diff options
authorPhilippe Mathieu-Daudé <philmd@redhat.com>2019-08-23 16:22:03 +0200
committerStefan Hajnoczi <stefanha@redhat.com>2019-08-27 15:12:36 +0100
commit9f591a5d95e1969969632ab44cf35e505c8ddc3b (patch)
parentdac03af5d5482ec7ee9c23db467bb7230b33c0d9 (diff)
trace: Clarify DTrace/SystemTap help message
Most tracing backends are implemented within QEMU, except the DTrace/SystemTap backends. One side effect is when running 'qemu -trace help', an incomplete list of trace events is displayed when using the DTrace/SystemTap backends. This is partly due to trace events registered as modules with trace_init(), and since the events are not used within QEMU, the linker optimize and remove the unused modules (which is OK in this particular case). Currently only the events compiled in trace-root.o and in the last trace.o member of libqemuutil.a are linked, resulting in an incomplete list of events. To avoid confusion, improve the help message, recommending to use the proper systemtap script to display the events list. Before: $ lm32-softmmu/qemu-system-lm32 -trace help 2>&1 | wc -l 70 After: $ lm32-softmmu/qemu-system-lm32 -trace help Run 'qemu-trace-stap list qemu-system-lm32' to print a list of names of trace points with the DTrace/SystemTap backends. $ qemu-trace-stap list qemu-system-lm32 | wc -l 1136 Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Message-id: 20190823142203.5210-1-philmd@redhat.com Message-Id: <20190823142203.5210-1-philmd@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 files changed, 6 insertions, 0 deletions
diff --git a/trace/control.c b/trace/control.c
index 43fb7868db..d9cafc161b 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -165,6 +165,12 @@ void trace_list_events(void)
while ((ev = trace_event_iter_next(&iter)) != NULL) {
fprintf(stderr, "%s\n", trace_event_get_name(ev));
+ fprintf(stderr, "This list of names of trace points may be incomplete "
+ "when using the DTrace/SystemTap backends.\n"
+ "Run 'qemu-trace-stap list %s' to print the full list.\n",
+ error_get_progname());
static void do_trace_enable_events(const char *line_buf)