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tracing: Use seq_buf for string concatenation

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In preparation for removing the strlcat API[1],
replace the string concatenation logic with a struct seq_buf,
which tracks the current position and the remaining space internally.

Use seq_buf_str() to NUL-terminate before passing to early_enable_events().

Link: https://github.com/KSPP/linux/issues/370 [1]

Link: https://patch.msgid.link/20260713045249.69942-1-woradorn.laon@gmail.com
Signed-off-by: Woradorn Laodhanadhaworn <woradorn.laon@gmail.com>
[ Moved placement of #include <linux/seq_buf.h> ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Woradorn Laodhanadhaworn
2026-07-28 07:18:50 -04:00
committed by Steven Rostedt
parent dca6a22aee
commit efdcfd9b4f
1 changed files with 13 additions and 3 deletions
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kernel/trace/trace_events.c
+13 -3
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@@ -14,6 +14,7 @@
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/spinlock.h>
#include <linux/seq_buf.h>
#include <linux/kthread.h>
#include <linux/tracefs.h>
#include <linux/uaccess.h>
@@ -4604,13 +4605,20 @@ extern struct trace_event_call *__start_ftrace_events[];
extern struct trace_event_call *__stop_ftrace_events[];
static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata;
static struct seq_buf bootup_event_seq __initdata = {
.buffer = bootup_event_buf,
.size = sizeof(bootup_event_buf),
};
static __init int setup_trace_event(char *str)
{
if (bootup_event_buf[0] != '\0')
strlcat(bootup_event_buf, ",", COMMAND_LINE_SIZE);
if (seq_buf_used(&bootup_event_seq) > 0)
seq_buf_puts(&bootup_event_seq, ",");
strlcat(bootup_event_buf, str, COMMAND_LINE_SIZE);
seq_buf_puts(&bootup_event_seq, str);
if (seq_buf_has_overflowed(&bootup_event_seq))
return -ENOMEM;
trace_set_ring_buffer_expanded(NULL);
disable_tracing_selftest("running event tracing");
@@ -4869,6 +4877,7 @@ static __init int event_trace_enable(void)
*/
__trace_early_add_events(tr);
seq_buf_str(&bootup_event_seq);
early_enable_events(tr, bootup_event_buf, false);
trace_printk_start_comm();
@@ -4897,6 +4906,7 @@ static __init int event_trace_enable_again(void)
if (!tr)
return -ENODEV;
seq_buf_str(&bootup_event_seq);
early_enable_events(tr, bootup_event_buf, true);
return 0;