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Subject[RFC PATCH v2 11/15] tracing: of: Add synthetic event support
Date
Add synthetic event node support. The synthetic event node must be
a child node of ftrace node, and the node must start with "synth@"
prefix. The synth node requires fields string (not string array),
which defines the fields as same as tracing/synth_events interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v2:
- Make synth property available only if CONFIG_HIST_TRIGGERS=y
---
kernel/trace/trace_events_hist.c | 5 +++
kernel/trace/trace_of.c | 64 ++++++++++++++++++++++++++++++++++++--
2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index db973928e580..e7f5d0a353e2 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1343,6 +1343,11 @@ 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];
diff --git a/kernel/trace/trace_of.c b/kernel/trace/trace_of.c
index 56c5deb45f54..e9142c63ece1 100644
--- a/kernel/trace/trace_of.c
+++ b/kernel/trace/trace_of.c
@@ -146,6 +146,49 @@ trace_of_add_kprobe_event(struct device_node *node,
}
#endif

+#ifdef CONFIG_HIST_TRIGGERS
+extern int synth_event_run_command(const char *command);
+
+static int __init
+trace_of_add_synth_event(struct device_node *node, const char *event)
+{
+ struct property *prop;
+ 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;
+
+ of_property_for_each_string(node, "fields", prop, 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_of_add_synth_event(struct device_node *node, const char *event)
+{
+ pr_err("Synthetic event is not supported.\n");
+ return -ENOTSUPP;
+}
+#endif
+
static void __init
trace_of_init_one_event(struct trace_array *tr, struct device_node *node)
{
@@ -173,15 +216,30 @@ trace_of_init_one_event(struct trace_array *tr, struct device_node *node)
event = buf;

group = strsep(&event, ":");
- /* For a kprobe event, we have to generates an event at first */
+
+ /* Generates kprobe/synth event at first */
if (of_find_property(node, "probes", NULL)) {
+ if (of_find_property(node, "fields", NULL)) {
+ pr_err("Error: %s node has both probes and fields\n",
+ of_node_full_name(node));
+ return;
+ }
if (!event) {
event = buf;
group = "kprobes";
}
- err = trace_of_add_kprobe_event(node, group, event);
- if (err < 0)
+ if (trace_of_add_kprobe_event(node, group, event) < 0)
+ return;
+ } else if (of_find_property(node, "fields", NULL)) {
+ if (!event)
+ event = buf;
+ else if (strcmp(group, "synthetic") != 0) {
+ pr_err("Synthetic event must be in synthetic group\n");
+ return;
+ }
+ if (trace_of_add_synth_event(node, event) < 0)
return;
+ group = "synthetic";
} else {
if (!event) {
pr_err("%s has no group name\n", buf);
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