DynamicLinker.cpp 24 KB

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  1. /*
  2. * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
  3. * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
  4. * Copyright (c) 2021, the SerenityOS developers.
  5. * Copyright (c) 2022, Jesse Buhagiar <jooster669@gmail.com>
  6. *
  7. * SPDX-License-Identifier: BSD-2-Clause
  8. */
  9. #include <AK/ByteBuffer.h>
  10. #include <AK/Debug.h>
  11. #include <AK/HashMap.h>
  12. #include <AK/HashTable.h>
  13. #include <AK/LexicalPath.h>
  14. #include <AK/NonnullRefPtrVector.h>
  15. #include <AK/ScopeGuard.h>
  16. #include <AK/Vector.h>
  17. #include <LibC/bits/pthread_integration.h>
  18. #include <LibC/link.h>
  19. #include <LibC/sys/mman.h>
  20. #include <LibC/unistd.h>
  21. #include <LibELF/AuxiliaryVector.h>
  22. #include <LibELF/DynamicLinker.h>
  23. #include <LibELF/DynamicLoader.h>
  24. #include <LibELF/DynamicObject.h>
  25. #include <LibELF/Hashes.h>
  26. #include <bits/dlfcn_integration.h>
  27. #include <dlfcn.h>
  28. #include <fcntl.h>
  29. #include <pthread.h>
  30. #include <string.h>
  31. #include <sys/types.h>
  32. #include <syscall.h>
  33. namespace ELF {
  34. static HashMap<String, NonnullRefPtr<ELF::DynamicLoader>> s_loaders;
  35. static String s_main_program_path;
  36. static OrderedHashMap<String, NonnullRefPtr<ELF::DynamicObject>> s_global_objects;
  37. using EntryPointFunction = int (*)(int, char**, char**);
  38. using LibCExitFunction = void (*)(int);
  39. using DlIteratePhdrCallbackFunction = int (*)(struct dl_phdr_info*, size_t, void*);
  40. using DlIteratePhdrFunction = int (*)(DlIteratePhdrCallbackFunction, void*);
  41. extern "C" [[noreturn]] void _invoke_entry(int argc, char** argv, char** envp, EntryPointFunction entry);
  42. static size_t s_current_tls_offset = 0;
  43. static size_t s_total_tls_size = 0;
  44. static size_t s_allocated_tls_block_size = 0;
  45. static char** s_envp = nullptr;
  46. static LibCExitFunction s_libc_exit = nullptr;
  47. static __pthread_mutex_t s_loader_lock = __PTHREAD_MUTEX_INITIALIZER;
  48. static String s_cwd;
  49. static bool s_allowed_to_check_environment_variables { false };
  50. static bool s_do_breakpoint_trap_before_entry { false };
  51. static StringView s_ld_library_path;
  52. static StringView s_main_program_pledge_promises;
  53. static String s_loader_pledge_promises;
  54. static Result<void, DlErrorMessage> __dlclose(void* handle);
  55. static Result<void*, DlErrorMessage> __dlopen(char const* filename, int flags);
  56. static Result<void*, DlErrorMessage> __dlsym(void* handle, char const* symbol_name);
  57. static Result<void, DlErrorMessage> __dladdr(void* addr, Dl_info* info);
  58. Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(StringView name)
  59. {
  60. Optional<DynamicObject::SymbolLookupResult> weak_result;
  61. auto symbol = DynamicObject::HashSymbol { name };
  62. for (auto& lib : s_global_objects) {
  63. auto res = lib.value->lookup_symbol(symbol);
  64. if (!res.has_value())
  65. continue;
  66. if (res.value().bind == STB_GLOBAL)
  67. return res;
  68. if (res.value().bind == STB_WEAK && !weak_result.has_value())
  69. weak_result = res;
  70. // We don't want to allow local symbols to be pulled in to other modules
  71. }
  72. return weak_result;
  73. }
  74. static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> map_library(String const& filepath, int fd)
  75. {
  76. VERIFY(filepath.starts_with('/'));
  77. auto loader = TRY(ELF::DynamicLoader::try_create(fd, filepath));
  78. s_loaders.set(filepath, *loader);
  79. s_current_tls_offset -= loader->tls_size_of_current_object();
  80. if (loader->tls_alignment_of_current_object())
  81. s_current_tls_offset = align_down_to(s_current_tls_offset, loader->tls_alignment_of_current_object());
  82. loader->set_tls_offset(s_current_tls_offset);
  83. // This actually maps the library at the intended and final place.
  84. auto main_library_object = loader->map();
  85. s_global_objects.set(filepath, *main_library_object);
  86. return loader;
  87. }
  88. static Optional<String> resolve_library(String const& name, DynamicObject const& parent_object)
  89. {
  90. // Absolute and relative (to the current working directory) paths are already considered resolved.
  91. // However, ensure that the returned path is absolute and canonical, so pass it through LexicalPath.
  92. if (name.contains('/'))
  93. return LexicalPath::absolute_path(s_cwd, name);
  94. Vector<StringView> search_paths;
  95. // Search RPATH values indicated by the ELF (only if RUNPATH is not present).
  96. if (parent_object.runpath().is_empty())
  97. search_paths.extend(parent_object.rpath().split_view(':'));
  98. // Scan the LD_LIBRARY_PATH environment variable if applicable.
  99. search_paths.extend(s_ld_library_path.split_view(':'));
  100. // Search RUNPATH values indicated by the ELF.
  101. search_paths.extend(parent_object.runpath().split_view(':'));
  102. // Last are the default search paths.
  103. search_paths.append("/usr/lib"sv);
  104. search_paths.append("/usr/local/lib"sv);
  105. for (auto const& search_path : search_paths) {
  106. LexicalPath library_path(search_path.replace("$ORIGIN"sv, LexicalPath::dirname(parent_object.filepath()), ReplaceMode::FirstOnly));
  107. String library_name = library_path.append(name).string();
  108. if (access(library_name.characters(), F_OK) == 0)
  109. return library_name;
  110. }
  111. return {};
  112. }
  113. static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> resolve_and_map_library(String const& name, DynamicObject const& parent_object)
  114. {
  115. auto resolved_library_name = resolve_library(name, parent_object);
  116. if (!resolved_library_name.has_value())
  117. return DlErrorMessage { String::formatted("Could not find required shared library: {}", name) };
  118. int fd = open(resolved_library_name.value().characters(), O_RDONLY);
  119. if (fd < 0)
  120. return DlErrorMessage { String::formatted("Could not open resolved shared library '{}': {}", resolved_library_name.value(), strerror(errno)) };
  121. return map_library(resolved_library_name.value(), fd);
  122. }
  123. static Vector<String> get_dependencies(String const& path)
  124. {
  125. VERIFY(path.starts_with('/'));
  126. auto name = LexicalPath::basename(path);
  127. auto lib = s_loaders.get(path).value();
  128. Vector<String> dependencies;
  129. lib->for_each_needed_library([&dependencies, &name](auto needed_name) {
  130. if (name == needed_name)
  131. return;
  132. dependencies.append(needed_name);
  133. });
  134. return dependencies;
  135. }
  136. static Result<void, DlErrorMessage> map_dependencies(String const& path)
  137. {
  138. VERIFY(path.starts_with('/'));
  139. dbgln_if(DYNAMIC_LOAD_DEBUG, "mapping dependencies for: {}", path);
  140. auto const& parent_object = (*s_loaders.get(path))->dynamic_object();
  141. for (auto const& needed_name : get_dependencies(path)) {
  142. dbgln_if(DYNAMIC_LOAD_DEBUG, "needed library: {}", needed_name.characters());
  143. auto dependency_path = resolve_library(needed_name, parent_object);
  144. if (!dependency_path.has_value())
  145. return DlErrorMessage { String::formatted("Could not find required shared library: {}", needed_name) };
  146. if (!s_loaders.contains(dependency_path.value()) && !s_global_objects.contains(dependency_path.value())) {
  147. auto loader = TRY(resolve_and_map_library(dependency_path.value(), parent_object));
  148. TRY(map_dependencies(loader->filepath()));
  149. }
  150. }
  151. dbgln_if(DYNAMIC_LOAD_DEBUG, "mapped dependencies for {}", path);
  152. return {};
  153. }
  154. static void allocate_tls()
  155. {
  156. s_total_tls_size = 0;
  157. for (auto const& data : s_loaders) {
  158. dbgln_if(DYNAMIC_LOAD_DEBUG, "{}: TLS Size: {}, TLS Alignment: {}", data.key, data.value->tls_size_of_current_object(), data.value->tls_alignment_of_current_object());
  159. s_total_tls_size += data.value->tls_size_of_current_object() + data.value->tls_alignment_of_current_object();
  160. }
  161. if (!s_total_tls_size)
  162. return;
  163. auto page_aligned_size = align_up_to(s_total_tls_size, PAGE_SIZE);
  164. auto initial_tls_data_result = ByteBuffer::create_zeroed(page_aligned_size);
  165. if (initial_tls_data_result.is_error()) {
  166. dbgln("Failed to allocate initial TLS data");
  167. VERIFY_NOT_REACHED();
  168. }
  169. auto& initial_tls_data = initial_tls_data_result.value();
  170. // Initialize TLS data
  171. for (auto const& entry : s_loaders) {
  172. entry.value->copy_initial_tls_data_into(initial_tls_data);
  173. }
  174. void* master_tls = ::allocate_tls((char*)initial_tls_data.data(), initial_tls_data.size());
  175. VERIFY(master_tls != (void*)-1);
  176. dbgln_if(DYNAMIC_LOAD_DEBUG, "from userspace, master_tls: {:p}", master_tls);
  177. s_allocated_tls_block_size = initial_tls_data.size();
  178. }
  179. static int __dl_iterate_phdr(DlIteratePhdrCallbackFunction callback, void* data)
  180. {
  181. pthread_mutex_lock(&s_loader_lock);
  182. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  183. for (auto& it : s_global_objects) {
  184. auto& object = it.value;
  185. auto info = dl_phdr_info {
  186. .dlpi_addr = (ElfW(Addr))object->base_address().as_ptr(),
  187. .dlpi_name = object->filepath().characters(),
  188. .dlpi_phdr = object->program_headers(),
  189. .dlpi_phnum = object->program_header_count()
  190. };
  191. auto res = callback(&info, sizeof(info), data);
  192. if (res != 0)
  193. return res;
  194. }
  195. return 0;
  196. }
  197. static void initialize_libc(DynamicObject& libc)
  198. {
  199. // Traditionally, `_start` of the main program initializes libc.
  200. // However, since some libs use malloc() and getenv() in global constructors,
  201. // we have to initialize libc just after it is loaded.
  202. // Also, we can't just mark `__libc_init` with "__attribute__((constructor))"
  203. // because it uses getenv() internally, so `environ` has to be initialized before we call `__libc_init`.
  204. auto res = libc.lookup_symbol("environ"sv);
  205. VERIFY(res.has_value());
  206. *((char***)res.value().address.as_ptr()) = s_envp;
  207. // __stack_chk_guard should be initialized before anything significant (read: global constructors) is running.
  208. // This is not done in __libc_init, as we definitely have to return from that, and it might affect Loader as well.
  209. res = libc.lookup_symbol("__stack_chk_guard"sv);
  210. VERIFY(res.has_value());
  211. arc4random_buf(res.value().address.as_ptr(), sizeof(size_t));
  212. res = libc.lookup_symbol("__environ_is_malloced"sv);
  213. VERIFY(res.has_value());
  214. *((bool*)res.value().address.as_ptr()) = false;
  215. res = libc.lookup_symbol("exit"sv);
  216. VERIFY(res.has_value());
  217. s_libc_exit = (LibCExitFunction)res.value().address.as_ptr();
  218. res = libc.lookup_symbol("__dl_iterate_phdr"sv);
  219. VERIFY(res.has_value());
  220. *((DlIteratePhdrFunction*)res.value().address.as_ptr()) = __dl_iterate_phdr;
  221. res = libc.lookup_symbol("__dlclose"sv);
  222. VERIFY(res.has_value());
  223. *((DlCloseFunction*)res.value().address.as_ptr()) = __dlclose;
  224. res = libc.lookup_symbol("__dlopen"sv);
  225. VERIFY(res.has_value());
  226. *((DlOpenFunction*)res.value().address.as_ptr()) = __dlopen;
  227. res = libc.lookup_symbol("__dlsym"sv);
  228. VERIFY(res.has_value());
  229. *((DlSymFunction*)res.value().address.as_ptr()) = __dlsym;
  230. res = libc.lookup_symbol("__dladdr"sv);
  231. VERIFY(res.has_value());
  232. *((DlAddrFunction*)res.value().address.as_ptr()) = __dladdr;
  233. res = libc.lookup_symbol("__libc_init"sv);
  234. VERIFY(res.has_value());
  235. typedef void libc_init_func();
  236. ((libc_init_func*)res.value().address.as_ptr())();
  237. }
  238. template<typename Callback>
  239. static void for_each_unfinished_dependency_of(String const& path, HashTable<String>& seen_names, Callback callback)
  240. {
  241. VERIFY(path.starts_with('/'));
  242. auto loader = s_loaders.get(path);
  243. if (!loader.has_value()) {
  244. // Not having a loader here means that the library has already been loaded in at an earlier point,
  245. // and the loader itself was cleared during the end of `linker_main`.
  246. return;
  247. }
  248. if (loader.value()->is_fully_relocated()) {
  249. if (!loader.value()->is_fully_initialized()) {
  250. // If we are ending up here, that possibly means that this library either dlopens itself or a library that depends
  251. // on it while running its initializers. Assuming that this is the only funny thing that the library does, there is
  252. // a reasonable chance that nothing breaks, so just warn and continue.
  253. dbgln("\033[33mWarning:\033[0m Querying for dependencies of '{}' while running its initializers", path);
  254. }
  255. return;
  256. }
  257. if (seen_names.contains(path))
  258. return;
  259. seen_names.set(path);
  260. for (auto const& needed_name : get_dependencies(path)) {
  261. auto dependency_path = *resolve_library(needed_name, loader.value()->dynamic_object());
  262. for_each_unfinished_dependency_of(dependency_path, seen_names, callback);
  263. }
  264. callback(*s_loaders.get(path).value());
  265. }
  266. static NonnullRefPtrVector<DynamicLoader> collect_loaders_for_library(String const& path)
  267. {
  268. VERIFY(path.starts_with('/'));
  269. HashTable<String> seen_names;
  270. NonnullRefPtrVector<DynamicLoader> loaders;
  271. for_each_unfinished_dependency_of(path, seen_names, [&](auto& loader) {
  272. loaders.append(loader);
  273. });
  274. return loaders;
  275. }
  276. static void drop_loader_promise(StringView promise_to_drop)
  277. {
  278. if (s_main_program_pledge_promises.is_empty() || s_loader_pledge_promises.is_empty())
  279. return;
  280. s_loader_pledge_promises = s_loader_pledge_promises.replace(promise_to_drop, ""sv, ReplaceMode::All);
  281. auto extended_promises = String::formatted("{} {}", s_main_program_pledge_promises, s_loader_pledge_promises);
  282. Syscall::SC_pledge_params params {
  283. { extended_promises.characters(), extended_promises.length() },
  284. { nullptr, 0 },
  285. };
  286. int rc = syscall(SC_pledge, &params);
  287. if (rc < 0 && rc > -EMAXERRNO) {
  288. warnln("Failed to drop loader pledge promise: {}. errno={}", promise_to_drop, errno);
  289. _exit(1);
  290. }
  291. }
  292. static Result<void, DlErrorMessage> link_main_library(String const& path, int flags)
  293. {
  294. VERIFY(path.starts_with('/'));
  295. auto loaders = collect_loaders_for_library(path);
  296. for (auto& loader : loaders) {
  297. auto dynamic_object = loader.map();
  298. if (dynamic_object)
  299. s_global_objects.set(dynamic_object->filepath(), *dynamic_object);
  300. }
  301. for (auto& loader : loaders) {
  302. bool success = loader.link(flags);
  303. if (!success) {
  304. return DlErrorMessage { String::formatted("Failed to link library {}", loader.filepath()) };
  305. }
  306. }
  307. for (auto& loader : loaders) {
  308. auto result = loader.load_stage_3(flags);
  309. VERIFY(!result.is_error());
  310. auto& object = result.value();
  311. if (loader.filepath().ends_with("/libsystem.so"sv)) {
  312. VERIFY(!loader.text_segments().is_empty());
  313. for (auto const& segment : loader.text_segments()) {
  314. if (syscall(SC_msyscall, segment.address().get())) {
  315. VERIFY_NOT_REACHED();
  316. }
  317. }
  318. }
  319. if (loader.filepath().ends_with("/libc.so"sv)) {
  320. initialize_libc(*object);
  321. }
  322. }
  323. drop_loader_promise("prot_exec"sv);
  324. for (auto& loader : loaders) {
  325. loader.load_stage_4();
  326. }
  327. return {};
  328. }
  329. static Result<void, DlErrorMessage> __dlclose(void* handle)
  330. {
  331. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlclose: {}", handle);
  332. pthread_mutex_lock(&s_loader_lock);
  333. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  334. // FIXME: this will not currently destroy the dynamic object
  335. // because we're intentionally holding a strong reference to it
  336. // via s_global_objects until there's proper unload support.
  337. auto object = static_cast<ELF::DynamicObject*>(handle);
  338. object->unref();
  339. return {};
  340. }
  341. static Optional<DlErrorMessage> verify_tls_for_dlopen(DynamicLoader const& loader)
  342. {
  343. if (loader.tls_size_of_current_object() == 0)
  344. return {};
  345. if (s_total_tls_size + loader.tls_size_of_current_object() + loader.tls_alignment_of_current_object() > s_allocated_tls_block_size)
  346. return DlErrorMessage("TLS size too large");
  347. bool tls_data_is_all_zero = true;
  348. loader.image().for_each_program_header([&loader, &tls_data_is_all_zero](ELF::Image::ProgramHeader program_header) {
  349. if (program_header.type() != PT_TLS)
  350. return IterationDecision::Continue;
  351. auto* tls_data = (const u8*)loader.image().base_address() + program_header.offset();
  352. for (size_t i = 0; i < program_header.size_in_image(); ++i) {
  353. if (tls_data[i] != 0) {
  354. tls_data_is_all_zero = false;
  355. break;
  356. }
  357. }
  358. return IterationDecision::Break;
  359. });
  360. if (tls_data_is_all_zero)
  361. return {};
  362. return DlErrorMessage("Using dlopen() with libraries that have non-zeroed TLS is currently not supported");
  363. }
  364. static Result<void*, DlErrorMessage> __dlopen(char const* filename, int flags)
  365. {
  366. // FIXME: RTLD_NOW and RTLD_LOCAL are not supported
  367. flags &= ~RTLD_NOW;
  368. flags |= RTLD_LAZY;
  369. flags &= ~RTLD_LOCAL;
  370. flags |= RTLD_GLOBAL;
  371. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlopen invoked, filename={}, flags={}", filename, flags);
  372. if (pthread_mutex_trylock(&s_loader_lock) != 0)
  373. return DlErrorMessage { "Nested calls to dlopen() are not permitted." };
  374. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  375. auto const& parent_object = **s_global_objects.get(s_main_program_path);
  376. auto library_path = (filename ? resolve_library(filename, parent_object) : s_main_program_path);
  377. if (!library_path.has_value())
  378. return DlErrorMessage { String::formatted("Could not find required shared library: {}", filename) };
  379. auto existing_elf_object = s_global_objects.get(library_path.value());
  380. if (existing_elf_object.has_value()) {
  381. // It's up to the caller to release the ref with dlclose().
  382. existing_elf_object.value()->ref();
  383. return *existing_elf_object;
  384. }
  385. auto loader = TRY(resolve_and_map_library(library_path.value(), parent_object));
  386. if (auto error = verify_tls_for_dlopen(loader); error.has_value())
  387. return error.value();
  388. TRY(map_dependencies(loader->filepath()));
  389. TRY(link_main_library(loader->filepath(), flags));
  390. s_total_tls_size += loader->tls_size_of_current_object() + loader->tls_alignment_of_current_object();
  391. auto object = s_global_objects.get(library_path.value());
  392. if (!object.has_value())
  393. return DlErrorMessage { "Could not load ELF object." };
  394. // It's up to the caller to release the ref with dlclose().
  395. object.value()->ref();
  396. return *object;
  397. }
  398. static Result<void*, DlErrorMessage> __dlsym(void* handle, char const* symbol_name)
  399. {
  400. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlsym: {}, {}", handle, symbol_name);
  401. pthread_mutex_lock(&s_loader_lock);
  402. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  403. StringView symbol_name_view { symbol_name, strlen(symbol_name) };
  404. Optional<DynamicObject::SymbolLookupResult> symbol;
  405. if (handle) {
  406. auto object = static_cast<DynamicObject*>(handle);
  407. symbol = object->lookup_symbol(symbol_name_view);
  408. } else {
  409. // When handle is 0 (RTLD_DEFAULT) we should look up the symbol in all global modules
  410. // https://pubs.opengroup.org/onlinepubs/009604499/functions/dlsym.html
  411. symbol = DynamicLinker::lookup_global_symbol(symbol_name_view);
  412. }
  413. if (!symbol.has_value())
  414. return DlErrorMessage { String::formatted("Symbol {} not found", symbol_name_view) };
  415. if (symbol.value().type == STT_GNU_IFUNC)
  416. return (void*)reinterpret_cast<DynamicObject::IfuncResolver>(symbol.value().address.as_ptr())();
  417. return symbol.value().address.as_ptr();
  418. }
  419. static Result<void, DlErrorMessage> __dladdr(void* addr, Dl_info* info)
  420. {
  421. VirtualAddress user_addr { addr };
  422. pthread_mutex_lock(&s_loader_lock);
  423. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  424. RefPtr<DynamicObject> best_matching_library;
  425. VirtualAddress best_library_offset;
  426. for (auto& lib : s_global_objects) {
  427. if (user_addr < lib.value->base_address())
  428. continue;
  429. auto offset = user_addr - lib.value->base_address();
  430. if (!best_matching_library || offset < best_library_offset) {
  431. best_matching_library = lib.value;
  432. best_library_offset = offset;
  433. }
  434. }
  435. if (!best_matching_library) {
  436. return DlErrorMessage { "No library found which contains the specified address" };
  437. }
  438. Optional<DynamicObject::Symbol> best_matching_symbol;
  439. best_matching_library->for_each_symbol([&](auto const& symbol) {
  440. if (user_addr < symbol.address() || user_addr > symbol.address().offset(symbol.size()))
  441. return;
  442. best_matching_symbol = symbol;
  443. });
  444. info->dli_fbase = best_matching_library->base_address().as_ptr();
  445. // This works because we don't support unloading objects.
  446. info->dli_fname = best_matching_library->filepath().characters();
  447. if (best_matching_symbol.has_value()) {
  448. info->dli_saddr = best_matching_symbol.value().address().as_ptr();
  449. info->dli_sname = best_matching_symbol.value().raw_name();
  450. } else {
  451. info->dli_saddr = nullptr;
  452. info->dli_sname = nullptr;
  453. }
  454. return {};
  455. }
  456. static void read_environment_variables()
  457. {
  458. for (char** env = s_envp; *env; ++env) {
  459. StringView env_string { *env, strlen(*env) };
  460. if (env_string == "_LOADER_BREAKPOINT=1"sv) {
  461. s_do_breakpoint_trap_before_entry = true;
  462. }
  463. constexpr auto library_path_string = "LD_LIBRARY_PATH="sv;
  464. if (env_string.starts_with(library_path_string)) {
  465. s_ld_library_path = env_string.substring_view(library_path_string.length());
  466. }
  467. constexpr auto main_pledge_promises_key = "_LOADER_MAIN_PROGRAM_PLEDGE_PROMISES="sv;
  468. if (env_string.starts_with(main_pledge_promises_key)) {
  469. s_main_program_pledge_promises = env_string.substring_view(main_pledge_promises_key.length());
  470. }
  471. constexpr auto loader_pledge_promises_key = "_LOADER_PLEDGE_PROMISES="sv;
  472. if (env_string.starts_with(loader_pledge_promises_key)) {
  473. s_loader_pledge_promises = env_string.substring_view(loader_pledge_promises_key.length());
  474. }
  475. }
  476. }
  477. void ELF::DynamicLinker::linker_main(String&& main_program_path, int main_program_fd, bool is_secure, int argc, char** argv, char** envp)
  478. {
  479. VERIFY(main_program_path.starts_with('/'));
  480. s_envp = envp;
  481. char* raw_current_directory = getcwd(nullptr, 0);
  482. s_cwd = raw_current_directory;
  483. free(raw_current_directory);
  484. s_allowed_to_check_environment_variables = !is_secure;
  485. if (s_allowed_to_check_environment_variables)
  486. read_environment_variables();
  487. s_main_program_path = main_program_path;
  488. // NOTE: We always map the main library first, since it may require
  489. // placement at a specific address.
  490. auto result1 = map_library(main_program_path, main_program_fd);
  491. if (result1.is_error()) {
  492. warnln("{}", result1.error().text);
  493. fflush(stderr);
  494. _exit(1);
  495. }
  496. (void)result1.release_value();
  497. auto result2 = map_dependencies(main_program_path);
  498. if (result2.is_error()) {
  499. warnln("{}", result2.error().text);
  500. fflush(stderr);
  501. _exit(1);
  502. }
  503. dbgln_if(DYNAMIC_LOAD_DEBUG, "loaded all dependencies");
  504. for ([[maybe_unused]] auto& lib : s_loaders) {
  505. dbgln_if(DYNAMIC_LOAD_DEBUG, "{} - tls size: {}, tls alignment: {}, tls offset: {}", lib.key, lib.value->tls_size_of_current_object(), lib.value->tls_alignment_of_current_object(), lib.value->tls_offset());
  506. }
  507. allocate_tls();
  508. auto entry_point_function = [&main_program_path] {
  509. auto result = link_main_library(main_program_path, RTLD_GLOBAL | RTLD_LAZY);
  510. if (result.is_error()) {
  511. warnln("{}", result.error().text);
  512. _exit(1);
  513. }
  514. drop_loader_promise("rpath"sv);
  515. auto& main_executable_loader = *s_loaders.get(main_program_path);
  516. auto entry_point = main_executable_loader->image().entry();
  517. if (main_executable_loader->is_dynamic())
  518. entry_point = entry_point.offset(main_executable_loader->base_address().get());
  519. return (EntryPointFunction)(entry_point.as_ptr());
  520. }();
  521. s_loaders.clear();
  522. int rc = syscall(SC_msyscall, nullptr);
  523. if (rc < 0) {
  524. VERIFY_NOT_REACHED();
  525. }
  526. dbgln_if(DYNAMIC_LOAD_DEBUG, "Jumping to entry point: {:p}", entry_point_function);
  527. if (s_do_breakpoint_trap_before_entry) {
  528. #ifdef AK_ARCH_AARCH64
  529. asm("brk #0");
  530. #else
  531. asm("int3");
  532. #endif
  533. }
  534. _invoke_entry(argc, argv, envp, entry_point_function);
  535. VERIFY_NOT_REACHED();
  536. }
  537. }