trace: Support for dynamically enabling/disabling trace events

This patch adds support for dynamically enabling/disabling of trace events.
This is done by internally maintaining each trace event's state, and
permitting logging of data from a trace event only if it is in an
'active' state.

Monitor commands added :
1) info trace-events 		: to view all available trace events and
				  their state.
2) trace-event NAME on|off 	: to enable/disable data logging from a
				  given trace event.
				  Eg, trace-event paio_submit off
				  	disables logging of data when
					paio_submit is hit.

By default, all trace-events are disabled. One can enable desired trace-events
via the monitor.

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
trace: Monitor command 'info trace'

Monitor command 'info trace' to display contents of trace buffer

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
trace: Remove monitor.h dependency from simpletrace

User-mode targets don't have a monitor so the simple trace backend
currently does not build on those targets.  This patch abstracts the
monitor printing interface so there is no direct coupling between
simpletrace and the monitor.

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

diff --git a/configure b/configure
index 6729dbe0bb9607d6c025dadc97e814dce4726141..5afb3b5ef1141a5b4f23af87c3f79ac7ffebea71 100755 (executable)
--- a/configure
+++ b/configure
@@ -2468,6 +2468,9 @@ bsd)
 esac
 
 echo "TRACE_BACKEND=$trace_backend" >> $config_host_mak
+if test "$trace_backend" = "simple"; then
+  echo "CONFIG_SIMPLE_TRACE=y" >> $config_host_mak
+fi
 echo "TOOLS=$tools" >> $config_host_mak
 echo "ROMS=$roms" >> $config_host_mak
 echo "MAKE=$make" >> $config_host_mak

diff --git a/monitor.c b/monitor.c
index e27f8d8d3be500dfdc0adc215decffad3df2339a..0e69bc8b9dedc61436b5c9e13f22e09192f43d30 100644 (file)
--- a/monitor.c
+++ b/monitor.c
@@ -56,6 +56,9 @@
 #include "json-parser.h"
 #include "osdep.h"
 #include "exec-all.h"
+#ifdef CONFIG_SIMPLE_TRACE
+#include "trace.h"
+#endif
 
 //#define DEBUG
 //#define DEBUG_COMPLETION
@@ -539,6 +542,15 @@ static void do_help_cmd(Monitor *mon, const QDict *qdict)
     help_cmd(mon, qdict_get_try_str(qdict, "name"));
 }
 
+#ifdef CONFIG_SIMPLE_TRACE
+static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
+{
+    const char *tp_name = qdict_get_str(qdict, "name");
+    bool new_state = qdict_get_bool(qdict, "option");
+    st_change_trace_event_state(tp_name, new_state);
+}
+#endif
+
 static void user_monitor_complete(void *opaque, QObject *ret_data)
 {
     MonitorCompletionData *data = (MonitorCompletionData *)opaque; 
@@ -938,6 +950,18 @@ static void do_info_cpu_stats(Monitor *mon)
 }
 #endif
 
+#if defined(CONFIG_SIMPLE_TRACE)
+static void do_info_trace(Monitor *mon)
+{
+    st_print_trace((FILE *)mon, &monitor_fprintf);
+}
+
+static void do_info_trace_events(Monitor *mon)
+{
+    st_print_trace_events((FILE *)mon, &monitor_fprintf);
+}
+#endif
+
 /**
  * do_quit(): Quit QEMU execution
  */
@@ -2594,6 +2618,22 @@ static const mon_cmd_t info_cmds[] = {
         .help       = "show roms",
         .mhandler.info = do_info_roms,
     },
+#if defined(CONFIG_SIMPLE_TRACE)
+    {
+        .name       = "trace",
+        .args_type  = "",
+        .params     = "",
+        .help       = "show current contents of trace buffer",
+        .mhandler.info = do_info_trace,
+    },
+    {
+        .name       = "trace-events",
+        .args_type  = "",
+        .params     = "",
+        .help       = "show available trace-events & their state",
+        .mhandler.info = do_info_trace_events,
+    },
+#endif
     {
         .name       = NULL,
     },

diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index 5c1da3398e0678c572af9ff0f2215e0ec3fd218b..c264c7d539d2ecf70b19920cfa1ba42c305389c1 100644 (file)
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -281,6 +281,22 @@ STEXI
 Output logs to @var{filename}.
 ETEXI
 
+#ifdef CONFIG_SIMPLE_TRACE
+    {
+        .name       = "trace-event",
+        .args_type  = "name:s,option:b",
+        .params     = "name on|off",
+        .help       = "changes status of a specific trace event",
+        .mhandler.cmd = do_change_trace_event_state,
+    },
+
+STEXI
+@item trace-event
+@findex trace-event
+changes status of a trace event
+ETEXI
+#endif
+
     {
         .name       = "log",
         .args_type  = "items:s",
@@ -2529,6 +2545,15 @@ show roms
 @end table
 ETEXI
 
+#ifdef CONFIG_SIMPLE_TRACE
+STEXI
+@item info trace
+show contents of trace buffer
+@item info trace-events
+show available trace events and their state
+ETEXI
+#endif
+
 HXCOMM DO NOT add new commands after 'info', move your addition before it!
 
 STEXI

diff --git a/simpletrace.c b/simpletrace.c
index 477730871c70950b36c80dfc9184ad0085fbd0b9..688959a9fee781963240d436e529387eecc04a6c 100644 (file)
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -101,6 +101,10 @@ static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
      */
     clock_gettime(CLOCK_MONOTONIC, &ts);
 
+    if (!trace_list[event].state) {
+        return;
+    }
+
     rec->event = event;
     rec->timestamp_ns = ts.tv_sec * 1000000000LL + ts.tv_nsec;
     rec->x1 = x1;
@@ -157,3 +161,50 @@ static void __attribute__((constructor)) st_init(void)
 {
     atexit(st_flush_trace_buffer);
 }
+
+void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
+{
+    unsigned int i;
+
+    for (i = 0; i < trace_idx; i++) {
+        stream_printf(stream, "Event %lu : %lx %lx %lx %lx %lx\n",
+                      trace_buf[i].event, trace_buf[i].x1, trace_buf[i].x2,
+                      trace_buf[i].x3, trace_buf[i].x4, trace_buf[i].x5);
+    }
+}
+
+void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
+{
+    unsigned int i;
+
+    for (i = 0; i < NR_TRACE_EVENTS; i++) {
+        stream_printf(stream, "%s [Event ID %u] : state %u\n",
+                      trace_list[i].tp_name, i, trace_list[i].state);
+    }
+}
+
+static TraceEvent* find_trace_event_by_name(const char *tname)
+{
+    unsigned int i;
+
+    if (!tname) {
+        return NULL;
+    }
+
+    for (i = 0; i < NR_TRACE_EVENTS; i++) {
+        if (!strcmp(trace_list[i].tp_name, tname)) {
+            return &trace_list[i];
+        }
+    }
+    return NULL; /* indicates end of list reached without a match */
+}
+
+void st_change_trace_event_state(const char *tname, bool tstate)
+{
+    TraceEvent *tp;
+
+    tp = find_trace_event_by_name(tname);
+    if (tp) {
+        tp->state = tstate;
+    }
+}

diff --git a/simpletrace.h b/simpletrace.h
index 7d0661b720873d0726f9ad950d96fd2444ab8d6a..b0161d1ff42a823f9ee96321e125fa4deac404fe 100644 (file)
--- a/simpletrace.h
+++ b/simpletrace.h
@@ -12,9 +12,16 @@
 #define SIMPLETRACE_H
 
 #include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
 
 typedef uint64_t TraceEventID;
 
+typedef struct {
+    const char *tp_name;
+    bool state;
+} TraceEvent;
+
 void trace0(TraceEventID event);
 void trace1(TraceEventID event, uint64_t x1);
 void trace2(TraceEventID event, uint64_t x1, uint64_t x2);
@@ -22,5 +29,8 @@ void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3);
 void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4);
 void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5);
 void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6);
+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);
 
 #endif /* SIMPLETRACE_H */

diff --git a/tracetool b/tracetool
index 19b1659bc0980211d8f3ff9b8656f6076bc17905..2e2e37dbd3a0a0a9a18ae2fd74b3d9276f7b53e4 100755 (executable)
--- a/tracetool
+++ b/tracetool
@@ -169,22 +169,38 @@ EOF
 
 linetoh_end_simple()
 {
-    return
+    cat <<EOF
+#define NR_TRACE_EVENTS $simple_event_num
+extern TraceEvent trace_list[NR_TRACE_EVENTS];
+EOF
 }
 
 linetoc_begin_simple()
 {
-    return
+    cat <<EOF
+#include "trace.h"
+
+TraceEvent trace_list[] = {
+EOF
+    simple_event_num=0
+
 }
 
 linetoc_simple()
 {
-    return
+    local name
+    name=$(get_name "$1")
+    cat <<EOF
+{.tp_name = "$name", .state=0},
+EOF
+    simple_event_num=$((simple_event_num + 1))
 }
 
 linetoc_end_simple()
 {
-    return
+    cat <<EOF
+};
+EOF
 }
 
 # Process stdin by calling begin, line, and end functions for the backend