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Subject[RFC PATCH v4 18/22] tracing/boot: Add synthetic event support
Date
Add synthetic event node support to boot time tracing.
The synthetic event is a kind of event node, but the group
name is "synthetic".

- ftrace.event.synthetic.EVENT.fields = FIELD[, FIELD2...]
Defines new synthetic event with FIELDs. Each field should be
"type varname".

The synthetic node requires "fields" string arraies, which defines
the fields as same as tracing/synth_events interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
kernel/trace/trace_boot.c | 47 ++++++++++++++++++++++++++++++++++++++
kernel/trace/trace_events_hist.c | 5 ++++
2 files changed, 52 insertions(+)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index a11dc60299fb..3054921b0877 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -118,6 +118,50 @@ trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
}
#endif

+#ifdef CONFIG_HIST_TRIGGERS
+extern int synth_event_run_command(const char *command);
+
+static int __init
+trace_boot_add_synth_event(struct xbc_node *node, const char *event)
+{
+ struct xbc_node *anode;
+ char buf[MAX_BUF_LEN], *q;
+ const char *p;
+ int len, delta, ret;
+
+ len = ARRAY_SIZE(buf);
+ delta = snprintf(buf, len, "%s", event);
+ if (delta >= len) {
+ pr_err("Event name is too long: %s\n", event);
+ return -E2BIG;
+ }
+ len -= delta; q = buf + delta;
+
+ xbc_node_for_each_array_value(node, "fields", anode, p) {
+ delta = snprintf(q, len, " %s;", p);
+ if (delta >= len) {
+ pr_err("fields string is too long: %s\n", p);
+ return -E2BIG;
+ }
+ len -= delta; q += delta;
+ }
+
+ ret = synth_event_run_command(buf);
+ if (ret < 0)
+ pr_err("Failed to add synthetic event: %s\n", buf);
+
+
+ return ret;
+}
+#else
+static inline int __init
+trace_boot_add_synth_event(struct xbc_node *node, const char *event)
+{
+ pr_err("Synthetic event is not supported.\n");
+ return -ENOTSUPP;
+}
+#endif
+
static void __init
trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
struct xbc_node *enode)
@@ -133,6 +177,9 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
if (!strcmp(group, "kprobes"))
if (trace_boot_add_kprobe_event(enode, event) < 0)
return;
+ if (!strcmp(group, "synthetic"))
+ if (trace_boot_add_synth_event(enode, event) < 0)
+ return;

mutex_lock(&event_mutex);
file = find_event_file(tr, group, event);
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index d902a61775c4..806ad38bec95 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1365,6 +1365,11 @@ static int create_or_delete_synth_event(int argc, char **argv)
return ret == -ECANCELED ? -EINVAL : ret;
}

+int synth_event_run_command(const char *command)
+{
+ return trace_run_command(command, create_or_delete_synth_event);
+}
+
static int synth_event_create(int argc, const char **argv)
{
const char *name = argv[0];
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