GDB stub over UNIX socket

This is available with the `GDBSocket` option in
`~/.dolphin-emu/Config/Dolphin.ini`.

GDB can connect to it with:

    $ powerpc-eabi-gdb
    (gdb) target remote |socat STDIO UNIX:foo.sock

Because I don't like so much binding the GDB stub socket to 0.0.0.0.
On Linux, with a suitable umask, we can make sure that another local
user cannot connect to the socket.

Source/Core/Core/ConfigManager.cpp

@@ -218,6 +218,9 @@ void SConfig::SaveGeneralSettings(IniFile& ini)
 	general->Set("WirelessMac", m_WirelessMac);
 
 #ifdef USE_GDBSTUB
+#ifndef _WIN32
+	general->Set("GDBSocket", m_LocalCoreStartupParameter.gdb_socket);
+#endif
 	general->Set("GDBPort", m_LocalCoreStartupParameter.iGDBPort);
 #endif
 }
@@ -421,6 +424,9 @@ void SConfig::LoadGeneralSettings(IniFile& ini)
 	general->Get("ShowLag", &m_ShowLag, false);
 	general->Get("ShowFrameCount", &m_ShowFrameCount, false);
 #ifdef USE_GDBSTUB
+#ifndef _WIN32
+	general->Get("GDBSocket", &m_LocalCoreStartupParameter.gdb_socket, "");
+#endif
 	general->Get("GDBPort", &(m_LocalCoreStartupParameter.iGDBPort), -1);
 #endif
 

Source/Core/Core/Core.cpp

@@ -325,6 +325,14 @@ static void CpuThread()
 
 
 	#ifdef USE_GDBSTUB
+	#ifndef _WIN32
+	if (!_CoreParameter.gdb_socket.empty())
+	{
+		gdb_init_local(_CoreParameter.gdb_socket.data());
+		gdb_break();
+	}
+	else
+	#endif
 	if (_CoreParameter.iGDBPort > 0)
 	{
 		gdb_init(_CoreParameter.iGDBPort);

Source/Core/Core/CoreParameter.cpp

@@ -65,6 +65,9 @@ void SCoreStartupParameter::LoadDefaults()
 
 	#ifdef USE_GDBSTUB
 	iGDBPort = -1;
+	#ifndef _WIN32
+	gdb_socket = "";
+	#endif
 	#endif
 
 	iCPUCore = PowerPC::CORE_JIT64;

Source/Core/Core/CoreParameter.h

@@ -133,6 +133,9 @@ struct SCoreStartupParameter
 	bool bEnableDebugging;
 	#ifdef USE_GDBSTUB
 	int  iGDBPort;
+	#ifndef _WIN32
+	std::string gdb_socket;
+	#endif
 	#endif
 	bool bAutomaticStart;
 	bool bBootToPause;

Source/Core/Core/PowerPC/GDBStub.cpp

@@ -16,6 +16,7 @@
 #else
 #include <sys/select.h>
 #include <sys/socket.h>
+#include <sys/un.h>
 #include <netinet/in.h>
 #endif
 
@@ -33,7 +34,6 @@
 
 static int tmpsock = -1;
 static int sock = -1;
-static struct sockaddr_in saddr_server, saddr_client;
 
 static u8 cmd_bfr[GDB_BFR_MAX];
 static u32 cmd_len;
@@ -800,9 +800,52 @@ WSADATA InitData;
 
 // exported functions
 
+static void gdb_init_generic(int domain,
+	const sockaddr *server_addr, socklen_t server_addrlen,
+	sockaddr *client_addr, socklen_t *client_addrlen);
+
+#ifndef _WIN32
+void gdb_init_local(const char *socket)
+{
+	unlink(socket);
+
+	sockaddr_un addr = {}
+	addr.sun_family = AF_UNIX;
+	strcpy(addr.sun_path, socket);
+
+	gdb_init_generic(PF_LOCAL, (const sockaddr *)&addr, sizeof(addr),
+		NULL, NULL);
+}
+#endif
+
 void gdb_init(u32 port)
 {
-	socklen_t len;
+	sockaddr_in saddr_server = {};
+	sockaddr_in saddr_client;
+
+	saddr_server.sin_family = AF_INET;
+	saddr_server.sin_port = htons(port);
+	saddr_server.sin_addr.s_addr = INADDR_ANY;
+
+	socklen_t client_addrlen = sizeof(saddr_client);
+
+	gdb_init_generic(PF_INET,
+		(const sockaddr *)&saddr_server, sizeof(saddr_server),
+		(sockaddr *)&saddr_client, &client_addrlen);
+
+	saddr_client.sin_addr.s_addr = ntohl(saddr_client.sin_addr.s_addr);
+	/*if (((saddr_client.sin_addr.s_addr >> 24) & 0xff) != 127 ||
+	*      ((saddr_client.sin_addr.s_addr >> 16) & 0xff) !=   0 ||
+	*      ((saddr_client.sin_addr.s_addr >>  8) & 0xff) !=   0 ||
+	*      ((saddr_client.sin_addr.s_addr >>  0) & 0xff) !=   1)
+	*      ERROR_LOG(GDB_STUB, "gdb: incoming connection not from localhost");
+	*/
+}
+
+static void gdb_init_generic(int domain,
+	const sockaddr *server_addr, socklen_t server_addrlen,
+	sockaddr *client_addr, socklen_t *client_addrlen)
+{
 	int on;
 	#ifdef _WIN32
 	WSAStartup(MAKEWORD(2,2), &InitData);
@@ -813,7 +856,7 @@ void gdb_init(u32 port)
 	memset(bp_w, 0, sizeof bp_w);
 	memset(bp_a, 0, sizeof bp_a);
 
-	tmpsock = socket(AF_INET, SOCK_STREAM, 0);
+	tmpsock = socket(domain, SOCK_STREAM, 0);
 	if (tmpsock == -1)
 		ERROR_LOG(GDB_STUB, "Failed to create gdb socket");
 
@@ -821,12 +864,7 @@ void gdb_init(u32 port)
 	if (setsockopt(tmpsock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof on) < 0)
 		ERROR_LOG(GDB_STUB, "Failed to setsockopt");
 
-	memset(&saddr_server, 0, sizeof saddr_server);
-	saddr_server.sin_family = AF_INET;
-	saddr_server.sin_port = htons(port);
-	saddr_server.sin_addr.s_addr = INADDR_ANY;
-
-	if (bind(tmpsock, (struct sockaddr *)&saddr_server, sizeof saddr_server) < 0)
+	if (bind(tmpsock, server_addr, server_addrlen) < 0)
 		ERROR_LOG(GDB_STUB, "Failed to bind gdb socket");
 
 	if (listen(tmpsock, 1) < 0)
@@ -834,18 +872,11 @@ void gdb_init(u32 port)
 
 	INFO_LOG(GDB_STUB, "Waiting for gdb to connect...\n");
 
-	sock = accept(tmpsock, (struct sockaddr *)&saddr_client, &len);
+	sock = accept(tmpsock, client_addr, client_addrlen);
 	if (sock < 0)
 		ERROR_LOG(GDB_STUB, "Failed to accept gdb client");
 	INFO_LOG(GDB_STUB, "Client connected.\n");
 
-	saddr_client.sin_addr.s_addr = ntohl(saddr_client.sin_addr.s_addr);
-	/*if (((saddr_client.sin_addr.s_addr >> 24) & 0xff) != 127 ||
-	 *      ((saddr_client.sin_addr.s_addr >> 16) & 0xff) !=   0 ||
-	 *      ((saddr_client.sin_addr.s_addr >>  8) & 0xff) !=   0 ||
-	 *      ((saddr_client.sin_addr.s_addr >>  0) & 0xff) !=   1)
-	 *      ERROR_LOG(GDB_STUB, "gdb: incoming connection not from localhost");
-	 */
 	close(tmpsock);
 	tmpsock = -1;
 }

Source/Core/Core/PowerPC/GDBStub.h

@@ -30,6 +30,7 @@ typedef enum {
 } gdb_bp_type;
 
 void gdb_init(u32 port);
+void gdb_init_local(const char *socket);
 void gdb_deinit();
 bool gdb_active();
 void gdb_break();