llvm-capstone/lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.cpp

//===-- GDBRemoteClientBase.cpp ---------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "GDBRemoteClientBase.h"

#include "llvm/ADT/StringExtras.h"

#include "lldb/Target/UnixSignals.h"
#include "lldb/Utility/LLDBAssert.h"

#include "ProcessGDBRemoteLog.h"

using namespace lldb;
using namespace lldb_private;
using namespace lldb_private::process_gdb_remote;

static const std::chrono::seconds kInterruptTimeout(5);

/////////////////////////
// GDBRemoteClientBase //
/////////////////////////

GDBRemoteClientBase::ContinueDelegate::~ContinueDelegate() = default;

GDBRemoteClientBase::GDBRemoteClientBase(const char *comm_name, const char *listener_name)
    : GDBRemoteCommunication(comm_name, listener_name), m_async_count(0), m_is_running(false), m_should_stop(false)
{
}

StateType
GDBRemoteClientBase::SendContinuePacketAndWaitForResponse(ContinueDelegate &delegate, const UnixSignals &signals,
                                                          llvm::StringRef payload, StringExtractorGDBRemote &response)
{
    Log *log(ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS));
    response.Clear();

    {
        std::lock_guard<std::mutex> lock(m_mutex);
        m_continue_packet = payload;
        m_should_stop = false;
    }
    ContinueLock cont_lock(*this);
    if (!cont_lock)
        return eStateInvalid;
    OnRunPacketSent(true);

    for (;;)
    {
        PacketResult read_result = ReadPacket(
            response, std::chrono::duration_cast<std::chrono::microseconds>(kInterruptTimeout).count(), false);
        switch (read_result)
        {
            case PacketResult::ErrorReplyTimeout:
            {
                std::lock_guard<std::mutex> lock(m_mutex);
                if (m_async_count == 0)
                    continue;
                if (std::chrono::steady_clock::now() >= m_interrupt_time + kInterruptTimeout)
                    return eStateInvalid;
            }
            case PacketResult::Success:
                break;
            default:
                if (log)
                    log->Printf("GDBRemoteClientBase::%s () ReadPacket(...) => false", __FUNCTION__);
                return eStateInvalid;
        }
        if (response.Empty())
            return eStateInvalid;

        const char stop_type = response.GetChar();
        if (log)
            log->Printf("GDBRemoteClientBase::%s () got packet: %s", __FUNCTION__, response.GetStringRef().c_str());

        switch (stop_type)
        {
            case 'W':
            case 'X':
                return eStateExited;
            case 'E':
                // ERROR
                return eStateInvalid;
            default:
                if (log)
                    log->Printf("GDBRemoteClientBase::%s () unrecognized async packet", __FUNCTION__);
                return eStateInvalid;
            case 'O':
            {
                std::string inferior_stdout;
                response.GetHexByteString(inferior_stdout);
                delegate.HandleAsyncStdout(inferior_stdout);
                break;
            }
            case 'A':
                delegate.HandleAsyncMisc(llvm::StringRef(response.GetStringRef()).substr(1));
                break;
            case 'T':
            case 'S':
                // Do this with the continue lock held.
                const bool should_stop = ShouldStop(signals, response);
                response.SetFilePos(0);

                // The packet we should resume with. In the future
                // we should check our thread list and "do the right thing"
                // for new threads that show up while we stop and run async
                // packets. Setting the packet to 'c' to continue all threads
                // is the right thing to do 99.99% of the time because if a
                // thread was single stepping, and we sent an interrupt, we
                // will notice above that we didn't stop due to an interrupt
                // but stopped due to stepping and we would _not_ continue.
                // This packet may get modified by the async actions (e.g. to send a signal).
                m_continue_packet = 'c';
                cont_lock.unlock();

                delegate.HandleStopReply();
                if (should_stop)
                    return eStateStopped;

                switch (cont_lock.lock())
                {
                    case ContinueLock::LockResult::Success:
                        break;
                    case ContinueLock::LockResult::Failed:
                        return eStateInvalid;
                    case ContinueLock::LockResult::Cancelled:
                        return eStateStopped;
                }
                OnRunPacketSent(false);
                break;
        }
    }
}

bool
GDBRemoteClientBase::SendAsyncSignal(int signo)
{
    Lock lock(*this, true);
    if (!lock || !lock.DidInterrupt())
        return false;

    m_continue_packet = 'C';
    m_continue_packet += llvm::hexdigit((signo / 16) % 16);
    m_continue_packet += llvm::hexdigit(signo % 16);
    return true;
}

bool
GDBRemoteClientBase::Interrupt()
{
    Lock lock(*this, true);
    if (!lock.DidInterrupt())
        return false;
    m_should_stop = true;
    return true;
}
GDBRemoteCommunication::PacketResult
GDBRemoteClientBase::SendPacketAndWaitForResponse(llvm::StringRef payload, StringExtractorGDBRemote &response,
                                                  bool send_async)
{
    Lock lock(*this, send_async);
    if (!lock)
    {
        if (Log *log = ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS))
            log->Printf("GDBRemoteClientBase::%s failed to get mutex, not sending packet '%.*s' (send_async=%d)",
                        __FUNCTION__, int(payload.size()), payload.data(), send_async);
        return PacketResult::ErrorSendFailed;
    }

    return SendPacketAndWaitForResponseNoLock(payload, response);
}

GDBRemoteCommunication::PacketResult
GDBRemoteClientBase::SendPacketAndWaitForResponseNoLock(llvm::StringRef payload, StringExtractorGDBRemote &response)
{
    PacketResult packet_result = SendPacketNoLock(payload.data(), payload.size());
    if (packet_result != PacketResult::Success)
        return packet_result;

    const size_t max_response_retries = 3;
    for (size_t i = 0; i < max_response_retries; ++i)
    {
        packet_result = ReadPacket(response, GetPacketTimeoutInMicroSeconds(), true);
        // Make sure we received a response
        if (packet_result != PacketResult::Success)
            return packet_result;
        // Make sure our response is valid for the payload that was sent
        if (response.ValidateResponse())
            return packet_result;
        // Response says it wasn't valid
        Log *log = ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PACKETS);
        if (log)
            log->Printf("error: packet with payload \"%.*s\" got invalid response \"%s\": %s", int(payload.size()),
                        payload.data(), response.GetStringRef().c_str(),
                        (i == (max_response_retries - 1)) ? "using invalid response and giving up"
                                                          : "ignoring response and waiting for another");
    }
    return packet_result;
}

bool
GDBRemoteClientBase::SendvContPacket(llvm::StringRef payload, StringExtractorGDBRemote &response)
{
    Log *log(ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS));
    if (log)
        log->Printf("GDBRemoteCommunicationClient::%s ()", __FUNCTION__);

    // we want to lock down packet sending while we continue
    Lock lock(*this, true);

    if (log)
        log->Printf("GDBRemoteCommunicationClient::%s () sending vCont packet: %.*s", __FUNCTION__, int(payload.size()),
                    payload.data());

    if (SendPacketNoLock(payload.data(), payload.size()) != PacketResult::Success)
        return false;

    OnRunPacketSent(true);

    // wait for the response to the vCont
    if (ReadPacket(response, UINT32_MAX, false) == PacketResult::Success)
    {
        if (response.IsOKResponse())
            return true;
    }

    return false;
}
bool
GDBRemoteClientBase::ShouldStop(const UnixSignals &signals, StringExtractorGDBRemote &response)
{
    std::lock_guard<std::mutex> lock(m_mutex);

    if (m_async_count == 0)
        return true; // We were not interrupted. The process stopped on its own.

    // Older debugserver stubs (before April 2016) can return two
    // stop-reply packets in response to a ^C packet.
    // Additionally, all debugservers still return two stop replies if
    // the inferior stops due to some other reason before the remote
    // stub manages to interrupt it. We need to wait for this
    // additional packet to make sure the packet sequence does not get
    // skewed.
    StringExtractorGDBRemote extra_stop_reply_packet;
    uint32_t timeout_usec = 100000; // 100ms
    ReadPacket(extra_stop_reply_packet, timeout_usec, false);

    // Interrupting is typically done using SIGSTOP or SIGINT, so if
    // the process stops with some other signal, we definitely want to
    // stop.
    const uint8_t signo = response.GetHexU8(UINT8_MAX);
    if (signo != signals.GetSignalNumberFromName("SIGSTOP") && signo != signals.GetSignalNumberFromName("SIGINT"))
        return true;

    // We probably only stopped to perform some async processing, so continue after that is done.
    // TODO: This is not 100% correct, as the process may have been stopped with SIGINT or SIGSTOP
    // that was not caused by us (e.g. raise(SIGINT)). This will normally cause a stop, but if it's
    // done concurrently with a async interrupt, that stop will get eaten (llvm.org/pr20231).
    return false;
}

void
GDBRemoteClientBase::OnRunPacketSent(bool first)
{
    if (first)
        BroadcastEvent(eBroadcastBitRunPacketSent, NULL);
}

///////////////////////////////////////
// GDBRemoteClientBase::ContinueLock //
///////////////////////////////////////

GDBRemoteClientBase::ContinueLock::ContinueLock(GDBRemoteClientBase &comm) : m_comm(comm), m_acquired(false)
{
    lock();
}

GDBRemoteClientBase::ContinueLock::~ContinueLock()
{
    if (m_acquired)
        unlock();
}

void
GDBRemoteClientBase::ContinueLock::unlock()
{
    lldbassert(m_acquired);
    {
        std::unique_lock<std::mutex> lock(m_comm.m_mutex);
        m_comm.m_is_running = false;
    }
    m_comm.m_cv.notify_all();
    m_acquired = false;
}

GDBRemoteClientBase::ContinueLock::LockResult
GDBRemoteClientBase::ContinueLock::lock()
{
    Log *log = ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS);
    if (log)
        log->Printf("GDBRemoteClientBase::ContinueLock::%s() resuming with %s", __FUNCTION__,
                    m_comm.m_continue_packet.c_str());

    lldbassert(!m_acquired);
    std::unique_lock<std::mutex> lock(m_comm.m_mutex);
    m_comm.m_cv.wait(lock, [this] { return m_comm.m_async_count == 0; });
    if (m_comm.m_should_stop)
    {
        m_comm.m_should_stop = false;
        if (log)
            log->Printf("GDBRemoteClientBase::ContinueLock::%s() cancelled", __FUNCTION__);
        return LockResult::Cancelled;
    }
    if (m_comm.SendPacketNoLock(m_comm.m_continue_packet.data(), m_comm.m_continue_packet.size()) !=
        PacketResult::Success)
        return LockResult::Failed;

    lldbassert(!m_comm.m_is_running);
    m_comm.m_is_running = true;
    m_acquired = true;
    return LockResult::Success;
}

///////////////////////////////
// GDBRemoteClientBase::Lock //
///////////////////////////////

GDBRemoteClientBase::Lock::Lock(GDBRemoteClientBase &comm, bool interrupt)
    : m_async_lock(comm.m_async_mutex, std::defer_lock), m_comm(comm), m_acquired(false), m_did_interrupt(false)
{
    SyncWithContinueThread(interrupt);
    if (m_acquired)
        m_async_lock.lock();
}

void
GDBRemoteClientBase::Lock::SyncWithContinueThread(bool interrupt)
{
    Log *log(ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS));
    std::unique_lock<std::mutex> lock(m_comm.m_mutex);
    if (m_comm.m_is_running && !interrupt)
        return; // We were asked to avoid interrupting the sender. Lock is not acquired.

    ++m_comm.m_async_count;
    if (m_comm.m_is_running)
    {
        if (m_comm.m_async_count == 1)
        {
            // The sender has sent the continue packet and we are the first async packet. Let's interrupt it.
            const char ctrl_c = '\x03';
            ConnectionStatus status = eConnectionStatusSuccess;
            size_t bytes_written = m_comm.Write(&ctrl_c, 1, status, NULL);
            if (bytes_written == 0)
            {
                --m_comm.m_async_count;
                if (log)
                    log->Printf("GDBRemoteClientBase::Lock::Lock failed to send interrupt packet");
                return;
            }
            if (log)
                log->PutCString("GDBRemoteClientBase::Lock::Lock sent packet: \\x03");
            m_comm.m_interrupt_time = std::chrono::steady_clock::now();
        }
        m_comm.m_cv.wait(lock, [this] { return m_comm.m_is_running == false; });
        m_did_interrupt = true;
    }
    m_acquired = true;
}

GDBRemoteClientBase::Lock::~Lock()
{
    if (!m_acquired)
        return;
    {
        std::unique_lock<std::mutex> lock(m_comm.m_mutex);
        --m_comm.m_async_count;
    }
    m_comm.m_cv.notify_one();
}