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DynamicLoader: Make everything thread safe 

This is kinda dumb implementation, but it works. We grap a global lock
on functions :)
This commit is contained in:
Bananymous 2025-11-02 22:44:45 +02:00
parent e258fde25a
commit 0be18c4a53
1 changed files with 55 additions and 5 deletions
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58
userspace/programs/DynamicLoader/main.cpp
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@ -4,6 +4,8 @@
#include <LibELF/Types.h> #include <LibELF/Types.h>
#include <LibELF/Values.h> #include <LibELF/Values.h>
#include <BAN/Atomic.h>
#include <dlfcn.h> #include <dlfcn.h>
#include <fcntl.h> #include <fcntl.h>
#include <limits.h> #include <limits.h>
@ -210,8 +212,34 @@ static size_t s_loaded_file_count = 0;
static const char* s_ld_library_path = nullptr; static const char* s_ld_library_path = nullptr;
static BAN::Atomic<pthread_t> s_global_locker = 0;
static uint32_t s_global_lock_depth = 0;
constexpr uintptr_t SYM_NOT_FOUND = -1; constexpr uintptr_t SYM_NOT_FOUND = -1;
static void lock_global_lock()
{
const pthread_t tid = syscall<>(SYS_PTHREAD_SELF);
pthread_t expected = 0;
while (!s_global_locker.compare_exchange(expected, tid))
{
if (expected == tid)
break;
syscall<>(SYS_YIELD);
expected = 0;
}
s_global_lock_depth++;
}
static void unlock_global_lock()
{
s_global_lock_depth--;
if (s_global_lock_depth == 0)
s_global_locker.store(false);
}
static uint32_t elf_hash(const char* name) static uint32_t elf_hash(const char* name)
{ {
uint32_t h = 0, g; uint32_t h = 0, g;
@ -725,13 +753,26 @@ extern "C"
__attribute__((used)) __attribute__((used))
uintptr_t resolve_symbol(const LoadedElf& elf, uintptr_t plt_entry) uintptr_t resolve_symbol(const LoadedElf& elf, uintptr_t plt_entry)
{ {
if (elf.pltrel == DT_REL) lock_global_lock();
return handle_relocation(elf, *reinterpret_cast<ElfNativeRelocation*>(elf.jmprel + plt_entry), true);
if (elf.pltrel == DT_RELA) uintptr_t result;
return handle_relocation(elf, reinterpret_cast<ElfNativeRelocationA*>(elf.jmprel)[plt_entry], true); switch (elf.pltrel)
{
case DT_REL:
result = handle_relocation(elf, *reinterpret_cast<ElfNativeRelocation*>(elf.jmprel + plt_entry), true);
break;
case DT_RELA:
result = handle_relocation(elf, reinterpret_cast<ElfNativeRelocationA*>(elf.jmprel)[plt_entry], true);
break;
default:
print_error_and_exit("invalid value for DT_PLTREL", 0); print_error_and_exit("invalid value for DT_PLTREL", 0);
} }
unlock_global_lock();
return result;
}
static LoadedElf& load_elf(const char* path, int fd); static LoadedElf& load_elf(const char* path, int fd);
static bool check_library(const char* library_dir, const char* library_name, char out[PATH_MAX]) static bool check_library(const char* library_dir, const char* library_name, char out[PATH_MAX])
@ -1022,9 +1063,16 @@ static bool load_symbol_table(LoadedElf& elf)
static LoadedElf& load_elf(const char* path, int fd) static LoadedElf& load_elf(const char* path, int fd)
{ {
lock_global_lock();
for (size_t i = 0; i < s_loaded_file_count; i++) for (size_t i = 0; i < s_loaded_file_count; i++)
{
if (strcmp(s_loaded_files[i].path, path) == 0) if (strcmp(s_loaded_files[i].path, path) == 0)
{
unlock_global_lock();
return s_loaded_files[i]; return s_loaded_files[i];
}
}
if (fd == -1 && (fd = syscall(SYS_OPENAT, AT_FDCWD, path, O_RDONLY)) < 0) if (fd == -1 && (fd = syscall(SYS_OPENAT, AT_FDCWD, path, O_RDONLY)) < 0)
print_error_and_exit("could not open library", fd); print_error_and_exit("could not open library", fd);
@ -1167,6 +1215,8 @@ static LoadedElf& load_elf(const char* path, int fd)
load_symbol_table(elf); load_symbol_table(elf);
unlock_global_lock();
return elf; return elf;
} }