[PATCH 6.12 183/460] tracing: Fix enabling multiple events on the kernel command line and bootconfig

Greg Kroah-Hartman
2026-03-23T14:21:28Z

6.12-stable review patch. If anyone has any objections, please let me know.

------------------

From: Andrei-Alexandru Tachici <andrei-alexandru.tachici@oss.qualcomm.com>

commit 3b1679e086bb869ca02722f6bd29b3573a6a0e7e upstream.

Multiple events can be enabled on the kernel command line via a comma
separator. But if the are specified one at a time, then only the last
event is enabled. This is because the event names are saved in a temporary
buffer, and each call by the init cmdline code will reset that buffer.

This also affects names in the boot config file, as it may call the
callback multiple times with an example of:

kernel.trace_event = ":mod:rproc_qcom_common", ":mod:qrtr", ":mod:qcom_aoss"

Change the cmdline callback function to append a comma and the next value
if the temporary buffer already has content.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20260302-trace-events-allow-multiple-modules-v1-1-ce4436e37fb8@oss.qualcomm.com
Signed-off-by: Andrei-Alexandru Tachici <andrei-alexandru.tachici@oss.qualcomm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/trace_events.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3999,7 +3999,11 @@ static char bootup_event_buf[COMMAND_LIN

static __init int setup_trace_event(char *str)
{
- strscpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
+ if (bootup_event_buf[0] != '\0')
+ strlcat(bootup_event_buf, ",", COMMAND_LINE_SIZE);
+
+ strlcat(bootup_event_buf, str, COMMAND_LINE_SIZE);
+
trace_set_ring_buffer_expanded(NULL);
disable_tracing_selftest("running event tracing");