linux-kernel - [for-next][PATCH 6/8] tracing/probe: Fix to allow user to enable events on unloaded modules

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Message-Id: <20190919232400.299074257@goodmis.org>
Date:   Thu, 19 Sep 2019 19:23:19 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>
Subject: [for-next][PATCH 6/8] tracing/probe: Fix to allow user to enable events on unloaded modules

From: Masami Hiramatsu <mhiramat@...nel.org>

Fix to allow user to enable probe events on unloaded modules.

This operations was allowed before commit 60d53e2c3b75 ("tracing/probe:
Split trace_event related data from trace_probe"), because if users
need to probe module init functions, they have to enable those probe
events before loading module.

Link: http://lkml.kernel.org/r/156879693733.31056.9331322616994665167.stgit@devnote2

Cc: stable@...r.kernel.org
Fixes: 60d53e2c3b75 ("tracing/probe: Split trace_event related data from trace_probe")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_kprobe.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 7579c53bb053..0ba3239c0270 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -371,31 +371,24 @@ static int enable_trace_kprobe(struct trace_event_call *call,
 	if (enabled)
 		return 0;
 
-	enabled = false;
 	list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
 		tk = container_of(pos, struct trace_kprobe, tp);
 		if (trace_kprobe_has_gone(tk))
 			continue;
 		ret = __enable_trace_kprobe(tk);
-		if (ret) {
-			if (enabled) {
-				__disable_trace_kprobe(tp);
-				enabled = false;
-			}
+		if (ret)
 			break;
-		}
 		enabled = true;
 	}
 
-	if (!enabled) {
-		/* No probe is enabled. Roll back */
+	if (ret) {
+		/* Failed to enable one of them. Roll back all */
+		if (enabled)
+			__disable_trace_kprobe(tp);
 		if (file)
 			trace_probe_remove_file(tp, file);
 		else
 			trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
-		if (!ret)
-			/* Since all probes are gone, this is not available */
-			ret = -EADDRNOTAVAIL;
 	}
 
 	return ret;
-- 
2.20.1