trace: Add wildcard trace event support

A basic wildcard matching is supported in both the monitor command
"trace-event" and the events list file. That means you can enable/disable
the events having a common prefix in a batch. For example, virtio-blk trace
events could be enabled using:
    trace-event virtio_blk_* on

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/trace/stderr.c b/trace/stderr.c
index 7107c4a131..0810d6f956 100644
--- a/trace/stderr.c
+++ b/trace/stderr.c
@@ -15,14 +15,29 @@ void trace_print_events(FILE *stream, fprintf_function stream_printf)
 bool trace_event_set_state(const char *name, bool state)
 {
     unsigned int i;
+    unsigned int len;
+    bool wildcard = false;
+    bool matched = false;
 
+    len = strlen(name);
+    if (len > 0 && name[len - 1] == '*') {
+        wildcard = true;
+        len -= 1;
+    }
     for (i = 0; i < NR_TRACE_EVENTS; i++) {
+        if (wildcard) {
+            if (!strncmp(trace_list[i].tp_name, name, len)) {
+                trace_list[i].state = state;
+                matched = true;
+            }
+            continue;
+        }
         if (!strcmp(trace_list[i].tp_name, name)) {
             trace_list[i].state = state;
             return true;
         }
     }
-    return false;
+    return matched;
 }
 
 bool trace_backend_init(const char *events, const char *file)