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([2001:fb1:d9:863a:ce08:349e:af46:efee]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37d4eede23esm6512438a91.2.2026.06.22.02.50.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2026 02:50:36 -0700 (PDT) From: Woradorn Laodhanadhaworn To: rostedt@goodmis.org Cc: mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, shuah@kernel.org, skhan@linuxfoundation.org, me@brighamcampbell.com, jkoolstra@xs4all.nl, woradorn.laon@gmail.com Subject: [PATCH v2] tracing: Use seq_buf for string concatenation Date: Mon, 22 Jun 2026 16:46:23 +0700 Message-ID: <20260622094623.18469-1-woradorn.laon@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- v1 -> v2: Fixed WARN_ON when booting with empty trace_event. v1: https://lore.kernel.org/all/20260620175441.223342-1-woradorn.laon@gmail.com kernel/trace/trace_events.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index c46e623e7e0d..1be62a46e49a 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -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; +static struct seq_buf bootup_event_buf __initdata = { + .buffer = (char[COMMAND_LINE_SIZE]) {}, + .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_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); 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); return 0; } -- 2.43.0