mirror of
https://github.com/RGBCube/serenity
synced 2025-07-25 19:07:35 +00:00
LibC+LibELF: Implement more fully-features dlfcn functionality
This implements more of the dlfcn functionality. Most notably: * It's now possible to dlopen() libraries which were already loaded at program startup time. This does not cause those libraries to be loaded twice. * Errors are reported via dlerror() rather than by crashing the program. * Calls to the dl*() functions are thread-safe.
This commit is contained in:
parent
549d9bd3ea
commit
f40ee1b03f
12 changed files with 371 additions and 200 deletions
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@ -12,38 +12,44 @@
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#include <AK/LexicalPath.h>
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#include <AK/NonnullRefPtrVector.h>
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#include <AK/ScopeGuard.h>
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#include <LibC/bits/pthread_integration.h>
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#include <LibC/link.h>
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#include <LibC/mman.h>
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#include <LibC/unistd.h>
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#include <LibDl/dlfcn.h>
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#include <LibDl/dlfcn_integration.h>
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#include <LibELF/AuxiliaryVector.h>
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#include <LibELF/DynamicLinker.h>
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#include <LibELF/DynamicLoader.h>
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#include <LibELF/DynamicObject.h>
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#include <LibELF/Hashes.h>
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#include <dlfcn.h>
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#include <fcntl.h>
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#include <sys/types.h>
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#include <syscall.h>
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namespace ELF {
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namespace {
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HashMap<String, NonnullRefPtr<ELF::DynamicLoader>> g_loaders;
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Vector<NonnullRefPtr<ELF::DynamicObject>> g_global_objects;
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static HashMap<String, NonnullRefPtr<ELF::DynamicLoader>> s_loaders;
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static String s_main_program_name;
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static HashMap<String, NonnullRefPtr<ELF::DynamicObject>> s_global_objects;
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using EntryPointFunction = int (*)(int, char**, char**);
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using LibCExitFunction = void (*)(int);
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using DlIteratePhdrCallbackFunction = int (*)(struct dl_phdr_info*, size_t, void*);
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using DlIteratePhdrFunction = int (*)(DlIteratePhdrCallbackFunction, void*);
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size_t g_current_tls_offset = 0;
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size_t g_total_tls_size = 0;
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char** g_envp = nullptr;
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LibCExitFunction g_libc_exit = nullptr;
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static size_t s_current_tls_offset = 0;
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static size_t s_total_tls_size = 0;
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static char** s_envp = nullptr;
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static LibCExitFunction s_libc_exit = nullptr;
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static __pthread_mutex_t s_loader_lock = __PTHREAD_MUTEX_INITIALIZER;
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bool g_allowed_to_check_environment_variables { false };
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bool g_do_breakpoint_trap_before_entry { false };
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}
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static bool s_allowed_to_check_environment_variables { false };
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static bool s_do_breakpoint_trap_before_entry { false };
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static Result<void, DlErrorMessage> __dlclose(void* handle);
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static Result<void*, DlErrorMessage> __dlopen(const char* filename, int flags);
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static Result<void*, DlErrorMessage> __dlsym(void* handle, const char* symbol_name);
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Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(const StringView& name)
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{
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@ -51,8 +57,8 @@ Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(
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auto symbol = DynamicObject::HashSymbol { name };
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for (auto& lib : g_global_objects) {
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auto res = lib->lookup_symbol(symbol);
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for (auto& lib : s_global_objects) {
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auto res = lib.value->lookup_symbol(symbol);
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if (!res.has_value())
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continue;
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if (res.value().bind == STB_GLOBAL)
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@ -64,22 +70,39 @@ Optional<DynamicObject::SymbolLookupResult> DynamicLinker::lookup_global_symbol(
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return weak_result;
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}
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static void map_library(const String& name, int fd)
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static String get_library_name(String path)
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{
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auto loader = ELF::DynamicLoader::try_create(fd, name);
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if (!loader) {
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dbgln("Failed to create ELF::DynamicLoader for fd={}, name={}", fd, name);
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VERIFY_NOT_REACHED();
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}
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loader->set_tls_offset(g_current_tls_offset);
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g_loaders.set(name, *loader);
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g_current_tls_offset += loader->tls_size();
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return LexicalPath(move(path)).basename();
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}
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static void map_library(const String& name)
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static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> map_library(const String& filename, int fd, bool is_program)
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{
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auto result = ELF::DynamicLoader::try_create(fd, filename);
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if (result.is_error()) {
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return result;
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}
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auto& loader = result.value();
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s_loaders.set(get_library_name(filename), *loader);
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if (is_program) {
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loader->set_tls_offset(s_current_tls_offset);
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s_current_tls_offset += loader->tls_size();
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}
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return loader;
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}
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static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> map_library(const String& name, bool is_program)
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{
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if (name.contains("/")) {
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int fd = open(name.characters(), O_RDONLY);
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if (fd < 0)
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return DlErrorMessage { String::formatted("Could not open shared library: {}", name) };
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return map_library(name, fd, is_program);
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}
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// TODO: Do we want to also look for libs in other paths too?
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const char* search_paths[] = { "/usr/lib/{}", "/usr/local/lib/{}" };
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for (auto& search_path : search_paths) {
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@ -87,22 +110,15 @@ static void map_library(const String& name)
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int fd = open(path.characters(), O_RDONLY);
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if (fd < 0)
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continue;
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map_library(name, fd);
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return;
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return map_library(name, fd, is_program);
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}
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fprintf(stderr, "Could not find required shared library: %s\n", name.characters());
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VERIFY_NOT_REACHED();
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}
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static String get_library_name(String path)
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{
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return LexicalPath(move(path)).basename();
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return DlErrorMessage { String::formatted("Could not find required shared library: {}", name) };
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}
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static Vector<String> get_dependencies(const String& name)
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{
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auto lib = g_loaders.get(name).value();
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auto lib = s_loaders.get(name).value();
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Vector<String> dependencies;
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lib->for_each_needed_library([&dependencies, &name](auto needed_name) {
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@ -114,7 +130,7 @@ static Vector<String> get_dependencies(const String& name)
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return dependencies;
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}
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static void map_dependencies(const String& name)
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static Result<void, DlErrorMessage> map_dependencies(const String& name)
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{
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dbgln_if(DYNAMIC_LOAD_DEBUG, "mapping dependencies for: {}", name);
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@ -122,18 +138,25 @@ static void map_dependencies(const String& name)
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dbgln_if(DYNAMIC_LOAD_DEBUG, "needed library: {}", needed_name.characters());
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String library_name = get_library_name(needed_name);
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if (!g_loaders.contains(library_name)) {
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map_library(library_name);
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map_dependencies(library_name);
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if (!s_loaders.contains(library_name) && !s_global_objects.contains(library_name)) {
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auto result1 = map_library(needed_name, false);
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if (result1.is_error()) {
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return result1.error();
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}
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auto result2 = map_dependencies(library_name);
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if (result2.is_error()) {
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return result2.error();
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}
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}
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}
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dbgln_if(DYNAMIC_LOAD_DEBUG, "mapped dependencies for {}", name);
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return {};
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}
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static void allocate_tls()
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{
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size_t total_tls_size = 0;
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for (const auto& data : g_loaders) {
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for (const auto& data : s_loaders) {
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dbgln_if(DYNAMIC_LOAD_DEBUG, "{}: TLS Size: {}", data.key, data.value->tls_size());
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total_tls_size += data.value->tls_size();
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}
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@ -141,12 +164,16 @@ static void allocate_tls()
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[[maybe_unused]] void* tls_address = ::allocate_tls(total_tls_size);
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dbgln_if(DYNAMIC_LOAD_DEBUG, "from userspace, tls_address: {:p}", tls_address);
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}
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g_total_tls_size = total_tls_size;
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s_total_tls_size = total_tls_size;
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}
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static int __dl_iterate_phdr(DlIteratePhdrCallbackFunction callback, void* data)
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{
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for (auto& object : g_global_objects) {
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__pthread_mutex_lock(&s_loader_lock);
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ScopeGuard unlock_guard = [] { __pthread_mutex_unlock(&s_loader_lock); };
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for (auto& it : s_global_objects) {
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auto& object = it.value;
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auto info = dl_phdr_info {
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.dlpi_addr = (ElfW(Addr))object->base_address().as_ptr(),
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.dlpi_name = object->filename().characters(),
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@ -171,7 +198,7 @@ static void initialize_libc(DynamicObject& libc)
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// because it uses getenv() internally, so `environ` has to be initialized before we call `__libc_init`.
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auto res = libc.lookup_symbol("environ"sv);
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VERIFY(res.has_value());
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*((char***)res.value().address.as_ptr()) = g_envp;
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*((char***)res.value().address.as_ptr()) = s_envp;
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res = libc.lookup_symbol("__environ_is_malloced"sv);
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VERIFY(res.has_value());
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@ -179,12 +206,24 @@ static void initialize_libc(DynamicObject& libc)
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res = libc.lookup_symbol("exit"sv);
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VERIFY(res.has_value());
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g_libc_exit = (LibCExitFunction)res.value().address.as_ptr();
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s_libc_exit = (LibCExitFunction)res.value().address.as_ptr();
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res = libc.lookup_symbol("__dl_iterate_phdr"sv);
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VERIFY(res.has_value());
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*((DlIteratePhdrFunction*)res.value().address.as_ptr()) = __dl_iterate_phdr;
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res = libc.lookup_symbol("__dlclose"sv);
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VERIFY(res.has_value());
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*((DlCloseFunction*)res.value().address.as_ptr()) = __dlclose;
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res = libc.lookup_symbol("__dlopen"sv);
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VERIFY(res.has_value());
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*((DlOpenFunction*)res.value().address.as_ptr()) = __dlopen;
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res = libc.lookup_symbol("__dlsym"sv);
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VERIFY(res.has_value());
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*((DlSymFunction*)res.value().address.as_ptr()) = __dlsym;
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res = libc.lookup_symbol("__libc_init"sv);
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VERIFY(res.has_value());
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typedef void libc_init_func();
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}
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template<typename Callback>
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static void for_each_dependency_of(const String& name, HashTable<String>& seen_names, Callback callback)
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static void for_each_unfinished_dependency_of(const String& name, HashTable<String>& seen_names, Callback callback)
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{
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if (!s_loaders.contains(name))
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return;
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if (seen_names.contains(name))
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return;
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seen_names.set(name);
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for (const auto& needed_name : get_dependencies(name))
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for_each_dependency_of(get_library_name(needed_name), seen_names, callback);
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for_each_unfinished_dependency_of(get_library_name(needed_name), seen_names, callback);
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callback(*g_loaders.get(name).value());
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callback(*s_loaders.get(name).value());
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}
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static NonnullRefPtrVector<DynamicLoader> collect_loaders_for_executable(const String& name)
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static NonnullRefPtrVector<DynamicLoader> collect_loaders_for_library(const String& name)
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{
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HashTable<String> seen_names;
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NonnullRefPtrVector<DynamicLoader> loaders;
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for_each_dependency_of(name, seen_names, [&](auto& loader) {
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for_each_unfinished_dependency_of(name, seen_names, [&](auto& loader) {
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loaders.append(loader);
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});
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return loaders;
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}
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static NonnullRefPtr<DynamicLoader> load_main_executable(const String& name)
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static Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> load_main_library(const String& name, int flags)
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{
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// NOTE: We always map the main executable first, since it may require
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// placement at a specific address.
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auto& main_executable_loader = *g_loaders.get(name).value();
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auto main_executable_object = main_executable_loader.map();
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g_global_objects.append(*main_executable_object);
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auto main_library_loader = *s_loaders.get(name);
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auto main_library_object = main_library_loader->map();
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s_global_objects.set(name, *main_library_object);
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auto loaders = collect_loaders_for_executable(name);
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auto loaders = collect_loaders_for_library(name);
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for (auto& loader : loaders) {
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auto dynamic_object = loader.map();
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if (dynamic_object)
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g_global_objects.append(*dynamic_object);
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s_global_objects.set(dynamic_object->filename(), *dynamic_object);
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}
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for (auto& loader : loaders) {
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bool success = loader.link(RTLD_GLOBAL | RTLD_LAZY, g_total_tls_size);
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VERIFY(success);
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bool success = loader.link(flags, s_total_tls_size);
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if (!success) {
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return DlErrorMessage { String::formatted("Failed to link library {}", loader.filename()) };
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}
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}
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for (auto& loader : loaders) {
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auto object = loader.load_stage_3(RTLD_GLOBAL | RTLD_LAZY, g_total_tls_size);
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VERIFY(object);
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auto result = loader.load_stage_3(flags, s_total_tls_size);
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VERIFY(!result.is_error());
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auto& object = result.value();
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if (loader.filename() == "libsystem.so") {
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if (syscall(SC_msyscall, object->base_address().as_ptr())) {
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loader.load_stage_4();
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}
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return main_executable_loader;
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return main_library_loader;
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}
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static Result<void, DlErrorMessage> __dlclose(void* handle)
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{
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dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlclose: {}", handle);
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__pthread_mutex_lock(&s_loader_lock);
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ScopeGuard unlock_guard = [] { __pthread_mutex_unlock(&s_loader_lock); };
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// FIXME: this will not currently destroy the dynamic object
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// because we're intentionally holding a strong reference to it
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// via s_global_objects until there's proper unload support.
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auto object = static_cast<ELF::DynamicObject*>(handle);
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object->unref();
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return {};
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}
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static Result<void*, DlErrorMessage> __dlopen(const char* filename, int flags)
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{
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// FIXME: RTLD_NOW and RTLD_LOCAL are not supported
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flags &= ~RTLD_NOW;
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flags |= RTLD_LAZY;
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flags &= ~RTLD_LOCAL;
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flags |= RTLD_GLOBAL;
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dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlopen invoked, filename={}, flags={}", filename, flags);
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auto library_name = get_library_name(filename ? filename : s_main_program_name);
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if (__pthread_mutex_trylock(&s_loader_lock) != 0)
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return DlErrorMessage { "Nested calls to dlopen() are not permitted." };
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ScopeGuard unlock_guard = [] { __pthread_mutex_unlock(&s_loader_lock); };
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auto existing_elf_object = s_global_objects.get(library_name);
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if (existing_elf_object.has_value()) {
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// It's up to the caller to release the ref with dlclose().
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return &existing_elf_object->leak_ref();
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}
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VERIFY(!library_name.is_empty());
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auto result1 = map_library(filename, false);
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if (result1.is_error()) {
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return result1.error();
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}
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auto result2 = map_dependencies(library_name);
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if (result2.is_error()) {
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return result2.error();
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}
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auto result = load_main_library(library_name, flags);
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if (result.is_error())
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return result.error();
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auto object = s_global_objects.get(library_name);
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if (!object.has_value())
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return DlErrorMessage { "Could not load ELF object." };
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// It's up to the caller to release the ref with dlclose().
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return &object->leak_ref();
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}
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static Result<void*, DlErrorMessage> __dlsym(void* handle, const char* symbol_name)
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{
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dbgln_if(DYNAMIC_LOAD_DEBUG, "__dlsym: {}, {}", handle, symbol_name);
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__pthread_mutex_lock(&s_loader_lock);
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ScopeGuard unlock_guard = [] { __pthread_mutex_unlock(&s_loader_lock); };
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auto object = static_cast<DynamicObject*>(handle);
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if (!handle) {
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auto library_name = get_library_name(s_main_program_name);
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auto global_object = s_global_objects.get(library_name);
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object = *global_object;
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}
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auto symbol = object->lookup_symbol(symbol_name);
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if (!symbol.has_value()) {
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return DlErrorMessage { String::formatted("Symbol {} not found", symbol_name) };
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}
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return symbol.value().address.as_ptr();
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}
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static void read_environment_variables()
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{
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for (char** env = g_envp; *env; ++env) {
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for (char** env = s_envp; *env; ++env) {
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if (StringView { *env } == "_LOADER_BREAKPOINT=1") {
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g_do_breakpoint_trap_before_entry = true;
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s_do_breakpoint_trap_before_entry = true;
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}
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}
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}
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void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_program_fd, bool is_secure, int argc, char** argv, char** envp)
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{
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g_envp = envp;
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s_envp = envp;
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g_allowed_to_check_environment_variables = !is_secure;
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||||
if (g_allowed_to_check_environment_variables)
|
||||
s_allowed_to_check_environment_variables = !is_secure;
|
||||
if (s_allowed_to_check_environment_variables)
|
||||
read_environment_variables();
|
||||
|
||||
map_library(main_program_name, main_program_fd);
|
||||
map_dependencies(main_program_name);
|
||||
s_main_program_name = main_program_name;
|
||||
|
||||
auto library_name = get_library_name(main_program_name);
|
||||
|
||||
// NOTE: We always map the main library first, since it may require
|
||||
// placement at a specific address.
|
||||
auto result1 = map_library(main_program_name, main_program_fd, true);
|
||||
if (result1.is_error()) {
|
||||
warnln("{}", result1.error().text);
|
||||
fflush(stderr);
|
||||
_exit(1);
|
||||
}
|
||||
result1.release_value();
|
||||
|
||||
auto result2 = map_dependencies(library_name);
|
||||
if (result2.is_error()) {
|
||||
warnln("{}", result2.error().text);
|
||||
fflush(stderr);
|
||||
_exit(1);
|
||||
}
|
||||
|
||||
dbgln_if(DYNAMIC_LOAD_DEBUG, "loaded all dependencies");
|
||||
for ([[maybe_unused]] auto& lib : g_loaders) {
|
||||
for ([[maybe_unused]] auto& lib : s_loaders) {
|
||||
dbgln_if(DYNAMIC_LOAD_DEBUG, "{} - tls size: {}, tls offset: {}", lib.key, lib.value->tls_size(), lib.value->tls_offset());
|
||||
}
|
||||
|
||||
allocate_tls();
|
||||
|
||||
auto entry_point_function = [&main_program_name] {
|
||||
auto main_executable_loader = load_main_executable(main_program_name);
|
||||
auto library_name = get_library_name(main_program_name);
|
||||
auto result = load_main_library(library_name, RTLD_GLOBAL | RTLD_LAZY);
|
||||
if (result.is_error()) {
|
||||
warnln("{}", result.error().text);
|
||||
_exit(1);
|
||||
}
|
||||
auto& main_executable_loader = result.value();
|
||||
auto entry_point = main_executable_loader->image().entry();
|
||||
if (main_executable_loader->is_dynamic())
|
||||
entry_point = entry_point.offset(main_executable_loader->base_address().get());
|
||||
return (EntryPointFunction)(entry_point.as_ptr());
|
||||
}();
|
||||
|
||||
g_loaders.clear();
|
||||
s_loaders.clear();
|
||||
|
||||
int rc = syscall(SC_msyscall, nullptr);
|
||||
if (rc < 0) {
|
||||
|
@ -300,13 +448,13 @@ void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_progra
|
|||
}
|
||||
|
||||
dbgln_if(DYNAMIC_LOAD_DEBUG, "Jumping to entry point: {:p}", entry_point_function);
|
||||
if (g_do_breakpoint_trap_before_entry) {
|
||||
if (s_do_breakpoint_trap_before_entry) {
|
||||
asm("int3");
|
||||
}
|
||||
rc = entry_point_function(argc, argv, envp);
|
||||
dbgln_if(DYNAMIC_LOAD_DEBUG, "rc: {}", rc);
|
||||
if (g_libc_exit != nullptr) {
|
||||
g_libc_exit(rc);
|
||||
if (s_libc_exit != nullptr) {
|
||||
s_libc_exit(rc);
|
||||
} else {
|
||||
_exit(rc);
|
||||
}
|
||||
|
|
Loading…
Add table
Add a link
Reference in a new issue