third_party/v8/src/debug/wasm/gdb-server/target.cc - cobalt - Git at Google

 // Copyright 2020 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "src/debug/wasm/gdb-server/target.h"

 #include <inttypes.h>
 #include "src/base/platform/time.h"
 #include "src/debug/wasm/gdb-server/gdb-remote-util.h"
 #include "src/debug/wasm/gdb-server/gdb-server.h"
 #include "src/debug/wasm/gdb-server/packet.h"
 #include "src/debug/wasm/gdb-server/session.h"
 #include "src/debug/wasm/gdb-server/transport.h"

 namespace v8 {
 namespace internal {
 namespace wasm {
 namespace gdb_server {

 static const int kThreadId = 1;

 // Signals.
 static const int kSigTrace = 5;
 static const int kSigSegv = 11;

 Target::Target(GdbServer* gdb_server)
     : gdb_server_(gdb_server),
       status_(Status::Running),
       cur_signal_(0),
       session_(nullptr),
       debugger_initial_suspension_(true),
       semaphore_(0),
       current_isolate_(nullptr) {
   InitQueryPropertyMap();
 }

 void Target::InitQueryPropertyMap() {
   // Request LLDB to send packets up to 4000 bytes for bulk transfers.
   query_properties_["Supported"] =
       "PacketSize=1000;vContSupported-;qXfer:libraries:read+;";

   query_properties_["Attached"] = "1";

   // There is only one register, named 'pc', in this architecture
   query_properties_["RegisterInfo0"] =
       "name:pc;alt-name:pc;bitsize:64;offset:0;encoding:uint;format:hex;set:"
       "General Purpose Registers;gcc:16;dwarf:16;generic:pc;";
   query_properties_["RegisterInfo1"] = "E45";

   // ProcessInfo for wasm32
   query_properties_["ProcessInfo"] =
       "pid:1;ppid:1;uid:1;gid:1;euid:1;egid:1;name:6c6c6462;triple:" +
       Mem2Hex("wasm32-unknown-unknown-wasm") + ";ptrsize:4;";
   query_properties_["Symbol"] = "OK";

   // Current thread info
   char buff[16];
   snprintf(buff, sizeof(buff), "QC%x", kThreadId);
   query_properties_["C"] = buff;
 }

 void Target::Terminate() {
   // Executed in the Isolate thread, when the process shuts down.
   SetStatus(Status::Terminated);
 }

 void Target::OnProgramBreak(Isolate* isolate,
                             const std::vector<wasm_addr_t>& call_frames) {
   OnSuspended(isolate, kSigTrace, call_frames);
 }
 void Target::OnException(Isolate* isolate,
                          const std::vector<wasm_addr_t>& call_frames) {
   OnSuspended(isolate, kSigSegv, call_frames);
 }
 void Target::OnSuspended(Isolate* isolate, int signal,
                          const std::vector<wasm_addr_t>& call_frames) {
   // This function will be called in the isolate thread, when the wasm
   // interpreter gets suspended.

   bool isWaitingForSuspension = (status_ == Status::WaitingForSuspension);
   SetStatus(Status::Suspended, signal, call_frames, isolate);
   if (isWaitingForSuspension) {
     // Wake the GdbServer thread that was blocked waiting for the Target
     // to suspend.
     semaphore_.Signal();
   } else if (session_) {
     session_->SignalThreadEvent();
   }
 }

 void Target::Run(Session* session) {
   // Executed in the GdbServer thread.
   session_ = session;
   do {
     WaitForDebugEvent();
     ProcessDebugEvent();
     ProcessCommands();
   } while (!IsTerminated() && session_->IsConnected());
   session_ = nullptr;
 }

 void Target::WaitForDebugEvent() {
   // Executed in the GdbServer thread.

   if (status_ == Status::Running) {
     // Wait for either:
     //   * the thread to fault (or single-step)
     //   * an interrupt from LLDB
     session_->WaitForDebugStubEvent();
   }
 }

 void Target::ProcessDebugEvent() {
   // Executed in the GdbServer thread

   if (status_ == Status::Running) {
     // Blocks, waiting for the engine to suspend.
     Suspend();
   }

   // Here, the wasm interpreter has suspended and we have updated the current
   // thread info.

   if (debugger_initial_suspension_) {
     // First time on a connection, we don't send the signal.
     // All other times, send the signal that triggered us.
     debugger_initial_suspension_ = false;
   } else {
     Packet pktOut;
     SetStopReply(&pktOut);
     session_->SendPacket(&pktOut, false);
   }
 }

 void Target::Suspend() {
   // Executed in the GdbServer thread
   if (status_ == Status::Running) {
     // TODO(paolosev) - this only suspends the wasm interpreter.
     gdb_server_->Suspend();

     status_ = Status::WaitingForSuspension;
   }

   while (status_ == Status::WaitingForSuspension) {
     if (semaphore_.WaitFor(base::TimeDelta::FromMilliseconds(500))) {
       // Here the wasm interpreter is suspended.
       return;
     }
   }
 }

 void Target::ProcessCommands() {
   // GDB-remote messages are processed in the GDBServer thread.

   if (IsTerminated()) {
     return;
   } else if (status_ != Status::Suspended) {
     // Don't process commands if we haven't stopped.
     return;
   }

   // Now we are ready to process commands.
   // Loop through packets until we process a continue packet or a detach.
   Packet recv, reply;
   while (session_->IsConnected()) {
     if (!session_->GetPacket(&recv)) {
       continue;
     }

     reply.Clear();
     ProcessPacketResult result = ProcessPacket(&recv, &reply);
     switch (result) {
       case ProcessPacketResult::Paused:
         session_->SendPacket(&reply);
         break;

       case ProcessPacketResult::Continue:
         DCHECK_EQ(status_, Status::Running);
         // If this is a continue type command, break out of this loop.
         gdb_server_->QuitMessageLoopOnPause();
         return;

       case ProcessPacketResult::Detach:
         SetStatus(Status::Running);
         session_->SendPacket(&reply);
         session_->Disconnect();
         gdb_server_->QuitMessageLoopOnPause();
         return;

       case ProcessPacketResult::Kill:
         session_->SendPacket(&reply);
         exit(-9);

       default:
         UNREACHABLE();
     }
   }

   if (!session_->IsConnected()) {
     debugger_initial_suspension_ = true;
   }
 }

 Target::ProcessPacketResult Target::ProcessPacket(Packet* pkt_in,
                                                   Packet* pkt_out) {
   ErrorCode err = ErrorCode::None;

   // Clear the outbound message.
   pkt_out->Clear();

   // Set the sequence number, if present.
   int32_t seq = -1;
   if (pkt_in->GetSequence(&seq)) {
     pkt_out->SetSequence(seq);
   }

   // A GDB-remote packet begins with an upper- or lower-case letter, which
   // generally represents a single command.
   // The letters 'q' and 'Q' introduce a "General query packets" and are used
   // to extend the protocol with custom commands.
   // The format of GDB-remote commands is documented here:
   // https://sourceware.org/gdb/onlinedocs/gdb/Overview.html#Overview.
   char cmd;
   pkt_in->GetRawChar(&cmd);

   switch (cmd) {
     // Queries the reason the target halted.
     // IN : $?
     // OUT: A Stop-reply packet
     case '?':
       SetStopReply(pkt_out);
       break;

     // Resumes execution
     // IN : $c
     // OUT: A Stop-reply packet is sent later, when the execution halts.
     case 'c':
       SetStatus(Status::Running);
       return ProcessPacketResult::Continue;

     // Detaches the debugger from this target
     // IN : $D
     // OUT: $OK
     case 'D':
       TRACE_GDB_REMOTE("Requested Detach.\n");
       pkt_out->AddString("OK");
       return ProcessPacketResult::Detach;

     // Read general registers (We only support register 'pc' that contains
     // the current instruction pointer).
     // IN : $g
     // OUT: $xx...xx
     case 'g': {
       uint64_t pc = GetCurrentPc();
       pkt_out->AddBlock(&pc, sizeof(pc));
       break;
     }

     // Write general registers - NOT SUPPORTED
     // IN : $Gxx..xx
     // OUT: $ (empty string)
     case 'G': {
       break;
     }

     // Set thread for subsequent operations. For Wasm targets, we currently
     // assume that there is only one thread with id = kThreadId (= 1).
     // IN : $H(c/g)(-1,0,xxxx)
     // OUT: $OK
     case 'H': {
       // Type of the operation (‘m’, ‘M’, ‘g’, ‘G’, ...)
       char operation;
       if (!pkt_in->GetRawChar(&operation)) {
         err = ErrorCode::BadFormat;
         break;
       }

       uint64_t thread_id;
       if (!pkt_in->GetNumberSep(&thread_id, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }

       // Ignore, only one thread supported for now.
       pkt_out->AddString("OK");
       break;
     }

     // Kills the debuggee.
     // IN : $k
     // OUT: $OK
     case 'k':
       TRACE_GDB_REMOTE("Requested Kill.\n");
       pkt_out->AddString("OK");
       return ProcessPacketResult::Kill;

     // Reads {llll} addressable memory units starting at address {aaaa}.
     // IN : $maaaa,llll
     // OUT: $xx..xx
     case 'm': {
       uint64_t address;
       if (!pkt_in->GetNumberSep(&address, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }
       wasm_addr_t wasm_addr(address);

       uint64_t len;
       if (!pkt_in->GetNumberSep(&len, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }

       if (len > Transport::kBufSize / 2) {
         err = ErrorCode::BadArgs;
         break;
       }

       uint32_t length = static_cast<uint32_t>(len);
       uint8_t buff[Transport::kBufSize];
       if (wasm_addr.ModuleId() > 0) {
         uint32_t read =
             gdb_server_->GetWasmModuleBytes(wasm_addr, buff, length);
         if (read > 0) {
           pkt_out->AddBlock(buff, read);
         } else {
           err = ErrorCode::Failed;
         }
       } else {
         err = ErrorCode::BadArgs;
       }
       break;
     }

     // Writes {llll} addressable memory units starting at address {aaaa}.
     // IN : $Maaaa,llll:xx..xx
     // OUT: $OK
     case 'M': {
       // Writing to memory not supported for Wasm.
       err = ErrorCode::Failed;
       break;
     }

     // pN: Reads the value of register N.
     // IN : $pxx
     // OUT: $xx..xx
     case 'p': {
       uint64_t pc = GetCurrentPc();
       pkt_out->AddBlock(&pc, sizeof(pc));
     } break;

     case 'q': {
       err = ProcessQueryPacket(pkt_in, pkt_out);
       break;
     }

     // Single step
     // IN : $s
     // OUT: A Stop-reply packet is sent later, when the execution halts.
     case 's': {
       if (status_ == Status::Suspended) {
         gdb_server_->PrepareStep();
         SetStatus(Status::Running);
       }
       return ProcessPacketResult::Continue;
     }

     // Find out if the thread 'id' is alive.
     // IN : $T
     // OUT: $OK if alive, $Enn if thread is dead.
     case 'T': {
       uint64_t id;
       if (!pkt_in->GetNumberSep(&id, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }
       if (id != kThreadId) {
         err = ErrorCode::BadArgs;
         break;
       }
       pkt_out->AddString("OK");
       break;
     }

     // Z: Adds a breakpoint
     // IN : $Z<type>,<addr>,<kind>
     //      <type>: 0: sw breakpoint, 1: hw breakpoint, 2: watchpoint
     // OUT: $OK (success) or $Enn (error)
     case 'Z': {
       uint64_t breakpoint_type;
       uint64_t breakpoint_address;
       uint64_t breakpoint_kind;
       // Only software breakpoints are supported.
       if (!pkt_in->GetNumberSep(&breakpoint_type, 0) || breakpoint_type != 0 ||
           !pkt_in->GetNumberSep(&breakpoint_address, 0) ||
           !pkt_in->GetNumberSep(&breakpoint_kind, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }

       wasm_addr_t wasm_breakpoint_addr(breakpoint_address);
       if (!gdb_server_->AddBreakpoint(wasm_breakpoint_addr.ModuleId(),
                                       wasm_breakpoint_addr.Offset())) {
         err = ErrorCode::Failed;
         break;
       }

       pkt_out->AddString("OK");
       break;
     }

     // z: Removes a breakpoint
     // IN : $z<type>,<addr>,<kind>
     //      <type>: 0: sw breakpoint, 1: hw breakpoint, 2: watchpoint
     // OUT: $OK (success) or $Enn (error)
     case 'z': {
       uint64_t breakpoint_type;
       uint64_t breakpoint_address;
       uint64_t breakpoint_kind;
       if (!pkt_in->GetNumberSep(&breakpoint_type, 0) || breakpoint_type != 0 ||
           !pkt_in->GetNumberSep(&breakpoint_address, 0) ||
           !pkt_in->GetNumberSep(&breakpoint_kind, 0)) {
         err = ErrorCode::BadFormat;
         break;
       }

       wasm_addr_t wasm_breakpoint_addr(breakpoint_address);
       if (!gdb_server_->RemoveBreakpoint(wasm_breakpoint_addr.ModuleId(),
                                          wasm_breakpoint_addr.Offset())) {
         err = ErrorCode::Failed;
         break;
       }

       pkt_out->AddString("OK");
       break;
     }

     // If the command is not recognized, ignore it by sending an empty reply.
     default: {
       TRACE_GDB_REMOTE("Unknown command: %s\n", pkt_in->GetPayload());
     }
   }

   // If there is an error, return the error code instead of a payload
   if (err != ErrorCode::None) {
     pkt_out->Clear();
     pkt_out->AddRawChar('E');
     pkt_out->AddWord8(static_cast<uint8_t>(err));
   }
   return ProcessPacketResult::Paused;
 }

 Target::ErrorCode Target::ProcessQueryPacket(const Packet* pkt_in,
                                              Packet* pkt_out) {
   const char* str = &pkt_in->GetPayload()[1];

   // Get first thread query
   // IN : $qfThreadInfo
   // OUT: $m<tid>
   //
   // Get next thread query
   // IN : $qsThreadInfo
   // OUT: $m<tid> or l to denote end of list.
   if (!strcmp(str, "fThreadInfo") || !strcmp(str, "sThreadInfo")) {
     if (str[0] == 'f') {
       pkt_out->AddString("m");
       pkt_out->AddNumberSep(kThreadId, 0);
     } else {
       pkt_out->AddString("l");
     }
     return ErrorCode::None;
   }

   // Get a list of loaded libraries
   // IN : $qXfer:libraries:read
   // OUT: an XML document which lists loaded libraries, with this format:
   // <library-list>
   //   <library name="foo.wasm">
   //     <section address="0x100000000"/>
   //   </library>
   //   <library name="bar.wasm">
   //     <section address="0x200000000"/>
   //   </library>
   // </library-list>
   // Note that LLDB must be compiled with libxml2 support to handle this packet.
   std::string tmp = "Xfer:libraries:read";
   if (!strncmp(str, tmp.data(), tmp.length())) {
     std::vector<GdbServer::WasmModuleInfo> modules =
         gdb_server_->GetLoadedModules();
     std::string result("l<library-list>");
     for (const auto& module : modules) {
       wasm_addr_t address(module.module_id, 0);
       char address_string[32];
       snprintf(address_string, sizeof(address_string), "%" PRIu64,
                static_cast<uint64_t>(address));
       result += "<library name=\"";
       result += module.module_name;
       result += "\"><section address=\"";
       result += address_string;
       result += "\"/></library>";
     }
     result += "</library-list>";
     pkt_out->AddString(result.c_str());
     return ErrorCode::None;
   }

   // Get the current call stack.
   // IN : $qWasmCallStack
   // OUT: $xx..xxyy..yyzz..zz (A sequence of uint64_t values represented as
   //                           consecutive 8-bytes blocks).
   std::vector<std::string> toks = StringSplit(str, ":;");
   if (toks[0] == "WasmCallStack") {
     std::vector<wasm_addr_t> call_stack_pcs = gdb_server_->GetWasmCallStack();
     std::vector<uint64_t> buffer;
     for (wasm_addr_t pc : call_stack_pcs) {
       buffer.push_back(pc);
     }
     pkt_out->AddBlock(buffer.data(),
                       static_cast<uint32_t>(sizeof(uint64_t) * buffer.size()));
     return ErrorCode::None;
   }

   // Get a Wasm global value in the Wasm module specified.
   // IN : $qWasmGlobal:frame_index;index
   // OUT: $xx..xx
   if (toks[0] == "WasmGlobal") {
     if (toks.size() == 3) {
       uint32_t frame_index =
           static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
       uint32_t index =
           static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
       uint8_t buff[16];
       uint32_t size = 0;
       if (gdb_server_->GetWasmGlobal(frame_index, index, buff, 16, &size)) {
         pkt_out->AddBlock(buff, size);
         return ErrorCode::None;
       } else {
         return ErrorCode::Failed;
       }
     }
     return ErrorCode::BadFormat;
   }

   // Get a Wasm local value in the stack frame specified.
   // IN : $qWasmLocal:frame_index;index
   // OUT: $xx..xx
   if (toks[0] == "WasmLocal") {
     if (toks.size() == 3) {
       uint32_t frame_index =
           static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
       uint32_t index =
           static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
       uint8_t buff[16];
       uint32_t size = 0;
       if (gdb_server_->GetWasmLocal(frame_index, index, buff, 16, &size)) {
         pkt_out->AddBlock(buff, size);
         return ErrorCode::None;
       } else {
         return ErrorCode::Failed;
       }
     }
     return ErrorCode::BadFormat;
   }

   // Get a Wasm local from the operand stack at the index specified.
   // IN : qWasmStackValue:frame_index;index
   // OUT: $xx..xx
   if (toks[0] == "WasmStackValue") {
     if (toks.size() == 3) {
       uint32_t frame_index =
           static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
       uint32_t index =
           static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
       uint8_t buff[16];
       uint32_t size = 0;
       if (gdb_server_->GetWasmStackValue(frame_index, index, buff, 16, &size)) {
         pkt_out->AddBlock(buff, size);
         return ErrorCode::None;
       } else {
         return ErrorCode::Failed;
       }
     }
     return ErrorCode::BadFormat;
   }

   // Read Wasm memory.
   // IN : $qWasmMem:frame_index;addr;len
   // OUT: $xx..xx
   if (toks[0] == "WasmMem") {
     if (toks.size() == 4) {
       uint32_t frame_index =
           static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
       uint32_t address =
           static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 16));
       uint32_t length =
           static_cast<uint32_t>(strtol(toks[3].data(), nullptr, 16));
       if (length > Transport::kBufSize / 2) {
         return ErrorCode::BadArgs;
       }
       uint8_t buff[Transport::kBufSize];
       uint32_t read =
           gdb_server_->GetWasmMemory(frame_index, address, buff, length);
       if (read > 0) {
         pkt_out->AddBlock(buff, read);
         return ErrorCode::None;
       } else {
         return ErrorCode::Failed;
       }
     }
     return ErrorCode::BadFormat;
   }

   // No match so far, check the property cache.
   QueryPropertyMap::const_iterator it = query_properties_.find(toks[0]);
   if (it != query_properties_.end()) {
     pkt_out->AddString(it->second.data());
   }
   // If not found, just send an empty response.
   return ErrorCode::None;
 }

 // A Stop-reply packet has the format:
 //   Sxx
 // or:
 //   Txx<name1>:<value1>;...;<nameN>:<valueN>
 // where 'xx' is a two-digit hex number that represents the stop signal
 // and the <name>:<value> pairs are used to report additional information,
 // like the thread id.
 void Target::SetStopReply(Packet* pkt_out) const {
   pkt_out->AddRawChar('T');
   pkt_out->AddWord8(cur_signal_);

   // Adds 'thread-pcs:<pc1>,...,<pcN>;' A list of pc values for all threads that
   // currently exist in the process.
   char buff[64];
   snprintf(buff, sizeof(buff), "thread-pcs:%" PRIx64 ";",
            static_cast<uint64_t>(GetCurrentPc()));
   pkt_out->AddString(buff);

   // Adds 'thread:<tid>;' pair. Note that a terminating ';' is required.
   pkt_out->AddString("thread:");
   pkt_out->AddNumberSep(kThreadId, ';');
 }

 void Target::SetStatus(Status status, int8_t signal,
                        std::vector<wasm_addr_t> call_frames, Isolate* isolate) {
   v8::base::MutexGuard guard(&mutex_);

   DCHECK((status == Status::Suspended && signal != 0 &&
           call_frames.size() > 0 && isolate != nullptr) ||
          (status != Status::Suspended && signal == 0 &&
           call_frames.size() == 0 && isolate == nullptr));

   current_isolate_ = isolate;
   status_ = status;
   cur_signal_ = signal;
   call_frames_ = call_frames;
 }

 const std::vector<wasm_addr_t> Target::GetCallStack() const {
   v8::base::MutexGuard guard(&mutex_);

   return call_frames_;
 }

 wasm_addr_t Target::GetCurrentPc() const {
   v8::base::MutexGuard guard(&mutex_);

   wasm_addr_t pc{0};
   if (call_frames_.size() > 0) {
     pc = call_frames_[0];
   }
   return pc;
 }

 }  // namespace gdb_server
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
	// Copyright 2020 the V8 project authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "src/debug/wasm/gdb-server/target.h"

	#include <inttypes.h>
	#include "src/base/platform/time.h"
	#include "src/debug/wasm/gdb-server/gdb-remote-util.h"
	#include "src/debug/wasm/gdb-server/gdb-server.h"
	#include "src/debug/wasm/gdb-server/packet.h"
	#include "src/debug/wasm/gdb-server/session.h"
	#include "src/debug/wasm/gdb-server/transport.h"

	namespace v8 {
	namespace internal {
	namespace wasm {
	namespace gdb_server {

	static const int kThreadId = 1;

	// Signals.
	static const int kSigTrace = 5;
	static const int kSigSegv = 11;

	Target::Target(GdbServer* gdb_server)
	: gdb_server_(gdb_server),
	status_(Status::Running),
	cur_signal_(0),
	session_(nullptr),
	debugger_initial_suspension_(true),
	semaphore_(0),
	current_isolate_(nullptr) {
	InitQueryPropertyMap();
	}

	void Target::InitQueryPropertyMap() {
	// Request LLDB to send packets up to 4000 bytes for bulk transfers.
	query_properties_["Supported"] =
	"PacketSize=1000;vContSupported-;qXfer:libraries:read+;";

	query_properties_["Attached"] = "1";

	// There is only one register, named 'pc', in this architecture
	query_properties_["RegisterInfo0"] =
	"name:pc;alt-name:pc;bitsize:64;offset:0;encoding:uint;format:hex;set:"
	"General Purpose Registers;gcc:16;dwarf:16;generic:pc;";
	query_properties_["RegisterInfo1"] = "E45";

	// ProcessInfo for wasm32
	query_properties_["ProcessInfo"] =
	"pid:1;ppid:1;uid:1;gid:1;euid:1;egid:1;name:6c6c6462;triple:" +
	Mem2Hex("wasm32-unknown-unknown-wasm") + ";ptrsize:4;";
	query_properties_["Symbol"] = "OK";

	// Current thread info
	char buff[16];
	snprintf(buff, sizeof(buff), "QC%x", kThreadId);
	query_properties_["C"] = buff;
	}

	void Target::Terminate() {
	// Executed in the Isolate thread, when the process shuts down.
	SetStatus(Status::Terminated);
	}

	void Target::OnProgramBreak(Isolate* isolate,
	const std::vector<wasm_addr_t>& call_frames) {
	OnSuspended(isolate, kSigTrace, call_frames);
	}
	void Target::OnException(Isolate* isolate,
	const std::vector<wasm_addr_t>& call_frames) {
	OnSuspended(isolate, kSigSegv, call_frames);
	}
	void Target::OnSuspended(Isolate* isolate, int signal,
	const std::vector<wasm_addr_t>& call_frames) {
	// This function will be called in the isolate thread, when the wasm
	// interpreter gets suspended.

	bool isWaitingForSuspension = (status_ == Status::WaitingForSuspension);
	SetStatus(Status::Suspended, signal, call_frames, isolate);
	if (isWaitingForSuspension) {
	// Wake the GdbServer thread that was blocked waiting for the Target
	// to suspend.
	semaphore_.Signal();
	} else if (session_) {
	session_->SignalThreadEvent();
	}
	}

	void Target::Run(Session* session) {
	// Executed in the GdbServer thread.
	session_ = session;
	do {
	WaitForDebugEvent();
	ProcessDebugEvent();
	ProcessCommands();
	} while (!IsTerminated() && session_->IsConnected());
	session_ = nullptr;
	}

	void Target::WaitForDebugEvent() {
	// Executed in the GdbServer thread.

	if (status_ == Status::Running) {
	// Wait for either:
	// * the thread to fault (or single-step)
	// * an interrupt from LLDB
	session_->WaitForDebugStubEvent();
	}
	}

	void Target::ProcessDebugEvent() {
	// Executed in the GdbServer thread

	if (status_ == Status::Running) {
	// Blocks, waiting for the engine to suspend.
	Suspend();
	}

	// Here, the wasm interpreter has suspended and we have updated the current
	// thread info.

	if (debugger_initial_suspension_) {
	// First time on a connection, we don't send the signal.
	// All other times, send the signal that triggered us.
	debugger_initial_suspension_ = false;
	} else {
	Packet pktOut;
	SetStopReply(&pktOut);
	session_->SendPacket(&pktOut, false);
	}
	}

	void Target::Suspend() {
	// Executed in the GdbServer thread
	if (status_ == Status::Running) {
	// TODO(paolosev) - this only suspends the wasm interpreter.
	gdb_server_->Suspend();

	status_ = Status::WaitingForSuspension;
	}

	while (status_ == Status::WaitingForSuspension) {
	if (semaphore_.WaitFor(base::TimeDelta::FromMilliseconds(500))) {
	// Here the wasm interpreter is suspended.
	return;
	}
	}
	}

	void Target::ProcessCommands() {
	// GDB-remote messages are processed in the GDBServer thread.

	if (IsTerminated()) {
	return;
	} else if (status_ != Status::Suspended) {
	// Don't process commands if we haven't stopped.
	return;
	}

	// Now we are ready to process commands.
	// Loop through packets until we process a continue packet or a detach.
	Packet recv, reply;
	while (session_->IsConnected()) {
	if (!session_->GetPacket(&recv)) {
	continue;
	}

	reply.Clear();
	ProcessPacketResult result = ProcessPacket(&recv, &reply);
	switch (result) {
	case ProcessPacketResult::Paused:
	session_->SendPacket(&reply);
	break;

	case ProcessPacketResult::Continue:
	DCHECK_EQ(status_, Status::Running);
	// If this is a continue type command, break out of this loop.
	gdb_server_->QuitMessageLoopOnPause();
	return;

	case ProcessPacketResult::Detach:
	SetStatus(Status::Running);
	session_->SendPacket(&reply);
	session_->Disconnect();
	gdb_server_->QuitMessageLoopOnPause();
	return;

	case ProcessPacketResult::Kill:
	session_->SendPacket(&reply);
	exit(-9);

	default:
	UNREACHABLE();
	}
	}

	if (!session_->IsConnected()) {
	debugger_initial_suspension_ = true;
	}
	}

	Target::ProcessPacketResult Target::ProcessPacket(Packet* pkt_in,
	Packet* pkt_out) {
	ErrorCode err = ErrorCode::None;

	// Clear the outbound message.
	pkt_out->Clear();

	// Set the sequence number, if present.
	int32_t seq = -1;
	if (pkt_in->GetSequence(&seq)) {
	pkt_out->SetSequence(seq);
	}

	// A GDB-remote packet begins with an upper- or lower-case letter, which
	// generally represents a single command.
	// The letters 'q' and 'Q' introduce a "General query packets" and are used
	// to extend the protocol with custom commands.
	// The format of GDB-remote commands is documented here:
	// https://sourceware.org/gdb/onlinedocs/gdb/Overview.html#Overview.
	char cmd;
	pkt_in->GetRawChar(&cmd);

	switch (cmd) {
	// Queries the reason the target halted.
	// IN : $?
	// OUT: A Stop-reply packet
	case '?':
	SetStopReply(pkt_out);
	break;

	// Resumes execution
	// IN : $c
	// OUT: A Stop-reply packet is sent later, when the execution halts.
	case 'c':
	SetStatus(Status::Running);
	return ProcessPacketResult::Continue;

	// Detaches the debugger from this target
	// IN : $D
	// OUT: $OK
	case 'D':
	TRACE_GDB_REMOTE("Requested Detach.\n");
	pkt_out->AddString("OK");
	return ProcessPacketResult::Detach;

	// Read general registers (We only support register 'pc' that contains
	// the current instruction pointer).
	// IN : $g
	// OUT: $xx...xx
	case 'g': {
	uint64_t pc = GetCurrentPc();
	pkt_out->AddBlock(&pc, sizeof(pc));
	break;
	}

	// Write general registers - NOT SUPPORTED
	// IN : $Gxx..xx
	// OUT: $ (empty string)
	case 'G': {
	break;
	}

	// Set thread for subsequent operations. For Wasm targets, we currently
	// assume that there is only one thread with id = kThreadId (= 1).
	// IN : $H(c/g)(-1,0,xxxx)
	// OUT: $OK
	case 'H': {
	// Type of the operation (‘m’, ‘M’, ‘g’, ‘G’, ...)
	char operation;
	if (!pkt_in->GetRawChar(&operation)) {
	err = ErrorCode::BadFormat;
	break;
	}

	uint64_t thread_id;
	if (!pkt_in->GetNumberSep(&thread_id, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}

	// Ignore, only one thread supported for now.
	pkt_out->AddString("OK");
	break;
	}

	// Kills the debuggee.
	// IN : $k
	// OUT: $OK
	case 'k':
	TRACE_GDB_REMOTE("Requested Kill.\n");
	pkt_out->AddString("OK");
	return ProcessPacketResult::Kill;

	// Reads {llll} addressable memory units starting at address {aaaa}.
	// IN : $maaaa,llll
	// OUT: $xx..xx
	case 'm': {
	uint64_t address;
	if (!pkt_in->GetNumberSep(&address, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}
	wasm_addr_t wasm_addr(address);

	uint64_t len;
	if (!pkt_in->GetNumberSep(&len, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}

	if (len > Transport::kBufSize / 2) {
	err = ErrorCode::BadArgs;
	break;
	}

	uint32_t length = static_cast<uint32_t>(len);
	uint8_t buff[Transport::kBufSize];
	if (wasm_addr.ModuleId() > 0) {
	uint32_t read =
	gdb_server_->GetWasmModuleBytes(wasm_addr, buff, length);
	if (read > 0) {
	pkt_out->AddBlock(buff, read);
	} else {
	err = ErrorCode::Failed;
	}
	} else {
	err = ErrorCode::BadArgs;
	}
	break;
	}

	// Writes {llll} addressable memory units starting at address {aaaa}.
	// IN : $Maaaa,llll:xx..xx
	// OUT: $OK
	case 'M': {
	// Writing to memory not supported for Wasm.
	err = ErrorCode::Failed;
	break;
	}

	// pN: Reads the value of register N.
	// IN : $pxx
	// OUT: $xx..xx
	case 'p': {
	uint64_t pc = GetCurrentPc();
	pkt_out->AddBlock(&pc, sizeof(pc));
	} break;

	case 'q': {
	err = ProcessQueryPacket(pkt_in, pkt_out);
	break;
	}

	// Single step
	// IN : $s
	// OUT: A Stop-reply packet is sent later, when the execution halts.
	case 's': {
	if (status_ == Status::Suspended) {
	gdb_server_->PrepareStep();
	SetStatus(Status::Running);
	}
	return ProcessPacketResult::Continue;
	}

	// Find out if the thread 'id' is alive.
	// IN : $T
	// OUT: $OK if alive, $Enn if thread is dead.
	case 'T': {
	uint64_t id;
	if (!pkt_in->GetNumberSep(&id, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}
	if (id != kThreadId) {
	err = ErrorCode::BadArgs;
	break;
	}
	pkt_out->AddString("OK");
	break;
	}

	// Z: Adds a breakpoint
	// IN : $Z<type>,<addr>,<kind>
	// <type>: 0: sw breakpoint, 1: hw breakpoint, 2: watchpoint
	// OUT: $OK (success) or $Enn (error)
	case 'Z': {
	uint64_t breakpoint_type;
	uint64_t breakpoint_address;
	uint64_t breakpoint_kind;
	// Only software breakpoints are supported.
	if (!pkt_in->GetNumberSep(&breakpoint_type, 0) \|\| breakpoint_type != 0 \|\|
	!pkt_in->GetNumberSep(&breakpoint_address, 0) \|\|
	!pkt_in->GetNumberSep(&breakpoint_kind, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}

	wasm_addr_t wasm_breakpoint_addr(breakpoint_address);
	if (!gdb_server_->AddBreakpoint(wasm_breakpoint_addr.ModuleId(),
	wasm_breakpoint_addr.Offset())) {
	err = ErrorCode::Failed;
	break;
	}

	pkt_out->AddString("OK");
	break;
	}

	// z: Removes a breakpoint
	// IN : $z<type>,<addr>,<kind>
	// <type>: 0: sw breakpoint, 1: hw breakpoint, 2: watchpoint
	// OUT: $OK (success) or $Enn (error)
	case 'z': {
	uint64_t breakpoint_type;
	uint64_t breakpoint_address;
	uint64_t breakpoint_kind;
	if (!pkt_in->GetNumberSep(&breakpoint_type, 0) \|\| breakpoint_type != 0 \|\|
	!pkt_in->GetNumberSep(&breakpoint_address, 0) \|\|
	!pkt_in->GetNumberSep(&breakpoint_kind, 0)) {
	err = ErrorCode::BadFormat;
	break;
	}

	wasm_addr_t wasm_breakpoint_addr(breakpoint_address);
	if (!gdb_server_->RemoveBreakpoint(wasm_breakpoint_addr.ModuleId(),
	wasm_breakpoint_addr.Offset())) {
	err = ErrorCode::Failed;
	break;
	}

	pkt_out->AddString("OK");
	break;
	}

	// If the command is not recognized, ignore it by sending an empty reply.
	default: {
	TRACE_GDB_REMOTE("Unknown command: %s\n", pkt_in->GetPayload());
	}
	}

	// If there is an error, return the error code instead of a payload
	if (err != ErrorCode::None) {
	pkt_out->Clear();
	pkt_out->AddRawChar('E');
	pkt_out->AddWord8(static_cast<uint8_t>(err));
	}
	return ProcessPacketResult::Paused;
	}

	Target::ErrorCode Target::ProcessQueryPacket(const Packet* pkt_in,
	Packet* pkt_out) {
	const char* str = &pkt_in->GetPayload()[1];

	// Get first thread query
	// IN : $qfThreadInfo
	// OUT: $m<tid>
	//
	// Get next thread query
	// IN : $qsThreadInfo
	// OUT: $m<tid> or l to denote end of list.
	if (!strcmp(str, "fThreadInfo") \|\| !strcmp(str, "sThreadInfo")) {
	if (str[0] == 'f') {
	pkt_out->AddString("m");
	pkt_out->AddNumberSep(kThreadId, 0);
	} else {
	pkt_out->AddString("l");
	}
	return ErrorCode::None;
	}

	// Get a list of loaded libraries
	// IN : $qXfer:libraries:read
	// OUT: an XML document which lists loaded libraries, with this format:
	// <library-list>
	// <library name="foo.wasm">
	// <section address="0x100000000"/>
	// </library>
	// <library name="bar.wasm">
	// <section address="0x200000000"/>
	// </library>
	// </library-list>
	// Note that LLDB must be compiled with libxml2 support to handle this packet.
	std::string tmp = "Xfer:libraries:read";
	if (!strncmp(str, tmp.data(), tmp.length())) {
	std::vector<GdbServer::WasmModuleInfo> modules =
	gdb_server_->GetLoadedModules();
	std::string result("l<library-list>");
	for (const auto& module : modules) {
	wasm_addr_t address(module.module_id, 0);
	char address_string[32];
	snprintf(address_string, sizeof(address_string), "%" PRIu64,
	static_cast<uint64_t>(address));
	result += "<library name=\"";
	result += module.module_name;
	result += "\"><section address=\"";
	result += address_string;
	result += "\"/></library>";
	}
	result += "</library-list>";
	pkt_out->AddString(result.c_str());
	return ErrorCode::None;
	}

	// Get the current call stack.
	// IN : $qWasmCallStack
	// OUT: $xx..xxyy..yyzz..zz (A sequence of uint64_t values represented as
	// consecutive 8-bytes blocks).
	std::vector<std::string> toks = StringSplit(str, ":;");
	if (toks[0] == "WasmCallStack") {
	std::vector<wasm_addr_t> call_stack_pcs = gdb_server_->GetWasmCallStack();
	std::vector<uint64_t> buffer;
	for (wasm_addr_t pc : call_stack_pcs) {
	buffer.push_back(pc);
	}
	pkt_out->AddBlock(buffer.data(),
	static_cast<uint32_t>(sizeof(uint64_t) * buffer.size()));
	return ErrorCode::None;
	}

	// Get a Wasm global value in the Wasm module specified.
	// IN : $qWasmGlobal:frame_index;index
	// OUT: $xx..xx
	if (toks[0] == "WasmGlobal") {
	if (toks.size() == 3) {
	uint32_t frame_index =
	static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
	uint32_t index =
	static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
	uint8_t buff[16];
	uint32_t size = 0;
	if (gdb_server_->GetWasmGlobal(frame_index, index, buff, 16, &size)) {
	pkt_out->AddBlock(buff, size);
	return ErrorCode::None;
	} else {
	return ErrorCode::Failed;
	}
	}
	return ErrorCode::BadFormat;
	}

	// Get a Wasm local value in the stack frame specified.
	// IN : $qWasmLocal:frame_index;index
	// OUT: $xx..xx
	if (toks[0] == "WasmLocal") {
	if (toks.size() == 3) {
	uint32_t frame_index =
	static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
	uint32_t index =
	static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
	uint8_t buff[16];
	uint32_t size = 0;
	if (gdb_server_->GetWasmLocal(frame_index, index, buff, 16, &size)) {
	pkt_out->AddBlock(buff, size);
	return ErrorCode::None;
	} else {
	return ErrorCode::Failed;
	}
	}
	return ErrorCode::BadFormat;
	}

	// Get a Wasm local from the operand stack at the index specified.
	// IN : qWasmStackValue:frame_index;index
	// OUT: $xx..xx
	if (toks[0] == "WasmStackValue") {
	if (toks.size() == 3) {
	uint32_t frame_index =
	static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
	uint32_t index =
	static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 10));
	uint8_t buff[16];
	uint32_t size = 0;
	if (gdb_server_->GetWasmStackValue(frame_index, index, buff, 16, &size)) {
	pkt_out->AddBlock(buff, size);
	return ErrorCode::None;
	} else {
	return ErrorCode::Failed;
	}
	}
	return ErrorCode::BadFormat;
	}

	// Read Wasm memory.
	// IN : $qWasmMem:frame_index;addr;len
	// OUT: $xx..xx
	if (toks[0] == "WasmMem") {
	if (toks.size() == 4) {
	uint32_t frame_index =
	static_cast<uint32_t>(strtol(toks[1].data(), nullptr, 10));
	uint32_t address =
	static_cast<uint32_t>(strtol(toks[2].data(), nullptr, 16));
	uint32_t length =
	static_cast<uint32_t>(strtol(toks[3].data(), nullptr, 16));
	if (length > Transport::kBufSize / 2) {
	return ErrorCode::BadArgs;
	}
	uint8_t buff[Transport::kBufSize];
	uint32_t read =
	gdb_server_->GetWasmMemory(frame_index, address, buff, length);
	if (read > 0) {
	pkt_out->AddBlock(buff, read);
	return ErrorCode::None;
	} else {
	return ErrorCode::Failed;
	}
	}
	return ErrorCode::BadFormat;
	}

	// No match so far, check the property cache.
	QueryPropertyMap::const_iterator it = query_properties_.find(toks[0]);
	if (it != query_properties_.end()) {
	pkt_out->AddString(it->second.data());
	}
	// If not found, just send an empty response.
	return ErrorCode::None;
	}

	// A Stop-reply packet has the format:
	// Sxx
	// or:
	// Txx<name1>:<value1>;...;<nameN>:<valueN>
	// where 'xx' is a two-digit hex number that represents the stop signal
	// and the <name>:<value> pairs are used to report additional information,
	// like the thread id.
	void Target::SetStopReply(Packet* pkt_out) const {
	pkt_out->AddRawChar('T');
	pkt_out->AddWord8(cur_signal_);

	// Adds 'thread-pcs:<pc1>,...,<pcN>;' A list of pc values for all threads that
	// currently exist in the process.
	char buff[64];
	snprintf(buff, sizeof(buff), "thread-pcs:%" PRIx64 ";",
	static_cast<uint64_t>(GetCurrentPc()));
	pkt_out->AddString(buff);

	// Adds 'thread:<tid>;' pair. Note that a terminating ';' is required.
	pkt_out->AddString("thread:");
	pkt_out->AddNumberSep(kThreadId, ';');
	}

	void Target::SetStatus(Status status, int8_t signal,
	std::vector<wasm_addr_t> call_frames, Isolate* isolate) {
	v8::base::MutexGuard guard(&mutex_);

	DCHECK((status == Status::Suspended && signal != 0 &&
	call_frames.size() > 0 && isolate != nullptr) \|\|
	(status != Status::Suspended && signal == 0 &&
	call_frames.size() == 0 && isolate == nullptr));

	current_isolate_ = isolate;
	status_ = status;
	cur_signal_ = signal;
	call_frames_ = call_frames;
	}

	const std::vector<wasm_addr_t> Target::GetCallStack() const {
	v8::base::MutexGuard guard(&mutex_);

	return call_frames_;
	}

	wasm_addr_t Target::GetCurrentPc() const {
	v8::base::MutexGuard guard(&mutex_);

	wasm_addr_t pc{0};
	if (call_frames_.size() > 0) {
	pc = call_frames_[0];
	}
	return pc;
	}

	} // namespace gdb_server
	} // namespace wasm
	} // namespace internal
	} // namespace v8