[Qemu-devel] [Tracing][PATCH v2] Add options to specify trace file name at startup and runtime.

[Prerna Saxena <prerna@linux.vnet.ibm.com>]

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.

Changelog from v1 :
- Cleanups.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
---
 monitor.c       |    6 ++++++
 qemu-monitor.hx |    6 +++---
 qemu-options.hx |   11 +++++++++++
 simpletrace.c   |   41 +++++++++++++++++++++++++++++++----------
 tracetool       |    1 +
 vl.c            |   20 ++++++++++++++++++++
 6 files changed, 72 insertions(+), 13 deletions(-)

diff --git a/monitor.c b/monitor.c
index 1e35a6b..1d6c4c0 100644
--- a/monitor.c
+++ b/monitor.c
@@ -544,6 +544,7 @@ static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
 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);
@@ -553,8 +554,13 @@ static void do_trace_file(Monitor *mon, const QDict *qdict)
         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
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 25887bd..adfaf2b 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -276,9 +276,9 @@ ETEXI
 
     {
         .name       = "trace-file",
-        .args_type  = "op:s?",
-        .params     = "op [on|off|flush]",
-        .help       = "open, close, or flush 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,
     },
 
diff --git a/qemu-options.hx b/qemu-options.hx
index d1d2272..aea9675 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2223,6 +2223,17 @@ Normally QEMU loads a configuration file from @var{sysconfdir}/qemu.conf and
 @var{sysconfdir}/target-@var{ARCH}.conf on startup.  The @code{-nodefconfig}
 option will prevent QEMU from loading these configuration files at startup.
 ETEXI
+#ifdef CONFIG_SIMPLE_TRACE
+DEF("trace", HAS_ARG, QEMU_OPTION_trace,
+    "-trace\n"
+    "                Specify a trace file to log traces to\n",
+    QEMU_ARCH_ALL)
+STEXI
+@item -trace
+@findex -trace
+Specify a trace file to log output traces to.
+ETEXI
+#endif
 
 HXCOMM This is the last statement. Insert new options before this line!
 STEXI
diff --git a/simpletrace.c b/simpletrace.c
index 71110b3..19855f4 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -20,25 +20,46 @@ enum {
 static TraceRecord trace_buf[TRACE_BUF_LEN];
 static unsigned int trace_idx;
 static FILE *trace_fp;
-static bool trace_file_enabled = true;
+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 \"" CONFIG_TRACE_FILE "\" %s.\n",
-                  getpid(), trace_file_enabled ? "on" : "off");
+    stream_printf(stream, "Trace file \"%s\" %s.\n",
+                  trace_file_name, trace_file_enabled ? "on" : "off");
 }
 
-static bool open_trace_file(void)
+static inline bool open_trace_file(void)
 {
-    char *filename;
+    trace_fp = fopen(trace_file_name, "w");
+    return trace_fp != NULL;
+}
+
+/**
+ * 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)
+{
+    st_set_trace_file_enabled(false);
 
-    if (asprintf(&filename, CONFIG_TRACE_FILE, getpid()) < 0) {
-        return false;
+    free(trace_file_name);
+
+    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;
+        }
     }
 
-    trace_fp = fopen(filename, "w");
-    free(filename);
-    return trace_fp != NULL;
+    st_set_trace_file_enabled(true);
+    return true;
 }
 
 static void flush_trace_file(void)
diff --git a/tracetool b/tracetool
index ac832af..5b979f5 100755
--- a/tracetool
+++ b/tracetool
@@ -158,6 +158,7 @@ void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, cons
 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...));
 void st_flush_trace_buffer(void);
 void st_set_trace_file_enabled(bool enable);
+bool st_set_trace_file(const char *file);
 void change_trace_event_state(const char *tname, bool tstate);
 EOF
 
diff --git a/vl.c b/vl.c
index 920717a..df1257c 100644
--- a/vl.c
+++ b/vl.c
@@ -47,6 +47,10 @@
 #include <dirent.h>
 #include <netdb.h>
 #include <sys/select.h>
+#ifdef CONFIG_SIMPLE_TRACE
+#include "trace.h"
+#endif
+
 #ifdef CONFIG_BSD
 #include <sys/stat.h>
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
@@ -1822,6 +1826,9 @@ int main(int argc, char **argv, char **envp)
     int show_vnc_port = 0;
     int defconfig = 1;
 
+#ifdef CONFIG_SIMPLE_TRACE
+    char *trace_file = NULL;
+#endif
     atexit(qemu_run_exit_notifiers);
     error_set_progname(argv[0]);
 
@@ -2590,6 +2597,12 @@ int main(int argc, char **argv, char **envp)
                 }
                 xen_mode = XEN_ATTACH;
                 break;
+#ifdef CONFIG_SIMPLE_TRACE
+            case QEMU_OPTION_trace:
+                trace_file = (char *) qemu_malloc(strlen(optarg) + 1);
+                strcpy(trace_file, optarg);
+                break;
+#endif
             case QEMU_OPTION_readconfig:
                 {
                     int ret = qemu_read_config_file(optarg);
@@ -2633,6 +2646,13 @@ int main(int argc, char **argv, char **envp)
         data_dir = CONFIG_QEMU_DATADIR;
     }
 
+#ifdef CONFIG_SIMPLE_TRACE
+    /*
+     * Set the trace file name, if specified.
+     */
+    st_set_trace_file(trace_file);
+    qemu_free(trace_file);
+#endif
     /*
      * Default to max_cpus = smp_cpus, in case the user doesn't
      * specify a max_cpus value.
-- 
1.6.2.5


-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India