llvm-project/lldb/source/Plugins/Process/MacOSX-Kernel/CommunicationKDP.cpp

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


#include "CommunicationKDP.h"

// C Includes
#include <limits.h>
#include <string.h>

// C++ Includes
// Other libraries and framework includes
#include "lldb/Core/Log.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Host/FileSpec.h"
#include "lldb/Host/Host.h"
#include "lldb/Host/TimeValue.h"
#include "lldb/Target/Process.h"
#include "Utility/StringExtractor.h"

// Project includes
#include "ProcessKDPLog.h"

#define DEBUGSERVER_BASENAME    "debugserver"

using namespace lldb;
using namespace lldb_private;

//----------------------------------------------------------------------
// CommunicationKDP constructor
//----------------------------------------------------------------------
CommunicationKDP::CommunicationKDP (const char *comm_name) :
    Communication(comm_name),
    m_packet_timeout (1),
    m_sequence_mutex (Mutex::eMutexTypeRecursive),
    m_public_is_running (false),
    m_private_is_running (false),
    m_send_acks (true)
{
}

//----------------------------------------------------------------------
// Destructor
//----------------------------------------------------------------------
CommunicationKDP::~CommunicationKDP()
{
    if (IsConnected())
    {
        Disconnect();
    }
}

char
CommunicationKDP::CalculcateChecksum (const char *payload, size_t payload_length)
{
    int checksum = 0;

    // We only need to compute the checksum if we are sending acks
    if (GetSendAcks ())
    {
        for (size_t i = 0; i < payload_length; ++i)
            checksum += payload[i];
    }
    return checksum & 255;
}

size_t
CommunicationKDP::SendAck ()
{
    LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS));
    if (log)
        log->Printf ("send packet: +");
    ConnectionStatus status = eConnectionStatusSuccess;
    char ack_char = '+';
    return Write (&ack_char, 1, status, NULL);
}

size_t
CommunicationKDP::SendNack ()
{
    LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS));
    if (log)
        log->Printf ("send packet: -");
    ConnectionStatus status = eConnectionStatusSuccess;
    char nack_char = '-';
    return Write (&nack_char, 1, status, NULL);
}

size_t
CommunicationKDP::SendPacket (lldb_private::StreamString &payload)
{
    Mutex::Locker locker(m_sequence_mutex);
    const std::string &p (payload.GetString());
    return SendPacketNoLock (p.c_str(), p.size());
}

size_t
CommunicationKDP::SendPacket (const char *payload)
{
    Mutex::Locker locker(m_sequence_mutex);
    return SendPacketNoLock (payload, ::strlen (payload));
}

size_t
CommunicationKDP::SendPacket (const char *payload, size_t payload_length)
{
    Mutex::Locker locker(m_sequence_mutex);
    return SendPacketNoLock (payload, payload_length);
}

size_t
CommunicationKDP::SendPacketNoLock (const char *payload, size_t payload_length)
{
    if (IsConnected())
    {
        StreamString packet(0, 4, eByteOrderBig);

        packet.PutChar('$');
        packet.Write (payload, payload_length);
        packet.PutChar('#');
        packet.PutHex8(CalculcateChecksum (payload, payload_length));

        LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS));
        if (log)
            log->Printf ("send packet: %.*s", (int)packet.GetSize(), packet.GetData());
        ConnectionStatus status = eConnectionStatusSuccess;
        size_t bytes_written = Write (packet.GetData(), packet.GetSize(), status, NULL);
        if (bytes_written == packet.GetSize())
        {
            if (GetSendAcks ())
            {
                if (GetAck () != '+')
                {
                    printf("get ack failed...");
                    return 0;
                }
            }
        }
        else
        {
            LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS));
            if (log)
                log->Printf ("error: failed to send packet: %.*s", (int)packet.GetSize(), packet.GetData());
        }
        return bytes_written;
    }
    return 0;
}

char
CommunicationKDP::GetAck ()
{
    StringExtractor packet;
    if (WaitForPacketWithTimeoutMicroSeconds (packet, GetPacketTimeoutInMicroSeconds ()) == 1)
        return packet.GetChar();
    return 0;
}

bool
CommunicationKDP::GetSequenceMutex (Mutex::Locker& locker)
{
    return locker.TryLock (m_sequence_mutex.GetMutex());
}


bool
CommunicationKDP::WaitForNotRunningPrivate (const TimeValue *timeout_ptr)
{
    return m_private_is_running.WaitForValueEqualTo (false, timeout_ptr, NULL);
}

size_t
CommunicationKDP::WaitForPacketWithTimeoutMicroSeconds (StringExtractor &packet, uint32_t timeout_usec)
{
    Mutex::Locker locker(m_sequence_mutex);
    return WaitForPacketWithTimeoutMicroSecondsNoLock (packet, timeout_usec);
}

size_t
CommunicationKDP::WaitForPacketWithTimeoutMicroSecondsNoLock (StringExtractor &packet, uint32_t timeout_usec)
{
    uint8_t buffer[8192];
    Error error;

    LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS | KDP_LOG_VERBOSE));

    // Check for a packet from our cache first without trying any reading...
    if (CheckForPacket (NULL, 0, packet))
        return packet.GetStringRef().size();

    bool timed_out = false;
    while (IsConnected() && !timed_out)
    {
        lldb::ConnectionStatus status;
        size_t bytes_read = Read (buffer, sizeof(buffer), timeout_usec, status, &error);
        
        if (log)
            log->Printf ("%s: Read (buffer, (sizeof(buffer), timeout_usec = 0x%x, status = %s, error = %s) => bytes_read = %zu",
                         __PRETTY_FUNCTION__,
                         timeout_usec, 
                         Communication::ConnectionStatusAsCString (status),
                         error.AsCString(), 
                         bytes_read);

        if (bytes_read > 0)
        {
            if (CheckForPacket (buffer, bytes_read, packet))
                return packet.GetStringRef().size();
        }
        else
        {
            switch (status)
            {
            case eConnectionStatusTimedOut:
                timed_out = true;
                break;
            case eConnectionStatusSuccess:
                //printf ("status = success but error = %s\n", error.AsCString("<invalid>"));
                break;
                
            case eConnectionStatusEndOfFile:
            case eConnectionStatusNoConnection:
            case eConnectionStatusLostConnection:
            case eConnectionStatusError:
                Disconnect();
                break;
            }
        }
    }
    packet.Clear ();    
    return 0;
}

bool
CommunicationKDP::CheckForPacket (const uint8_t *src, size_t src_len, StringExtractor &packet)
{
    // Put the packet data into the buffer in a thread safe fashion
    Mutex::Locker locker(m_bytes_mutex);
    
    LogSP log (ProcessKDPLog::GetLogIfAllCategoriesSet (KDP_LOG_PACKETS));

    if (src && src_len > 0)
    {
        if (log && log->GetVerbose())
        {
            StreamString s;
            log->Printf ("CommunicationKDP::%s adding %u bytes: %.*s",
                         __FUNCTION__, 
                         (uint32_t)src_len, 
                         (uint32_t)src_len, 
                         src);
        }
        m_bytes.append ((const char *)src, src_len);
    }

    // Parse up the packets into gdb remote packets
    if (!m_bytes.empty())
    {
        // end_idx must be one past the last valid packet byte. Start
        // it off with an invalid value that is the same as the current
        // index.
        size_t content_start = 0;
        size_t content_length = 0;
        size_t total_length = 0;
        size_t checksum_idx = std::string::npos;

        switch (m_bytes[0])
        {
            case '+':       // Look for ack
            case '-':       // Look for cancel
            case '\x03':    // ^C to halt target
                content_length = total_length = 1;  // The command is one byte long...
                break;

            case '$':
                // Look for a standard gdb packet?
                {
                    size_t hash_pos = m_bytes.find('#');
                    if (hash_pos != std::string::npos)
                    {
                        if (hash_pos + 2 < m_bytes.size())
                        {
                            checksum_idx = hash_pos + 1;
                            // Skip the dollar sign
                            content_start = 1; 
                            // Don't include the # in the content or the $ in the content length
                            content_length = hash_pos - 1;  
                            
                            total_length = hash_pos + 3; // Skip the # and the two hex checksum bytes
                        }
                        else
                        {
                            // Checksum bytes aren't all here yet
                            content_length = std::string::npos;
                        }
                    }
                }
                break;

            default:
                {
                    // We have an unexpected byte and we need to flush all bad 
                    // data that is in m_bytes, so we need to find the first
                    // byte that is a '+' (ACK), '-' (NACK), \x03 (CTRL+C interrupt),
                    // or '$' character (start of packet header) or of course,
                    // the end of the data in m_bytes...
                    const size_t bytes_len = m_bytes.size();
                    bool done = false;
                    uint32_t idx;
                    for (idx = 1; !done && idx < bytes_len; ++idx)
                    {
                        switch (m_bytes[idx])
                        {
                        case '+':
                        case '-':
                        case '\x03':
                        case '$':
                            done = true;
                            break;
                                
                        default:
                            break;
                        }
                    }
                    if (log)
                        log->Printf ("CommunicationKDP::%s tossing %u junk bytes: '%.*s'",
                                     __FUNCTION__, idx, idx, m_bytes.c_str());
                    m_bytes.erase(0, idx);
                }
                break;
        }

        if (content_length == std::string::npos)
        {
            packet.Clear();
            return false;
        }
        else if (total_length > 0)
        {

            // We have a valid packet...
            assert (content_length <= m_bytes.size());
            assert (total_length <= m_bytes.size());
            assert (content_length <= total_length);
            
            bool success = true;
            std::string &packet_str = packet.GetStringRef();
            packet_str.assign (m_bytes, content_start, content_length);
            if (m_bytes[0] == '$')
            {
                assert (checksum_idx < m_bytes.size());
                if (::isxdigit (m_bytes[checksum_idx+0]) || 
                    ::isxdigit (m_bytes[checksum_idx+1]))
                {
                    if (GetSendAcks ())
                    {
                        const char *packet_checksum_cstr = &m_bytes[checksum_idx];
                        char packet_checksum = strtol (packet_checksum_cstr, NULL, 16);
                        char actual_checksum = CalculcateChecksum (packet_str.c_str(), packet_str.size());
                        success = packet_checksum == actual_checksum;
                        if (!success)
                        {
                            if (log)
                                log->Printf ("error: checksum mismatch: %.*s expected 0x%2.2x, got 0x%2.2x", 
                                             (int)(total_length), 
                                             m_bytes.c_str(),
                                             (uint8_t)packet_checksum,
                                             (uint8_t)actual_checksum);
                        }
                        // Send the ack or nack if needed
                        if (!success)
                            SendNack();
                        else
                            SendAck();
                    }
                    if (success)
                    {
                        if (log)
                            log->Printf ("read packet: %.*s", (int)(total_length), m_bytes.c_str());
                    }
                }
                else
                {
                    success = false;
                    if (log)
                        log->Printf ("error: invalid checksum in packet: '%s'\n", (int)(total_length), m_bytes.c_str());
                }
            }
            m_bytes.erase(0, total_length);
            packet.SetFilePos(0);
            return success;
        }
    }
    packet.Clear();
    return false;
}