Loader.so+LibELF: Move most of Loader.so's logic into ELF::DynamicLinker

Loader.so now just performs the initial self relocations and static
LibC initialisation before handing over to ELF::DynamicLinker::linker_main
to handle the rest of the process.

As a trade-off, ELF::DynamicLinker needs to be explicitly excluded from
Lagom unless we really want to try writing a cross platform dynamic loader

Libraries/LibELF/DynamicLinker.cpp

@@ -0,0 +1,250 @@
+/*
+ * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
+ * Copyright (c) 2021, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/HashMap.h>
+#include <AK/HashTable.h>
+#include <AK/LexicalPath.h>
+#include <AK/LogStream.h>
+#include <AK/ScopeGuard.h>
+#include <LibC/mman.h>
+#include <LibC/stdio.h>
+#include <LibC/sys/internals.h>
+#include <LibC/unistd.h>
+#include <LibCore/File.h>
+#include <LibELF/AuxiliaryVector.h>
+#include <LibELF/DynamicLinker.h>
+#include <LibELF/DynamicLoader.h>
+#include <LibELF/DynamicObject.h>
+#include <LibELF/Image.h>
+#include <LibELF/exec_elf.h>
+#include <dlfcn.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+// #define DYNAMIC_LOAD_VERBOSE
+
+#ifdef DYNAMIC_LOAD_VERBOSE
+#    define VERBOSE(fmt, ...) dbgprintf(fmt, ##__VA_ARGS__)
+#else
+#    define VERBOSE(fmt, ...) \
+        do {                  \
+        } while (0)
+#endif
+#define TLS_VERBOSE(fmt, ...) dbgprintf(fmt, ##__VA_ARGS__)
+
+namespace ELF {
+
+namespace {
+HashMap<String, NonnullRefPtr<ELF::DynamicLoader>> g_loaders;
+HashMap<String, NonnullRefPtr<ELF::DynamicObject>> g_loaded_objects;
+Vector<NonnullRefPtr<ELF::DynamicObject>> g_global_objects;
+
+using MainFunction = int (*)(int, char**, char**);
+using LibCExitFunction = void (*)(int);
+
+size_t g_current_tls_offset = 0;
+size_t g_total_tls_size = 0;
+char** g_envp = nullptr;
+LibCExitFunction g_libc_exit = nullptr;
+}
+
+DynamicObject::SymbolLookupResult DynamicLinker::lookup_global_symbol(const char* symbol_name)
+{
+    DynamicObject::SymbolLookupResult weak_result = {};
+    for (auto& lib : g_global_objects) {
+        auto res = lib->lookup_symbol(symbol_name);
+        if (res.found) {
+            if (res.bind == STB_GLOBAL) {
+                return res;
+            } else if (res.bind == STB_WEAK && !weak_result.found) {
+                weak_result = res;
+            }
+            // We don't want to allow local symbols to be pulled in to other modules
+        }
+    }
+    return weak_result;
+}
+
+static void map_library(const String& name, int fd)
+{
+    struct stat lib_stat;
+    int rc = fstat(fd, &lib_stat);
+    ASSERT(!rc);
+
+    auto loader = ELF::DynamicLoader::construct(name.characters(), fd, lib_stat.st_size);
+    loader->set_tls_offset(g_current_tls_offset);
+
+    g_loaders.set(name, loader);
+
+    g_current_tls_offset += loader->tls_size();
+}
+
+static void map_library(const String& name)
+{
+    // TODO: Do we want to also look for libs in other paths too?
+    String path = String::format("/usr/lib/%s", name.characters());
+    int fd = open(path.characters(), O_RDONLY);
+    ASSERT(fd >= 0);
+    map_library(name, fd);
+}
+
+static String get_library_name(const StringView& path)
+{
+    return LexicalPath(path).basename();
+}
+
+static Vector<String> get_dependencies(const String& name)
+{
+    auto lib = g_loaders.get(name).value();
+    Vector<String> dependencies;
+
+    lib->for_each_needed_library([&dependencies, &name](auto needed_name) {
+        if (name == needed_name)
+            return IterationDecision::Continue;
+        dependencies.append(needed_name);
+        return IterationDecision::Continue;
+    });
+    return dependencies;
+}
+
+static void map_dependencies(const String& name)
+{
+    VERBOSE("mapping dependencies for: %s\n", name.characters());
+
+    for (const auto& needed_name : get_dependencies(name)) {
+        VERBOSE("needed library: %s\n", needed_name.characters());
+        String library_name = get_library_name(needed_name);
+
+        if (!g_loaders.contains(library_name)) {
+            map_library(library_name);
+            map_dependencies(library_name);
+        }
+    }
+    VERBOSE("mapped dependencies for %s\n", name.characters());
+}
+
+static void allocate_tls()
+{
+    size_t total_tls_size = 0;
+    for (const auto& data : g_loaders) {
+        VERBOSE("%s: TLS Size: %zu\n", data.key.characters(), data.value->tls_size());
+        total_tls_size += data.value->tls_size();
+    }
+    if (total_tls_size) {
+        [[maybe_unused]] void* tls_address = ::allocate_tls(total_tls_size);
+        VERBOSE("from userspace, tls_address: %p\n", tls_address);
+    }
+    g_total_tls_size = total_tls_size;
+}
+
+static void initialize_libc(DynamicObject& libc)
+{
+    // Traditionally, `_start` of the main program initializes libc.
+    // However, since some libs use malloc() and getenv() in global constructors,
+    // we have to initialize libc just after it is loaded.
+    // Also, we can't just mark `__libc_init` with "__attribute__((constructor))"
+    // because it uses getenv() internally, so `environ` has to be initialized before we call `__libc_init`.
+    auto res = libc.lookup_symbol("environ");
+    ASSERT(res.found);
+    *((char***)res.address) = g_envp;
+
+    res = libc.lookup_symbol("__environ_is_malloced");
+    ASSERT(res.found);
+    *((bool*)res.address) = false;
+
+    res = libc.lookup_symbol("exit");
+    ASSERT(res.found);
+    g_libc_exit = (LibCExitFunction)res.address;
+
+    res = libc.lookup_symbol("__libc_init");
+    ASSERT(res.found);
+    typedef void libc_init_func();
+    ((libc_init_func*)res.address)();
+}
+
+static void load_elf(const String& name)
+{
+    VERBOSE("load_elf: %s\n", name.characters());
+    auto loader = g_loaders.get(name).value();
+    VERBOSE("a1\n");
+    for (const auto& needed_name : get_dependencies(name)) {
+        VERBOSE("needed library: %s\n", needed_name.characters());
+        String library_name = get_library_name(needed_name);
+        if (!g_loaded_objects.contains(library_name)) {
+            load_elf(library_name);
+        }
+    }
+
+    auto dynamic_object = loader->load_from_image(RTLD_GLOBAL | RTLD_LAZY, g_total_tls_size);
+    ASSERT(dynamic_object);
+
+    g_loaded_objects.set(name, *dynamic_object);
+    g_global_objects.append(*dynamic_object);
+
+    VERBOSE("load_elf: done %s\n", name.characters());
+    if (name == "libc.so") {
+        initialize_libc(*dynamic_object);
+    }
+}
+
+void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_program_fd, int argc, char** argv, char** envp)
+{
+    g_envp = envp;
+    map_library(main_program_name, main_program_fd);
+    map_dependencies(main_program_name);
+
+    VERBOSE("loaded all dependencies");
+    for ([[maybe_unused]] auto& lib : g_loaders) {
+        VERBOSE("%s - tls size: %zu, tls offset: %zu\n", lib.key.characters(), lib.value->tls_size(), lib.value->tls_offset());
+    }
+
+    allocate_tls();
+
+    load_elf(main_program_name);
+    auto main_program_lib = g_loaders.get(main_program_name).value();
+
+    FlatPtr entry_point = reinterpret_cast<FlatPtr>(main_program_lib->image().entry().as_ptr());
+    if (main_program_lib->is_dynamic())
+        entry_point += reinterpret_cast<FlatPtr>(main_program_lib->text_segment_load_address().as_ptr());
+
+    VERBOSE("entry point: %p\n", (void*)entry_point);
+    g_loaders.clear();
+
+    MainFunction main_function = (MainFunction)(entry_point);
+    VERBOSE("jumping to main program entry point: %p\n", main_function);
+    int rc = main_function(argc, argv, envp);
+    VERBOSE("rc: %d\n", rc);
+    if (g_libc_exit != nullptr) {
+        g_libc_exit(rc);
+    } else {
+        _exit(rc);
+    }
+
+    ASSERT_NOT_REACHED();
+}
+}

Libraries/LibELF/DynamicLinker.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2021 (c), the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Result.h>
+#include <AK/Vector.h>
+#include <LibELF/DynamicObject.h>
+
+namespace ELF {
+
+class DynamicLinker {
+public:
+    static DynamicObject::SymbolLookupResult lookup_global_symbol(const char* symbol);
+    [[noreturn]] static void linker_main(String&& main_program_name, int fd, int argc, char** argv, char** envp);
+
+private:
+    DynamicLinker() = delete;
+    ~DynamicLinker() = delete;
+};
+
+}

Libraries/LibELF/DynamicLoader.cpp

@@ -162,8 +162,6 @@ RefPtr<DynamicObject> DynamicLoader::load_from_image(unsigned flags, size_t tota
     m_dynamic_object = DynamicObject::construct(m_text_segment_load_address, m_dynamic_section_address);
     m_dynamic_object->set_tls_offset(m_tls_offset);
     m_dynamic_object->set_tls_size(m_tls_size);
-    ASSERT(m_global_symbol_lookup_func);
-    m_dynamic_object->m_global_symbol_lookup_func = m_global_symbol_lookup_func;
 
     auto rc = load_stage_2(flags, total_tls_size);
     if (!rc) {

Libraries/LibELF/DynamicLoader.h

@@ -75,9 +75,6 @@ public:
     template<typename F>
     void for_each_needed_library(F) const;
 
-    DynamicObject::SymbolLookupFunction m_global_symbol_lookup_func { nullptr };
-    void set_global_symbol_lookup_function(DynamicObject::SymbolLookupFunction func) { m_global_symbol_lookup_func = func; }
-
     VirtualAddress text_segment_load_address() const { return m_text_segment_load_address; }
     bool is_dynamic() const { return m_elf_image.is_dynamic(); }
 

Libraries/LibELF/DynamicObject.cpp

@@ -27,6 +27,7 @@
 
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
+#include <LibELF/DynamicLinker.h>
 #include <LibELF/DynamicObject.h>
 #include <LibELF/exec_elf.h>
 #include <stdio.h>
@@ -406,12 +407,12 @@ static const char* name_for_dtag(Elf32_Sword d_tag)
     }
 }
 
-Optional<DynamicObject::SymbolLookupResult> DynamicObject::lookup_symbol(const char* name) const
+DynamicObject::SymbolLookupResult DynamicObject::lookup_symbol(const char* name) const
 {
     auto res = hash_section().lookup_symbol(name);
     if (res.is_undefined())
         return {};
-    return SymbolLookupResult { true, res.value(), (FlatPtr)res.address().as_ptr(), this };
+    return SymbolLookupResult { true, res.value(), (FlatPtr)res.address().as_ptr(), res.bind(), this };
 }
 
 NonnullRefPtr<DynamicObject> DynamicObject::construct(VirtualAddress base_address, VirtualAddress dynamic_section_address)
@@ -450,10 +451,9 @@ DynamicObject::SymbolLookupResult DynamicObject::lookup_symbol(const ELF::Dynami
     VERBOSE("looking up symbol: %s\n", symbol.name());
     if (!symbol.is_undefined()) {
         VERBOSE("symbol is defined in its object\n");
-        return { true, symbol.value(), (FlatPtr)symbol.address().as_ptr(), &symbol.object() };
+        return { true, symbol.value(), (FlatPtr)symbol.address().as_ptr(), symbol.bind(), &symbol.object() };
     }
-    ASSERT(m_global_symbol_lookup_func);
-    return m_global_symbol_lookup_func(symbol.name());
+    return DynamicLinker::lookup_global_symbol(symbol.name());
 }
 
 } // end namespace ELF

Libraries/LibELF/DynamicObject.h

@@ -276,9 +276,10 @@ public:
         bool found { false };
         FlatPtr value { 0 };
         FlatPtr address { 0 };
+        unsigned bind { STB_LOCAL };
         const ELF::DynamicObject* dynamic_object { nullptr }; // The object in which the symbol is defined
     };
-    Optional<SymbolLookupResult> lookup_symbol(const char* name) const;
+    SymbolLookupResult lookup_symbol(const char* name) const;
 
     // Will be called from _fixup_plt_entry, as part of the PLT trampoline
     Elf32_Addr patch_plt_entry(u32 relocation_offset);

Meta/Lagom/CMakeLists.txt

@@ -44,6 +44,10 @@ file(GLOB LIBREGEX_LIBC_SOURCES "../../Libraries/LibRegex/C/Regex.cpp")
 file(GLOB LIBREGEX_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibRegex/*.cpp")
 file(GLOB LIBCORE_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibCore/*.cpp")
 file(GLOB LIBELF_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibELF/*.cpp")
+# There's no way we can reliably make this cross platform
+list(REMOVE_ITEM LIBELF_SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/../../Libraries/LibELF/DynamicLinker.cpp")
+
+
 file(GLOB LIBGEMINI_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibGemini/*.cpp")
 file(GLOB LIBGFX_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibGfx/*.cpp")
 file(GLOB LIBHTTP_SOURCES CONFIGURE_DEPENDS "../../Libraries/LibHTTP/*.cpp")

Userland/DynamicLoader/main.cpp

@@ -35,6 +35,7 @@
 #include <LibC/unistd.h>
 #include <LibCore/File.h>
 #include <LibELF/AuxiliaryVector.h>
+#include <LibELF/DynamicLinker.h>
 #include <LibELF/DynamicLoader.h>
 #include <LibELF/DynamicObject.h>
 #include <LibELF/Image.h>
@@ -57,23 +58,14 @@
 
 char* __static_environ[] = { nullptr }; // We don't get the environment without some libc workarounds..
 
-static HashMap<String, NonnullRefPtr<ELF::DynamicLoader>> g_loaders;
-static HashMap<String, NonnullRefPtr<ELF::DynamicObject>> g_loaded_objects;
-
-using MainFunction = int (*)(int, char**, char**);
-using LibCExitFunction = void (*)(int);
-
-static size_t g_current_tls_offset = 0;
-static size_t g_total_tls_size = 0;
-static char** g_envp = nullptr;
-static LibCExitFunction g_libc_exit = nullptr;
-
 static void init_libc()
 {
     environ = __static_environ;
     __environ_is_malloced = false;
     __stdio_is_initialized = false;
-    __malloc_init();
+    // Initialise the copy of libc included statically in Loader.so,
+    // initialisation of the dynamic libc.so is done by the DynamicLinker
+    __libc_init();
 }
 
 static void perform_self_relocations(auxv_t* auxvp)
@@ -112,144 +104,6 @@ static void perform_self_relocations(auxv_t* auxvp)
     });
 }
 
-static ELF::DynamicObject::SymbolLookupResult global_symbol_lookup(const char* symbol_name)
-{
-    VERBOSE("global symbol lookup: %s\n", symbol_name);
-    for (auto& lib : g_loaded_objects) {
-        VERBOSE("looking up in object: %s\n", lib.key.characters());
-        auto res = lib.value->lookup_symbol(symbol_name);
-        if (!res.has_value())
-            continue;
-        return res.value();
-    }
-    // ASSERT_NOT_REACHED();
-    return {};
-}
-
-static void map_library(const String& name, int fd)
-{
-    struct stat lib_stat;
-    int rc = fstat(fd, &lib_stat);
-    ASSERT(!rc);
-
-    auto loader = ELF::DynamicLoader::construct(name.characters(), fd, lib_stat.st_size);
-    loader->set_tls_offset(g_current_tls_offset);
-    loader->set_global_symbol_lookup_function(global_symbol_lookup);
-
-    g_loaders.set(name, loader);
-
-    g_current_tls_offset += loader->tls_size();
-}
-
-static void map_library(const String& name)
-{
-    // TODO: Do we want to also look for libs in other paths too?
-    String path = String::format("/usr/lib/%s", name.characters());
-    int fd = open(path.characters(), O_RDONLY);
-    ASSERT(fd >= 0);
-    map_library(name, fd);
-}
-
-static String get_library_name(const StringView& path)
-{
-    return LexicalPath(path).basename();
-}
-
-static Vector<String> get_dependencies(const String& name)
-{
-    auto lib = g_loaders.get(name).value();
-    Vector<String> dependencies;
-
-    lib->for_each_needed_library([&dependencies, &name](auto needed_name) {
-        if (name == needed_name)
-            return IterationDecision::Continue;
-        dependencies.append(needed_name);
-        return IterationDecision::Continue;
-    });
-    return dependencies;
-}
-
-static void map_dependencies(const String& name)
-{
-    VERBOSE("mapping dependencies for: %s\n", name.characters());
-
-    for (const auto& needed_name : get_dependencies(name)) {
-        VERBOSE("needed library: %s\n", needed_name.characters());
-        String library_name = get_library_name(needed_name);
-
-        if (!g_loaders.contains(library_name)) {
-            map_library(library_name);
-            map_dependencies(library_name);
-        }
-    }
-}
-
-static void allocate_tls()
-{
-    size_t total_tls_size = 0;
-    for (const auto& data : g_loaders) {
-        VERBOSE("%s: TLS Size: %zu\n", data.key.characters(), data.value->tls_size());
-        total_tls_size += data.value->tls_size();
-    }
-    if (total_tls_size) {
-        [[maybe_unused]] void* tls_address = allocate_tls(total_tls_size);
-        VERBOSE("from userspace, tls_address: %p\n", tls_address);
-    }
-    g_total_tls_size = total_tls_size;
-}
-
-static void initialize_libc()
-{
-    // Traditionally, `_start` of the main program initializes libc.
-    // However, since some libs use malloc() and getenv() in global constructors,
-    // we have to initialize libc just after it is loaded.
-    // Also, we can't just mark `__libc_init` with "__attribute__((constructor))"
-    // because it uses getenv() internally, so `environ` has to be initialized before we call `__libc_init`.
-    auto res = global_symbol_lookup("environ");
-    *((char***)res.address) = g_envp;
-    ASSERT(res.found);
-    res = global_symbol_lookup("__environ_is_malloced");
-    ASSERT(res.found);
-    *((bool*)res.address) = false;
-
-    res = global_symbol_lookup("exit");
-    ASSERT(res.found);
-    g_libc_exit = (LibCExitFunction)res.address;
-
-    res = global_symbol_lookup("__libc_init");
-    ASSERT(res.found);
-    typedef void libc_init_func();
-    ((libc_init_func*)res.address)();
-}
-
-static void load_elf(const String& name)
-{
-    VERBOSE("load_elf: %s\n", name.characters());
-    auto loader = g_loaders.get(name).value();
-    VERBOSE("a1\n");
-    for (const auto& needed_name : get_dependencies(name)) {
-        VERBOSE("needed library: %s\n", needed_name.characters());
-        String library_name = get_library_name(needed_name);
-        if (!g_loaded_objects.contains(library_name)) {
-            load_elf(library_name);
-        }
-    }
-
-    auto dynamic_object = loader->load_from_image(RTLD_GLOBAL | RTLD_LAZY, g_total_tls_size);
-    ASSERT(!dynamic_object.is_null());
-    g_loaded_objects.set(name, dynamic_object.release_nonnull());
-
-    if (name == "libc.so") {
-        initialize_libc();
-    }
-}
-
-static void clear_temporary_objects_mappings()
-{
-
-    g_loaders.clear();
-}
-
 static void display_help()
 {
     const char message[] =
@@ -261,11 +115,24 @@ This helper program loads the shared libraries needed by the program,
 prepares the program to run, and runs it. You do not need to invoke
 this helper program directly.
 )";
-    write(1, message, sizeof(message));
+    fprintf(stderr, "%s", message);
 }
 
-static FlatPtr loader_main(auxv_t* auxvp)
+extern "C" {
+
+// The compiler expects a previous declaration
+void _start(int, char**, char**);
+
+void _start(int argc, char** argv, char** envp)
 {
+    char** env;
+    for (env = envp; *env; ++env) {
+    }
+
+    auxv_t* auxvp = (auxv_t*)++env;
+    perform_self_relocations(auxvp);
+    init_libc();
+
     int main_program_fd = -1;
     String main_program_name;
     for (; auxvp->a_type != AT_NULL; ++auxvp) {
@@ -288,62 +155,7 @@ static FlatPtr loader_main(auxv_t* auxvp)
         _exit(1);
     }
 
-    map_library(main_program_name, main_program_fd);
-    map_dependencies(main_program_name);
-
-    VERBOSE("loaded all dependencies");
-    for ([[maybe_unused]] auto& lib : g_loaders) {
-        VERBOSE("%s - tls size: %zu, tls offset: %zu\n", lib.key.characters(), lib.value->tls_size(), lib.value->tls_offset());
-    }
-
-    allocate_tls();
-
-    load_elf(main_program_name);
-
-    auto main_program_lib = g_loaders.get(main_program_name).value();
-
-    FlatPtr entry_point = reinterpret_cast<FlatPtr>(main_program_lib->image().entry().as_ptr());
-    if (main_program_lib->is_dynamic())
-        entry_point += reinterpret_cast<FlatPtr>(main_program_lib->text_segment_load_address().as_ptr());
-
-    VERBOSE("entry point: %p\n", (void*)entry_point);
-
-    // This will unmap the temporary memory maps we had for loading the libraries
-    clear_temporary_objects_mappings();
-
-    return entry_point;
-}
-
-extern "C" {
-
-// The compiler expects a previous declaration
-void _start(int, char**, char**);
-
-void _start(int argc, char** argv, char** envp)
-{
-    g_envp = envp;
-    char** env;
-    for (env = envp; *env; ++env) {
-    }
-
-    auxv_t* auxvp = (auxv_t*)++env;
-    perform_self_relocations(auxvp);
-    init_libc();
-
-    FlatPtr entry = loader_main(auxvp);
-    VERBOSE("Loaded libs:\n");
-    for ([[maybe_unused]] auto& obj : g_loaded_objects) {
-        VERBOSE("%s: %p\n", obj.key.characters(), obj.value->base_address().as_ptr());
-    }
-
-    MainFunction main_function = (MainFunction)(entry);
-    VERBOSE("jumping to main program entry point: %p\n", main_function);
-    int rc = main_function(argc, argv, envp);
-    VERBOSE("rc: %d\n", rc);
-    if (g_libc_exit != nullptr) {
-        g_libc_exit(rc);
-    } else {
-        _exit(rc);
-    }
+    ELF::DynamicLinker::linker_main(move(main_program_name), main_program_fd, argc, argv, envp);
+    ASSERT_NOT_REACHED();
 }
 }