From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3B7F02C032E; Wed, 24 Jun 2026 05:03:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782277390; cv=none; b=dzU89mXiqz0H7VOcwio9gd/5RQB36ad3VVnXpJsZIDWQrszVILSqDac5O6cSuDZkghAfM9lRfJ5c5ZJOpGXxysk0BX6JCYzPFOg2Ud29oCnsWmbi18w8hx0KA8K5e8VXsNCP2OfXQHcwbWc0s+9fMaNNxBauQyJFc/i5GITdoQ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782277390; c=relaxed/simple; bh=R+429pqsrrwtoJ7O+R+xci3ETjFCL+XKHwd1gisU358=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=XhgeEcH1uqnDCS+hg4TnoXt0ds2Tp4qANkkBDqyWrJ+md0T1wbMMm1hAzwr9OBmtZi1tXZxyOnHikD+/YPMwemyPRLP+Rtwuz9K/BsvuSUNyIjcjnC6PpzcERXNAZ0UQmGNhRNEjoimEMwAlYSLIBbrWztKpY/eGO0/htuPquGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QoAPTeFS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QoAPTeFS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4240F1F000E9; Wed, 24 Jun 2026 05:03:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782277388; bh=etJNdBG9SqZBVpsZZzBAhAVFoG3Scky9EQ1NQqsVgKY=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=QoAPTeFSy04CNMgmiYffzBaHsAkyx9wchogQN4XaR9KxO6voTqDtwFwvbhkScuT58 I6XjKwoCHQJo9OAmdQBsjJuHt2/o//O+nMQo9mxniKB7ko+QLmC9wlk2KWvV2O9vgv mwDfiWyTnriaYpPpJyrAxmyB8JQqr0wFLvSjdwfIU6P449r0JERLXDMowAnliJKBJo EjQycuTVukK2xT15/lNc5UQ+lwom3dswCv2uDq04xEG2cNcgwBHtS9zRg5z0NS7NWS 505P2rZ7KvumA7sQWkJJSXXtmSwt2OG/66Wp+7O7gSE9wWT95x/ZUj6N4TB3RB3uRt LJwUjaq4FjOsQ== Date: Wed, 24 Jun 2026 14:03:05 +0900 From: Masami Hiramatsu (Google) To: Woradorn Laodhanadhaworn Cc: rostedt@goodmis.org, 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 Subject: Re: [PATCH v3] tracing: Use seq_buf for string concatenation Message-Id: <20260624140305.3827bbb32f84c62dd9f09222@kernel.org> In-Reply-To: <20260623145147.12145-1-woradorn.laon@gmail.com> References: <20260623145147.12145-1-woradorn.laon@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 23 Jun 2026 21:51:47 +0700 Woradorn Laodhanadhaworn wrote: > 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] > Looks good to me. Acked-by: Masami Hiramatsu (Google) Thanks, > Signed-off-by: Woradorn Laodhanadhaworn > --- > 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 > v2: https://lore.kernel.org/all/20260622094623.18469-1-woradorn.laon@gmail.com > 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 > #include > #include > +#include > > #include > #include > @@ -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 > -- Masami Hiramatsu (Google)