linux-kernel - [PATCH 1/2] tracing/boot: Add per-group/all events enablement

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Message-Id: <162264438005.302580.12019174481201855444.stgit@devnote2>
Date:   Wed,  2 Jun 2021 23:33:00 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] tracing/boot: Add per-group/all events enablement

Add ftrace.event.<GROUP>.enable and ftrace.event.enable
boot-time tracing, which enables all events under
given GROUP and all events respectivly.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/trace/trace_boot.c |   27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index a82f03f385f8..94ef2d099e32 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -225,14 +225,37 @@ static void __init
 trace_boot_init_events(struct trace_array *tr, struct xbc_node *node)
 {
 	struct xbc_node *gnode, *enode;
+	bool enable, enable_all = false;
+	const char *data;
 
 	node = xbc_node_find_child(node, "event");
 	if (!node)
 		return;
 	/* per-event key starts with "event.GROUP.EVENT" */
-	xbc_node_for_each_child(node, gnode)
-		xbc_node_for_each_child(gnode, enode)
+	xbc_node_for_each_child(node, gnode) {
+		data = xbc_node_get_data(gnode);
+		if (!strcmp(data, "enable")) {
+			enable_all = true;
+			continue;
+		}
+		enable = false;
+		xbc_node_for_each_child(gnode, enode) {
+			data = xbc_node_get_data(enode);
+			if (!strcmp(data, "enable")) {
+				enable = true;
+				continue;
+			}
 			trace_boot_init_one_event(tr, gnode, enode);
+		}
+		/* Event enablement must be done after event settings */
+		if (enable) {
+			data = xbc_node_get_data(gnode);
+			trace_array_set_clr_event(tr, data, NULL, true);
+		}
+	}
+	/* Ditto */
+	if (enable_all)
+		trace_array_set_clr_event(tr, NULL, NULL, true);
 }
 #else
 #define trace_boot_enable_events(tr, node) do {} while (0)