From 40a8b009dbda856caa699e8d0a879ca13b647e16 Mon Sep 17 00:00:00 2001 From: Liav A Date: Sun, 17 Sep 2023 12:08:35 +0300 Subject: [PATCH] DynamicLoader: Add an option to list all ELF loaded dependencies This actually allows us to re-introduce the ldd utility as a symlink to our dynamic loader, so now ldd behaves exactly like on Linux - it will load all dynamic dependencies for an ELF exectuable. This has the advantage that running ldd on an ELF executable will provide an exact preview of how the order in which the dynamic loader loads the executable and its dependencies. --- Userland/DynamicLoader/main.cpp | 21 +++++++++++++++++++-- Userland/Libraries/LibELF/DynamicLinker.cpp | 5 +++++ Userland/Libraries/LibELF/DynamicLinker.h | 1 + Userland/Utilities/CMakeLists.txt | 1 + 4 files changed, 26 insertions(+), 2 deletions(-) diff --git a/Userland/DynamicLoader/main.cpp b/Userland/DynamicLoader/main.cpp index 68778e41767..6857aa5f44b 100644 --- a/Userland/DynamicLoader/main.cpp +++ b/Userland/DynamicLoader/main.cpp @@ -4,6 +4,7 @@ * SPDX-License-Identifier: BSD-2-Clause */ +#include #include #include #include @@ -48,6 +49,12 @@ static ErrorOr open_executable(StringView path) return checked_fd; } +static int print_loaded_libraries_callback(struct dl_phdr_info* info, size_t, void*) +{ + outln("{}", info->dlpi_name); + return 0; +} + static int _main(int argc, char** argv, char** envp, bool is_secure) { Vector arguments; @@ -56,14 +63,22 @@ static int _main(int argc, char** argv, char** envp, bool is_secure) arguments.unchecked_append({ argv[i], strlen(argv[i]) }); bool flag_dry_run { false }; + bool flag_list_loaded_dependencies { false }; Vector command; StringView argv0; Core::ArgsParser args_parser; args_parser.set_general_help("Run dynamically-linked ELF executables"); args_parser.set_stop_on_first_non_option(true); - args_parser.add_option(flag_dry_run, "Run in dry-run mode", "dry-run", 'd'); - args_parser.add_option(argv0, "Run with custom argv0", "argv0", 'E', "custom argv0"); + + if (LexicalPath::basename(arguments[0]) == "ldd"sv) { + flag_list_loaded_dependencies = true; + flag_dry_run = true; + } else { + args_parser.add_option(flag_dry_run, "Run in dry-run mode", "dry-run", 'd'); + args_parser.add_option(flag_list_loaded_dependencies, "List all loaded dependencies", "list", 'l'); + args_parser.add_option(argv0, "Run with custom argv0", "argv0", 'E', "custom argv0"); + } args_parser.add_positional_argument(command, "Command to execute", "command"); // NOTE: Don't use regular PrintUsageAndExit policy for ArgsParser, as it will simply // fail with a nullptr-dereference as the LibC exit function is not suitable for usage @@ -97,6 +112,8 @@ static int _main(int argc, char** argv, char** envp, bool is_secure) argv[0] = const_cast(argv0.characters_without_null_termination()); auto entry_point = ELF::DynamicLinker::linker_main(move(main_program_path), main_program_fd, is_secure, envp); + if (flag_list_loaded_dependencies) + ELF::DynamicLinker::iterate_over_loaded_shared_objects(print_loaded_libraries_callback, nullptr); if (flag_dry_run) return 0; _invoke_entry(command.size(), argv, envp, entry_point); diff --git a/Userland/Libraries/LibELF/DynamicLinker.cpp b/Userland/Libraries/LibELF/DynamicLinker.cpp index 5ed91404f1e..e2c06051d35 100644 --- a/Userland/Libraries/LibELF/DynamicLinker.cpp +++ b/Userland/Libraries/LibELF/DynamicLinker.cpp @@ -336,6 +336,11 @@ static int __dl_iterate_phdr(DlIteratePhdrCallbackFunction callback, void* data) return 0; } +int DynamicLinker::iterate_over_loaded_shared_objects(int (*callback)(struct dl_phdr_info* info, size_t size, void* data), void* data) +{ + return __dl_iterate_phdr(callback, data); +} + static void initialize_libc(DynamicObject& libc) { auto res = libc.lookup_symbol("__libc_init"sv); diff --git a/Userland/Libraries/LibELF/DynamicLinker.h b/Userland/Libraries/LibELF/DynamicLinker.h index eac607777d8..64e7d0bb6ee 100644 --- a/Userland/Libraries/LibELF/DynamicLinker.h +++ b/Userland/Libraries/LibELF/DynamicLinker.h @@ -18,6 +18,7 @@ class DynamicLinker { public: static Optional lookup_global_symbol(StringView symbol); static EntryPointFunction linker_main(ByteString&& main_program_path, int fd, bool is_secure, char** envp); + static int iterate_over_loaded_shared_objects(int (*callback)(struct dl_phdr_info* info, size_t size, void* data), void* data); static Optional resolve_library(ByteString const& name, DynamicObject const& parent_object); diff --git a/Userland/Utilities/CMakeLists.txt b/Userland/Utilities/CMakeLists.txt index ad6aff695eb..5db3628b582 100644 --- a/Userland/Utilities/CMakeLists.txt +++ b/Userland/Utilities/CMakeLists.txt @@ -72,6 +72,7 @@ install(CODE "file(CREATE_LINK grep ${CMAKE_INSTALL_PREFIX}/bin/fgrep SYMBOLIC)" install(CODE "file(CREATE_LINK grep ${CMAKE_INSTALL_PREFIX}/bin/rgrep SYMBOLIC)") install(CODE "file(CREATE_LINK gzip ${CMAKE_INSTALL_PREFIX}/bin/gunzip SYMBOLIC)") install(CODE "file(CREATE_LINK gzip ${CMAKE_INSTALL_PREFIX}/bin/zcat SYMBOLIC)") +install(CODE "file(CREATE_LINK /usr/lib/Loader.so ${CMAKE_INSTALL_PREFIX}/bin/ldd SYMBOLIC)") target_link_libraries(abench PRIVATE LibAudio LibFileSystem) target_link_libraries(aconv PRIVATE LibAudio LibFileSystem)