@@ -146,6 +146,11 @@ source tree. It may not be as powerful as platform-specific or third-party
trace backends but it is portable. This is the recommended trace backend
unless you have specific needs for more advanced backends.
+==== Enabling trace events from the command line ====
+
+The "-trace events=<file>" command line argument can be used to enable the
+events listed in <file> from the very beginning of the program.
+
==== Monitor commands ====
* info trace
@@ -306,6 +306,9 @@ static QemuOptsList qemu_trace_opts = {
{
.name = "file",
.type = QEMU_OPT_STRING,
+ },{
+ .name = "events",
+ .type = QEMU_OPT_STRING,
},
{ /* end if list */ }
},
@@ -2358,13 +2358,23 @@ 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",
+ "-trace [file=<file>][,events=<file>]\n"
+ " specify tracing options\n",
QEMU_ARCH_ALL)
STEXI
-@item -trace
+@item -trace [file=@var{file}][,events=@var{file}]
@findex -trace
-Specify a trace file to log output traces to.
+
+Specify tracing options.
+
+@table @option
+@item file=@var{file}
+Log output traces to @var{file}.
+@item events=@var{file}
+Immediately enable events listed in @var{file}.
+The file must contain one event name (as listed in the @var{trace-events} file)
+per line.
+@end table
ETEXI
#endif
@@ -1968,6 +1968,7 @@ int main(int argc, char **argv, char **envp)
int defconfig = 1;
#if defined(CONFIG_SIMPLE_TRACE)
const char *trace_file = NULL;
+ const char *trace_events_file = NULL;
#endif
atexit(qemu_run_exit_notifiers);
@@ -2766,6 +2767,7 @@ int main(int argc, char **argv, char **envp)
opts = qemu_opts_parse(qemu_find_opts("trace"), optarg, 0);
if (opts) {
trace_file = qemu_opt_get(opts, "file");
+ trace_events_file = qemu_opt_get(opts, "events");
}
break;
#endif
@@ -2818,6 +2820,30 @@ int main(int argc, char **argv, char **envp)
if (!st_init(trace_file)) {
fprintf(stderr, "warning: unable to initialize simple trace backend\n");
}
+ if (trace_events_file) {
+ FILE *trace_events_fp = fopen(trace_events_file, "r");
+ if (!trace_events_fp) {
+ fprintf(stderr, "could not open trace events file '%s': %s\n",
+ trace_events_file, strerror(errno));
+ exit(1);
+ }
+ char line_buf[1024];
+ while (fgets(line_buf, sizeof(line_buf), trace_events_fp)) {
+ size_t len = strlen(line_buf);
+ if (len > 1) { /* skip empty lines */
+ line_buf[len - 1] = '\0';
+ if (!st_change_trace_event_state(line_buf, true)) {
+ fprintf(stderr, "trace event '%s' does not exist\n", line_buf);
+ exit(1);
+ }
+ }
+ }
+ if (fclose(trace_events_fp) != 0) {
+ fprintf(stderr, "error closing file '%s': %s\n",
+ trace_events_file, strerror(errno));
+ exit(1);
+ }
+ }
#endif
/* If no data_dir is specified then try to find it relative to the
When using the "simple" tracing backend, all events are in disabled state by default. The "-trace events" argument can be used to provide a file with a list of trace event names that will be enabled prior to starting execution. This saves the user from manually toggling event states through the monitor interface, as well as enables early tracing for the selected points, much like other more-sophisticated backends like "ust" or "dtrace". Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu> --- docs/tracing.txt | 5 +++++ qemu-config.c | 3 +++ qemu-options.hx | 18 ++++++++++++++---- vl.c | 26 ++++++++++++++++++++++++++ 4 files changed, 48 insertions(+), 4 deletions(-)