", linker_get_error_buffer()); });
2319 
2320   if (sym_name == nullptr) {
2321     DL_SYM_ERR("dlsym failed: symbol name is null");
2322     return false;
2323   }
2324 
2325   version_info vi_instance;
2326   version_info* vi = nullptr;
2327 
2328   if (sym_ver != nullptr) {
2329     vi_instance.name = sym_ver;
2330     vi_instance.elf_hash = calculate_elf_hash(sym_ver);
2331     vi = &vi_instance;
2332   }
2333 
2334   if (handle == RTLD_DEFAULT || handle == RTLD_NEXT) {
2335     sym = dlsym_linear_lookup(ns, sym_name, vi, &found, caller, handle);
2336   } else {
2337     if (si == nullptr) {
2338       DL_SYM_ERR("dlsym failed: invalid handle: %p", handle);
2339       return false;
2340     }
2341     sym = dlsym_handle_lookup(si, &found, sym_name, vi);
2342   }
2343 
2344   if (sym != nullptr) {
2345     uint32_t bind = ELF_ST_BIND(sym->st_info);
2346     uint32_t type = ELF_ST_TYPE(sym->st_info);
2347 
2348     if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
2349       if (type == STT_TLS) {
2350         // For a TLS symbol, dlsym returns the address of the current thread's
2351         // copy of the symbol.
2352         const soinfo_tls* tls_module = found->get_tls();
2353         if (tls_module == nullptr) {
2354           DL_SYM_ERR("TLS symbol \"%s\" in solib \"%s\" with no TLS segment",
2355                      sym_name, found->get_realpath());
2356           return false;
2357         }
2358         void* tls_block = get_tls_block_for_this_thread(tls_module, /*should_alloc=*/true);
2359         *symbol = static_cast<char*>(tls_block) + sym->st_value;
2360       } else {
2361         *symbol = reinterpret_cast<void*>(found->resolve_symbol_address(sym));
2362       }
2363       failure_guard.Disable();
2364       LD_LOG(kLogDlsym,
2365              "... dlsym successful: sym_name=\"%s\", sym_ver=\"%s\", found in=\"%s\", address=%p",
2366              sym_name, sym_ver, found->get_soname(), *symbol);
2367       return true;
2368     }
2369 
2370     DL_SYM_ERR("symbol \"%s\" found but not global", symbol_display_name(sym_name, sym_ver).c_str());
2371     return false;
2372   }
2373 
2374   DL_SYM_ERR("undefined symbol: %s", symbol_display_name(sym_name, sym_ver).c_str());
2375   return false;
2376 }
2377 
do_dlclose(void * handle)2378 int do_dlclose(void* handle) {
2379   ScopedTrace trace("dlclose");
2380   ProtectedDataGuard guard;
2381   soinfo* si = soinfo_from_handle(handle);
2382   if (si == nullptr) {
2383     DL_OPEN_ERR("invalid handle: %p", handle);
2384     return -1;
2385   }
2386 
2387   LD_LOG(kLogDlopen,
2388          "dlclose(handle=%p, realpath=\"%s\"@%p) ...",
2389          handle,
2390          si->get_realpath(),
2391          si);
2392   soinfo_unload(si);
2393   LD_LOG(kLogDlopen,
2394          "dlclose(handle=%p) ... done",
2395          handle);
2396   return 0;
2397 }
2398 
2399 // Make ns as the anonymous namespace that is a namespace used when
2400 // we fail to determine the caller address (e.g., call from mono-jited code)
2401 // Since there can be multiple anonymous namespace in a process, subsequent
2402 // call to this function causes an error.
set_anonymous_namespace(android_namespace_t * ns)2403 static bool set_anonymous_namespace(android_namespace_t* ns) {
2404   if (!g_anonymous_namespace_set && ns != nullptr) {
2405     CHECK(ns->is_also_used_as_anonymous());
2406     g_anonymous_namespace = ns;
2407     g_anonymous_namespace_set = true;
2408     return true;
2409   }
2410   return false;
2411 }
2412 
2413 // TODO(b/130388701) remove this. Currently, this is used only for testing
2414 // where we don't have classloader namespace.
init_anonymous_namespace(const char * shared_lib_sonames,const char * library_search_path)2415 bool init_anonymous_namespace(const char* shared_lib_sonames, const char* library_search_path) {
2416   ProtectedDataGuard guard;
2417 
2418   // Test-only feature: we need to change the anonymous namespace multiple times
2419   // while the test is running.
2420   g_anonymous_namespace_set = false;
2421 
2422   // create anonymous namespace
2423   // When the caller is nullptr - create_namespace will take global group
2424   // from the anonymous namespace, which is fine because anonymous namespace
2425   // is still pointing to the default one.
2426   android_namespace_t* anon_ns =
2427       create_namespace(nullptr,
2428                        "(anonymous)",
2429                        nullptr,
2430                        library_search_path,
2431                        ANDROID_NAMESPACE_TYPE_ISOLATED |
2432                        ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS,
2433                        nullptr,
2434                        &g_default_namespace);
2435 
2436   CHECK(anon_ns != nullptr);
2437 
2438   if (!link_namespaces(anon_ns, &g_default_namespace, shared_lib_sonames)) {
2439     // TODO: delete anon_ns
2440     return false;
2441   }
2442 
2443   return true;
2444 }
2445 
add_soinfos_to_namespace(const soinfo_list_t & soinfos,android_namespace_t * ns)2446 static void add_soinfos_to_namespace(const soinfo_list_t& soinfos, android_namespace_t* ns) {
2447   ns->add_soinfos(soinfos);
2448   for (auto si : soinfos) {
2449     si->add_secondary_namespace(ns);
2450   }
2451 }
2452 
fix_lib_paths(std::vector<std::string> paths)2453 std::vector<std::string> fix_lib_paths(std::vector<std::string> paths) {
2454   // For the bootstrap linker, insert /system/${LIB}/bootstrap in front of /system/${LIB} in any
2455   // namespace search path. The bootstrap linker should prefer to use the bootstrap bionic libraries
2456   // (e.g. libc.so).
2457 #if !defined(__ANDROID_APEX__)
2458   for (size_t i = 0; i < paths.size(); ++i) {
2459     if (paths[i] == kSystemLibDir) {
2460       paths.insert(paths.begin() + i, std::string(kSystemLibDir) + "/bootstrap");
2461       ++i;
2462     }
2463   }
2464 #endif
2465   return paths;
2466 }
2467 
create_namespace(const void * caller_addr,const char * name,const char * ld_library_path,const char * default_library_path,uint64_t type,const char * permitted_when_isolated_path,android_namespace_t * parent_namespace)2468 android_namespace_t* create_namespace(const void* caller_addr,
2469                                       const char* name,
2470                                       const char* ld_library_path,
2471                                       const char* default_library_path,
2472                                       uint64_t type,
2473                                       const char* permitted_when_isolated_path,
2474                                       android_namespace_t* parent_namespace) {
2475   if (parent_namespace == nullptr) {
2476     // if parent_namespace is nullptr -> set it to the caller namespace
2477     soinfo* caller_soinfo = find_containing_library(caller_addr);
2478 
2479     parent_namespace = caller_soinfo != nullptr ?
2480                        caller_soinfo->get_primary_namespace() :
2481                        g_anonymous_namespace;
2482   }
2483 
2484   ProtectedDataGuard guard;
2485   std::vector<std::string> ld_library_paths;
2486   std::vector<std::string> default_library_paths;
2487   std::vector<std::string> permitted_paths;
2488 
2489   parse_path(ld_library_path, ":", &ld_library_paths);
2490   parse_path(default_library_path, ":", &default_library_paths);
2491   parse_path(permitted_when_isolated_path, ":", &permitted_paths);
2492 
2493   android_namespace_t* ns = new (g_namespace_allocator.alloc()) android_namespace_t();
2494   ns->set_name(name);
2495   ns->set_isolated((type & ANDROID_NAMESPACE_TYPE_ISOLATED) != 0);
2496   ns->set_exempt_list_enabled((type & ANDROID_NAMESPACE_TYPE_EXEMPT_LIST_ENABLED) != 0);
2497   ns->set_also_used_as_anonymous((type & ANDROID_NAMESPACE_TYPE_ALSO_USED_AS_ANONYMOUS) != 0);
2498 
2499   if ((type & ANDROID_NAMESPACE_TYPE_SHARED) != 0) {
2500     // append parent namespace paths.
2501     std::copy(parent_namespace->get_ld_library_paths().begin(),
2502               parent_namespace->get_ld_library_paths().end(),
2503               back_inserter(ld_library_paths));
2504 
2505     std::copy(parent_namespace->get_default_library_paths().begin(),
2506               parent_namespace->get_default_library_paths().end(),
2507               back_inserter(default_library_paths));
2508 
2509     std::copy(parent_namespace->get_permitted_paths().begin(),
2510               parent_namespace->get_permitted_paths().end(),
2511               back_inserter(permitted_paths));
2512 
2513     // If shared - clone the parent namespace
2514     add_soinfos_to_namespace(parent_namespace->soinfo_list(), ns);
2515     // and copy parent namespace links
2516     for (auto& link : parent_namespace->linked_namespaces()) {
2517       ns->add_linked_namespace(link.linked_namespace(), link.shared_lib_sonames(),
2518                                link.allow_all_shared_libs());
2519     }
2520   } else {
2521     // If not shared - copy only the shared group
2522     add_soinfos_to_namespace(parent_namespace->get_shared_group(), ns);
2523   }
2524 
2525   ns->set_ld_library_paths(std::move(ld_library_paths));
2526   ns->set_default_library_paths(std::move(default_library_paths));
2527   ns->set_permitted_paths(std::move(permitted_paths));
2528 
2529   if (ns->is_also_used_as_anonymous() && !set_anonymous_namespace(ns)) {
2530     DL_ERR("failed to set namespace: [name=\"%s\", ld_library_path=\"%s\", default_library_paths=\"%s\""
2531            " permitted_paths=\"%s\"] as the anonymous namespace",
2532            ns->get_name(),
2533            android::base::Join(ns->get_ld_library_paths(), ':').c_str(),
2534            android::base::Join(ns->get_default_library_paths(), ':').c_str(),
2535            android::base::Join(ns->get_permitted_paths(), ':').c_str());
2536     return nullptr;
2537   }
2538 
2539   return ns;
2540 }
2541 
link_namespaces(android_namespace_t * namespace_from,android_namespace_t * namespace_to,const char * shared_lib_sonames)2542 bool link_namespaces(android_namespace_t* namespace_from,
2543                      android_namespace_t* namespace_to,
2544                      const char* shared_lib_sonames) {
2545   if (namespace_to == nullptr) {
2546     namespace_to = &g_default_namespace;
2547   }
2548 
2549   if (namespace_from == nullptr) {
2550     DL_ERR("error linking namespaces: namespace_from is null.");
2551     return false;
2552   }
2553 
2554   if (shared_lib_sonames == nullptr || shared_lib_sonames[0] == '\0') {
2555     DL_ERR("error linking namespaces \"%s\"->\"%s\": the list of shared libraries is empty.",
2556            namespace_from->get_name(), namespace_to->get_name());
2557     return false;
2558   }
2559 
2560   std::vector<std::string> sonames = android::base::Split(shared_lib_sonames, ":");
2561   std::unordered_set<std::string> sonames_set(std::make_move_iterator(sonames.begin()),
2562                                               std::make_move_iterator(sonames.end()));
2563 
2564   ProtectedDataGuard guard;
2565   namespace_from->add_linked_namespace(namespace_to, std::move(sonames_set), false);
2566 
2567   return true;
2568 }
2569 
link_namespaces_all_libs(android_namespace_t * namespace_from,android_namespace_t * namespace_to)2570 bool link_namespaces_all_libs(android_namespace_t* namespace_from,
2571                               android_namespace_t* namespace_to) {
2572   if (namespace_from == nullptr) {
2573     DL_ERR("error linking namespaces: namespace_from is null.");
2574     return false;
2575   }
2576 
2577   if (namespace_to == nullptr) {
2578     DL_ERR("error linking namespaces: namespace_to is null.");
2579     return false;
2580   }
2581 
2582   ProtectedDataGuard guard;
2583   namespace_from->add_linked_namespace(namespace_to, std::unordered_set<std::string>(), true);
2584 
2585   return true;
2586 }
2587 
call_ifunc_resolver(ElfW (Addr)resolver_addr)2588 ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
2589   if (g_is_ldd) return 0;
2590 
2591   ElfW(Addr) ifunc_addr = __bionic_call_ifunc_resolver(resolver_addr);
2592   TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p",
2593       reinterpret_cast<void *>(resolver_addr), reinterpret_cast<void*>(ifunc_addr));
2594 
2595   return ifunc_addr;
2596 }
2597 
get_version_info(ElfW (Versym)source_symver) const2598 const version_info* VersionTracker::get_version_info(ElfW(Versym) source_symver) const {
2599   if (source_symver < 2 ||
2600       source_symver >= version_infos.size() ||
2601       version_infos[source_symver].name == nullptr) {
2602     return nullptr;
2603   }
2604 
2605   return &version_infos[source_symver];
2606 }
2607 
add_version_info(size_t source_index,ElfW (Word)elf_hash,const char * ver_name,const soinfo * target_si)2608 void VersionTracker::add_version_info(size_t source_index,
2609                                       ElfW(Word) elf_hash,
2610                                       const char* ver_name,
2611                                       const soinfo* target_si) {
2612   if (source_index >= version_infos.size()) {
2613     version_infos.resize(source_index+1);
2614   }
2615 
2616   version_infos[source_index].elf_hash = elf_hash;
2617   version_infos[source_index].name = ver_name;
2618   version_infos[source_index].target_si = target_si;
2619 }
2620 
init_verneed(const soinfo * si_from)2621 bool VersionTracker::init_verneed(const soinfo* si_from) {
2622   uintptr_t verneed_ptr = si_from->get_verneed_ptr();
2623 
2624   if (verneed_ptr == 0) {
2625     return true;
2626   }
2627 
2628   size_t verneed_cnt = si_from->get_verneed_cnt();
2629 
2630   for (size_t i = 0, offset = 0; i<verneed_cnt; ++i) {
2631     const ElfW(Verneed)* verneed = reinterpret_cast<ElfW(Verneed)*>(verneed_ptr + offset);
2632     size_t vernaux_offset = offset + verneed->vn_aux;
2633     offset += verneed->vn_next;
2634 
2635     if (verneed->vn_version != 1) {
2636       DL_ERR("unsupported verneed[%zd] vn_version: %d (expected 1)", i, verneed->vn_version);
2637       return false;
2638     }
2639 
2640     const char* target_soname = si_from->get_string(verneed->vn_file);
2641     // find it in dependencies
2642     soinfo* target_si = si_from->get_children().find_if(
2643         [&](const soinfo* si) { return strcmp(si->get_soname(), target_soname) == 0; });
2644 
2645     if (target_si == nullptr) {
2646       DL_ERR("cannot find \"%s\" from verneed[%zd] in DT_NEEDED list for \"%s\"",
2647           target_soname, i, si_from->get_realpath());
2648       return false;
2649     }
2650 
2651     for (size_t j = 0; j<verneed->vn_cnt; ++j) {
2652       const ElfW(Vernaux)* vernaux = reinterpret_cast<ElfW(Vernaux)*>(verneed_ptr + vernaux_offset);
2653       vernaux_offset += vernaux->vna_next;
2654 
2655       const ElfW(Word) elf_hash = vernaux->vna_hash;
2656       const char* ver_name = si_from->get_string(vernaux->vna_name);
2657       ElfW(Half) source_index = vernaux->vna_other;
2658 
2659       add_version_info(source_index, elf_hash, ver_name, target_si);
2660     }
2661   }
2662 
2663   return true;
2664 }
2665 
2666 template <typename F>
for_each_verdef(const soinfo * si,F functor)2667 static bool for_each_verdef(const soinfo* si, F functor) {
2668   if (!si->has_min_version(2)) {
2669     return true;
2670   }
2671 
2672   uintptr_t verdef_ptr = si->get_verdef_ptr();
2673   if (verdef_ptr == 0) {
2674     return true;
2675   }
2676 
2677   size_t offset = 0;
2678 
2679   size_t verdef_cnt = si->get_verdef_cnt();
2680   for (size_t i = 0; i<verdef_cnt; ++i) {
2681     const ElfW(Verdef)* verdef = reinterpret_cast<ElfW(Verdef)*>(verdef_ptr + offset);
2682     size_t verdaux_offset = offset + verdef->vd_aux;
2683     offset += verdef->vd_next;
2684 
2685     if (verdef->vd_version != 1) {
2686       DL_ERR("unsupported verdef[%zd] vd_version: %d (expected 1) library: %s",
2687           i, verdef->vd_version, si->get_realpath());
2688       return false;
2689     }
2690 
2691     if ((verdef->vd_flags & VER_FLG_BASE) != 0) {
2692       // "this is the version of the file itself.  It must not be used for
2693       //  matching a symbol. It can be used to match references."
2694       //
2695       // http://www.akkadia.org/drepper/symbol-versioning
2696       continue;
2697     }
2698 
2699     if (verdef->vd_cnt == 0) {
2700       DL_ERR("invalid verdef[%zd] vd_cnt == 0 (version without a name)", i);
2701       return false;
2702     }
2703 
2704     const ElfW(Verdaux)* verdaux = reinterpret_cast<ElfW(Verdaux)*>(verdef_ptr + verdaux_offset);
2705 
2706     if (functor(i, verdef, verdaux) == true) {
2707       break;
2708     }
2709   }
2710 
2711   return true;
2712 }
2713 
find_verdef_version_index(const soinfo * si,const version_info * vi)2714 ElfW(Versym) find_verdef_version_index(const soinfo* si, const version_info* vi) {
2715   if (vi == nullptr) {
2716     return kVersymNotNeeded;
2717   }
2718 
2719   ElfW(Versym) result = kVersymGlobal;
2720 
2721   if (!for_each_verdef(si,
2722     [&](size_t, const ElfW(Verdef)* verdef, const ElfW(Verdaux)* verdaux) {
2723       if (verdef->vd_hash == vi->elf_hash &&
2724           strcmp(vi->name, si->get_string(verdaux->vda_name)) == 0) {
2725         result = verdef->vd_ndx;
2726         return true;
2727       }
2728 
2729       return false;
2730     }
2731   )) {
2732     // verdef should have already been validated in prelink_image.
2733     async_safe_fatal("invalid verdef after prelinking: %s, %s",
2734                      si->get_realpath(), linker_get_error_buffer());
2735   }
2736 
2737   return result;
2738 }
2739 
2740 // Validate the library's verdef section. On error, returns false and invokes DL_ERR.
validate_verdef_section(const soinfo * si)2741 bool validate_verdef_section(const soinfo* si) {
2742   return for_each_verdef(si,
2743     [&](size_t, const ElfW(Verdef)*, const ElfW(Verdaux)*) {
2744       return false;
2745     });
2746 }
2747 
init_verdef(const soinfo * si_from)2748 bool VersionTracker::init_verdef(const soinfo* si_from) {
2749   return for_each_verdef(si_from,
2750     [&](size_t, const ElfW(Verdef)* verdef, const ElfW(Verdaux)* verdaux) {
2751       add_version_info(verdef->vd_ndx, verdef->vd_hash,
2752           si_from->get_string(verdaux->vda_name), si_from);
2753       return false;
2754     }
2755   );
2756 }
2757 
init(const soinfo * si_from)2758 bool VersionTracker::init(const soinfo* si_from) {
2759   if (!si_from->has_min_version(2)) {
2760     return true;
2761   }
2762 
2763   return init_verneed(si_from) && init_verdef(si_from);
2764 }
2765 
2766 // TODO (dimitry): Methods below need to be moved out of soinfo
2767 // and in more isolated file in order minimize dependencies on
2768 // unnecessary object in the linker binary. Consider making them
2769 // independent from soinfo (?).
lookup_version_info(const VersionTracker & version_tracker,ElfW (Word)sym,const char * sym_name,const version_info ** vi)2770 bool soinfo::lookup_version_info(const VersionTracker& version_tracker, ElfW(Word) sym,
2771                                  const char* sym_name, const version_info** vi) {
2772   const ElfW(Versym)* sym_ver_ptr = get_versym(sym);
2773   ElfW(Versym) sym_ver = sym_ver_ptr == nullptr ? 0 : *sym_ver_ptr;
2774 
2775   if (sym_ver != VER_NDX_LOCAL && sym_ver != VER_NDX_GLOBAL) {
2776     *vi = version_tracker.get_version_info(sym_ver);
2777 
2778     if (*vi == nullptr) {
2779       DL_ERR("cannot find verneed/verdef for version index=%d "
2780           "referenced by symbol \"%s\" at \"%s\"", sym_ver, sym_name, get_realpath());
2781       return false;
2782     }
2783   } else {
2784     // there is no version info
2785     *vi = nullptr;
2786   }
2787 
2788   return true;
2789 }
2790 
apply_relr_reloc(ElfW (Addr)offset,ElfW (Addr)load_bias)2791 static void apply_relr_reloc(ElfW(Addr) offset, ElfW(Addr) load_bias) {
2792   ElfW(Addr) address = offset + load_bias;
2793   *reinterpret_cast<ElfW(Addr)*>(address) += load_bias;
2794 }
2795 
2796 // Process relocations in SHT_RELR section (experimental).
2797 // Details of the encoding are described in this post:
2798 //   https://groups.google.com/d/msg/generic-abi/bX460iggiKg/Pi9aSwwABgAJ
relocate_relr(const ElfW (Relr)* begin,const ElfW (Relr)* end,ElfW (Addr)load_bias)2799 bool relocate_relr(const ElfW(Relr)* begin, const ElfW(Relr)* end, ElfW(Addr) load_bias) {
2800   constexpr size_t wordsize = sizeof(ElfW(Addr));
2801 
2802   ElfW(Addr) base = 0;
2803   for (const ElfW(Relr)* current = begin; current < end; ++current) {
2804     ElfW(Relr) entry = *current;
2805     ElfW(Addr) offset;
2806 
2807     if ((entry&1) == 0) {
2808       // Even entry: encodes the offset for next relocation.
2809       offset = static_cast<ElfW(Addr)>(entry);
2810       apply_relr_reloc(offset, load_bias);
2811       // Set base offset for subsequent bitmap entries.
2812       base = offset + wordsize;
2813       continue;
2814     }
2815 
2816     // Odd entry: encodes bitmap for relocations starting at base.
2817     offset = base;
2818     while (entry != 0) {
2819       entry >>= 1;
2820       if ((entry&1) != 0) {
2821         apply_relr_reloc(offset, load_bias);
2822       }
2823       offset += wordsize;
2824     }
2825 
2826     // Advance base offset by 63 words for 64-bit platforms,
2827     // or 31 words for 32-bit platforms.
2828     base += (8*wordsize - 1) * wordsize;
2829   }
2830   return true;
2831 }
2832 
2833 // An empty list of soinfos
2834 static soinfo_list_t g_empty_list;
2835 
prelink_image()2836 bool soinfo::prelink_image() {
2837   if (flags_ & FLAG_PRELINKED) return true;
2838   /* Extract dynamic section */
2839   ElfW(Word) dynamic_flags = 0;
2840   phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
2841 
2842   /* We can't log anything until the linker is relocated */
2843   bool relocating_linker = (flags_ & FLAG_LINKER) != 0;
2844   if (!relocating_linker) {
2845     INFO("[ Linking \"%s\" ]", get_realpath());
2846     DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags_);
2847   }
2848 
2849   if (dynamic == nullptr) {
2850     if (!relocating_linker) {
2851       DL_ERR("missing PT_DYNAMIC in \"%s\"", get_realpath());
2852     }
2853     return false;
2854   } else {
2855     if (!relocating_linker) {
2856       DEBUG("dynamic = %p", dynamic);
2857     }
2858   }
2859 
2860 #if defined(__arm__)
2861   (void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
2862                                   &ARM_exidx, &ARM_exidx_count);
2863 #endif
2864 
2865   TlsSegment tls_segment;
2866   if (__bionic_get_tls_segment(phdr, phnum, load_bias, &tls_segment)) {
2867     // The loader does not (currently) support ELF TLS, so it shouldn't have
2868     // a TLS segment.
2869     CHECK(!relocating_linker && "TLS not supported in loader");
2870     if (!__bionic_check_tls_align(tls_segment.aligned_size.align.value)) {
2871       DL_ERR("TLS segment alignment in \"%s\" is not a power of 2: %zu", get_realpath(),
2872              tls_segment.aligned_size.align.value);
2873       return false;
2874     }
2875     tls_ = std::make_unique<soinfo_tls>();
2876     tls_->segment = tls_segment;
2877   }
2878 
2879   // Extract useful information from dynamic section.
2880   // Note that: "Except for the DT_NULL element at the end of the array,
2881   // and the relative order of DT_NEEDED elements, entries may appear in any order."
2882   //
2883   // source: http://www.sco.com/developers/gabi/1998-04-29/ch5.dynamic.html
2884   uint32_t needed_count = 0;
2885   for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
2886     DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
2887           d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
2888     switch (d->d_tag) {
2889       case DT_SONAME:
2890         // this is parsed after we have strtab initialized (see below).
2891         break;
2892 
2893       case DT_HASH:
2894         nbucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
2895         nchain_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
2896         bucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
2897         chain_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket_ * 4);
2898         break;
2899 
2900       case DT_GNU_HASH:
2901         gnu_nbucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
2902         // skip symndx
2903         gnu_maskwords_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[2];
2904         gnu_shift2_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[3];
2905 
2906         gnu_bloom_filter_ = reinterpret_cast<ElfW(Addr)*>(load_bias + d->d_un.d_ptr + 16);
2907         gnu_bucket_ = reinterpret_cast<uint32_t*>(gnu_bloom_filter_ + gnu_maskwords_);
2908         // amend chain for symndx = header[1]
2909         gnu_chain_ = gnu_bucket_ + gnu_nbucket_ -
2910             reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
2911 
2912         if (!powerof2(gnu_maskwords_)) {
2913           DL_ERR("invalid maskwords for gnu_hash = 0x%x, in \"%s\" expecting power to two",
2914               gnu_maskwords_, get_realpath());
2915           return false;
2916         }
2917         --gnu_maskwords_;
2918 
2919         flags_ |= FLAG_GNU_HASH;
2920         break;
2921 
2922       case DT_STRTAB:
2923         strtab_ = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
2924         break;
2925 
2926       case DT_STRSZ:
2927         strtab_size_ = d->d_un.d_val;
2928         break;
2929 
2930       case DT_SYMTAB:
2931         symtab_ = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
2932         break;
2933 
2934       case DT_SYMENT:
2935         if (d->d_un.d_val != sizeof(ElfW(Sym))) {
2936           DL_ERR("invalid DT_SYMENT: %zd in \"%s\"",
2937               static_cast<size_t>(d->d_un.d_val), get_realpath());
2938           return false;
2939         }
2940         break;
2941 
2942       case DT_PLTREL:
2943 #if defined(USE_RELA)
2944         if (d->d_un.d_val != DT_RELA) {
2945           DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_RELA", get_realpath());
2946           return false;
2947         }
2948 #else
2949         if (d->d_un.d_val != DT_REL) {
2950           DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_REL", get_realpath());
2951           return false;
2952         }
2953 #endif
2954         break;
2955 
2956       case DT_JMPREL:
2957 #if defined(USE_RELA)
2958         plt_rela_ = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2959 #else
2960         plt_rel_ = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
2961 #endif
2962         break;
2963 
2964       case DT_PLTRELSZ:
2965 #if defined(USE_RELA)
2966         plt_rela_count_ = d->d_un.d_val / sizeof(ElfW(Rela));
2967 #else
2968         plt_rel_count_ = d->d_un.d_val / sizeof(ElfW(Rel));
2969 #endif
2970         break;
2971 
2972       case DT_PLTGOT:
2973         // Ignored (because RTLD_LAZY is not supported).
2974         break;
2975 
2976       case DT_DEBUG:
2977         // Set the DT_DEBUG entry to the address of _r_debug for GDB
2978         // if the dynamic table is writable
2979         if ((dynamic_flags & PF_W) != 0) {
2980           d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
2981         }
2982         break;
2983 #if defined(USE_RELA)
2984       case DT_RELA:
2985         rela_ = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
2986         break;
2987 
2988       case DT_RELASZ:
2989         rela_count_ = d->d_un.d_val / sizeof(ElfW(Rela));
2990         break;
2991 
2992       case DT_ANDROID_RELA:
2993         android_relocs_ = reinterpret_cast<uint8_t*>(load_bias + d->d_un.d_ptr);
2994         break;
2995 
2996       case DT_ANDROID_RELASZ:
2997         android_relocs_size_ = d->d_un.d_val;
2998         break;
2999 
3000       case DT_ANDROID_REL:
3001         DL_ERR("unsupported DT_ANDROID_REL in \"%s\"", get_realpath());
3002         return false;
3003 
3004       case DT_ANDROID_RELSZ:
3005         DL_ERR("unsupported DT_ANDROID_RELSZ in \"%s\"", get_realpath());
3006         return false;
3007 
3008       case DT_RELAENT:
3009         if (d->d_un.d_val != sizeof(ElfW(Rela))) {
3010           DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
3011           return false;
3012         }
3013         break;
3014 
3015       // Ignored (see DT_RELCOUNT comments for details).
3016       case DT_RELACOUNT:
3017         break;
3018 
3019       case DT_REL:
3020         DL_ERR("unsupported DT_REL in \"%s\"", get_realpath());
3021         return false;
3022 
3023       case DT_RELSZ:
3024         DL_ERR("unsupported DT_RELSZ in \"%s\"", get_realpath());
3025         return false;
3026 
3027 #else
3028       case DT_REL:
3029         rel_ = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
3030         break;
3031 
3032       case DT_RELSZ:
3033         rel_count_ = d->d_un.d_val / sizeof(ElfW(Rel));
3034         break;
3035 
3036       case DT_RELENT:
3037         if (d->d_un.d_val != sizeof(ElfW(Rel))) {
3038           DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
3039           return false;
3040         }
3041         break;
3042 
3043       case DT_ANDROID_REL:
3044         android_relocs_ = reinterpret_cast<uint8_t*>(load_bias + d->d_un.d_ptr);
3045         break;
3046 
3047       case DT_ANDROID_RELSZ:
3048         android_relocs_size_ = d->d_un.d_val;
3049         break;
3050 
3051       case DT_ANDROID_RELA:
3052         DL_ERR("unsupported DT_ANDROID_RELA in \"%s\"", get_realpath());
3053         return false;
3054 
3055       case DT_ANDROID_RELASZ:
3056         DL_ERR("unsupported DT_ANDROID_RELASZ in \"%s\"", get_realpath());
3057         return false;
3058 
3059       // "Indicates that all RELATIVE relocations have been concatenated together,
3060       // and specifies the RELATIVE relocation count."
3061       //
3062       // TODO: Spec also mentions that this can be used to optimize relocation process;
3063       // Not currently used by bionic linker - ignored.
3064       case DT_RELCOUNT:
3065         break;
3066 
3067       case DT_RELA:
3068         DL_ERR("unsupported DT_RELA in \"%s\"", get_realpath());
3069         return false;
3070 
3071       case DT_RELASZ:
3072         DL_ERR("unsupported DT_RELASZ in \"%s\"", get_realpath());
3073         return false;
3074 
3075 #endif
3076       case DT_RELR:
3077       case DT_ANDROID_RELR:
3078         relr_ = reinterpret_cast<ElfW(Relr)*>(load_bias + d->d_un.d_ptr);
3079         break;
3080 
3081       case DT_RELRSZ:
3082       case DT_ANDROID_RELRSZ:
3083         relr_count_ = d->d_un.d_val / sizeof(ElfW(Relr));
3084         break;
3085 
3086       case DT_RELRENT:
3087       case DT_ANDROID_RELRENT:
3088         if (d->d_un.d_val != sizeof(ElfW(Relr))) {
3089           DL_ERR("invalid DT_RELRENT: %zd", static_cast<size_t>(d->d_un.d_val));
3090           return false;
3091         }
3092         break;
3093 
3094       // Ignored (see DT_RELCOUNT comments for details).
3095       // There is no DT_RELRCOUNT specifically because it would only be ignored.
3096       case DT_ANDROID_RELRCOUNT:
3097         break;
3098 
3099       case DT_INIT:
3100         init_func_ = reinterpret_cast<linker_ctor_function_t>(load_bias + d->d_un.d_ptr);
3101         DEBUG("%s constructors (DT_INIT) found at %p", get_realpath(), init_func_);
3102         break;
3103 
3104       case DT_FINI:
3105         fini_func_ = reinterpret_cast<linker_dtor_function_t>(load_bias + d->d_un.d_ptr);
3106         DEBUG("%s destructors (DT_FINI) found at %p", get_realpath(), fini_func_);
3107         break;
3108 
3109       case DT_INIT_ARRAY:
3110         init_array_ = reinterpret_cast<linker_ctor_function_t*>(load_bias + d->d_un.d_ptr);
3111         DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", get_realpath(), init_array_);
3112         break;
3113 
3114       case DT_INIT_ARRAYSZ:
3115         init_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
3116         break;
3117 
3118       case DT_FINI_ARRAY:
3119         fini_array_ = reinterpret_cast<linker_dtor_function_t*>(load_bias + d->d_un.d_ptr);
3120         DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", get_realpath(), fini_array_);
3121         break;
3122 
3123       case DT_FINI_ARRAYSZ:
3124         fini_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
3125         break;
3126 
3127       case DT_PREINIT_ARRAY:
3128         preinit_array_ = reinterpret_cast<linker_ctor_function_t*>(load_bias + d->d_un.d_ptr);
3129         DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", get_realpath(), preinit_array_);
3130         break;
3131 
3132       case DT_PREINIT_ARRAYSZ:
3133         preinit_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
3134         break;
3135 
3136       case DT_TEXTREL:
3137 #if defined(__LP64__)
3138         DL_ERR("\"%s\" has text relocations", get_realpath());
3139         return false;
3140 #else
3141         has_text_relocations = true;
3142         break;
3143 #endif
3144 
3145       case DT_SYMBOLIC:
3146         has_DT_SYMBOLIC = true;
3147         break;
3148 
3149       case DT_NEEDED:
3150         ++needed_count;
3151         break;
3152 
3153       case DT_FLAGS:
3154         if (d->d_un.d_val & DF_TEXTREL) {
3155 #if defined(__LP64__)
3156           DL_ERR("\"%s\" has text relocations", get_realpath());
3157           return false;
3158 #else
3159           has_text_relocations = true;
3160 #endif
3161         }
3162         if (d->d_un.d_val & DF_SYMBOLIC) {
3163           has_DT_SYMBOLIC = true;
3164         }
3165         break;
3166 
3167       case DT_FLAGS_1:
3168         set_dt_flags_1(d->d_un.d_val);
3169 
3170         if ((d->d_un.d_val & ~SUPPORTED_DT_FLAGS_1) != 0) {
3171           DL_WARN("Warning: \"%s\" has unsupported flags DT_FLAGS_1=%p "
3172                   "(ignoring unsupported flags)",
3173                   get_realpath(), reinterpret_cast<void*>(d->d_un.d_val));
3174         }
3175         break;
3176 
3177       // Ignored: "Its use has been superseded by the DF_BIND_NOW flag"
3178       case DT_BIND_NOW:
3179         break;
3180 
3181       case DT_VERSYM:
3182         versym_ = reinterpret_cast<ElfW(Versym)*>(load_bias + d->d_un.d_ptr);
3183         break;
3184 
3185       case DT_VERDEF:
3186         verdef_ptr_ = load_bias + d->d_un.d_ptr;
3187         break;
3188       case DT_VERDEFNUM:
3189         verdef_cnt_ = d->d_un.d_val;
3190         break;
3191 
3192       case DT_VERNEED:
3193         verneed_ptr_ = load_bias + d->d_un.d_ptr;
3194         break;
3195 
3196       case DT_VERNEEDNUM:
3197         verneed_cnt_ = d->d_un.d_val;
3198         break;
3199 
3200       case DT_RUNPATH:
3201         // this is parsed after we have strtab initialized (see below).
3202         break;
3203 
3204       case DT_TLSDESC_GOT:
3205       case DT_TLSDESC_PLT:
3206         // These DT entries are used for lazy TLSDESC relocations. Bionic
3207         // resolves everything eagerly, so these can be ignored.
3208         break;
3209 
3210 #if defined(__aarch64__)
3211       case DT_AARCH64_BTI_PLT:
3212       case DT_AARCH64_PAC_PLT:
3213       case DT_AARCH64_VARIANT_PCS:
3214         // Ignored: AArch64 processor-specific dynamic array tags.
3215         break;
3216       case DT_AARCH64_MEMTAG_MODE:
3217         memtag_dynamic_entries_.has_memtag_mode = true;
3218         memtag_dynamic_entries_.memtag_mode = d->d_un.d_val;
3219         break;
3220       case DT_AARCH64_MEMTAG_HEAP:
3221         memtag_dynamic_entries_.memtag_heap = d->d_un.d_val;
3222         break;
3223       // The AArch64 MemtagABI originally erroneously defined
3224       // DT_AARCH64_MEMTAG_STACK as `d_ptr`, which is why the dynamic tag value
3225       // is odd (`0x7000000c`). `d_val` is clearly the correct semantics, and so
3226       // this was fixed in the ABI, but the value (0x7000000c) didn't change
3227       // because we already had Android binaries floating around with dynamic
3228       // entries, and didn't want to create a whole new dynamic entry and
3229       // reserve a value just to fix that tiny mistake. P.S. lld was always
3230       // outputting DT_AARCH64_MEMTAG_STACK as `d_val` anyway.
3231       case DT_AARCH64_MEMTAG_STACK:
3232         memtag_dynamic_entries_.memtag_stack = d->d_un.d_val;
3233         break;
3234       // Same as above, except DT_AARCH64_MEMTAG_GLOBALS was incorrectly defined
3235       // as `d_val` (hence an even value of `0x7000000d`), when it should have
3236       // been `d_ptr` all along. lld has always outputted this as `d_ptr`.
3237       case DT_AARCH64_MEMTAG_GLOBALS:
3238         memtag_dynamic_entries_.memtag_globals = reinterpret_cast<void*>(load_bias + d->d_un.d_ptr);
3239         break;
3240       case DT_AARCH64_MEMTAG_GLOBALSSZ:
3241         memtag_dynamic_entries_.memtag_globalssz = d->d_un.d_val;
3242         break;
3243 #endif
3244 
3245       default:
3246         if (!relocating_linker) {
3247           const char* tag_name;
3248           if (d->d_tag == DT_RPATH) {
3249             tag_name = "DT_RPATH";
3250           } else if (d->d_tag == DT_ENCODING) {
3251             tag_name = "DT_ENCODING";
3252           } else if (d->d_tag >= DT_LOOS && d->d_tag <= DT_HIOS) {
3253             tag_name = "unknown OS-specific";
3254           } else if (d->d_tag >= DT_LOPROC && d->d_tag <= DT_HIPROC) {
3255             tag_name = "unknown processor-specific";
3256           } else {
3257             tag_name = "unknown";
3258           }
3259           DL_WARN("Warning: \"%s\" unused DT entry: %s (type %p arg %p) (ignoring)",
3260                   get_realpath(),
3261                   tag_name,
3262                   reinterpret_cast<void*>(d->d_tag),
3263                   reinterpret_cast<void*>(d->d_un.d_val));
3264         }
3265         break;
3266     }
3267   }
3268 
3269   DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
3270         reinterpret_cast<void*>(base), strtab_, symtab_);
3271 
3272   // Validity checks.
3273   if (relocating_linker && needed_count != 0) {
3274     DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
3275     return false;
3276   }
3277   if (nbucket_ == 0 && gnu_nbucket_ == 0) {
3278     DL_ERR("empty/missing DT_HASH/DT_GNU_HASH in \"%s\" "
3279         "(new hash type from the future?)", get_realpath());
3280     return false;
3281   }
3282   if (strtab_ == nullptr) {
3283     DL_ERR("empty/missing DT_STRTAB in \"%s\"", get_realpath());
3284     return false;
3285   }
3286   if (symtab_ == nullptr) {
3287     DL_ERR("empty/missing DT_SYMTAB in \"%s\"", get_realpath());
3288     return false;
3289   }
3290 
3291   // Second pass - parse entries relying on strtab. Skip this while relocating the linker so as to
3292   // avoid doing heap allocations until later in the linker's initialization.
3293   if (!relocating_linker) {
3294     for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
3295       switch (d->d_tag) {
3296         case DT_SONAME:
3297           set_soname(get_string(d->d_un.d_val));
3298           break;
3299         case DT_RUNPATH:
3300           set_dt_runpath(get_string(d->d_un.d_val));
3301           break;
3302       }
3303     }
3304   }
3305 
3306   // Before M release, linker was using basename in place of soname. In the case when DT_SONAME is
3307   // absent some apps stop working because they can't find DT_NEEDED library by soname. This
3308   // workaround should keep them working. (Applies only for apps targeting sdk version < M.) Make
3309   // an exception for the main executable, which does not need to have DT_SONAME. The linker has an
3310   // DT_SONAME but the soname_ field is initialized later on.
3311   if (soname_.empty() && this != solist_get_somain() && !relocating_linker &&
3312       get_application_target_sdk_version() < 23) {
3313     soname_ = basename(realpath_.c_str());
3314     DL_WARN_documented_change(23, "missing-soname-enforced-for-api-level-23",
3315                               "\"%s\" has no DT_SONAME (will use %s instead)", get_realpath(),
3316                               soname_.c_str());
3317 
3318     // Don't call add_dlwarning because a missing DT_SONAME isn't important enough to show in the UI
3319   }
3320 
3321   // Validate each library's verdef section once, so we don't have to validate
3322   // it each time we look up a symbol with a version.
3323   if (!validate_verdef_section(this)) return false;
3324 
3325   flags_ |= FLAG_PRELINKED;
3326   return true;
3327 }
3328 
link_image(const SymbolLookupList & lookup_list,soinfo * local_group_root,const android_dlextinfo * extinfo,size_t * relro_fd_offset)3329 bool soinfo::link_image(const SymbolLookupList& lookup_list, soinfo* local_group_root,
3330                         const android_dlextinfo* extinfo, size_t* relro_fd_offset) {
3331   if (is_image_linked()) {
3332     // already linked.
3333     return true;
3334   }
3335 
3336   if (g_is_ldd && !is_main_executable()) {
3337     async_safe_format_fd(STDOUT_FILENO, "\t%s => %s (%p)\n", get_soname(),
3338                          get_realpath(), reinterpret_cast<void*>(base));
3339   }
3340 
3341   local_group_root_ = local_group_root;
3342   if (local_group_root_ == nullptr) {
3343     local_group_root_ = this;
3344   }
3345 
3346   if ((flags_ & FLAG_LINKER) == 0 && local_group_root_ == this) {
3347     target_sdk_version_ = get_application_target_sdk_version();
3348   }
3349 
3350 #if !defined(__LP64__)
3351   if (has_text_relocations) {
3352     // Fail if app is targeting M or above.
3353     int app_target_api_level = get_application_target_sdk_version();
3354     if (app_target_api_level >= 23) {
3355       DL_ERR_AND_LOG("\"%s\" has text relocations (%s#Text-Relocations-Enforced-for-API-level-23)",
3356                      get_realpath(), kBionicChangesUrl);
3357       return false;
3358     }
3359     // Make segments writable to allow text relocations to work properly. We will later call
3360     // phdr_table_protect_segments() after all of them are applied.
3361     DL_WARN_documented_change(23,
3362                               "Text-Relocations-Enforced-for-API-level-23",
3363                               "\"%s\" has text relocations",
3364                               get_realpath());
3365     add_dlwarning(get_realpath(), "text relocations");
3366     if (phdr_table_unprotect_segments(phdr, phnum, load_bias, should_pad_segments_) < 0) {
3367       DL_ERR("can't unprotect loadable segments for \"%s\": %s", get_realpath(), strerror(errno));
3368       return false;
3369     }
3370   }
3371 #endif
3372 
3373   if (!relocate(lookup_list)) {
3374     return false;
3375   }
3376 
3377   DEBUG("[ finished linking %s ]", get_realpath());
3378 
3379 #if !defined(__LP64__)
3380   if (has_text_relocations) {
3381     // All relocations are done, we can protect our segments back to read-only.
3382     if (phdr_table_protect_segments(phdr, phnum, load_bias, should_pad_segments_) < 0) {
3383       DL_ERR("can't protect segments for \"%s\": %s",
3384              get_realpath(), strerror(errno));
3385       return false;
3386     }
3387   }
3388 #endif
3389 
3390   // We can also turn on GNU RELRO protection if we're not linking the dynamic linker
3391   // itself --- it can't make system calls yet, and will have to call protect_relro later.
3392   if (!is_linker() && !protect_relro()) {
3393     return false;
3394   }
3395 
3396   /* Handle serializing/sharing the RELRO segment */
3397   if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
3398     if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
3399                                        extinfo->relro_fd, relro_fd_offset) < 0) {
3400       DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
3401              get_realpath(), strerror(errno));
3402       return false;
3403     }
3404   } else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
3405     if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
3406                                  extinfo->relro_fd, relro_fd_offset) < 0) {
3407       DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
3408              get_realpath(), strerror(errno));
3409       return false;
3410     }
3411   }
3412 
3413   ++g_module_load_counter;
3414   notify_gdb_of_load(this);
3415   set_image_linked();
3416   return true;
3417 }
3418 
protect_relro()3419 bool soinfo::protect_relro() {
3420   if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias, should_pad_segments_) < 0) {
3421     DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
3422            get_realpath(), strerror(errno));
3423     return false;
3424   }
3425   return true;
3426 }
3427 
init_default_namespace_no_config(bool is_asan,bool is_hwasan)3428 static std::vector<android_namespace_t*> init_default_namespace_no_config(bool is_asan, bool is_hwasan) {
3429   g_default_namespace.set_isolated(false);
3430   auto default_ld_paths = is_asan ? kAsanDefaultLdPaths : (
3431     is_hwasan ? kHwsanDefaultLdPaths : kDefaultLdPaths);
3432 
3433   char real_path[PATH_MAX];
3434   std::vector<std::string> ld_default_paths;
3435   for (size_t i = 0; default_ld_paths[i] != nullptr; ++i) {
3436     if (realpath(default_ld_paths[i], real_path) != nullptr) {
3437       ld_default_paths.push_back(real_path);
3438     } else {
3439       ld_default_paths.push_back(default_ld_paths[i]);
3440     }
3441   }
3442 
3443   g_default_namespace.set_default_library_paths(std::move(ld_default_paths));
3444 
3445   std::vector<android_namespace_t*> namespaces;
3446   namespaces.push_back(&g_default_namespace);
3447   return namespaces;
3448 }
3449 
3450 // Given an `executable_path` starting with "/apex/<name>/bin/, return
3451 // "/linkerconfig/<name>/ld.config.txt", which is the auto-generated config file for the APEX by the
3452 // linkerconfig tool.
get_ld_config_file_apex_path(const char * executable_path)3453 static std::string get_ld_config_file_apex_path(const char* executable_path) {
3454   std::vector<std::string> paths = android::base::Split(executable_path, "/");
3455   if (paths.size() >= 5 && paths[1] == "apex" && paths[3] == "bin") {
3456     std::string generated_apex_config = "/linkerconfig/" + paths[2] + "/ld.config.txt";
3457     if (file_exists(generated_apex_config.c_str())) {
3458       return generated_apex_config;
3459     }
3460   }
3461   return "";
3462 }
3463 
get_ld_config_file_vndk_path()3464 static std::string get_ld_config_file_vndk_path() {
3465   if (android::base::GetBoolProperty("ro.vndk.lite", false)) {
3466     return kLdConfigVndkLiteFilePath;
3467   }
3468 
3469   std::string ld_config_file_vndk = kLdConfigFilePath;
3470   size_t insert_pos = ld_config_file_vndk.find_last_of('.');
3471   if (insert_pos == std::string::npos) {
3472     insert_pos = ld_config_file_vndk.length();
3473   }
3474   ld_config_file_vndk.insert(insert_pos, Config::get_vndk_version_string('.'));
3475   return ld_config_file_vndk;
3476 }
3477 
is_linker_config_expected(const char * executable_path)3478 bool is_linker_config_expected(const char* executable_path) {
3479   // Do not raise message from a host environment which is expected to miss generated linker
3480   // configuration.
3481 #if !defined(__ANDROID__)
3482   return false;
3483 #endif
3484 
3485   if (strcmp(executable_path, "/system/bin/init") == 0) {
3486     // Generated linker configuration can be missed from processes executed
3487     // with init binary
3488     return false;
3489   }
3490 
3491   return true;
3492 }
3493 
get_ld_config_file_path(const char * executable_path)3494 static std::string get_ld_config_file_path(const char* executable_path) {
3495 #ifdef USE_LD_CONFIG_FILE
3496   // This is a debugging/testing only feature. Must not be available on
3497   // production builds.
3498   const char* ld_config_file_env = getenv("LD_CONFIG_FILE");
3499   if (ld_config_file_env != nullptr && file_exists(ld_config_file_env)) {
3500     return ld_config_file_env;
3501   }
3502 #endif
3503 
3504   std::string path = get_ld_config_file_apex_path(executable_path);
3505   if (!path.empty()) {
3506     if (file_exists(path.c_str())) {
3507       return path;
3508     }
3509     DL_WARN("Warning: couldn't read config file \"%s\" for \"%s\"",
3510             path.c_str(), executable_path);
3511   }
3512 
3513   path = kLdConfigArchFilePath;
3514   if (file_exists(path.c_str())) {
3515     return path;
3516   }
3517 
3518   if (file_exists(kLdGeneratedConfigFilePath)) {
3519     return kLdGeneratedConfigFilePath;
3520   }
3521 
3522   if (is_linker_config_expected(executable_path)) {
3523     DL_WARN("Warning: failed to find generated linker configuration from \"%s\"",
3524             kLdGeneratedConfigFilePath);
3525   }
3526 
3527   path = get_ld_config_file_vndk_path();
3528   if (file_exists(path.c_str())) {
3529     return path;
3530   }
3531 
3532   return kLdConfigFilePath;
3533 }
3534 
3535 
init_default_namespaces(const char * executable_path)3536 std::vector<android_namespace_t*> init_default_namespaces(const char* executable_path) {
3537   g_default_namespace.set_name("(default)");
3538 
3539   soinfo* somain = solist_get_somain();
3540 
3541   const char *interp = phdr_table_get_interpreter_name(somain->phdr, somain->phnum,
3542                                                        somain->load_bias);
3543   const char* bname = (interp != nullptr) ? basename(interp) : nullptr;
3544 
3545   g_is_asan = bname != nullptr &&
3546               (strcmp(bname, "linker_asan") == 0 ||
3547                strcmp(bname, "linker_asan64") == 0);
3548 
3549 #if defined(__aarch64__)
3550   // HWASan is only supported on AArch64.
3551   // The AT_SECURE restriction is because this is a debug feature that does
3552   // not need to work on secure binaries, it doesn't hurt to disallow the
3553   // environment variable for them, as it impacts the program execution.
3554   char* hwasan_env = getenv("LD_HWASAN");
3555   g_is_hwasan = (bname != nullptr &&
3556               strcmp(bname, "linker_hwasan64") == 0) ||
3557               (hwasan_env != nullptr && !getauxval(AT_SECURE) && strcmp(hwasan_env, "1") == 0);
3558 #endif
3559   const Config* config = nullptr;
3560 
3561   {
3562     std::string ld_config_file_path = get_ld_config_file_path(executable_path);
3563     INFO("[ Reading linker config \"%s\" ]", ld_config_file_path.c_str());
3564     ScopedTrace trace(("linker config " + ld_config_file_path).c_str());
3565     std::string error_msg;
3566     if (!Config::read_binary_config(ld_config_file_path.c_str(), executable_path, g_is_asan, g_is_hwasan,
3567                                     &config, &error_msg)) {
3568       if (!error_msg.empty()) {
3569         DL_WARN("Warning: couldn't read '%s' for '%s' (using default configuration instead): %s",
3570                 ld_config_file_path.c_str(), executable_path, error_msg.c_str());
3571       }
3572       config = nullptr;
3573     }
3574   }
3575 
3576   if (config == nullptr) {
3577     return init_default_namespace_no_config(g_is_asan, g_is_hwasan);
3578   }
3579 
3580   const auto& namespace_configs = config->namespace_configs();
3581   std::unordered_map<std::string, android_namespace_t*> namespaces;
3582 
3583   // 1. Initialize default namespace
3584   const NamespaceConfig* default_ns_config = config->default_namespace_config();
3585 
3586   g_default_namespace.set_isolated(default_ns_config->isolated());
3587   g_default_namespace.set_default_library_paths(default_ns_config->search_paths());
3588   g_default_namespace.set_permitted_paths(default_ns_config->permitted_paths());
3589 
3590   namespaces[default_ns_config->name()] = &g_default_namespace;
3591   if (default_ns_config->visible()) {
3592     g_exported_namespaces[default_ns_config->name()] = &g_default_namespace;
3593   }
3594 
3595   // 2. Initialize other namespaces
3596 
3597   for (auto& ns_config : namespace_configs) {
3598     if (namespaces.find(ns_config->name()) != namespaces.end()) {
3599       continue;
3600     }
3601 
3602     android_namespace_t* ns = new (g_namespace_allocator.alloc()) android_namespace_t();
3603     ns->set_name(ns_config->name());
3604     ns->set_isolated(ns_config->isolated());
3605     ns->set_default_library_paths(ns_config->search_paths());
3606     ns->set_permitted_paths(ns_config->permitted_paths());
3607     ns->set_allowed_libs(ns_config->allowed_libs());
3608 
3609     namespaces[ns_config->name()] = ns;
3610     if (ns_config->visible()) {
3611       g_exported_namespaces[ns_config->name()] = ns;
3612     }
3613   }
3614 
3615   // 3. Establish links between namespaces
3616   for (auto& ns_config : namespace_configs) {
3617     auto it_from = namespaces.find(ns_config->name());
3618     CHECK(it_from != namespaces.end());
3619     android_namespace_t* namespace_from = it_from->second;
3620     for (const NamespaceLinkConfig& ns_link : ns_config->links()) {
3621       auto it_to = namespaces.find(ns_link.ns_name());
3622       CHECK(it_to != namespaces.end());
3623       android_namespace_t* namespace_to = it_to->second;
3624       if (ns_link.allow_all_shared_libs()) {
3625         link_namespaces_all_libs(namespace_from, namespace_to);
3626       } else {
3627         link_namespaces(namespace_from, namespace_to, ns_link.shared_libs().c_str());
3628       }
3629     }
3630   }
3631   // we can no longer rely on the fact that libdl.so is part of default namespace
3632   // this is why we want to add ld-android.so to all namespaces from ld.config.txt
3633   soinfo* ld_android_so = solist_get_head();
3634 
3635   // we also need vdso to be available for all namespaces (if present)
3636   soinfo* vdso = solist_get_vdso();
3637   for (auto it : namespaces) {
3638     if (it.second != &g_default_namespace) {
3639       it.second->add_soinfo(ld_android_so);
3640       if (vdso != nullptr) {
3641         it.second->add_soinfo(vdso);
3642       }
3643       // somain and ld_preloads are added to these namespaces after LD_PRELOAD libs are linked
3644     }
3645   }
3646 
3647   set_application_target_sdk_version(config->target_sdk_version());
3648 
3649   std::vector<android_namespace_t*> created_namespaces;
3650   created_namespaces.reserve(namespaces.size());
3651   for (const auto& kv : namespaces) {
3652     created_namespaces.push_back(kv.second);
3653   }
3654   return created_namespaces;
3655 }
3656 
3657 // This function finds a namespace exported in ld.config.txt by its name.
3658 // A namespace can be exported by setting .visible property to true.
get_exported_namespace(const char * name)3659 android_namespace_t* get_exported_namespace(const char* name) {
3660   if (name == nullptr) {
3661     return nullptr;
3662   }
3663   auto it = g_exported_namespaces.find(std::string(name));
3664   if (it == g_exported_namespaces.end()) {
3665     return nullptr;
3666   }
3667   return it->second;
3668 }
3669 
purge_unused_memory()3670 void purge_unused_memory() {
3671   // For now, we only purge the memory used by LoadTask because we know those
3672   // are temporary objects.
3673   //
3674   // Purging other LinkerBlockAllocator hardly yields much because they hold
3675   // information about namespaces and opened libraries, which are not freed
3676   // when the control leaves the linker.
3677   //
3678   // Purging BionicAllocator may give us a few dirty pages back, but those pages
3679   // would be already zeroed out, so they compress easily in ZRAM.  Therefore,
3680   // it is not worth munmap()'ing those pages.
3681   TypeBasedAllocator<LoadTask>::purge();
3682 }
3683