[RFC PATCH v3 14/19] tracing/boot: Add synthetic event support

[Masami Hiramatsu]

Add synthetic event node support. 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 <mhira...@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 40c89c7ceee0..2e9fddff660f 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -142,6 +142,50 @@ trace_boot_add_kprobe_event(struct skc_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 skc_node *node, const char *event)
+{
+       struct skc_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;
+
+       skc_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 skc_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 skc_node *gnode,
                          struct skc_node *enode)
@@ -157,6 +201,9 @@ trace_boot_init_one_event(struct trace_array *tr, struct 
skc_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 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];