From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f172.google.com (mail-pg1-f172.google.com [209.85.215.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C55E838F23D for ; Mon, 22 Jun 2026 08:18:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782116297; cv=none; b=qYUOOSAOmNqWM1qpxCHu9+V0LUJJnA70e9clCOghdraVRgyWbeEwRCF0uOxHw6/tL4lItvokZK4ajViCryvMHM0RQ08FHQS19J+YeRlCsxfELeuwUj5DaeSGlF2td/N90/Kl2ZyJGTTxG6Cm7N3G7pEwElipZIyS+zPVBjdpIG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782116297; c=relaxed/simple; bh=kchaHGbuD3Cp5Gw9qsC+6xIIPUpTFqc4APXbX8vshqo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OnpdT3X/gva0VSGEtljhpzYSbyi9KnmWk73Gnhat7Ri+tHT7bT4kY/LsI9DwAuDa6AFnKsfuUysY/So5wY/S7LEcE2XTDb39do6pi8k5E4jWRaW/urWOeuujKpC24Y8r6eTYLrnLyKzh6rnaNGcVCF/YClqiPbp7r5C8SPccHSA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=s5zlPutt; arc=none smtp.client-ip=209.85.215.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="s5zlPutt" Received: by mail-pg1-f172.google.com with SMTP id 41be03b00d2f7-c85d4b4245aso2907408a12.1 for ; Mon, 22 Jun 2026 01:18:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782116295; x=1782721095; darn=lists.linux.dev; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=WnzEGAPdTbj50+aOsUk+pqnINR3riAsvsyCwurmkB1E=; b=s5zlPuttGLvvd+GUx410u3iheqqDHo+oldYLZMCsAUaDvZ/ZanvrwHhOcAY3ZqUrNw Cl1pT+77UNftJC7654R37PucMiPUIobB0HRh32h2a6Gbnh/xifHvK9BnlqwVARNZZZG7 BD2afCCWmAU9WeJBa/u6f45DnXaTVnocBjqnLakqBG7e498fHSwXEpX2FTBghqMCRoIH LgsvDSF/jU8LGLfsShGaYeFfUg+VXhnFR3+/gA595Ptq8LPk0KTDX9s9LRAiX9U/lU0K fiZdZPBaTiYJdQjzjWFRXqcnLjbmOa9ChzwlyJPeTEjcGOWvyAAycaDHfdUIGWD+69yL 3xrg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782116295; x=1782721095; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=WnzEGAPdTbj50+aOsUk+pqnINR3riAsvsyCwurmkB1E=; b=dkbKPlHb3kxuAYsw0pIpwsA8/FjSJJyoiGeOavzIgc/WV3qfZf7yaAJkXZak6jPS7L E2+WqWNCjoOOFSYBgMRbl8KIX0qIoDbVLsG1zR08CQYWW8pUszgK/OpsaMzCwK/xkwgK HkmYy9KEZl8gGYXiEdxTb9TjvOIYVCVjX+GcmFh7F/HjZtBtUcSCaEnSHUc9KKJUMELq /IiRh5LEkbW/UpeU7dFtxyoQIeoNRb1N9/UVSZhgyvUUtbeiT3Oo5S2rLwUhdvZryz4G 0Zj62bhbAD3dbJKgltnfl5Yzbd5wxMMNrJE3aeHrVZXv6bQDzQZXIA/SvvxvkDB6zKst fjCQ== X-Forwarded-Encrypted: i=1; AFNElJ+KIDwjmPr45TFX/e7rwP7IMMA/fYo7mtMRhBaSOH9Zpu1OIkj0afYcrznVL5gHXJaxHvgeYzaXTONTuge2LbC1XrLkcg==@lists.linux.dev X-Gm-Message-State: AOJu0YyKzpi8RIU2I7RtvcGq0r61mYpPOnlPFDV9p/jdEhTcLX31uBy8 MThTu2qEqQwzRKDzBUhxvNBK3lTdIDWwB3Sxx551yI5J8sBF6nCwTs6X X-Gm-Gg: AfdE7cnHceBwOPRy7vtAjKv4CWiYWWzsa91HLWYyqj9QFdJwDzr5LGfc1CExsRbmtGU C6JqFaTE7R/acZCBUd+2+a+7xG+o95Xv/gfxqPa0RvR1hdJ0ns3mpXNHPS2a9jnf5rJuK2jCNKb uPMCUs2FGkctuNKtQ9jTQWu9j/8mw6FyIXC8xnAF+crq2MlsZGclr/0RIGxB5/5Kj/c+5lVnOvg 2acVWdv7iA6GceqeuFGrNtAr5IA4StXBlHB19WgfveIuQCoFi0zJEwvLDkI4/QhWeiTPMp73ks+ DlgRIvIx3W9O3CUHYEN3S09LokVLOFq09v3swLGAYnjvqlJpCLGOUyW+FzAOdDCPSGYFGrIxEUO 2rsvq/3kr5JIF7ly/OZ6obRGWgfOcqV/220lXKx12kU0U0RvdOfyZFloO+OhScLMTa+ugagK0PA LzuX5wrVA17/Y6+0pkL32EfUuG0ttOGs0MFU0aRBGdOa3JEBLpC3cVNhXsSyOqQO0PZvB/hWdLR 23B X-Received: by 2002:a05:6a20:431a:b0:3b4:640e:f6b1 with SMTP id adf61e73a8af0-3bb32914066mr14471224637.10.1782116294931; Mon, 22 Jun 2026 01:18:14 -0700 (PDT) Received: from ?IPV6:2001:fb1:d9:863a:1c8e:6f40:7f4b:ee15? ([2001:fb1:d9:863a:1c8e:6f40:7f4b:ee15]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c8bc5efcb1csm5846563a12.30.2026.06.22.01.18.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Jun 2026 01:18:14 -0700 (PDT) Message-ID: Date: Mon, 22 Jun 2026 15:18:08 +0700 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tracing: Use seq_buf for string concatenation To: Jori Koolstra , 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 References: <20260620175441.223342-1-woradorn.laon@gmail.com> <70408559.2499685.1782062190117@kpc.webmail.kpnmail.nl> Content-Language: en-US From: Woradorn Laodhanadhaworn In-Reply-To: <70408559.2499685.1782062190117@kpc.webmail.kpnmail.nl> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 22/6/2569 BE 00:16, Jori Koolstra wrote: > >> Op 20-06-2026 19:54 CEST schreef Woradorn Laodhanadhaworn : >> >> >> 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. >> >> The backing buffer bootup_event_buf allocation is unchanged. >> 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 >> --- >> kernel/trace/trace_events.c | 21 ++++++++++++++++----- >> 1 file changed, 16 insertions(+), 5 deletions(-) >> >> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c >> index c46e623e7e0d..15164723e028 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 +4502,23 @@ 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; > > Isn't this now unused? > >> +static struct seq_buf bootup_event_seq; >> +static bool bootup_event_seq_initialized; >> > > I think this can be refactored to avoid the bool. And should bootup_event_seq not be > __initdata? > >> static __init int setup_trace_event(char *str) >> { >> - if (bootup_event_buf[0] != '\0') >> - strlcat(bootup_event_buf, ",", COMMAND_LINE_SIZE); >> + if (!bootup_event_seq_initialized) { >> + seq_buf_init(&bootup_event_seq, bootup_event_buf, COMMAND_LINE_SIZE); >> + bootup_event_seq_initialized = true; >> + } >> + >> + 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"); >> @@ -4766,7 +4777,7 @@ 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); > > What if trace_event is empty? Then setup_trace_event does not run AFAIK. See the > WARN_ON in seq_buf_str too. Have you tested this? > >> >> trace_printk_start_comm(); >> >> @@ -4794,7 +4805,7 @@ 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 > > Thanks, > Jori. Thank you, Jori, for your review. I will send v2. I tested both empty and non-empty trace_event cases with QEMU, and both now boot successfully. The logs below demonstrate this. Non-empty trace_event: qemu-system-x86_64 \ -kernel arch/x86/boot/bzImage \ -initrd initramfs.cpio.gz \ -append "console=ttyS0 trace_event=:mod:rproc_qcom_common,:mod:qrtr,:mod:qcom_aoss trace_event=:mod:rproc_qcom_common" \ -nographic \ -m 512M [ 0.082316] Kernel command line: console=ttyS0 trace_event=:mod:rproc_qcom_common,:mod:qrtr,:mod:qcom_aoss trace_event=:mod:rproc_qcom_common [ 0.083324] bootup_event_buf: :mod:rproc_qcom_common,:mod:qrtr,:mod:qcom_aoss [ 0.083413] bootup_event_buf: :mod:rproc_qcom_common,:mod:qrtr,:mod:qcom_aoss,:mod:rproc_qcom_common [ 0.083689] printk: log buffer data + meta data: 262144 + 917504 = 1179648 bytes Empty trace_event: qemu-system-x86_64 \ -kernel arch/x86/boot/bzImage \ -initrd initramfs.cpio.gz \ -append "console=ttyS0" \ -nographic \ -m 512M [ 0.085213] Kernel command line: console=ttyS0 [ 0.086458] printk: log buffer data + meta data: 262144 + 917504 = 1179648 bytes Thanks, Woradorn