tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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tracing: Preserve repeated trace_trigger boot parameters

trace_trigger= tokenizes bootup_trigger_buf in place and stores pointers
into that buffer for later trigger registration. Repeated trace_trigger=
parameters overwrite the buffer contents from earlier calls, leaving
only the last set of parsed event and trigger strings.

Keep each new trace_trigger= string at the end of bootup_trigger_buf and
parse only the appended range. That preserves the earlier event and
trigger strings while still letting repeated parameters queue additional
boot-time triggers.

This also lets Bootconfig array values work naturally when they expand
to repeated trace_trigger= entries.

Before this change, only the last trace_trigger= instance survived boot.

Link: https://patch.msgid.link/20260330181103.1851230-2-atwellwea@gmail.com
Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

authored by

Wesley Atwell and committed by
Steven Rostedt (Google) d1a03c29 842b74e5

+10 -3
+10 -3
kernel/trace/trace_events.c
··· 3675 3675 } bootup_triggers[MAX_BOOT_TRIGGERS]; 3676 3676 3677 3677 static char bootup_trigger_buf[COMMAND_LINE_SIZE]; 3678 + static int boot_trigger_buf_len; 3678 3679 static int nr_boot_triggers; 3679 3680 3680 3681 static __init int setup_trace_triggers(char *str) 3681 3682 { 3682 3683 char *trigger; 3683 3684 char *buf; 3685 + int len = boot_trigger_buf_len; 3684 3686 int i; 3685 3687 3686 - strscpy(bootup_trigger_buf, str, COMMAND_LINE_SIZE); 3688 + if (len >= COMMAND_LINE_SIZE) 3689 + return 1; 3690 + 3691 + strscpy(bootup_trigger_buf + len, str, COMMAND_LINE_SIZE - len); 3687 3692 trace_set_ring_buffer_expanded(NULL); 3688 3693 disable_tracing_selftest("running event triggers"); 3689 3694 3690 - buf = bootup_trigger_buf; 3691 - for (i = 0; i < MAX_BOOT_TRIGGERS; i++) { 3695 + buf = bootup_trigger_buf + len; 3696 + boot_trigger_buf_len += strlen(buf) + 1; 3697 + 3698 + for (i = nr_boot_triggers; i < MAX_BOOT_TRIGGERS; i++) { 3692 3699 trigger = strsep(&buf, ","); 3693 3700 if (!trigger) 3694 3701 break;