flycast/core/debug/gdb_server.cpp

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/*
Copyright 2021 flyinghead
This file is part of Flycast.
Flycast is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
Flycast is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Flycast. If not, see <https://www.gnu.org/licenses/>.
*/
#include "types.h"
#ifdef GDB_SERVER
#include "gdb_server.h"
#include "debug_agent.h"
#include "network/net_platform.h"
#include <stdexcept>
#include <thread>
#include <chrono>
#include <mutex>
#define SERVER_PORT 3263
namespace debugger {
static void emuEventCallback(Event event);
class GdbServer
{
public:
struct Error : public std::runtime_error {
Error(const char *reason) : std::runtime_error(reason) {}
};
void init()
{
if (VALID(serverSocket))
return;
serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (!VALID(serverSocket))
throw Error("gdb: Cannot create server socket");
int option = 1;
setsockopt(serverSocket, SOL_SOCKET, SO_REUSEADDR, (const char *)&option, sizeof(option));
struct sockaddr_in serveraddr;
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(SERVER_PORT);
if (::bind(serverSocket, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0)
{
closesocket(serverSocket);
throw Error("gdb: bind() failed");
}
if (::listen(serverSocket, 5) < 0)
{
closesocket(serverSocket);
throw Error("gdb: listen() failed");
}
EventManager::listen(Event::Resume, emuEventCallback);
EventManager::listen(Event::Terminate, emuEventCallback);
}
void term()
{
stop();
if (VALID(clientSocket))
{
closesocket(clientSocket);
clientSocket = INVALID_SOCKET;
}
if (VALID(serverSocket))
{
closesocket(serverSocket);
serverSocket = INVALID_SOCKET;
}
}
void run()
{
DEBUG_LOG(COMMON, "GdbServer starting");
thread = std::thread(&GdbServer::serverThread, this);
}
void stop()
{
if (thread.joinable())
{
DEBUG_LOG(COMMON, "GdbServer stopping");
agent.resetAgent();
stopRequested = true;
thread.join();
}
}
bool isRunning() const {
return thread.joinable();
}
// called on the emu thread
void debugTrap(u32 event)
{
if (!attached)
return;
agent.debugTrap(event);
reportException();
postDebugTrapNeeded = true;
throw Stop();
}
private:
const u32 EXCEPT_NONE = 1;
void serverThread()
{
while (!stopRequested)
{
fd_set fds;
FD_ZERO(&fds);
sock_t max_fd = serverSocket;
FD_SET(serverSocket, &fds);
if (VALID(clientSocket))
{
max_fd = std::max(max_fd, clientSocket);
FD_SET(clientSocket, &fds);
}
timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 100 * 1000;
if (::select(max_fd + 1, &fds, nullptr, nullptr, &tv) > 0)
{
if (FD_ISSET(serverSocket, &fds))
{
try {
acceptClientConnection();
} catch (const Error& e) {
ERROR_LOG(COMMON, "%s", e.what());
closesocket(serverSocket);
serverSocket = INVALID_SOCKET;
break;
}
}
else if (FD_ISSET(clientSocket, &fds))
{
readCommand();
}
}
}
if (VALID(clientSocket))
{
closesocket(clientSocket);
clientSocket = INVALID_SOCKET;
}
attached = false;
stopRequested = false;
}
void acceptClientConnection()
{
if (VALID(clientSocket))
closesocket(clientSocket);
sockaddr_in src_addr{};
socklen_t addr_len = sizeof(src_addr);
clientSocket = ::accept(serverSocket, (sockaddr *)&src_addr, &addr_len);
if (!VALID(clientSocket))
{
if (get_last_error() != L_EAGAIN && get_last_error() != L_EWOULDBLOCK)
throw Error("accept failed");
}
else
{
NOTICE_LOG(NETWORK, "gdb: client connection");
attached = true;
agent.interrupt();
}
}
void readCommand()
{
if (postDebugTrapNeeded)
{
postDebugTrapNeeded = false;
agent.postDebugTrap();
}
try {
std::string packet = recvPacket();
if (packet.empty())
return;
DEBUG_LOG(NETWORK, "gdb: recv %s", packet.c_str());
switch (packet[0])
{
case '!': // Enable extended mode
sendPacket("OK");
break;
case '?': // Sent when connection is first established to query the reason the target halted
reportException();
break;
case 'A': // Initialized argv[] array passed into program. not supported
sendPacket("E01");
break;;
case 'b': // Change the serial line speed to baud. deprecated
break;
case 'B': // Set or clear a breakpoint at addr. deprecated
break;
case 'c': // Continue at addr, which is the address to resume.
// If addr is omitted, resume at current address
sendContinue(packet);
break;
case 'C': // Continue with signal sig
sendContinue(packet);
break;
case 'd': // Toggle debug flag. deprecated
break;
case 'D': // Detach GDB from the remote system
sendPacket("OK");
agent.detach();
break;
case 'F': // File-I/O protocol extension not currently supported
break;;
case 'g': // Read general registers
readAllRegs();
break;
case 'G': // Write general registers
writeAllRegs(packet);
break;
case 'H': // Set thread for subsequent operations
sendPacket("OK");
break;
case 'i': // Step the remote target by a single clock cycle
case 'I': // Signal, then cycle step
// not supported
sendPacket("");
break;
case 'k': // Kill request. Stop process/system
agent.kill();
break;
case 'm': // Read length addressable memory units
readMem(packet);
break;
case 'M': // Write length addressable memory units
writeMem(packet);
break;
case 'p': // Read the value of register
readReg(packet);
break;
case 'P': // Write register
writeReg(packet);
break;
case 'q': // General query packets
query(packet);
break;
case 'Q': // General set packets
set(packet);
break;
case 'r': // Reset the entire system. Deprecated (use 'R' instead)
break;
case 'R': // Restart the program being debugged.
restart();
break;
case 's': // Single step
step(EXCEPT_NONE);
break;
case 'S': // Step with signal
step();
break;
case 't': // Search backwards. unsupported
break;
case 'T': // Find out if the thread is alive
sendPacket("OK");
break;
case 'v': // 'v' packets to control execution
vpacket(packet);
break;
case 'X': // Write binary data to memory
writeMemBin(packet);
break;
case 'z': // Remove a breakpoint/watchpoint.
removeMatchpoint(packet);
break;
case 'Z': // Insert a breakpoint/watchpoint.
insertMatchpoint(packet);
break;
case 3:
interrupt();
break;
default:
// Unknown commands are ignored
WARN_LOG(COMMON, "Unknown gdb command: %s", packet.c_str());
break;;
}
} catch (const Error& e) {
ERROR_LOG(COMMON, "%s", e.what());
closesocket(clientSocket);
clientSocket = INVALID_SOCKET;
attached = false;
}
}
void reportException()
{
char s[4];
sprintf(s, "S%02X", agent.currentException());
sendPacket(s);
}
void sendContinue(const std::string& pkt)
{
if (pkt[0] != 'c') {
WARN_LOG(COMMON, "Continue with signal not supported");
return;
}
if (pkt == "c")
agent.doContinue();
else
{
// Get the pc at which to resume
u32 addr;
if (sscanf(pkt.c_str(), "c%x", &addr) != 1)
{
WARN_LOG(COMMON, "Continue address invalid %s", pkt.c_str());
return;
}
agent.doContinue(addr);
}
}
void readAllRegs()
{
u32 *regs;
int c = agent.readAllRegs(&regs);
std::string outpkt;
for (int i = 0; i < c; i++)
outpkt += pack(regs[i]);
sendPacket(outpkt);
}
void writeAllRegs(const std::string& pkt)
{
std::vector<u32> regs;
for (auto it = pkt.begin() + 1; it <= pkt.end() - 8; it += 8)
regs.push_back(unpack(&*it, 8));
agent.writeAllRegs(regs);
sendPacket("OK");
}
void readMem(const std::string& pkt)
{
u32 addr;
u32 len;
if (sscanf(pkt.c_str(), "m%x,%x:", &addr, &len) != 2)
{
WARN_LOG(COMMON, "readMem: invalid packet %s", pkt.c_str());
sendPacket("E01");
return;
}
const u8 *mem = agent.readMem(addr, len);
std::string outpkt;
for (u32 i = 0; i < len; i++)
{
char s[3];
sprintf(s,"%02x", mem[i]);
outpkt += s;
}
sendPacket(outpkt);
}
void writeMem(const std::string& pkt)
{
u32 addr;
u32 len;
if (sscanf(pkt.c_str(), "M%x,%x:", &addr, &len) != 2)
{
WARN_LOG(COMMON, "writeMem: invalid packet %s", pkt.c_str());
sendPacket("E01");
return;
}
std::vector<u8> data(len);
const char *p = &pkt[pkt.find(':')] + 1;
for (u32 i = 0; i < len; i++, p += 2)
{
u32 b;
sscanf(p,"%2x", &b);
data[i] = (u8)b;
}
agent.writeMem(addr, data);
sendPacket("OK");
}
void writeMemBin(const std::string& pkt)
{
u32 addr;
u32 len;
if (sscanf(pkt.c_str(), "X%x,%x:", &addr, &len) != 2)
{
WARN_LOG(COMMON, "writeMemBin invalid command: %s", pkt.c_str());
sendPacket("E01");
return;
}
const char *p = &pkt[pkt.find(':')] + 1;
std::vector<u8> data;
data.reserve(pkt.length() - (p - &pkt[0]));
for (; p <= &pkt.back(); p++)
{
u8 b = *p;
if (b == '}')
{
b = *++p ^ 0x20;
}
data.push_back(b);
}
agent.writeMem(addr, data);
sendPacket("OK");
}
void readReg(const std::string& pkt)
{
u32 regNum;
if (sscanf(pkt.c_str(), "p%x", &regNum) != 1)
{
WARN_LOG(COMMON, "readReg: invalid packet %s", pkt.c_str());
sendPacket("E01");
return;
}
u32 v = agent.readReg(regNum);
sendPacket(pack(v));
}
void writeReg(const std::string& pkt)
{
u32 regNum;
char vstr[9];
if (sscanf(pkt.c_str(), "P%x=%8s", &regNum, vstr) != 2)
{
WARN_LOG(COMMON, "writeReg: invalid packet %s", pkt.c_str());
sendPacket("E01");
return;
}
agent.writeReg(regNum, unpack(vstr, 8));
sendPacket("OK");
}
void query(const std::string& pkt)
{
if (pkt == "qC")
// Return the current thread ID. 0 is "any thread"
sendPacket("QC0.01");
else if (pkt.rfind("qCRC", 0) == 0)
{
WARN_LOG(COMMON, "CRC compute not supported %s", pkt.c_str());
sendPacket("E01");
}
else if (pkt == "qfThreadInfo")
// Obtain a list of all active thread IDs (first call)
sendPacket("m0");
else if (pkt == "qsThreadInfo")
// Obtain a list of all active thread IDs (subsequent calls -> 'l' == end of list)
sendPacket("l");
else if (pkt.rfind("qGetTLSAddr:", 0) == 0)
// Fetch the address associated with thread local storage
sendPacket("");
else if (pkt.rfind("qL", 0) == 0)
// Obtain thread information. deprecated
sendPacket("qM001");
else if (pkt == "qOffsets")
// Get section offsets. Not supported
sendPacket("");
else if (pkt.rfind("qP", 0) == 0)
// Returns information on thread. deprecated
sendPacket("");
else if (pkt.rfind("qRcmd,", 0) == 0)
{
std::string customCmd;
for (const char *p = pkt.c_str() + 6; *p != '\0'; p += 2)
customCmd += (char)unpack(p, 2);
DEBUG_LOG(COMMON, "query: custom command %s", customCmd.c_str());
if (customCmd == "reset")
restart();
else if (customCmd == "stack")
{
u32 len;
const u32 *data = agent.getStack(len);
len /= 4;
char reply[len * 9 * 2 + 1];
char *r = reply;
for (u32 i = 0; i < len; i++)
{
char n[10];
sprintf(n, "%08x ", *data++);
for (char *p = n; *p != 0; p++)
{
*r++ = packnb((*p >> 4) & 0xf);
*r++ = packnb(*p & 0xf);
}
}
*r = 0;
sendPacket(reply);
}
else
sendPacket("");
}
else if (pkt.rfind("qSupported", 0) == 0)
// Tell the remote stub about features supported by GDB,
// and query the stub for features it supports
sendPacket("PacketSize=10000");
else if (pkt.rfind("qSymbol:", 0) == 0)
// Notify the target that GDB is prepared to serve symbol lookup requests
sendPacket("OK");
else if (pkt.rfind("qThreadExtraInfo,", 0) == 0)
{
// Obtain from the target OS a printable string description of thread attributes
char s[19];
sprintf(s, "%02x%02x%02x%02x%02x%02x%02x%02x%02x", 'R', 'u', 'n', 'n', 'a', 'b', 'l', 'e', 0);
sendPacket(std::string(s, 18));
}
else if (pkt.rfind("qXfer:", 0) == 0)
// Read uninterpreted bytes from the targets special data area identified by the keyword object
sendPacket("");
else if (pkt.rfind("qAttached", 0) == 0)
// Return an indication of whether the remote server attached to an existing process
// or created a new process
sendPacket("1"); // existing process
else if (pkt.rfind("qTfV", 0) == 0)
// request data about trace state variables
sendPacket("");
else if (pkt.rfind("qTfP", 0) == 0)
// request data about tracepoints
sendPacket("");
else if (pkt.rfind("qTStatus", 0) == 0)
// Ask the stub if there is a trace experiment running right now
sendPacket("");
else
WARN_LOG(COMMON, "query not supported %s", pkt.c_str());
}
void set(const std::string& pkt)
{
if (pkt.rfind("QPassSignals:", 0) == 0)
// Passing signals not supported
sendPacket("");
else if (pkt.rfind("QTDP", 0) == 0
|| pkt.rfind("QFrame", 0) == 0
|| pkt.rfind("QTStart", 0) == 0
|| pkt.rfind("QTStop", 0) == 0
|| pkt.rfind("QTinit", 0) == 0
|| pkt.rfind("QTro", 0) == 0)
// No tracepoint feature supported
sendPacket("");
else
WARN_LOG(COMMON, "set not supported %s", pkt.c_str());
}
void vpacket(const std::string& pkt)
{
if (pkt.rfind("vAttach;", 0) == 0)
sendPacket("S05");
else if (pkt.rfind("vCont?", 0) == 0)
// not supported
sendPacket("vCont;s;c");
else if (pkt.rfind("vCont", 0) == 0)
// not supported
WARN_LOG(COMMON, "vCont not supported %s", pkt.c_str());
else if (pkt.rfind("vFile:", 0) == 0)
// not supported
sendPacket("");
else if (pkt.rfind("vFlashErase:", 0) == 0)
// not supported
sendPacket("E01");
else if (pkt.rfind("vFlashWrite:", 0) == 0)
// not supported
sendPacket("E01");
else if (pkt.rfind("vFlashDone:", 0) == 0)
// not supported
sendPacket("E01");
else if (pkt.rfind("vRun;", 0) == 0)
{
if (pkt != "vRun;")
WARN_LOG(COMMON, "unexpected vRun args ignored: %s", pkt.c_str());
agent.restart();
sendPacket("S05");
}
else if (pkt.rfind("vKill", 0) == 0)
{
sendPacket("OK");
agent.kill();
}
else if (pkt.rfind("vMustReplyEmpty", 0) == 0)
// Reply empty packet
sendPacket("");
else
WARN_LOG(COMMON, "unknown v packet: %s", pkt.c_str());
}
void restart()
{
agent.restart();
}
void step(u32 what = 0)
{
agent.step();
sendPacket("S05");
}
void insertMatchpoint(const std::string& pkt)
{
u32 type;
u32 addr;
u32 len;
if (sscanf(pkt.c_str(), "Z%1d,%x,%1d", &type, &addr, &len) != 3) {
WARN_LOG(COMMON, "insertMatchpoint: unknown packet: %s", pkt.c_str());
sendPacket("E01");
}
switch (type) {
case 0: // soft bp
if (agent.insertMatchpoint(0, addr, len))
sendPacket("OK");
else
sendPacket("E01");
break;
case 1: // hardware bp
sendPacket("");
break;
case 2: // write watchpoint
sendPacket("");
break;
case 3: // read watchpoint
sendPacket("");
break;
case 4: // access watchpoint
sendPacket("");
break;
default:
sendPacket("");
break;
}
}
void removeMatchpoint(const std::string& pkt)
{
u32 type;
u32 addr;
u32 len;
if (sscanf(pkt.c_str(), "z%1d,%x,%1d", &type, &addr, &len) != 3) {
WARN_LOG(COMMON, "removeMatchpoint: unknown packet: %s", pkt.c_str());
sendPacket("E01");
}
switch (type) {
case 0: // soft bp
if (agent.removeMatchpoint(0, addr, len))
sendPacket("OK");
else
sendPacket("E01");
break;
case 1: // hardware bp
sendPacket("");
break;
case 2: // write watchpoint
sendPacket("");
break;
case 3: // read watchpoint
sendPacket("");
break;
case 4: // access watchpoint
sendPacket("");
break;
default:
sendPacket("");
break;
}
}
void interrupt()
{
u32 signal = agent.interrupt();
char s[10];
sprintf(s, "S%02x", signal);
sendPacket(s);
}
char recvChar()
{
char c;
int rc = ::recv(clientSocket, &c, 1, 0);
if (rc <= 0)
throw Error("gdb: I/O error");
return c;
}
void sendChar(char c)
{
std::unique_lock<std::mutex> lock(outMutex);
int rc = ::send(clientSocket, &c, 1, 0);
if (rc <= 0)
throw Error("gdb: I/O error");
}
u8 unpack(char c)
{
c = std::tolower(c);
if (c <= '9')
return c - '0';
else
return c - 'a' + 10;
}
char packnb(u8 b)
{
if (b < 10)
return '0' + b;
else
return 'a' + b - 10;
}
std::string packb(u8 v)
{
std::string s(1, packnb((v >> 4) & 0xf));
s += packnb(v & 0xf);
return s;
}
std::string pack(u32 v)
{
return packb(v & 0xff) + packb((v >> 8) & 0xff)
+ packb((v >> 16) & 0xff) + packb((v >> 24) & 0xff);
}
u32 unpack(const char *s, int l)
{
u32 r = 0;
for (int i = 0; i < l && *s != '\0'; i += 2, s += 2)
{
r |= (unpack(s[0]) << 4 | unpack(s[1])) << (i * 4);
}
return r;
}
std::string recvPacket()
{
std::string pkt;
// look for start character ('$') or BREAK
char c = recvChar();
if (c == 3)
return std::string("\03");
if (c != '$')
return pkt;
// read until '#'
u8 checksum = 0;
while (!stopRequested)
{
c = recvChar();
if (c == '$')
{
checksum = 0;
pkt.clear();
continue;
}
if (c == '#')
break;
checksum += (u8)c;
pkt.push_back(c);
}
if (stopRequested)
{
pkt.clear();
return pkt;
}
u8 recvchk = unpack(recvChar()) << 4;
recvchk |= unpack(recvChar());
// If the checksums don't match print a warning, and put the
// negative ack back to the client. Otherwise put a positive ack.
if (checksum != recvchk)
{
sendChar('-'); // Failed checksum
return "";
}
else
{
sendChar('+'); // Successful transfer
return pkt;
}
}
void sendPacket(const std::string& pkt)
{ DEBUG_LOG(NETWORK, "gdb: sending pkt");
std::unique_lock<std::mutex> lock(outMutex);
std::string data{'$'};
u8 checksum = 0;
for (char c : pkt)
{
if (c == '$' || c == '#' || c == '*' || c == '}')
{
c ^= 0x20;
checksum += (u8)'}';
data.push_back('}');
}
checksum += (u8)c;
data.push_back(c);
}
data.push_back('#');
char s[9];
sprintf(s, "%02x", checksum);
data += s;
DEBUG_LOG(NETWORK, "gdb: sent %s", data.c_str());
int ret = ::send(clientSocket, data.c_str(), data.length(), 0);
if (ret < (int)data.length())
throw Error("I/O error");
}
bool stopRequested = false;
bool attached = false;
bool postDebugTrapNeeded = false;
sock_t serverSocket = INVALID_SOCKET;
sock_t clientSocket = INVALID_SOCKET;
std::thread thread;
std::mutex outMutex;
public:
DebugAgent agent;
};
static GdbServer gdbServer;
void init()
{
gdbServer.init();
}
void term()
{
gdbServer.term();
}
void debugTrap(u32 event)
{
gdbServer.debugTrap(event);
}
void subroutineCall()
{
gdbServer.agent.subroutineCall();
}
void subroutineReturn()
{
gdbServer.agent.subroutineReturn();
}
static void emuEventCallback(Event event)
{
switch (event)
{
case Event::Resume:
if (!gdbServer.isRunning())
gdbServer.run();
break;
case Event::Terminate:
gdbServer.stop();
break;
default:
break;
}
}
}
#endif