767f4c7421
Separate some responsibilities: ELFDynamicLoader is responsible for loading elf binaries from disk and performing relocations, calling init functions, and eventually calling finalizer functions. ELFDynamicObject is a helper class to parse the .dynamic section of an elf binary, or the table of Elf32_Dyn entries at the _DYNAMIC symbol. ELFDynamicObject now owns the helper classes for Relocations, Symbols, Sections and the like that ELFDynamicLoader will use to perform relocations and symbol lookup. Because these new helpers are constructed from offsets into the .dynamic section within the loaded .data section of the binary, we don't need the ELFImage for nearly as much of the loading processes as we did before. Therefore we can remove most of the extra DynamicXXX classes and just keep the one that lets us find the location of _DYNAMIC in the new ELF. And finally, since we changed the name of the class that dlopen/dlsym care about, we need to compile/link and use the new ELFDynamicLoader class in LibC.
103 lines
2.8 KiB
C++
103 lines
2.8 KiB
C++
#include <assert.h>
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#include <dlfcn.h>
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#include <fcntl.h>
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#include <mman.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#include <AK/FileSystemPath.h>
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#include <AK/HashMap.h>
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#include <AK/RefPtr.h>
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#include <AK/ScopeGuard.h>
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#include <AK/String.h>
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#include <AK/StringBuilder.h>
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#include <LibELF/ELFDynamicLoader.h>
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// NOTE: The string here should never include a trailing newline (according to POSIX)
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String g_dlerror_msg;
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HashMap<String, RefPtr<ELFDynamicLoader>> g_elf_objects;
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extern "C" {
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int dlclose(void*)
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{
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g_dlerror_msg = "dlclose not implemented!";
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return -1;
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}
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char* dlerror()
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{
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return const_cast<char*>(g_dlerror_msg.characters());
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}
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void* dlopen(const char* filename, int flags)
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{
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// FIXME: Create a global mutex/semaphore/lock for dlopen/dlclose/dlsym and (?) dlerror
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// FIXME: refcount?
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if (!filename) {
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// FIXME: Return the handle for "the main executable"
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// The Serenity Kernel will keep a mapping of the main elf binary resident in memory,
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// But a future dynamic loader might have a different idea/way of letting us access this information
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ASSERT_NOT_REACHED();
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}
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FileSystemPath file_path(filename);
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auto existing_elf_object = g_elf_objects.get(file_path.basename());
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if (existing_elf_object.has_value()) {
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void* referenced_object = existing_elf_object.value().leak_ref();
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return referenced_object;
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}
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int fd = open(filename, O_RDONLY);
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if (!fd) {
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g_dlerror_msg = String::format("Unable to open file %s", filename);
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return nullptr;
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}
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ScopeGuard close_fd_guard([fd]() { close(fd); });
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struct stat file_stats{};
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int ret = fstat(fd, &file_stats);
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if (ret < 0) {
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g_dlerror_msg = String::format("Unable to stat file %s", filename);
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return nullptr;
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}
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auto loader = ELFDynamicLoader::construct(filename, fd, file_stats.st_size);
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if (!loader->is_valid()) {
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g_dlerror_msg = String::format("%s is not a valid ELF dynamic shared object!", filename);
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return nullptr;
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}
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if (!loader->load_from_image(flags)) {
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g_dlerror_msg = String::format("Failed to load ELF object %s", filename);
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return nullptr;
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}
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g_elf_objects.set(file_path.basename(), move(loader));
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g_dlerror_msg = "Successfully loaded ELF object.";
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// we have one refcount already
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return g_elf_objects.get(file_path.basename()).value().ptr();
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}
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void* dlsym(void* handle, const char* symbol_name)
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{
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// FIXME: When called with a NULL handle we're supposed to search every dso in the process... that'll get expensive
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ASSERT(handle);
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auto* dso = reinterpret_cast<ELFDynamicLoader*>(handle);
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void* symbol = dso->symbol_for_name(symbol_name);
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if (!symbol) {
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g_dlerror_msg = "Symbol not found";
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return nullptr;
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}
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return symbol;
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}
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} // extern "C"
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