[v3,09/10] trace-state: [stderr] add support for dynamically enabling/disabling events

diff --git a/configure b/configure
index fef7d35..b4f050d 100755
--- a/configure
+++ b/configure
@@ -2950,6 +2950,9 @@  if test "$trace_backend" = "nop"; then
 elif test "$trace_backend" = "simple"; then
   echo "CONFIG_SIMPLE_TRACE=y" >> $config_host_mak
 fi
+if test "$trace_backend" = "stderr"; then
+  echo "CONFIG_STDERR_TRACE=y" >> $config_host_mak
+fi
 # Set the appropriate trace file.
 if test "$trace_backend" = "simple"; then
   trace_file="\"$trace_file-%u\""
diff --git a/docs/tracing.txt b/docs/tracing.txt
index c443171..9c17497 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -163,11 +163,6 @@  effectively turns trace events into debug printfs.
 This is the simplest backend and can be used together with existing code that
 uses DPRINTF().
 
-Note that with this backend trace events cannot be programmatically
-enabled/disabled. Thus, in order to trim down the amount of output and the
-performance impact of tracing, you might want to add the "disable" property in
-the "trace-events" file for those events you are not interested in.
-
 === Simpletrace ===
 
 The "simple" backend supports common use cases and comes as part of the QEMU
diff --git a/scripts/tracetool b/scripts/tracetool
index c740080..743d246 100755
--- a/scripts/tracetool
+++ b/scripts/tracetool
@@ -241,7 +241,12 @@  linetoh_begin_stderr()
 {
     cat <<EOF
 #include <stdio.h>
+#include "trace/stderr.h"
+
+extern TraceEvent trace_list[];
 EOF
+
+    stderr_event_num=0
 }
 
 linetoh_stderr()
@@ -260,29 +265,47 @@  linetoh_stderr()
     cat <<EOF
 static inline void trace_$name($args)
 {
-    fprintf(stderr, "$name $fmt\n" $argnames);
+    if (trace_list[$stderr_event_num].state != 0) {
+        fprintf(stderr, "$name $fmt\n" $argnames);
+    }
 }
 EOF
+    stderr_event_num=$((stderr_event_num + 1))
+
 }
 
 linetoh_end_stderr()
 {
-return
+    cat <<EOF
+#define NR_TRACE_EVENTS $stderr_event_num
+EOF
 }
 
 linetoc_begin_stderr()
 {
-return
+    cat <<EOF
+#include "trace.h"
+
+TraceEvent trace_list[] = {
+EOF
+    stderr_event_num=0
 }
 
 linetoc_stderr()
 {
-return
+    local name
+    name=$(get_name "$1")
+    cat <<EOF
+{.tp_name = "$name", .state=0},
+EOF
+    stderr_event_num=$(($stderr_event_num + 1))
 }
 
 linetoc_end_stderr()
 {
-return
+    cat <<EOF
+};
+EOF
 }
 #END OF STDERR
 
diff --git a/trace/control.c b/trace/control.c
index 3ebdd31..0454426 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -5,7 +5,7 @@ 
 
 void trace_print_events(FILE *stream, fprintf_function stream_printf)
 {
-#if defined(CONFIG_SIMPLE_TRACE)
+#if defined(CONFIG_SIMPLE_TRACE) || defined(CONFIG_TRACE_STDERR)
     unsigned int i;
 
     for (i = 0; i < NR_TRACE_EVENTS; i++) {
@@ -20,7 +20,7 @@  void trace_print_events(FILE *stream, fprintf_function stream_printf)
 
 bool trace_event_set_state (const char *name, bool state)
 {
-#if defined(CONFIG_SIMPLE_TRACE)
+#if defined(CONFIG_SIMPLE_TRACE) || defined(CONFIG_TRACE_STDERR)
     unsigned int i;
 
     for (i = 0; i < NR_TRACE_EVENTS; i++) {
diff --git a/trace/stderr.h b/trace/stderr.h
new file mode 100644
index 0000000..d575b61
--- /dev/null
+++ b/trace/stderr.h
@@ -0,0 +1,11 @@ 
+#ifndef TRACE_STDERR_H
+#define TRACE_STDERR_H
+
+typedef uint64_t TraceEventID;
+
+typedef struct {
+    const char *tp_name;
+    bool state;
+} TraceEvent;
+
+#endif /* ! TRACE_STDERR_H */