Function TopLevelFilter

src/runtime/crash_handler.cpp:201–263

}

LONG WINAPI TopLevelFilter(EXCEPTION_POINTERS* ep) {
    bool expected = false;
    if (!g_handling.compare_exchange_strong(expected, true)) {
        // Already handling a prior crash on another thread: just terminate.
        return EXCEPTION_EXECUTE_HANDLER;
    }

    EnsureCrashDir();
    char stamp[64];
    FormatStamp(stamp, sizeof(stamp));

    // Snapshot guest console first (cheap, no external calls).
    std::string guest_tail;
    {
        // Best-effort: if the lock is currently held by the faulting thread
        // try_lock prevents a deadlock at the cost of missing a few bytes.
        if (g_guest.mu.try_lock()) {
            guest_tail = SnapshotLocked(g_guest);
            g_guest.mu.unlock();
        }
    }

    if (!g_config.crash_dir.empty()) {
        std::string dump_path = JoinPath(g_config.crash_dir,
                                        std::string("crash_") + stamp + ".dmp");

        HANDLE file = CreateFileA(dump_path.c_str(), GENERIC_WRITE, 0, nullptr,
                                   CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
        if (file != INVALID_HANDLE_VALUE) {
            MINIDUMP_EXCEPTION_INFORMATION info{};
            info.ThreadId = GetCurrentThreadId();
            info.ExceptionPointers = ep;
            info.ClientPointers = FALSE;

            // MiniDumpWithDataSegs + indirectly referenced memory gives a
            // useful stack-walkable dump without bloating to a full heap.
            // Keep the size manageable — host VM process may have many GB of
            // guest RAM mapped, which we deliberately omit.
            MINIDUMP_TYPE type = static_cast<MINIDUMP_TYPE>(
                MiniDumpWithDataSegs |
                MiniDumpWithHandleData |
                MiniDumpWithIndirectlyReferencedMemory |
                MiniDumpWithThreadInfo |
                MiniDumpWithUnloadedModules);

            MiniDumpWriteDump(GetCurrentProcess(), GetCurrentProcessId(),
                               file, type, ep ? &info : nullptr, nullptr, nullptr);
            FlushFileBuffers(file);
            CloseHandle(file);
        }

        WriteMetaFile(stamp, ep, guest_tail);

        // Also write a line to stderr so it shows up in runtime.log.
        std::fprintf(stderr, "\n[FATAL] tenbox-vm-runtime crashed: code=0x%08lx "
                             "dump=%s\n",
                     ep && ep->ExceptionRecord ? ep->ExceptionRecord->ExceptionCode : 0ul,
                     dump_path.c_str());