Add support for user callbacks

src/windows-emulator/process_context.hpp

@@ -76,6 +76,8 @@ struct process_context
                const mapped_module& executable, const mapped_module& ntdll, const apiset::container& apiset_container,
                const mapped_module* ntdll32 = nullptr);
 
+    void setup_callback_hook(windows_emulator& win_emu, memory_manager& memory);
+
     handle create_thread(memory_manager& memory, uint64_t start_address, uint64_t argument, uint64_t stack_size, uint32_t create_flags,
                          bool initial_thread = false);
 
@@ -147,6 +149,8 @@ struct process_context
     handle_store<handle_types::thread, emulator_thread> threads{};
     emulator_thread* active_thread{nullptr};
 
+    emulator_pointer callback_sentinel_addr{0};
+
     // Extended parameters from last NtMapViewOfSectionEx call
     // These can be used by other syscalls like NtAllocateVirtualMemoryEx
     uint64_t last_extended_params_numa_node{0};