ladybird/Libraries/LibWebView/MachPortServer.cpp

/*
 * Copyright (c) 2024, Andrew Kaster <akaster@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Debug.h>
#include <LibCore/Platform/MachMessageTypes.h>
#include <LibThreading/Thread.h>
#include <LibWebView/MachPortServer.h>

namespace WebView {

MachPortServer::MachPortServer(ByteString server_port_name)
    : m_thread(Threading::Thread::construct("MachPortServer"sv, [this]() -> intptr_t { thread_loop(); return 0; }))
    , m_server_port_name(move(server_port_name))
{
    if (auto err = allocate_server_port(); err.is_error())
        dbgln("Failed to allocate server port: {}", err.error());
    else
        start();
}

MachPortServer::~MachPortServer()
{
    stop();
}

void MachPortServer::start()
{
    m_thread->start();
}

void MachPortServer::stop()
{
    // FIXME: We should join instead (after storing should_stop = false) when we have a way to interrupt the thread's mach_msg call
    m_thread->detach();
    m_should_stop.store(true, MemoryOrder::memory_order_release);
}

bool MachPortServer::is_initialized()
{
    return MACH_PORT_VALID(m_server_port_recv_right.port()) && MACH_PORT_VALID(m_server_port_send_right.port());
}

ErrorOr<void> MachPortServer::allocate_server_port()
{
    m_server_port_recv_right = TRY(Core::MachPort::create_with_right(Core::MachPort::PortRight::Receive));
    m_server_port_send_right = TRY(m_server_port_recv_right.insert_right(Core::MachPort::MessageRight::MakeSend));
    TRY(m_server_port_recv_right.register_with_bootstrap_server(m_server_port_name));

    dbgln_if(MACH_PORT_DEBUG, "Success! we created and attached mach port {:x} to bootstrap server with name {}", m_server_port_recv_right.port(), m_server_port_name);
    return {};
}

void MachPortServer::thread_loop()
{
    while (!m_should_stop.load(MemoryOrder::memory_order_acquire)) {
        Core::Platform::ReceivedMachMessage message {};

        // Get the pid of the child from the audit trailer so we can associate the port w/it
        mach_msg_options_t const options = MACH_RCV_MSG | MACH_RCV_TRAILER_TYPE(MACH_RCV_TRAILER_AUDIT) | MACH_RCV_TRAILER_ELEMENTS(MACH_RCV_TRAILER_AUDIT);

        // FIXME: How can we interrupt this call during application shutdown?
        auto const ret = mach_msg(&message.header, options, 0, sizeof(message), m_server_port_recv_right.port(), MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
        if (ret != KERN_SUCCESS) {
            dbgln("mach_msg failed: {}", mach_error_string(ret));
            break;
        }

        if (message.header.msgh_id == Core::Platform::BACKING_STORE_IOSURFACES_MESSAGE_ID) {
            auto pid = static_cast<pid_t>(message.body.parent_iosurface.trailer.msgh_audit.val[5]);
            auto const& backing_stores_message = message.body.parent_iosurface;
            auto front_child_port = Core::MachPort::adopt_right(backing_stores_message.front_descriptor.name, Core::MachPort::PortRight::Send);
            auto back_child_port = Core::MachPort::adopt_right(backing_stores_message.back_descriptor.name, Core::MachPort::PortRight::Send);
            auto const& metadata = backing_stores_message.metadata;
            if (on_receive_backing_stores)
                on_receive_backing_stores({ .pid = pid,
                    .page_id = metadata.page_id,
                    .front_backing_store_id = metadata.front_backing_store_id,
                    .back_backing_store_id = metadata.back_backing_store_id,
                    .front_backing_store_port = move(front_child_port),
                    .back_backing_store_port = move(back_child_port) });
            continue;
        }

        if (message.header.msgh_id == Core::Platform::SELF_TASK_PORT_MESSAGE_ID) {
            auto const& task_port_message = message.body.parent;
            VERIFY(MACH_MSGH_BITS_LOCAL(message.header.msgh_bits) == MACH_MSG_TYPE_MOVE_SEND);
            VERIFY(task_port_message.body.msgh_descriptor_count == 1);
            VERIFY(task_port_message.port_descriptor.type == MACH_MSG_PORT_DESCRIPTOR);
            auto pid = static_cast<pid_t>(task_port_message.trailer.msgh_audit.val[5]);
            auto child_port = Core::MachPort::adopt_right(task_port_message.port_descriptor.name, Core::MachPort::PortRight::Send);

            // Extract reply port from the message header (kernel swaps local/remote on receive)
            auto reply_port = Core::MachPort::adopt_right(message.header.msgh_remote_port, Core::MachPort::PortRight::SendOnce);

            dbgln_if(MACH_PORT_DEBUG, "Received child port {:x} from pid {} (reply port {:x})", child_port.port(), pid, reply_port.port());
            if (on_receive_child_mach_port)
                on_receive_child_mach_port({ pid, move(child_port), move(reply_port) });
            continue;
        }

        VERIFY_NOT_REACHED();
    }
}

}