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 String get_library_name(String path)
  75. {
  76. return LexicalPath::basename(move(path));
  77. }
  78. static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> map_library(String const& filepath, int fd)
  79. {
  80. VERIFY(filepath.starts_with('/'));
  81. auto loader = TRY(ELF::DynamicLoader::try_create(fd, filepath));
  82. s_loaders.set(get_library_name(filepath), *loader);
  83. s_current_tls_offset -= loader->tls_size_of_current_object();
  84. if (loader->tls_alignment_of_current_object())
  85. s_current_tls_offset = align_down_to(s_current_tls_offset, loader->tls_alignment_of_current_object());
  86. loader->set_tls_offset(s_current_tls_offset);
  87. // This actually maps the library at the intended and final place.
  88. auto main_library_object = loader->map();
  89. s_global_objects.set(get_library_name(filepath), *main_library_object);
  90. return loader;
  91. }
  92. static Optional<String> resolve_library(String const& name, DynamicObject const& parent_object)
  93. {
  94. // Absolute and relative (to the current working directory) paths are already considered resolved.
  95. // However, ensure that the returned path is absolute and canonical, so pass it through LexicalPath.
  96. if (name.contains('/'))
  97. return LexicalPath::absolute_path(s_cwd, name);
  98. Vector<StringView> search_paths;
  99. // Search RPATH values indicated by the ELF (only if RUNPATH is not present).
  100. if (parent_object.runpath().is_empty())
  101. search_paths.extend(parent_object.rpath().split_view(':'));
  102. // Scan the LD_LIBRARY_PATH environment variable if applicable.
  103. search_paths.extend(s_ld_library_path.split_view(':'));
  104. // Search RUNPATH values indicated by the ELF.
  105. search_paths.extend(parent_object.runpath().split_view(':'));
  106. // Last are the default search paths.
  107. search_paths.append("/usr/lib"sv);
  108. search_paths.append("/usr/local/lib"sv);
  109. for (auto const& search_path : search_paths) {
  110. LexicalPath library_path(search_path.replace("$ORIGIN"sv, LexicalPath::dirname(parent_object.filepath()), ReplaceMode::FirstOnly));
  111. String library_name = library_path.append(name).string();
  112. if (access(library_name.characters(), F_OK) == 0)
  113. return library_name;
  114. }
  115. return {};
  116. }
  117. static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> resolve_and_map_library(String const& name, DynamicObject const& parent_object)
  118. {
  119. auto resolved_library_name = resolve_library(name, parent_object);
  120. if (!resolved_library_name.has_value())
  121. return DlErrorMessage { String::formatted("Could not find required shared library: {}", name) };
  122. int fd = open(resolved_library_name.value().characters(), O_RDONLY);
  123. if (fd < 0)
  124. return DlErrorMessage { String::formatted("Could not open resolved shared library '{}': {}", resolved_library_name.value(), strerror(errno)) };
  125. return map_library(resolved_library_name.value(), fd);
  126. }
  127. static Vector<String> get_dependencies(String const& path)
  128. {
  129. VERIFY(path.starts_with('/'));
  130. auto name = get_library_name(path);
  131. auto lib = s_loaders.get(name).value();
  132. Vector<String> dependencies;
  133. lib->for_each_needed_library([&dependencies, &name](auto needed_name) {
  134. if (name == needed_name)
  135. return;
  136. dependencies.append(needed_name);
  137. });
  138. return dependencies;
  139. }
  140. static Result<void, DlErrorMessage> map_dependencies(String const& path)
  141. {
  142. VERIFY(path.starts_with('/'));
  143. dbgln_if(DYNAMIC_LOAD_DEBUG, "mapping dependencies for: {}", path);
  144. auto const& parent_object = (*s_loaders.get(get_library_name(path)))->dynamic_object();
  145. for (auto const& needed_name : get_dependencies(path)) {
  146. dbgln_if(DYNAMIC_LOAD_DEBUG, "needed library: {}", needed_name.characters());
  147. String library_name = get_library_name(needed_name);
  148. if (!s_loaders.contains(library_name) && !s_global_objects.contains(library_name)) {
  149. auto loader = TRY(resolve_and_map_library(needed_name, parent_object));
  150. TRY(map_dependencies(loader->filepath()));
  151. }
  152. }
  153. dbgln_if(DYNAMIC_LOAD_DEBUG, "mapped dependencies for {}", path);
  154. return {};
  155. }
  156. static void allocate_tls()
  157. {
  158. s_total_tls_size = 0;
  159. for (auto const& data : s_loaders) {
  160. 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());
  161. s_total_tls_size += data.value->tls_size_of_current_object() + data.value->tls_alignment_of_current_object();
  162. }
  163. if (!s_total_tls_size)
  164. return;
  165. auto page_aligned_size = align_up_to(s_total_tls_size, PAGE_SIZE);
  166. auto initial_tls_data_result = ByteBuffer::create_zeroed(page_aligned_size);
  167. if (initial_tls_data_result.is_error()) {
  168. dbgln("Failed to allocate initial TLS data");
  169. VERIFY_NOT_REACHED();
  170. }
  171. auto& initial_tls_data = initial_tls_data_result.value();
  172. // Initialize TLS data
  173. for (auto const& entry : s_loaders) {
  174. entry.value->copy_initial_tls_data_into(initial_tls_data);
  175. }
  176. void* master_tls = ::allocate_tls((char*)initial_tls_data.data(), initial_tls_data.size());
  177. VERIFY(master_tls != (void*)-1);
  178. dbgln_if(DYNAMIC_LOAD_DEBUG, "from userspace, master_tls: {:p}", master_tls);
  179. s_allocated_tls_block_size = initial_tls_data.size();
  180. }
  181. static int __dl_iterate_phdr(DlIteratePhdrCallbackFunction callback, void* data)
  182. {
  183. pthread_mutex_lock(&s_loader_lock);
  184. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  185. for (auto& it : s_global_objects) {
  186. auto& object = it.value;
  187. auto info = dl_phdr_info {
  188. .dlpi_addr = (ElfW(Addr))object->base_address().as_ptr(),
  189. .dlpi_name = object->filepath().characters(),
  190. .dlpi_phdr = object->program_headers(),
  191. .dlpi_phnum = object->program_header_count()
  192. };
  193. auto res = callback(&info, sizeof(info), data);
  194. if (res != 0)
  195. return res;
  196. }
  197. return 0;
  198. }
  199. static void initialize_libc(DynamicObject& libc)
  200. {
  201. // Traditionally, `_start` of the main program initializes libc.
  202. // However, since some libs use malloc() and getenv() in global constructors,
  203. // we have to initialize libc just after it is loaded.
  204. // Also, we can't just mark `__libc_init` with "__attribute__((constructor))"
  205. // because it uses getenv() internally, so `environ` has to be initialized before we call `__libc_init`.
  206. auto res = libc.lookup_symbol("environ"sv);
  207. VERIFY(res.has_value());
  208. *((char***)res.value().address.as_ptr()) = s_envp;
  209. // __stack_chk_guard should be initialized before anything significant (read: global constructors) is running.
  210. // This is not done in __libc_init, as we definitely have to return from that, and it might affect Loader as well.
  211. res = libc.lookup_symbol("__stack_chk_guard"sv);
  212. VERIFY(res.has_value());
  213. arc4random_buf(res.value().address.as_ptr(), sizeof(size_t));
  214. res = libc.lookup_symbol("__environ_is_malloced"sv);
  215. VERIFY(res.has_value());
  216. *((bool*)res.value().address.as_ptr()) = false;
  217. res = libc.lookup_symbol("exit"sv);
  218. VERIFY(res.has_value());
  219. s_libc_exit = (LibCExitFunction)res.value().address.as_ptr();
  220. res = libc.lookup_symbol("__dl_iterate_phdr"sv);
  221. VERIFY(res.has_value());
  222. *((DlIteratePhdrFunction*)res.value().address.as_ptr()) = __dl_iterate_phdr;
  223. res = libc.lookup_symbol("__dlclose"sv);
  224. VERIFY(res.has_value());
  225. *((DlCloseFunction*)res.value().address.as_ptr()) = __dlclose;
  226. res = libc.lookup_symbol("__dlopen"sv);
  227. VERIFY(res.has_value());
  228. *((DlOpenFunction*)res.value().address.as_ptr()) = __dlopen;
  229. res = libc.lookup_symbol("__dlsym"sv);
  230. VERIFY(res.has_value());
  231. *((DlSymFunction*)res.value().address.as_ptr()) = __dlsym;
  232. res = libc.lookup_symbol("__dladdr"sv);
  233. VERIFY(res.has_value());
  234. *((DlAddrFunction*)res.value().address.as_ptr()) = __dladdr;
  235. res = libc.lookup_symbol("__libc_init"sv);
  236. VERIFY(res.has_value());
  237. typedef void libc_init_func();
  238. ((libc_init_func*)res.value().address.as_ptr())();
  239. }
  240. template<typename Callback>
  241. static void for_each_unfinished_dependency_of(String const& path, HashTable<String>& seen_names, Callback callback)
  242. {
  243. VERIFY(path.starts_with('/'));
  244. auto loader = s_loaders.get(get_library_name(path));
  245. if (!loader.has_value())
  246. return;
  247. if (loader.value()->is_fully_relocated()) {
  248. if (!loader.value()->is_fully_initialized()) {
  249. // If we are ending up here, that possibly means that this library either dlopens itself or a library that depends
  250. // on it while running its initializers. Assuming that this is the only funny thing that the library does, there is
  251. // a reasonable chance that nothing breaks, so just warn and continue.
  252. dbgln("\033[33mWarning:\033[0m Querying for dependencies of '{}' while running its initializers", path);
  253. }
  254. return;
  255. }
  256. if (seen_names.contains(path))
  257. return;
  258. seen_names.set(path);
  259. for (auto const& needed_name : get_dependencies(path)) {
  260. auto dependency_loader = s_loaders.get(get_library_name(needed_name));
  261. if (!dependency_loader.has_value()) {
  262. // Not having a loader here means that the library has already been loaded in at an earlier point,
  263. // and the loader itself was cleared during the end of `linker_main`.
  264. continue;
  265. }
  266. for_each_unfinished_dependency_of(dependency_loader.value()->filepath(), seen_names, callback);
  267. }
  268. callback(*s_loaders.get(get_library_name(path)).value());
  269. }
  270. static NonnullRefPtrVector<DynamicLoader> collect_loaders_for_library(String const& path)
  271. {
  272. VERIFY(path.starts_with('/'));
  273. HashTable<String> seen_names;
  274. NonnullRefPtrVector<DynamicLoader> loaders;
  275. for_each_unfinished_dependency_of(path, seen_names, [&](auto& loader) {
  276. loaders.append(loader);
  277. });
  278. return loaders;
  279. }
  280. static void drop_loader_promise(StringView promise_to_drop)
  281. {
  282. if (s_main_program_pledge_promises.is_empty() || s_loader_pledge_promises.is_empty())
  283. return;
  284. s_loader_pledge_promises = s_loader_pledge_promises.replace(promise_to_drop, ""sv, ReplaceMode::All);
  285. auto extended_promises = String::formatted("{} {}", s_main_program_pledge_promises, s_loader_pledge_promises);
  286. Syscall::SC_pledge_params params {
  287. { extended_promises.characters(), extended_promises.length() },
  288. { nullptr, 0 },
  289. };
  290. int rc = syscall(SC_pledge, &params);
  291. if (rc < 0 && rc > -EMAXERRNO) {
  292. warnln("Failed to drop loader pledge promise: {}. errno={}", promise_to_drop, errno);
  293. _exit(1);
  294. }
  295. }
  296. static Result<void, DlErrorMessage> link_main_library(String const& path, int flags)
  297. {
  298. VERIFY(path.starts_with('/'));
  299. auto loaders = collect_loaders_for_library(path);
  300. for (auto& loader : loaders) {
  301. auto dynamic_object = loader.map();
  302. if (dynamic_object)
  303. s_global_objects.set(get_library_name(dynamic_object->filepath()), *dynamic_object);
  304. }
  305. for (auto& loader : loaders) {
  306. bool success = loader.link(flags);
  307. if (!success) {
  308. return DlErrorMessage { String::formatted("Failed to link library {}", loader.filepath()) };
  309. }
  310. }
  311. for (auto& loader : loaders) {
  312. auto result = loader.load_stage_3(flags);
  313. VERIFY(!result.is_error());
  314. auto& object = result.value();
  315. if (loader.filepath().ends_with("/libsystem.so"sv)) {
  316. VERIFY(!loader.text_segments().is_empty());
  317. for (auto const& segment : loader.text_segments()) {
  318. if (syscall(SC_msyscall, segment.address().get())) {
  319. VERIFY_NOT_REACHED();
  320. }
  321. }
  322. }
  323. if (loader.filepath().ends_with("/libc.so"sv)) {
  324. initialize_libc(*object);
  325. }
  326. }
  327. drop_loader_promise("prot_exec"sv);
  328. for (auto& loader : loaders) {
  329. loader.load_stage_4();
  330. }
  331. return {};
  332. }
  333. static Result<void, DlErrorMessage> __dlclose(void* handle)
  334. {
  335. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlclose: {}", handle);
  336. pthread_mutex_lock(&s_loader_lock);
  337. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  338. // FIXME: this will not currently destroy the dynamic object
  339. // because we're intentionally holding a strong reference to it
  340. // via s_global_objects until there's proper unload support.
  341. auto object = static_cast<ELF::DynamicObject*>(handle);
  342. object->unref();
  343. return {};
  344. }
  345. static Optional<DlErrorMessage> verify_tls_for_dlopen(DynamicLoader const& loader)
  346. {
  347. if (loader.tls_size_of_current_object() == 0)
  348. return {};
  349. if (s_total_tls_size + loader.tls_size_of_current_object() + loader.tls_alignment_of_current_object() > s_allocated_tls_block_size)
  350. return DlErrorMessage("TLS size too large");
  351. bool tls_data_is_all_zero = true;
  352. loader.image().for_each_program_header([&loader, &tls_data_is_all_zero](ELF::Image::ProgramHeader program_header) {
  353. if (program_header.type() != PT_TLS)
  354. return IterationDecision::Continue;
  355. auto* tls_data = (const u8*)loader.image().base_address() + program_header.offset();
  356. for (size_t i = 0; i < program_header.size_in_image(); ++i) {
  357. if (tls_data[i] != 0) {
  358. tls_data_is_all_zero = false;
  359. break;
  360. }
  361. }
  362. return IterationDecision::Break;
  363. });
  364. if (tls_data_is_all_zero)
  365. return {};
  366. return DlErrorMessage("Using dlopen() with libraries that have non-zeroed TLS is currently not supported");
  367. }
  368. static Result<void*, DlErrorMessage> __dlopen(char const* filename, int flags)
  369. {
  370. // FIXME: RTLD_NOW and RTLD_LOCAL are not supported
  371. flags &= ~RTLD_NOW;
  372. flags |= RTLD_LAZY;
  373. flags &= ~RTLD_LOCAL;
  374. flags |= RTLD_GLOBAL;
  375. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlopen invoked, filename={}, flags={}", filename, flags);
  376. auto library_name = get_library_name(filename ? filename : s_main_program_path);
  377. if (pthread_mutex_trylock(&s_loader_lock) != 0)
  378. return DlErrorMessage { "Nested calls to dlopen() are not permitted." };
  379. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  380. auto existing_elf_object = s_global_objects.get(library_name);
  381. if (existing_elf_object.has_value()) {
  382. // It's up to the caller to release the ref with dlclose().
  383. existing_elf_object.value()->ref();
  384. return *existing_elf_object;
  385. }
  386. VERIFY(!library_name.is_empty());
  387. auto const& parent_object = **s_global_objects.get(get_library_name(s_main_program_path));
  388. auto loader = TRY(resolve_and_map_library(filename, parent_object));
  389. if (auto error = verify_tls_for_dlopen(loader); error.has_value())
  390. return error.value();
  391. TRY(map_dependencies(loader->filepath()));
  392. TRY(link_main_library(loader->filepath(), flags));
  393. s_total_tls_size += loader->tls_size_of_current_object() + loader->tls_alignment_of_current_object();
  394. auto object = s_global_objects.get(library_name);
  395. if (!object.has_value())
  396. return DlErrorMessage { "Could not load ELF object." };
  397. // It's up to the caller to release the ref with dlclose().
  398. object.value()->ref();
  399. return *object;
  400. }
  401. static Result<void*, DlErrorMessage> __dlsym(void* handle, char const* symbol_name)
  402. {
  403. dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlsym: {}, {}", handle, symbol_name);
  404. pthread_mutex_lock(&s_loader_lock);
  405. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  406. StringView symbol_name_view { symbol_name, strlen(symbol_name) };
  407. Optional<DynamicObject::SymbolLookupResult> symbol;
  408. if (handle) {
  409. auto object = static_cast<DynamicObject*>(handle);
  410. symbol = object->lookup_symbol(symbol_name_view);
  411. } else {
  412. // When handle is 0 (RTLD_DEFAULT) we should look up the symbol in all global modules
  413. // https://pubs.opengroup.org/onlinepubs/009604499/functions/dlsym.html
  414. symbol = DynamicLinker::lookup_global_symbol(symbol_name_view);
  415. }
  416. if (!symbol.has_value())
  417. return DlErrorMessage { String::formatted("Symbol {} not found", symbol_name_view) };
  418. if (symbol.value().type == STT_GNU_IFUNC)
  419. return (void*)reinterpret_cast<DynamicObject::IfuncResolver>(symbol.value().address.as_ptr())();
  420. return symbol.value().address.as_ptr();
  421. }
  422. static Result<void, DlErrorMessage> __dladdr(void* addr, Dl_info* info)
  423. {
  424. VirtualAddress user_addr { addr };
  425. pthread_mutex_lock(&s_loader_lock);
  426. ScopeGuard unlock_guard = [] { pthread_mutex_unlock(&s_loader_lock); };
  427. RefPtr<DynamicObject> best_matching_library;
  428. VirtualAddress best_library_offset;
  429. for (auto& lib : s_global_objects) {
  430. if (user_addr < lib.value->base_address())
  431. continue;
  432. auto offset = user_addr - lib.value->base_address();
  433. if (!best_matching_library || offset < best_library_offset) {
  434. best_matching_library = lib.value;
  435. best_library_offset = offset;
  436. }
  437. }
  438. if (!best_matching_library) {
  439. return DlErrorMessage { "No library found which contains the specified address" };
  440. }
  441. Optional<DynamicObject::Symbol> best_matching_symbol;
  442. best_matching_library->for_each_symbol([&](auto const& symbol) {
  443. if (user_addr < symbol.address() || user_addr > symbol.address().offset(symbol.size()))
  444. return;
  445. best_matching_symbol = symbol;
  446. });
  447. info->dli_fbase = best_matching_library->base_address().as_ptr();
  448. // This works because we don't support unloading objects.
  449. info->dli_fname = best_matching_library->filepath().characters();
  450. if (best_matching_symbol.has_value()) {
  451. info->dli_saddr = best_matching_symbol.value().address().as_ptr();
  452. info->dli_sname = best_matching_symbol.value().raw_name();
  453. } else {
  454. info->dli_saddr = nullptr;
  455. info->dli_sname = nullptr;
  456. }
  457. return {};
  458. }
  459. static void read_environment_variables()
  460. {
  461. for (char** env = s_envp; *env; ++env) {
  462. StringView env_string { *env, strlen(*env) };
  463. if (env_string == "_LOADER_BREAKPOINT=1"sv) {
  464. s_do_breakpoint_trap_before_entry = true;
  465. }
  466. constexpr auto library_path_string = "LD_LIBRARY_PATH="sv;
  467. if (env_string.starts_with(library_path_string)) {
  468. s_ld_library_path = env_string.substring_view(library_path_string.length());
  469. }
  470. constexpr auto main_pledge_promises_key = "_LOADER_MAIN_PROGRAM_PLEDGE_PROMISES="sv;
  471. if (env_string.starts_with(main_pledge_promises_key)) {
  472. s_main_program_pledge_promises = env_string.substring_view(main_pledge_promises_key.length());
  473. }
  474. constexpr auto loader_pledge_promises_key = "_LOADER_PLEDGE_PROMISES="sv;
  475. if (env_string.starts_with(loader_pledge_promises_key)) {
  476. s_loader_pledge_promises = env_string.substring_view(loader_pledge_promises_key.length());
  477. }
  478. }
  479. }
  480. void ELF::DynamicLinker::linker_main(String&& main_program_path, int main_program_fd, bool is_secure, int argc, char** argv, char** envp)
  481. {
  482. VERIFY(main_program_path.starts_with('/'));
  483. s_envp = envp;
  484. char* raw_current_directory = getcwd(nullptr, 0);
  485. s_cwd = raw_current_directory;
  486. free(raw_current_directory);
  487. s_allowed_to_check_environment_variables = !is_secure;
  488. if (s_allowed_to_check_environment_variables)
  489. read_environment_variables();
  490. s_main_program_path = main_program_path;
  491. // NOTE: We always map the main library first, since it may require
  492. // placement at a specific address.
  493. auto result1 = map_library(main_program_path, main_program_fd);
  494. if (result1.is_error()) {
  495. warnln("{}", result1.error().text);
  496. fflush(stderr);
  497. _exit(1);
  498. }
  499. (void)result1.release_value();
  500. auto result2 = map_dependencies(main_program_path);
  501. if (result2.is_error()) {
  502. warnln("{}", result2.error().text);
  503. fflush(stderr);
  504. _exit(1);
  505. }
  506. dbgln_if(DYNAMIC_LOAD_DEBUG, "loaded all dependencies");
  507. for ([[maybe_unused]] auto& lib : s_loaders) {
  508. 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());
  509. }
  510. allocate_tls();
  511. auto entry_point_function = [&main_program_path] {
  512. auto result = link_main_library(main_program_path, RTLD_GLOBAL | RTLD_LAZY);
  513. if (result.is_error()) {
  514. warnln("{}", result.error().text);
  515. _exit(1);
  516. }
  517. drop_loader_promise("rpath"sv);
  518. auto& main_executable_loader = *s_loaders.get(get_library_name(main_program_path));
  519. auto entry_point = main_executable_loader->image().entry();
  520. if (main_executable_loader->is_dynamic())
  521. entry_point = entry_point.offset(main_executable_loader->base_address().get());
  522. return (EntryPointFunction)(entry_point.as_ptr());
  523. }();
  524. s_loaders.clear();
  525. int rc = syscall(SC_msyscall, nullptr);
  526. if (rc < 0) {
  527. VERIFY_NOT_REACHED();
  528. }
  529. dbgln_if(DYNAMIC_LOAD_DEBUG, "Jumping to entry point: {:p}", entry_point_function);
  530. if (s_do_breakpoint_trap_before_entry) {
  531. #ifdef AK_ARCH_AARCH64
  532. asm("brk #0");
  533. #else
  534. asm("int3");
  535. #endif
  536. }
  537. _invoke_entry(argc, argv, envp, entry_point_function);
  538. VERIFY_NOT_REACHED();
  539. }
  540. }