Re: [PATCH v2] tracing: Use seq_buf for string concatenation
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2026-06-29 18:47:59
Also in:
linux-hardening, linux-kernel-mentees, lkml
On Mon, 22 Jun 2026 16:46:23 +0700 Woradorn Laodhanadhaworn [off-list ref] wrote:
quoted hunk ↗ jump to hunk
#include <trace/events/sched.h> #include <trace/syscall.h>@@ -4500,14 +4501,20 @@ static void __add_event_to_tracers(struct trace_event_call *call) 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;
Keep the above string and just assign it.
+static struct seq_buf bootup_event_buf __initdata = {
+ .buffer = (char[COMMAND_LINE_SIZE]) {},
+ .size = COMMAND_LINE_SIZE,
+};
static struct seq_buf bootup_event_seq __initdata = {
.buffer = bootup_event_buf;
.size = sizeof(bootup_event_buf);
};
quoted hunk ↗ jump to hunk
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_buf) > 0) + seq_buf_puts(&bootup_event_buf, ","); + + seq_buf_puts(&bootup_event_buf, str); - strlcat(bootup_event_buf, str, COMMAND_LINE_SIZE); + if (seq_buf_has_overflowed(&bootup_event_buf)) + return -ENOMEM; trace_set_ring_buffer_expanded(NULL); disable_tracing_selftest("running event tracing");@@ -4766,7 +4773,7 @@ static __init int event_trace_enable(void) */ __trace_early_add_events(tr); - early_enable_events(tr, bootup_event_buf, false); + early_enable_events(tr, (char *)seq_buf_str(&bootup_event_buf), false);
The above then would be: seq_buf_str(&bootup_event_seq); early_enable_events(tr, bootup_event_buf, false); Don't typecast a const char* to non const.
quoted hunk ↗ jump to hunk
trace_printk_start_comm();@@ -4794,7 +4801,7 @@ static __init int event_trace_enable_again(void) if (!tr) return -ENODEV; - early_enable_events(tr, bootup_event_buf, true); + early_enable_events(tr, (char *)seq_buf_str(&bootup_event_buf), true);
Same here. -- Steve
return 0; }