From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dl1-f44.google.com (mail-dl1-f44.google.com [74.125.82.44]) (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 64CE73D6465 for ; Tue, 23 Jun 2026 14:54:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782226486; cv=none; b=C0cwtlsdXjp+fhDDs2LcyiKZl4r1oHEPNq/8wQqKNB3w4KS8bosw96QcuZLV6Cl9Pm5V1cG4e+kcOPGkGTAWxucD0PFIA0pcIu5/R1k9RQrB7lumtI1v3gJ/i7TfAX6eVCs43R4xzj2mMe/lpkGriD0iyQ3lMaNoBEgPvnCspeU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782226486; c=relaxed/simple; bh=L90/AkyCB9U0geyi1lWA/eHf7voiXgf417DXWgwVaXs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Lt0qKVW+AMB4C92xKWbMxChh7lRYlIV3RD+dKkpyBDfPy7JwtBHLcJnqqo8RCMfhz1OTsV4hMYGls/CgHgt8yCglZpEtCH7F0kYoSLxVmUgTUMlNgfMHW/f8tzjRy0Fku/h+xNV77Zh+PRExA4mjvPHmvGRIQ3DiBSsk5uIH6g0= 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=SRbupCAR; arc=none smtp.client-ip=74.125.82.44 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="SRbupCAR" Received: by mail-dl1-f44.google.com with SMTP id a92af1059eb24-1390f75d8bbso6240542c88.0 for ; Tue, 23 Jun 2026 07:54:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782226484; x=1782831284; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=IY3KFhICfndG+RHDKCrSaeQPMXM8dmxeDhVM/4MoFI4=; b=SRbupCARI7MYaWuFBF0iNPDW3bnl1Yvh5aNmuzOLlmacehSE3eZ1uu6844w0iwmcPl YifKmvZwdTMr9m/HJTG2dV+VtEZ3mVOHtJ5I0yNml/5T3W5PVnQcldvjX6LdzKEpc8sp sMssFA+3h8u0Lu9VaF7o5dEtipVvSCrxocqQT7RihS28qI7cRttyzwl0/usFYhD2+VkS 6IpBZjxyEonjgrO8ECMEtlRx7OjmEvimsTku0/KUa6EmITpuzbDF3oUri4V9FBj1zwbo H+vHOSLgj6UDWHZb9LWhiF26YqGlYILI9eO+5bADxQZbAvuyi5eO2S+yoZzAf54etk40 Km3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782226484; x=1782831284; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=IY3KFhICfndG+RHDKCrSaeQPMXM8dmxeDhVM/4MoFI4=; b=fxt2EPgDrVVGSdW5851AN+9k8s6XBOAE+OwE388bge2qxNTUIY0+Ms1+s2MRFqMZoV n4ZglyQiau72jGld6GpnIR4Vpu2g1sH0VFNDXrk96idRmB+iHHf7lnLe1lfydrhbT25M 0DwmYxJPlJa2nT2xL6q2zuSROtJSr+/Ltm4r9JuAHcpoIx1qBRWGVaiXFPMmnRGmvDO4 7nZmbL9KNaNbjv5N+AuQ72gVsCNjGuXgBCGiQ6Oiu+Db//i0AdZRMEB5yMulwYSsaB6Q 66eNMXin4ur1WnvK5cA3INz0EjbithGBMUTgkmOFGSrs2ghaDL78YZsdlhBB655OydC7 Utrw== X-Forwarded-Encrypted: i=1; AFNElJ9bf6urxDSRjbJWgCsN/MC43LHHTfS3ebNnvRLxBwBgUuerh3AtbAUIqBOr86HYQG1RUWyL2luoyKduywA=@vger.kernel.org X-Gm-Message-State: AOJu0YxaEM/3A9eGYdfWic2HMJa6UCSBlnIca+kD4dQuosDKqn92lGhr +FeLlNfZG9AhQQRM+MAm82XorTHipz2BeHE52+C1dX09ZHhTPMZ4UFa4 X-Gm-Gg: AfdE7ckZr89FnG4rjZVmGHjlKvWUM0CIHI+xIinZpm6Cy72fOo8AgZSZ4J6AcbTlwmu c+w9Fn00cyAA6tr1y59gkn6CTr31K5bcEXN/zKeM6TaCp6lT0XppLuBzVDIUwtaYbHtdr9Ey4cm 0QUJzIQpdQdFSF35/LtnivVnD9hkjG7PkO0ENkF5kmU1HQdL1mhNPtnR9i0/y4AFEBtGO3YWHh+ +648LsiAOOPmubfRD2iyrqhS1GvwO+mqQ1GJjTurfEVavLRtjU8nIF4kCWP0PnQOi0GnbLLjszs cX04lvBBRY34rIUg3xoy+kOLQWGiXqO/2infAvId48i4vu8Vv7n6PcZU3OzVk9qedF7ed15ejIp VRc5AGvClbVeT22KlWh6PHh2WMp6rwmZCpgNbb5vhvFfUgDadY0fvmLMPmulRxH3PW3naA2o4zn /I7hPSn1JVqNYgZV82nHoZKydtZNieTd1NTOlH5A== X-Received: by 2002:a05:7022:90d:b0:12a:6fb7:87e3 with SMTP id a92af1059eb24-139c5e033b1mr2686422c88.31.1782226484332; Tue, 23 Jun 2026 07:54:44 -0700 (PDT) Received: from mo-Inspiron-5559.. ([2001:fb1:d9:863a:37d9:e7c4:e450:11e4]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-139adca1b00sm12963863c88.2.2026.06.23.07.54.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2026 07:54:43 -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 v3] tracing: Use seq_buf for string concatenation Date: Tue, 23 Jun 2026 21:51:47 +0700 Message-ID: <20260623145147.12145-1-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. 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