trace: Add trace-file command to open/close/flush trace file

This patch adds the trace-file command:

  trace-file [on|off|flush]

  Open, close, or flush the trace file.  If no argument is given,
  the status of the trace file is displayed.

The trace file is turned on by default but is only written out when the
trace buffer becomes full.  The flush operation can be used to force
write out at any time.

Turning off the trace file does not change the state of trace events;
tracing will continue to the trace buffer.  When the trace file is off,
use "info trace" to display the contents of the trace buffer in memory.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
This commit also contains the trace-file sub-command from the following
commit:

commit 5ce8d1a957afae2c52ad748944ce72848ccf57bd
Author: Prerna Saxena <prerna@linux.vnet.ibm.com>
Date:   Wed Aug 4 16:23:54 2010 +0530

    trace: Add options to specify trace file name at startup and runtime

    This patch adds an optional command line switch '-trace' to specify the
    filename to write traces to, when qemu starts.
    Eg, If compiled with the 'simple' trace backend,
    [temp@system]$ qemu -trace FILENAME IMAGE
    Allows the binary traces to be written to FILENAME instead of the option
    set at config-time.

    Also, this adds monitor sub-command 'set' to trace-file commands to
    dynamically change trace log file at runtime.
    Eg,
    (qemu)trace-file set FILENAME
    This allows one to set trace outputs to FILENAME from the default
    specified at startup.

    Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
    Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

diff --git a/monitor.c b/monitor.c
index 0e69bc8b9dedc61436b5c9e13f22e09192f43d30..e602480ebb39bb15aae749d09fd5d9089074ef79 100644 (file)
--- a/monitor.c
+++ b/monitor.c
@@ -549,6 +549,29 @@ static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
     bool new_state = qdict_get_bool(qdict, "option");
     st_change_trace_event_state(tp_name, new_state);
 }
+
+static void do_trace_file(Monitor *mon, const QDict *qdict)
+{
+    const char *op = qdict_get_try_str(qdict, "op");
+    const char *arg = qdict_get_try_str(qdict, "arg");
+
+    if (!op) {
+        st_print_trace_file_status((FILE *)mon, &monitor_fprintf);
+    } else if (!strcmp(op, "on")) {
+        st_set_trace_file_enabled(true);
+    } else if (!strcmp(op, "off")) {
+        st_set_trace_file_enabled(false);
+    } else if (!strcmp(op, "flush")) {
+        st_flush_trace_buffer();
+    } else if (!strcmp(op, "set")) {
+        if (arg) {
+            st_set_trace_file(arg);
+        }
+    } else {
+        monitor_printf(mon, "unexpected argument \"%s\"\n", op);
+        help_cmd(mon, "trace-file");
+    }
+}
 #endif
 
 static void user_monitor_complete(void *opaque, QObject *ret_data)

diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index c264c7d539d2ecf70b19920cfa1ba42c305389c1..49bcd8d32467544a43b496405b18a76c1fd476ab 100644 (file)
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -294,6 +294,20 @@ STEXI
 @item trace-event
 @findex trace-event
 changes status of a trace event
+ETEXI
+
+    {
+        .name       = "trace-file",
+        .args_type  = "op:s?,arg:F?",
+        .params     = "on|off|flush|set [arg]",
+        .help       = "open, close, or flush trace file, or set a new file name",
+        .mhandler.cmd = do_trace_file,
+    },
+
+STEXI
+@item trace-file on|off|flush
+@findex trace-file
+Open, close, or flush the trace file.  If no argument is given, the status of the trace file is displayed.
 ETEXI
 #endif
 

diff --git a/simpletrace.c b/simpletrace.c
index 97045a673277b2263b879339bcd879021b04a8a4..f849e429145d3d193b86d6cd373428dd47ed0fb4 100644 (file)
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -42,6 +42,14 @@ enum {
 static TraceRecord trace_buf[TRACE_BUF_LEN];
 static unsigned int trace_idx;
 static FILE *trace_fp;
+static char *trace_file_name = NULL;
+static bool trace_file_enabled = false;
+
+void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
+{
+    stream_printf(stream, "Trace file \"%s\" %s.\n",
+                  trace_file_name, trace_file_enabled ? "on" : "off");
+}
 
 static bool write_header(FILE *fp)
 {
@@ -54,31 +62,57 @@ static bool write_header(FILE *fp)
     return fwrite(&header, sizeof header, 1, fp) == 1;
 }
 
-static bool open_trace_file(void)
+/**
+ * set_trace_file : To set the name of a trace file.
+ * @file : pointer to the name to be set.
+ *         If NULL, set to the default name-<pid> set at config time.
+ */
+bool st_set_trace_file(const char *file)
 {
-    char *filename;
+    st_set_trace_file_enabled(false);
 
-    if (asprintf(&filename, CONFIG_TRACE_FILE, getpid()) < 0) {
-        return false;
-    }
+    free(trace_file_name);
 
-    trace_fp = fopen(filename, "w");
-    free(filename);
-    if (!trace_fp) {
-        return false;
+    if (!file) {
+        if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
+            trace_file_name = NULL;
+            return false;
+        }
+    } else {
+        if (asprintf(&trace_file_name, "%s", file) < 0) {
+            trace_file_name = NULL;
+            return false;
+        }
     }
-    return write_header(trace_fp);
+
+    st_set_trace_file_enabled(true);
+    return true;
 }
 
-static void flush_trace_buffer(void)
+static void flush_trace_file(void)
 {
+    /* If the trace file is not open yet, open it now */
     if (!trace_fp) {
-        open_trace_file();
+        trace_fp = fopen(trace_file_name, "w");
+        if (!trace_fp) {
+            /* Avoid repeatedly trying to open file on failure */
+            trace_file_enabled = false;
+            return;
+        }
+        write_header(trace_fp);
     }
+
     if (trace_fp) {
         size_t unused; /* for when fwrite(3) is declared warn_unused_result */
         unused = fwrite(trace_buf, trace_idx * sizeof(trace_buf[0]), 1, trace_fp);
     }
+}
+
+void st_flush_trace_buffer(void)
+{
+    if (trace_file_enabled) {
+        flush_trace_file();
+    }
 
     /* Discard written trace records */
     trace_idx = 0;
@@ -128,7 +162,7 @@ static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
     rec->x6 = x6;
 
     if (++trace_idx == TRACE_BUF_LEN) {
-        flush_trace_buffer();
+        st_flush_trace_buffer();
     }
 }
 

diff --git a/simpletrace.h b/simpletrace.h
index b0161d1ff42a823f9ee96321e125fa4deac404fe..cf3589774b438f31214837eec14de25555277281 100644 (file)
--- a/simpletrace.h
+++ b/simpletrace.h
@@ -32,5 +32,9 @@ void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t
 void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
 void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
 void st_change_trace_event_state(const char *tname, bool tstate);
+void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
+void st_set_trace_file_enabled(bool enable);
+bool st_set_trace_file(const char *file);
+void st_flush_trace_buffer(void);
 
 #endif /* SIMPLETRACE_H */