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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.
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12 changed files with 371 additions and 200 deletions
6
Userland/Libraries/LibDl/CMakeLists.txt
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6
Userland/Libraries/LibDl/CMakeLists.txt
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set(SOURCES
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dlfcn.cpp
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)
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serenity_libc(LibDl dl)
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target_link_libraries(LibDl LibC)
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62
Userland/Libraries/LibDl/dlfcn.cpp
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62
Userland/Libraries/LibDl/dlfcn.cpp
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/*
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* Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/String.h>
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#include <AK/Types.h>
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#include <LibDl/dlfcn.h>
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#include <LibDl/dlfcn_integration.h>
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#include <string.h>
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// FIXME: use thread_local and a String once TLS works
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__thread char* s_dlerror_text = NULL;
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__thread bool s_dlerror_retrieved = false;
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static void store_error(const String& error)
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{
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free(s_dlerror_text);
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s_dlerror_text = strdup(error.characters());
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s_dlerror_retrieved = false;
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}
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int dlclose(void* handle)
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{
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auto result = __dlclose(handle);
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if (result.is_error()) {
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store_error(result.error().text);
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return -1;
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}
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return 0;
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}
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char* dlerror()
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{
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if (s_dlerror_retrieved) {
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free(s_dlerror_text);
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s_dlerror_text = nullptr;
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}
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s_dlerror_retrieved = true;
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return const_cast<char*>(s_dlerror_text);
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}
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void* dlopen(const char* file_name, int flags)
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{
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auto result = __dlopen(file_name, flags);
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if (result.is_error()) {
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store_error(result.error().text);
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return nullptr;
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}
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return result.value();
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}
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void* dlsym(void* handle, const char* symbol_name)
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{
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auto result = __dlsym(handle, symbol_name);
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if (result.is_error()) {
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store_error(result.error().text);
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return nullptr;
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}
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return result.value();
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}
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24
Userland/Libraries/LibDl/dlfcn.h
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24
Userland/Libraries/LibDl/dlfcn.h
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/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <sys/cdefs.h>
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__BEGIN_DECLS
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#define RTLD_DEFAULT 0
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#define RTLD_LAZY 2
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#define RTLD_NOW 4
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#define RTLD_GLOBAL 8
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#define RTLD_LOCAL 16
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int dlclose(void*);
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char* dlerror();
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void* dlopen(const char*, int);
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void* dlsym(void*, const char*);
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__END_DECLS
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34
Userland/Libraries/LibDl/dlfcn_integration.h
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34
Userland/Libraries/LibDl/dlfcn_integration.h
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/*
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* Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Result.h>
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#include <AK/String.h>
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struct DlErrorMessage {
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DlErrorMessage(String&& other)
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: text(move(other))
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{
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}
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// The virtual destructor is required because we're passing this
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// struct to the dynamic loader - whose operator delete differs
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// from the one in libc.so
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virtual ~DlErrorMessage() { }
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String text;
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};
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typedef Result<void, DlErrorMessage> (*DlCloseFunction)(void*);
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typedef Result<void*, DlErrorMessage> (*DlOpenFunction)(const char*, int);
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typedef Result<void*, DlErrorMessage> (*DlSymFunction)(void*, const char*);
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extern "C" {
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extern DlCloseFunction __dlclose;
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extern DlOpenFunction __dlopen;
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extern DlSymFunction __dlsym;
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}
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