trace: [qmp] Add commands to query and control event tracing state

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Message-id: 20140825111957.31112.31733.stgit@fimbulvetr.bsc.es
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

trace/qmp.c

@@ -0,0 +1,75 @@
+/*
+ * QMP commands for tracing events.
+ *
+ * Copyright (C) 2014 Lluís Vilanova <vilanova@ac.upc.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/typedefs.h"
+#include "qmp-commands.h"
+#include "trace/control.h"
+
+
+TraceEventInfoList *qmp_trace_event_get_state(const char *name, Error **errp)
+{
+    TraceEventInfoList *events = NULL;
+    bool found = false;
+    TraceEvent *ev;
+
+    ev = NULL;
+    while ((ev = trace_event_pattern(name, ev)) != NULL) {
+        TraceEventInfoList *elem = g_new(TraceEventInfoList, 1);
+        elem->value = g_new(TraceEventInfo, 1);
+        elem->value->name = g_strdup(trace_event_get_name(ev));
+        if (!trace_event_get_state_static(ev)) {
+            elem->value->state = TRACE_EVENT_STATE_UNAVAILABLE;
+        } else if (!trace_event_get_state_dynamic(ev)) {
+            elem->value->state = TRACE_EVENT_STATE_DISABLED;
+        } else {
+            elem->value->state = TRACE_EVENT_STATE_ENABLED;
+        }
+        elem->next = events;
+        events = elem;
+        found = true;
+    }
+
+    if (!found && !trace_event_is_pattern(name)) {
+        error_setg(errp, "unknown event \"%s\"", name);
+    }
+
+    return events;
+}
+
+void qmp_trace_event_set_state(const char *name, bool enable,
+                               bool has_ignore_unavailable,
+                               bool ignore_unavailable, Error **errp)
+{
+    bool found = false;
+    TraceEvent *ev;
+
+    /* Check all selected events are dynamic */
+    ev = NULL;
+    while ((ev = trace_event_pattern(name, ev)) != NULL) {
+        found = true;
+        if (!(has_ignore_unavailable && ignore_unavailable) &&
+            !trace_event_get_state_static(ev)) {
+            error_setg(errp, "cannot set dynamic tracing state for \"%s\"",
+                       trace_event_get_name(ev));
+            return;
+        }
+    }
+    if (!found && !trace_event_is_pattern(name)) {
+        error_setg(errp, "unknown event \"%s\"", name);
+        return;
+    }
+
+    /* Apply changes */
+    ev = NULL;
+    while ((ev = trace_event_pattern(name, ev)) != NULL) {
+        if (trace_event_get_state_static(ev)) {
+            trace_event_set_state_dynamic(ev, enable);
+        }
+    }
+}