[Qemu-devel] [PATCH 08/14] trace: Support for dynamically enabling/disabling trace events.

[Stefan Hajnoczi]

From: Prerna Saxena <address@hidden>

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 <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>

trace: Monitor command 'info trace'

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

Signed-off-by: Prerna Saxena <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>

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 <address@hidden>
---
 configure       |    3 +++
 monitor.c       |   40 ++++++++++++++++++++++++++++++++++++++++
 qemu-monitor.hx |   25 +++++++++++++++++++++++++
 simpletrace.c   |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 simpletrace.h   |    9 +++++++++
 tracetool       |   24 ++++++++++++++++++++----
 6 files changed, 149 insertions(+), 4 deletions(-)

diff --git a/configure b/configure
index 62dd10d..830e49e 100755
--- a/configure
+++ b/configure
@@ -2466,6 +2466,9 @@ 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 c313d5a..4f1639d 100644
--- 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; 
@@ -923,6 +935,18 @@ 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
  */
@@ -2579,6 +2603,22 @@ 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 2af3de6..a9f4221 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -259,6 +259,22 @@ 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
address@hidden trace-event
address@hidden trace-event
+changes status of a trace event
+ETEXI
+#endif
+
     {
         .name       = "log",
         .args_type  = "items:s",
@@ -2495,6 +2511,15 @@ show roms
 @end table
 ETEXI
 
+#ifdef CONFIG_SIMPLE_TRACE
+STEXI
address@hidden info trace
+show contents of trace buffer
address@hidden 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 a6afc51..311fa44 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -11,6 +11,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <time.h>
 #include "trace.h"
 
 /** Trace file header event ID */
@@ -83,6 +84,10 @@ static void trace(TraceEventID event, unsigned long x1,
      */
     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;
@@ -125,3 +130,50 @@ void trace5(TraceEventID event, uint64_t x1, uint64_t x2, 
uint64_t x3, uint64_t
 {
     trace(event, x1, x2, x3, x4, x5);
 }
+
+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 e4e9759..ee30ae9 100644
--- a/simpletrace.h
+++ b/simpletrace.h
@@ -13,14 +13,23 @@
 
 #include <stdbool.h>
 #include <stdint.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);
 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 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 66df685..30dc812 100755
--- 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
-- 
1.7.1