gdbstub: eliminate gdbserver_fd global

We don't really need to track this fd beyond the initial creation of
the socket. We already know if the system has been initialised by
virtue of the gdbserver_state so lets remove it. This makes the later
re-factoring easier.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200430190122.4592-6-alex.bennee@linaro.org>

gdbstub.c

@@ -398,8 +398,6 @@ static void reset_gdbserver_state(void)
 bool gdb_has_xml;
 
 #ifdef CONFIG_USER_ONLY
-/* XXX: This is not thread safe.  Do we care?  */
-static int gdbserver_fd = -1;
 
 static int get_char(void)
 {
@@ -2964,7 +2962,7 @@ void gdb_exit(CPUArchState *env, int code)
       return;
   }
 #ifdef CONFIG_USER_ONLY
-  if (gdbserver_fd < 0 || gdbserver_state.fd < 0) {
+  if (gdbserver_state.fd < 0) {
       return;
   }
 #endif
@@ -3011,7 +3009,7 @@ gdb_handlesig(CPUState *cpu, int sig)
     char buf[256];
     int n;
 
-    if (gdbserver_fd < 0 || gdbserver_state.fd < 0) {
+    if (!gdbserver_state.init || gdbserver_state.fd < 0) {
         return sig;
     }
 
@@ -3060,7 +3058,7 @@ void gdb_signalled(CPUArchState *env, int sig)
 {
     char buf[4];
 
-    if (gdbserver_fd < 0 || gdbserver_state.fd < 0) {
+    if (!gdbserver_state.init || gdbserver_state.fd < 0) {
         return;
     }
 
@@ -3068,7 +3066,7 @@ void gdb_signalled(CPUArchState *env, int sig)
     put_packet(buf);
 }
 
-static bool gdb_accept(void)
+static bool gdb_accept(int gdb_fd)
 {
     struct sockaddr_in sockaddr;
     socklen_t len;
@@ -3076,7 +3074,7 @@ static bool gdb_accept(void)
 
     for(;;) {
         len = sizeof(sockaddr);
-        fd = accept(gdbserver_fd, (struct sockaddr *)&sockaddr, &len);
+        fd = accept(gdb_fd, (struct sockaddr *)&sockaddr, &len);
         if (fd < 0 && errno != EINTR) {
             perror("accept");
             return false;
@@ -3137,13 +3135,13 @@ static int gdbserver_open(int port)
 
 int gdbserver_start(int port)
 {
-    gdbserver_fd = gdbserver_open(port);
-    if (gdbserver_fd < 0)
+    int gdb_fd = gdbserver_open(port);
+    if (gdb_fd < 0) {
         return -1;
+    }
     /* accept connections */
-    if (!gdb_accept()) {
-        close(gdbserver_fd);
-        gdbserver_fd = -1;
+    if (!gdb_accept(gdb_fd)) {
+        close(gdb_fd);
         return -1;
     }
     return 0;
@@ -3152,7 +3150,7 @@ int gdbserver_start(int port)
 /* Disable gdb stub for child processes.  */
 void gdbserver_fork(CPUState *cpu)
 {
-    if (gdbserver_fd < 0 || gdbserver_state.fd < 0) {
+    if (!gdbserver_state.init || gdbserver_state.fd < 0) {
         return;
     }
     close(gdbserver_state.fd);