From nobody Sun Feb 8 20:32:40 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8C2CD823CD for ; Fri, 23 Feb 2024 14:17:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708697830; cv=none; b=fKt284zUtIsGd4ZzCPB4cCv3tZwGy5tkdCVuCCW4pVdisREr55yPCxKVRXO8YnGbuQzSndBPFZHE1bGauIkeaO+X+PJghuSD6nC5VagW2Lk/VjrRWqNoKtGqGHkemjHiHP89HuRZ1C6t1V2a8B0wfENiR4gelGxGTzL+IW1HqQQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708697830; c=relaxed/simple; bh=TRTlBeIWlLJicEJm6c+SDXQxnX8BueJpz4S9NWvpEnU=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=Xp6O3B8SNT3o2JWIkVf3+tFGHIxNCfUELQ9SMsng5iXmBEd9bFFtL+xeAbBFSSpPKZh91FKJkGMiFDrQ8dRSpUf3yJzArkdTvgRnaFs6jiCTGmm3zZTytJOgVYWDp7nzvlyjTuovZ2aJ2gAvxx6qMBWVVr6O4clrLA9/RGl3Fes= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 079ADC433C7; Fri, 23 Feb 2024 14:17:10 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rdWOF-000000077PA-03aA; Fri, 23 Feb 2024 09:19:03 -0500 Message-ID: <20240223141902.873290088@goodmis.org> User-Agent: quilt/0.67 Date: Fri, 23 Feb 2024 09:18:47 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , =?utf-8?b?VmlsbGUgU3lyasOkbMOk?= , Rodrigo Vivi , Chuck Lever Subject: [for-next][PATCH 09/13] tracing: Do not calculate strlen() twice for __string() fields References: <20240223141838.985298316@goodmis.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" The TRACE_EVENT() macro handles dynamic strings by having: TP_PROTO(struct some_struct *s), TP_ARGS(s), TP_STRUCT__entry( __string(my_string, s->string) ), TP_fast_assign( __assign_str(my_string, s->string); ) TP_printk("%s", __get_str(my_string)) There's even some code that may call a function helper to find the s->string value. The problem with the above is that the work to get the s->string is done twice. Once at the __string() and again in the __assign_str(). The length of the string is calculated via a strlen(), not once, but twice. Once during the __string() macro and again in __assign_str(). But the length is actually already recorded in the data location and here's no reason to call strlen() again. Just use the saved length that was saved in the __string() code for the __assign_str() code. Link: https://lore.kernel.org/linux-trace-kernel/20240222211442.793074999@g= oodmis.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: =3D?utf-8?b?VmlsbGUgU3lyasOkbMOk?=3D Cc: Rodrigo Vivi Cc: Chuck Lever Signed-off-by: Steven Rostedt (Google) --- include/trace/stages/stage6_event_callback.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/include/trace/stages/stage6_event_callback.h b/include/trace/s= tages/stage6_event_callback.h index b3e2f321e787..c0e5d097324e 100644 --- a/include/trace/stages/stage6_event_callback.h +++ b/include/trace/stages/stage6_event_callback.h @@ -32,8 +32,9 @@ =20 #undef __assign_str #define __assign_str(dst, src) \ - strcpy(__get_str(dst), __data_offsets.dst##_ptr_ ? \ - __data_offsets.dst##_ptr_ : "(null)") + memcpy(__get_str(dst), __data_offsets.dst##_ptr_ ? \ + __data_offsets.dst##_ptr_ : "(null)", \ + __get_dynamic_array_len(dst)) =20 #undef __assign_str_len #define __assign_str_len(dst, src, len) \ @@ -94,8 +95,9 @@ =20 #undef __assign_rel_str #define __assign_rel_str(dst, src) \ - strcpy(__get_rel_str(dst), __data_offsets.dst##_ptr_ ? \ - __data_offsets.dst##_ptr_ : "(null)") + memcpy(__get_rel_str(dst), __data_offsets.dst##_ptr_ ? \ + __data_offsets.dst##_ptr_ : "(null)", \ + __get_rel_dynamic_array_len(dst)) =20 #undef __assign_rel_str_len #define __assign_rel_str_len(dst, src, len) \ --=20 2.43.0