[PATCH v3] tracing: Use seq_buf for string concatenation
From: Woradorn Laodhanadhaworn <hidden>
Date: 2026-06-23 14:54:45
Also in:
linux-hardening, linux-trace-kernel, lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
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] Signed-off-by: Woradorn Laodhanadhaworn <redacted> --- v1 -> v2: - Fixed WARN_ON when booting with empty trace_event. v2 -> v3: - Addressed Sashiko's concern about the compound literal backing buffer. - Replaced the compund literal with an explicit declared buffer and pointed seq_buf.buffer to it. This guarantees the backing storage is placed in `.init.data` and reclaimed after boot. v1: https://lore.kernel.org/all/20260620175441.223342-1-woradorn.laon@gmail.com (local) v2: https://lore.kernel.org/all/20260622094623.18469-1-woradorn.laon@gmail.com (local) Sashiko: https://sashiko.dev/#/patchset/20260622094623.18469-1-woradorn.laon%40gmail.com kernel/trace/trace_events.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c46e623e7e0d..5ab630155ab6 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c@@ -22,6 +22,7 @@ #include <linux/sort.h> #include <linux/slab.h> #include <linux/delay.h> +#include <linux/seq_buf.h> #include <trace/events/sched.h> #include <trace/syscall.h>
@@ -4501,13 +4502,20 @@ 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 = COMMAND_LINE_SIZE, +}; 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, ","); + + seq_buf_puts(&bootup_event_seq, str); - strlcat(bootup_event_buf, str, COMMAND_LINE_SIZE); + if (seq_buf_has_overflowed(&bootup_event_seq)) + return -ENOMEM; trace_set_ring_buffer_expanded(NULL); disable_tracing_selftest("running event tracing");
@@ -4766,7 +4774,7 @@ 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_seq), false); trace_printk_start_comm();
@@ -4794,7 +4802,7 @@ 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_seq), true); return 0; }
--
2.43.0