RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-27 09:47:35 +00:00
Code Issues Activity Actions

LibC+LibELF: Implement more fully-features dlfcn functionality

Browse source 
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:
Gunnar Beutner 2021-04-24 20:39:58 +02:00 • committed by Andreas Kling
parent 549d9bd3ea
commit f40ee1b03f
12 changed files with 371 additions and 200 deletions
Download patch file Download diff file Expand all files Collapse all files

95
Userland/Libraries/LibC/dlfcn.cpp
View file

@ -1,95 +1,12 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/HashMap.h>
#include <AK/LexicalPath.h>
#include <AK/RefPtr.h>
#include <AK/ScopeGuard.h>
#include <AK/String.h>
#include <LibELF/DynamicLoader.h>
#include <assert.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <unistd.h>
#include <LibDl/dlfcn_integration.h>
// NOTE: The string here should never include a trailing newline (according to POSIX)
String g_dlerror_msg;
HashMap<String, RefPtr<ELF::DynamicLoader>> g_elf_objects;
extern "C" {
int dlclose(void*)
{
g_dlerror_msg = "dlclose not implemented!";
return -1;
}
char* dlerror()
{
return const_cast<char*>(g_dlerror_msg.characters());
}
void* dlopen(const char* filename, int flags)
{
// FIXME: Create a global mutex/semaphore/lock for dlopen/dlclose/dlsym and (?) dlerror
// FIXME: refcount?
if (!filename) {
// FIXME: Return the handle for "the main executable"
// The Serenity Kernel will keep a mapping of the main elf binary resident in memory,
// But a future dynamic loader might have a different idea/way of letting us access this information
TODO();
}
auto basename = LexicalPath(filename).basename();
auto existing_elf_object = g_elf_objects.get(basename);
if (existing_elf_object.has_value()) {
return const_cast<ELF::DynamicLoader*>(existing_elf_object.value());
}
int fd = open(filename, O_RDONLY);
if (fd < 0) {
g_dlerror_msg = String::formatted("Unable to open file {}", filename);
return nullptr;
}
ScopeGuard close_fd_guard([fd]() { close(fd); });
auto loader = ELF::DynamicLoader::try_create(fd, filename);
if (!loader || !loader->is_valid()) {
g_dlerror_msg = String::formatted("{} is not a valid ELF dynamic shared object!", filename);
return nullptr;
}
auto object = loader->map();
if (!object || !loader->link(flags, /* total_tls_size (FIXME) */ 0)) {
g_dlerror_msg = String::formatted("Failed to load ELF object {}", filename);
return nullptr;
}
g_elf_objects.set(basename, move(loader));
g_dlerror_msg = "Successfully loaded ELF object.";
// we have one refcount already
return const_cast<ELF::DynamicLoader*>(g_elf_objects.get(basename).value());
}
void* dlsym(void* handle, const char* symbol_name)
{
// FIXME: When called with a NULL handle we're supposed to search every dso in the process... that'll get expensive
VERIFY(handle);
auto* dso = reinterpret_cast<ELF::DynamicLoader*>(handle);
void* symbol = dso->symbol_for_name(symbol_name);
if (!symbol) {
g_dlerror_msg = "Symbol not found";
return nullptr;
}
return symbol;
}
} // extern "C"
// These are used by libdl and are filled in by the dynamic loader.
DlCloseFunction __dlclose;
DlOpenFunction __dlopen;
DlSymFunction __dlsym;

24
Userland/Libraries/LibC/dlfcn.h
View file

@ -1,24 +0,0 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <sys/cdefs.h>
__BEGIN_DECLS
#define RTLD_DEFAULT 0
#define RTLD_LAZY 2
#define RTLD_NOW 4
#define RTLD_GLOBAL 8
#define RTLD_LOCAL 16
int dlclose(void*);
char* dlerror();
void* dlopen(const char*, int);
void* dlsym(void*, const char*);
__END_DECLS