From nobody Mon Sep 29 21:26:48 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B740C25B0D for ; Tue, 16 Aug 2022 00:58:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347243AbiHPA5P (ORCPT ); Mon, 15 Aug 2022 20:57:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346568AbiHPAvM (ORCPT ); Mon, 15 Aug 2022 20:51:12 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41AEE199B3C; Mon, 15 Aug 2022 13:46:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 8D9C6B81197; Mon, 15 Aug 2022 20:46:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C304AC433D6; Mon, 15 Aug 2022 20:46:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660596414; bh=UdYZI1riOsDbDH0atDWZkwjVT6LhIpkFlQ5M1a7XQrg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fByKYwfpaimidRyhHM3aAsPiSCBiNwyjJ8D6mz1k4w4rVczWx3D2F0g5unzZCSBgW akV58qOl2jqxNKywPYyb3hddmDrlFuejjEwxkO5mLAMj4Rv/U6QShvzDSFvk+Gr72u gJ4SSY0UlqJ9lv2qt/rM4gAK37lTdIctWj9Aj9iE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dennis Dalessandro , Ingo Molnar , Andrew Morton , Jason Gunthorpe , Leon Romanovsky , Kalle Valo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Arend van Spriel , Franky Lin , Hante Meuleman , Gregory Greenman , Peter Chen , Mathias Nyman , Chunfeng Yun , Bin Liu , Marek Lindner , Simon Wunderlich , Antonio Quartulli , Sven Eckelmann , Johannes Berg , Jim Cromie , "Steven Rostedt (Google)" , Sasha Levin Subject: [PATCH 5.19 1072/1157] tracing/events: Add __vstring() and __assign_vstr() helper macros Date: Mon, 15 Aug 2022 20:07:08 +0200 Message-Id: <20220815180523.005866092@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180439.416659447@linuxfoundation.org> References: <20220815180439.416659447@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Steven Rostedt (Google) [ Upstream commit 0563231f93c6d1f582b168a47753b345c1e20d81 ] There's several places that open code the following logic: TP_STRUCT__entry(__dynamic_array(char, msg, MSG_MAX)), TP_fast_assign(vsnprintf(__get_str(msg), MSG_MAX, vaf->fmt, *vaf->va);) To load a string created by variable array va_list. The main issue with this approach is that "MSG_MAX" usage in the __dynamic_array() portion. That actually just reserves the MSG_MAX in the event, and even wastes space because there's dynamic meta data also saved in the event to denote the offset and size of the dynamic array. It would have been better to just use a static __array() field. Instead, create __vstring() and __assign_vstr() that work like __string and __assign_str() but instead of taking a destination string to copy, take a format string and a va_list pointer and fill in the values. It uses the helper: #define __trace_event_vstr_len(fmt, va) \ ({ \ va_list __ap; \ int __ret; \ \ va_copy(__ap, *(va)); \ __ret =3D vsnprintf(NULL, 0, fmt, __ap) + 1; \ va_end(__ap); \ \ min(__ret, TRACE_EVENT_STR_MAX); \ }) To figure out the length to store the string. It may be slightly slower as it needs to run the vsnprintf() twice, but it now saves space on the ring buffer. Link: https://lkml.kernel.org/r/20220705224749.053570613@goodmis.org Cc: Dennis Dalessandro Cc: Ingo Molnar Cc: Andrew Morton Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Kalle Valo Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: Arend van Spriel Cc: Franky Lin Cc: Hante Meuleman Cc: Gregory Greenman Cc: Peter Chen Cc: Greg Kroah-Hartman Cc: Mathias Nyman Cc: Chunfeng Yun Cc: Bin Liu Cc: Marek Lindner Cc: Simon Wunderlich Cc: Antonio Quartulli Cc: Sven Eckelmann Cc: Johannes Berg Cc: Jim Cromie Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- include/linux/trace_events.h | 18 ++++++++++++++++++ include/trace/stages/stage1_struct_define.h | 3 +++ include/trace/stages/stage2_data_offsets.h | 3 +++ include/trace/stages/stage4_event_fields.h | 3 +++ include/trace/stages/stage5_get_offsets.h | 4 ++++ include/trace/stages/stage6_event_callback.h | 7 +++++++ 6 files changed, 38 insertions(+) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index e6e95a9f07a5..b18759a673c6 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -916,6 +916,24 @@ perf_trace_buf_submit(void *raw_data, int size, int rc= tx, u16 type, =20 #endif =20 +#define TRACE_EVENT_STR_MAX 512 + +/* + * gcc warns that you can not use a va_list in an inlined + * function. But lets me make it into a macro :-/ + */ +#define __trace_event_vstr_len(fmt, va) \ +({ \ + va_list __ap; \ + int __ret; \ + \ + va_copy(__ap, *(va)); \ + __ret =3D vsnprintf(NULL, 0, fmt, __ap) + 1; \ + va_end(__ap); \ + \ + min(__ret, TRACE_EVENT_STR_MAX); \ +}) + #endif /* _LINUX_TRACE_EVENT_H */ =20 /* diff --git a/include/trace/stages/stage1_struct_define.h b/include/trace/st= ages/stage1_struct_define.h index a16783419687..1b7bab60434c 100644 --- a/include/trace/stages/stage1_struct_define.h +++ b/include/trace/stages/stage1_struct_define.h @@ -26,6 +26,9 @@ #undef __string_len #define __string_len(item, src, len) __dynamic_array(char, item, -1) =20 +#undef __vstring +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) + #undef __bitmask #define __bitmask(item, nr_bits) __dynamic_array(char, item, -1) =20 diff --git a/include/trace/stages/stage2_data_offsets.h b/include/trace/sta= ges/stage2_data_offsets.h index 42fd1e8813ec..1b7a8f764fdd 100644 --- a/include/trace/stages/stage2_data_offsets.h +++ b/include/trace/stages/stage2_data_offsets.h @@ -32,6 +32,9 @@ #undef __string_len #define __string_len(item, src, len) __dynamic_array(char, item, -1) =20 +#undef __vstring +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) + #undef __bitmask #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1) =20 diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/sta= ges/stage4_event_fields.h index e80cdc397a43..c3790ec7a453 100644 --- a/include/trace/stages/stage4_event_fields.h +++ b/include/trace/stages/stage4_event_fields.h @@ -38,6 +38,9 @@ #undef __string_len #define __string_len(item, src, len) __dynamic_array(char, item, -1) =20 +#undef __vstring +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) + #undef __bitmask #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1) =20 diff --git a/include/trace/stages/stage5_get_offsets.h b/include/trace/stag= es/stage5_get_offsets.h index 7ee5931300e6..fba4c24ed9e6 100644 --- a/include/trace/stages/stage5_get_offsets.h +++ b/include/trace/stages/stage5_get_offsets.h @@ -39,6 +39,10 @@ #undef __string_len #define __string_len(item, src, len) __dynamic_array(char, item, (len) + 1) =20 +#undef __vstring +#define __vstring(item, fmt, ap) __dynamic_array(char, item, \ + __trace_event_vstr_len(fmt, ap)) + #undef __rel_dynamic_array #define __rel_dynamic_array(type, item, len) \ __item_length =3D (len) * sizeof(type); \ diff --git a/include/trace/stages/stage6_event_callback.h b/include/trace/s= tages/stage6_event_callback.h index e1724f73594b..0f51f6b3ab70 100644 --- a/include/trace/stages/stage6_event_callback.h +++ b/include/trace/stages/stage6_event_callback.h @@ -24,6 +24,9 @@ #undef __string_len #define __string_len(item, src, len) __dynamic_array(char, item, -1) =20 +#undef __vstring +#define __vstring(item, fmt, ap) __dynamic_array(char, item, -1) + #undef __assign_str #define __assign_str(dst, src) \ strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)"); @@ -35,6 +38,10 @@ __get_str(dst)[len] =3D '\0'; \ } while(0) =20 +#undef __assign_vstr +#define __assign_vstr(dst, fmt, va) \ + vsnprintf(__get_str(dst), TRACE_EVENT_STR_MAX, fmt, *(va)) + #undef __bitmask #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1) =20 --=20 2.35.1