gdbstub: Report the actual qemu-user pid

Currently qemu-user reports pid 1 to GDB. Resolve the TODO and report
the actual PID. Using getpid() relies on the assumption that there is
only one GDBProcess. Add an assertion to make sure that future changes
don't break it.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230621203627.1808446-6-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230630180423.558337-36-alex.bennee@linaro.org>

gdbstub/gdbstub.c

@@ -202,13 +202,16 @@ void gdb_memtox(GString *buf, const char *mem, int len)
 
 static uint32_t gdb_get_cpu_pid(CPUState *cpu)
 {
-    /* TODO: In user mode, we should use the task state PID */
+#ifdef CONFIG_USER_ONLY
+    return getpid();
+#else
     if (cpu->cluster_index == UNASSIGNED_CLUSTER_INDEX) {
         /* Return the default process' PID */
         int index = gdbserver_state.process_num - 1;
         return gdbserver_state.processes[index].pid;
     }
     return cpu->cluster_index + 1;
+#endif
 }
 
 GDBProcess *gdb_get_process(uint32_t pid)
@@ -2137,19 +2140,25 @@ void gdb_read_byte(uint8_t ch)
 void gdb_create_default_process(GDBState *s)
 {
     GDBProcess *process;
-    int max_pid = 0;
+    int pid;
 
+#ifdef CONFIG_USER_ONLY
+    assert(gdbserver_state.process_num == 0);
+    pid = getpid();
+#else
     if (gdbserver_state.process_num) {
-        max_pid = s->processes[s->process_num - 1].pid;
+        pid = s->processes[s->process_num - 1].pid;
+    } else {
+        pid = 0;
     }
+    /* We need an available PID slot for this process */
+    assert(pid < UINT32_MAX);
+    pid++;
+#endif
 
     s->processes = g_renew(GDBProcess, s->processes, ++s->process_num);
     process = &s->processes[s->process_num - 1];
-
-    /* We need an available PID slot for this process */
-    assert(max_pid < UINT32_MAX);
-
-    process->pid = max_pid + 1;
+    process->pid = pid;
     process->attached = false;
     process->target_xml[0] = '\0';
 }