runstate_set(): Check for valid transitions

This commit could have been folded with the previous one, however
doing it separately will allow for easy bisect and revert if needed.

Checking and testing all valid transitions wasn't trivial, chances
are this will need broader testing to become more stable.

This is a transition table as suggested by Lluís Vilanova.
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

sysemu.h

@@ -36,6 +36,7 @@ extern uint8_t qemu_uuid[];
 int qemu_uuid_parse(const char *str, uint8_t *uuid);
 #define UUID_FMT "%02hhx%02hhx%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx"
 
+void runstate_init(void);
 bool runstate_check(RunState state);
 void runstate_set(RunState new_state);
 typedef struct vm_change_state_entry VMChangeStateEntry;

vl.c

@@ -327,14 +327,84 @@ static int default_driver_check(QemuOpts *opts, void *opaque)
 
 static RunState current_run_state = RSTATE_NO_STATE;
 
+typedef struct {
+    RunState from;
+    RunState to;
+} RunStateTransition;
+
+static const RunStateTransition runstate_transitions_def[] = {
+    /*     from      ->     to      */
+    { RSTATE_NO_STATE, RSTATE_RUNNING },
+    { RSTATE_NO_STATE, RSTATE_IN_MIGRATE },
+    { RSTATE_NO_STATE, RSTATE_PRE_LAUNCH },
+
+    { RSTATE_DEBUG, RSTATE_RUNNING },
+
+    { RSTATE_IN_MIGRATE, RSTATE_RUNNING },
+    { RSTATE_IN_MIGRATE, RSTATE_PRE_LAUNCH },
+
+    { RSTATE_PANICKED, RSTATE_PAUSED },
+
+    { RSTATE_IO_ERROR, RSTATE_RUNNING },
+
+    { RSTATE_PAUSED, RSTATE_RUNNING },
+
+    { RSTATE_POST_MIGRATE, RSTATE_RUNNING },
+
+    { RSTATE_PRE_LAUNCH, RSTATE_RUNNING },
+    { RSTATE_PRE_LAUNCH, RSTATE_POST_MIGRATE },
+
+    { RSTATE_PRE_MIGRATE, RSTATE_RUNNING },
+    { RSTATE_PRE_MIGRATE, RSTATE_POST_MIGRATE },
+
+    { RSTATE_RESTORE, RSTATE_RUNNING },
+
+    { RSTATE_RUNNING, RSTATE_DEBUG },
+    { RSTATE_RUNNING, RSTATE_PANICKED },
+    { RSTATE_RUNNING, RSTATE_IO_ERROR },
+    { RSTATE_RUNNING, RSTATE_PAUSED },
+    { RSTATE_RUNNING, RSTATE_PRE_MIGRATE },
+    { RSTATE_RUNNING, RSTATE_RESTORE },
+    { RSTATE_RUNNING, RSTATE_SAVEVM },
+    { RSTATE_RUNNING, RSTATE_SHUTDOWN },
+    { RSTATE_RUNNING, RSTATE_WATCHDOG },
+
+    { RSTATE_SAVEVM, RSTATE_RUNNING },
+
+    { RSTATE_SHUTDOWN, RSTATE_PAUSED },
+
+    { RSTATE_WATCHDOG, RSTATE_RUNNING },
+
+    { RSTATE_MAX, RSTATE_MAX },
+};
+
+static bool runstate_valid_transitions[RSTATE_MAX][RSTATE_MAX];
+
 bool runstate_check(RunState state)
 {
     return current_run_state == state;
 }
 
+void runstate_init(void)
+{
+    const RunStateTransition *p;
+
+    memset(&runstate_valid_transitions, 0, sizeof(runstate_valid_transitions));
+
+    for (p = &runstate_transitions_def[0]; p->from != RSTATE_MAX; p++) {
+        runstate_valid_transitions[p->from][p->to] = true;
+    }
+}
+
+/* This function will abort() on invalid state transitions */
 void runstate_set(RunState new_state)
 {
-    assert(new_state < RSTATE_MAX);
+    if (new_state >= RSTATE_MAX ||
+        !runstate_valid_transitions[current_run_state][new_state]) {
+        fprintf(stderr, "invalid runstate transition\n");
+        abort();
+    }
+
     current_run_state = new_state;
 }
 
@@ -2219,6 +2289,8 @@ int main(int argc, char **argv, char **envp)
     g_mem_set_vtable(&mem_trace);
     g_thread_init(NULL);
 
+    runstate_init();
+
     init_clocks();
 
     qemu_cache_utils_init(envp);