linux-kernel - [PATCH 2/3] trace/ring-buffer: Do not create module or dynamic events in boot mapped buffers

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Message-ID: <20241217173520.483964366@goodmis.org>
Date: Tue, 17 Dec 2024 12:32:39 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 stable@...r.kernel.org
Subject: [PATCH 2/3] trace/ring-buffer: Do not create module or dynamic events in boot
 mapped buffers

From: Steven Rostedt <rostedt@...dmis.org>

When a ring buffer is mapped across boots, an delta is saved between the
addresses of the previous kernel and the current kernel. But this does not
handle module events nor dynamic events.

Simply do not create module or dynamic events to a boot mapped instance.
This will keep them from ever being enabled and therefore not part of the
previous kernel trace.

Cc: stable@...r.kernel.org
Fixes: e645535a954ad ("tracing: Add option to use memmapped memory for trace boot instance")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 77e68efbd43e..d6359318d5c1 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2984,6 +2984,12 @@ trace_create_new_event(struct trace_event_call *call,
 	if (!event_in_systems(call, tr->system_names))
 		return NULL;
 
+	/* Boot mapped instances cannot use modules or dynamic events */
+	if (tr->flags & TRACE_ARRAY_FL_BOOT) {
+		if ((call->flags & TRACE_EVENT_FL_DYNAMIC) || call->module)
+			return NULL;
+	}
+
 	file = kmem_cache_alloc(file_cachep, GFP_TRACE);
 	if (!file)
 		return ERR_PTR(-ENOMEM);
-- 
2.45.2