trace: add "-trace enable=..."

Allow enabling events without going through a file, for example:

   qemu-system-x86_64 -trace bdrv_aio_writev -trace bdrv_aio_readv

or with globbing too:

   qemu-system-x86_64 -trace 'bdrv_aio_*'

if an appropriate backend is enabled (simple, stderr, ftrace).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 1452174932-28657-6-git-send-email-den@openvz.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

qemu-options.hx

@@ -3544,7 +3544,7 @@ config files on @var{sysconfdir}, but won't make it skip the QEMU-provided confi
 files from @var{datadir}.
 ETEXI
 DEF("trace", HAS_ARG, QEMU_OPTION_trace,
-    "-trace [events=<file>][,file=<file>]\n"
+    "-trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n"
     "                specify tracing options\n",
     QEMU_ARCH_ALL)
 STEXI
@@ -3556,6 +3556,14 @@ HXCOMM HX does not support conditional compilation of text.
 Specify tracing options.
 
 @table @option
+@item [enable=]@var{pattern}
+Immediately enable events matching @var{pattern}.
+The file must contain one event name (as listed in the @file{trace-events} file)
+per line; globbing patterns are accepted too.  This option is only
+available if QEMU has been compiled with the @var{simple}, @var{stderr}
+or @var{ftrace} tracing backend.  To specify multiple events or patterns,
+specify the @option{-trace} option multiple times.
+
 @item events=@var{file}
 Immediately enable events listed in @var{file}.
 The file must contain one event name (as listed in the @file{trace-events} file)

trace/control.c

@@ -88,6 +88,32 @@ TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev)
     return NULL;
 }
 
+void trace_enable_events(const char *line_buf)
+{
+    const bool enable = ('-' != line_buf[0]);
+    const char *line_ptr = enable ? line_buf : line_buf + 1;
+
+    if (trace_event_is_pattern(line_ptr)) {
+        TraceEvent *ev = NULL;
+        while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
+            if (trace_event_get_state_static(ev)) {
+                trace_event_set_state_dynamic(ev, enable);
+            }
+        }
+    } else {
+        TraceEvent *ev = trace_event_name(line_ptr);
+        if (ev == NULL) {
+            error_report("WARNING: trace event '%s' does not exist",
+                         line_ptr);
+        } else if (!trace_event_get_state_static(ev)) {
+            error_report("WARNING: trace event '%s' is not traceable",
+                         line_ptr);
+        } else {
+            trace_event_set_state_dynamic(ev, enable);
+        }
+    }
+}
+
 void trace_init_events(const char *fname)
 {
     Location loc;
@@ -114,27 +140,7 @@ void trace_init_events(const char *fname)
             if ('#' == line_buf[0]) { /* skip commented lines */
                 continue;
             }
-            const bool enable = ('-' != line_buf[0]);
+            trace_enable_events(line_buf);
-            char *line_ptr = enable ? line_buf : line_buf + 1;
-            if (trace_event_is_pattern(line_ptr)) {
-                TraceEvent *ev = NULL;
-                while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
-                    if (trace_event_get_state_static(ev)) {
-                        trace_event_set_state_dynamic(ev, enable);
-                    }
-                }
-            } else {
-                TraceEvent *ev = trace_event_name(line_ptr);
-                if (ev == NULL) {
-                    error_report("WARNING: trace event '%s' does not exist",
-                                 line_ptr);
-                } else if (!trace_event_get_state_static(ev)) {
-                    error_report("WARNING: trace event '%s' is not traceable",
-                                 line_ptr);
-                } else {
-                    trace_event_set_state_dynamic(ev, enable);
-                }
-            }
         }
     }
     if (fclose(fp) != 0) {

trace/control.h

@@ -181,6 +181,15 @@ void trace_init_events(const char *file);
  */
 void trace_init_file(const char *file);
 
+/**
+ * trace_enable_events:
+ * @line_buf: A string with a glob pattern of events to be enabled or,
+ *            if the string starts with '-', disabled.
+ *
+ * Enable or disable matching events.
+ */
+void trace_enable_events(const char *line_buf);
+
 
 #include "trace/control-internal.h"
 

vl.c

@@ -270,9 +270,13 @@ static QemuOptsList qemu_sandbox_opts = {
 
 static QemuOptsList qemu_trace_opts = {
     .name = "trace",
-    .implied_opt_name = "trace",
+    .implied_opt_name = "enable",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_trace_opts.head),
     .desc = {
+        {
+            .name = "enable",
+            .type = QEMU_OPT_STRING,
+        },
         {
             .name = "events",
             .type = QEMU_OPT_STRING,
@@ -3900,10 +3904,13 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_trace:
             {
                 opts = qemu_opts_parse_noisily(qemu_find_opts("trace"),
-                                               optarg, false);
+                                               optarg, true);
                 if (!opts) {
                     exit(1);
                 }
+                if (qemu_opt_get(opts, "enable")) {
+                    trace_enable_events(qemu_opt_get(opts, "enable"));
+                }
                 trace_init_events(qemu_opt_get(opts, "events"));
                 if (trace_file) {
                     g_free(trace_file);