[RFC PATCH v3 13/19] tracing/boot Add kprobe event support

[Masami Hiramatsu]

Add kprobe event support on event node. If the group name of event
is "kprobes", boottime trace defines new probe event according
to "probes" values.

 - ftrace.event.kprobes.EVENT.probes = PROBE[, PROBE2...];
   Defines new kprobe event based on PROBEs. It is able to define
   multiple probes on one event, but those must have same type of
   arguments.

For example,

 ftrace.events.kprobes.myevent {
        probes = "vfs_read $arg1 $arg2";
        enable;
 }

This will add kprobes:myevent on vfs_read with the 1st and the 2nd
arguments.

Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
---
 kernel/trace/trace_boot.c   |   46 +++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_kprobe.c |    5 +++++
 2 files changed, 51 insertions(+)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index cfd628c16761..40c89c7ceee0 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -100,6 +100,48 @@ trace_boot_enable_events(struct trace_array *tr, struct 
skc_node *node)
        }
 }
 
+#ifdef CONFIG_KPROBE_EVENTS
+extern int trace_kprobe_run_command(const char *command);
+
+static int __init
+trace_boot_add_kprobe_event(struct skc_node *node, const char *event)
+{
+       struct skc_node *anode;
+       char buf[MAX_BUF_LEN];
+       const char *val;
+       char *p;
+       int len;
+
+       len = snprintf(buf, ARRAY_SIZE(buf) - 1, "p:kprobes/%s ", event);
+       if (len >= ARRAY_SIZE(buf)) {
+               pr_err("Event name is too long: %s\n", event);
+               return -E2BIG;
+       }
+       p = buf + len;
+       len = ARRAY_SIZE(buf) - len;
+
+       skc_node_for_each_array_value(node, "probes", anode, val) {
+               if (strlcpy(p, val, len) >= len) {
+                       pr_err("Probe definition is too long: %s\n", val);
+                       return -E2BIG;
+               }
+               if (trace_kprobe_run_command(buf) < 0) {
+                       pr_err("Failed to add probe: %s\n", buf);
+                       return -EINVAL;
+               }
+       }
+
+       return 0;
+}
+#else
+static inline int __init
+trace_boot_add_kprobe_event(struct skc_node *node, const char *event)
+{
+       pr_err("Kprobe 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)
@@ -112,6 +154,10 @@ trace_boot_init_one_event(struct trace_array *tr, struct 
skc_node *gnode,
        group = skc_node_get_data(gnode);
        event = skc_node_get_data(enode);
 
+       if (!strcmp(group, "kprobes"))
+               if (trace_boot_add_kprobe_event(enode, event) < 0)
+                       return;
+
        mutex_lock(&event_mutex);
        file = find_event_file(tr, group, event);
        if (!file) {
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5135c07b6557..03ce60928c18 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -728,6 +728,11 @@ static int create_or_delete_trace_kprobe(int argc, char 
**argv)
        return ret == -ECANCELED ? -EINVAL : ret;
 }
 
+int trace_kprobe_run_command(const char *command)
+{
+       return trace_run_command(command, create_or_delete_trace_kprobe);
+}
+
 static int trace_kprobe_release(struct dyn_event *ev)
 {
        struct trace_kprobe *tk = to_trace_kprobe(ev);