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LibC+LibELF: Implement more fully-features dlfcn functionality

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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
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38
Userland/Libraries/LibELF/DynamicLoader.cpp
View file

@ -10,12 +10,14 @@
#include <AK/Optional.h>
#include <AK/QuickSort.h>
#include <AK/StringBuilder.h>
#include <LibDl/dlfcn.h>
#include <LibDl/dlfcn_integration.h>
#include <LibELF/DynamicLinker.h>
#include <LibELF/DynamicLoader.h>
#include <LibELF/Hashes.h>
#include <LibELF/Validation.h>
#include <assert.h>
#include <dlfcn.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@ -34,24 +36,22 @@ static void* mmap_with_name(void* addr, size_t length, int prot, int flags, int
namespace ELF {
RefPtr<DynamicLoader> DynamicLoader::try_create(int fd, String filename)
Result<NonnullRefPtr<DynamicLoader>, DlErrorMessage> DynamicLoader::try_create(int fd, String filename)
{
struct stat stat;
if (fstat(fd, &stat) < 0) {
perror("DynamicLoader::try_create fstat");
return {};
return DlErrorMessage { "DynamicLoader::try_create fstat" };
}
VERIFY(stat.st_size >= 0);
auto size = static_cast<size_t>(stat.st_size);
if (size < sizeof(Elf32_Ehdr))
return {};
return DlErrorMessage { String::formatted("File {} has invalid ELF header", filename) };
String file_mmap_name = String::formatted("ELF_DYN: {}", filename);
auto* data = mmap_with_name(nullptr, size, PROT_READ, MAP_PRIVATE, fd, 0, file_mmap_name.characters());
if (data == MAP_FAILED) {
perror("DynamicLoader::try_create mmap");
return {};
return DlErrorMessage { "DynamicLoader::try_create mmap" };
}
return adopt_ref(*new DynamicLoader(fd, move(filename), data, size));
@ -123,17 +123,6 @@ bool DynamicLoader::validate()
return true;
}
void* DynamicLoader::symbol_for_name(const StringView& name)
{
auto result = m_dynamic_object->hash_section().lookup_symbol(name);
if (!result.has_value())
return nullptr;
auto symbol = result.value();
if (symbol.is_undefined())
return nullptr;
return m_dynamic_object->base_address().offset(symbol.value()).as_ptr();
}
RefPtr<DynamicObject> DynamicLoader::map()
{
if (m_dynamic_object) {
@ -207,7 +196,7 @@ void DynamicLoader::do_main_relocations(size_t total_tls_size)
m_dynamic_object->plt_relocation_section().for_each_relocation(do_single_relocation);
}
RefPtr<DynamicObject> DynamicLoader::load_stage_3(unsigned flags, size_t total_tls_size)
Result<NonnullRefPtr<DynamicObject>, DlErrorMessage> DynamicLoader::load_stage_3(unsigned flags, size_t total_tls_size)
{
do_lazy_relocations(total_tls_size);
if (flags & RTLD_LAZY) {
@ -217,26 +206,23 @@ RefPtr<DynamicObject> DynamicLoader::load_stage_3(unsigned flags, size_t total_t
for (auto& text_segment : m_text_segments) {
if (mprotect(text_segment.address().as_ptr(), text_segment.size(), PROT_READ | PROT_EXEC) < 0) {
perror("mprotect .text: PROT_READ | PROT_EXEC"); // FIXME: dlerror?
return nullptr;
return DlErrorMessage { String::formatted("mprotect .text: PROT_READ | PROT_EXEC: {}", strerror(errno)) };
}
}
if (m_relro_segment_size) {
if (mprotect(m_relro_segment_address.as_ptr(), m_relro_segment_size, PROT_READ) < 0) {
perror("mprotect .relro: PROT_READ");
return nullptr;
return DlErrorMessage { String::formatted("mprotect .text: PROT_READ: {}", strerror(errno)) };
}
#if __serenity__
if (set_mmap_name(m_relro_segment_address.as_ptr(), m_relro_segment_size, String::formatted("{}: .relro", m_filename).characters()) < 0) {
perror("set_mmap_name .relro");
return nullptr;
return DlErrorMessage { String::formatted("set_mmap_name .relro: {}", strerror(errno)) };
}
#endif
}
return m_dynamic_object;
return NonnullRefPtr<DynamicObject> { *m_dynamic_object };
}
void DynamicLoader::load_stage_4()