From nobody Mon Sep 8 19:00:54 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 EAC8CC6FA8E for ; Sun, 26 Feb 2023 17:31:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229786AbjBZRbE (ORCPT ); Sun, 26 Feb 2023 12:31:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229379AbjBZRbC (ORCPT ); Sun, 26 Feb 2023 12:31:02 -0500 Received: from msg-4.mailo.com (msg-4.mailo.com [213.182.54.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4EF339EDA; Sun, 26 Feb 2023 09:31:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1677432612; bh=kbszH9m85sjV1+wRhwLfMuDJ81RvA1n+6wdLTFkDGHo=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:In-Reply-To; b=b9UBNZ3njp8Q3JxreIHTwITHrQVDR5FqkhQQgBQI5MIM+qV1/s6YGDpcEcG1dY4FC +caKAGNEmnVgLOp1dOsLWwolhIIQlWDcmTsRLf5Jsn/amajpVnXTw6Q94/sZlWQ3or jZ4VmXylgjA8dicOsY3IIx4aevc2twnZv+UvBApo= Received: by b-4.in.mailobj.net [192.168.90.14] with ESMTP via ip-206.mailobj.net [213.182.55.206] Sun, 26 Feb 2023 18:30:12 +0100 (CET) X-EA-Auth: XhjWn0297xPJSHS7FHXDD0OmaaUOkOqIx9ectiF4tFqsu0nxWKVrOT/JDOqNFYoDmelxxAbqRdV2V6eLAfm1h82mL63nuXtZ Date: Sun, 26 Feb 2023 23:00:06 +0530 From: Deepak R Varma To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v3 1/3] perf/x86/core: Use sysfs_emit() in show() callback function Message-ID: <4fa04945ae4b6ee35943da25c6b75dbcaeaf6af0.1677431992.git.drv@mailo.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As per C99 standard, snprintf() returns the number of bytes that would be encoded in the destination buffer when it is sufficiently large. This return value may be different from what the caller is expecting and hence may lead to potential errors in the program. Kernel release 2.6.2 introduced scnprintf() & vscnprintf() which precisely return the actual bytes encoded into the destination buffer. For the sysfs attribute show() callback functions, which returns the number of bytes to the user space, a more recent recommendation is to use sysfs_emit() or sysfs_emit_at() instead of sprintf() family of functions. This is recorded in the Documentation/filesystems/sysfs.rst Kernel documentation file. Issue identified using the coccinelle device_attr_show.cocci script. Signed-off-by: Deepak R Varma --- Changes in v3: - Remove incorrect/erroneous change proposed. Feedback provided by Peter Zijlstra Changes in v2: - Revise patch log message to include details on the potential issues wi= th current implementation and how the proposal is a better solution. Feedback provided by Peter Zijlstra arch/x86/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index d096b04bf80e..87a7f0cd77fd 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2544,7 +2544,7 @@ static ssize_t get_attr_rdpmc(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, 40, "%d\n", x86_pmu.attr_rdpmc); + return sysfs_emit(buf, "%d\n", x86_pmu.attr_rdpmc); } =20 static ssize_t set_attr_rdpmc(struct device *cdev, @@ -2602,7 +2602,7 @@ static ssize_t max_precise_show(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, PAGE_SIZE, "%d\n", x86_pmu_max_precise()); + return sysfs_emit(buf, "%d\n", x86_pmu_max_precise()); } =20 static DEVICE_ATTR_RO(max_precise); --=20 2.34.1 From nobody Mon Sep 8 19:00:54 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 C5C88C64ED6 for ; Sun, 26 Feb 2023 17:31:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229737AbjBZRbs (ORCPT ); Sun, 26 Feb 2023 12:31:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbjBZRbq (ORCPT ); Sun, 26 Feb 2023 12:31:46 -0500 Received: from msg-2.mailo.com (msg-2.mailo.com [213.182.54.12]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 474F610A9A; Sun, 26 Feb 2023 09:31:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1677432661; bh=FUv+i389hmPzzyl//w0rLznwQlGkudoXVMjLfF5PGXs=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:In-Reply-To; b=GFUPRG+Uvy0YHGbBCmEAosqIphTiWbVTfiBnDz4WjsWj3fj30lIii5ZSTxIvwW2At fkaCPdvwpCJN2UGXFo5S+J7d1GMBH0/nBrhVQb/npTJqQr00nUxffvP8917/D6s8hd GcLPJdsJLnPbCGQK1nHqIhzHoR6E1YeICidJ75xk= Received: by b-3.in.mailobj.net [192.168.90.13] with ESMTP via ip-206.mailobj.net [213.182.55.206] Sun, 26 Feb 2023 18:31:01 +0100 (CET) X-EA-Auth: UYA4gYz7D9V2aFReAIXs4riiAX7Stq0WbKggzsV7kUiYzpjS12D0Vt3vktvYVHBFlAZJKQGg6WS8Pw6M1Vf/bVe10ieV+Rw9 Date: Sun, 26 Feb 2023 23:00:56 +0530 From: Deepak R Varma To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v3 2/3] perf/x86/intel/pt: Use sysfs_emit() in show() callback function Message-ID: <75e2b1f55156d8341e722eb923c9304a13def2b2.1677431992.git.drv@mailo.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As per C99 standard, snprintf() returns the number of bytes that would be encoded in the destination buffer when it is sufficiently large. This return value may be different from what the caller is expecting and hence may lead to potential errors in the program. Kernel release 2.6.2 introduced scnprintf() & vscnprintf() which precisely return the actual bytes encoded into the destination buffer. For the sysfs attribute show() callback functions, which returns the number of bytes to the user space, a more recent recommendation is to use sysfs_emit() or sysfs_emit_at() instead of sprintf() family of functions. This is recorded in the Documentation/filesystems/sysfs.rst Kernel documentation file. Issue identified using the coccinelle device_attr_show.cocci script. Signed-off-by: Deepak R Varma --- Changes in v3: - None. Changes in v2: - Revise patch log message to include details on the potential issues wi= th current implementation and how the proposal is a better solution. Feedback provided by Peter Zijlstra arch/x86/events/intel/pt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 42a55794004a..d9e6d771b458 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -96,7 +96,7 @@ static ssize_t pt_cap_show(struct device *cdev, container_of(attr, struct dev_ext_attribute, attr); enum pt_capabilities cap =3D (long)ea->var; =20 - return snprintf(buf, PAGE_SIZE, "%x\n", intel_pt_validate_hw_cap(cap)); + return sysfs_emit(buf, "%x\n", intel_pt_validate_hw_cap(cap)); } =20 static struct attribute_group pt_cap_group __ro_after_init =3D { --=20 2.34.1 From nobody Mon Sep 8 19:00:54 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 CC99FC6FA8E for ; Sun, 26 Feb 2023 17:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229751AbjBZRcQ (ORCPT ); Sun, 26 Feb 2023 12:32:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58000 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229790AbjBZRcO (ORCPT ); Sun, 26 Feb 2023 12:32:14 -0500 Received: from msg-1.mailo.com (msg-1.mailo.com [213.182.54.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45B9613DC1; Sun, 26 Feb 2023 09:32:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1677432705; bh=G3YJe+kKHyMy1tZ4zRvdixDsMk9Nsq26rrWMIw2P9PI=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:In-Reply-To; b=WWmwd75Wg7zo53mZy7rXFj9vSaArWZ5y7XT49N3fcen580mffuBOYc5ni7X5XCP5x 8p/Jy/cUbIqKH+zgxX7de8COpLf+lTNbRI2XiCWLAp4tbI/K8US2qZSZZvR5G3yu15 +VyuLLK+JicyVq5YZyyBT99uaGGD0iRodSdGDwSU= Received: by b-3.in.mailobj.net [192.168.90.13] with ESMTP via ip-206.mailobj.net [213.182.55.206] Sun, 26 Feb 2023 18:31:45 +0100 (CET) X-EA-Auth: pRYlgKORJEAre/qpX2WFvfeHJfJwl+ydoWZtKitRbEvAfMuTYx5eU4HewOUNtO0sQwssNeMGNKTBHEGOccQrbsaQXUWczipn Date: Sun, 26 Feb 2023 23:01:39 +0530 From: Deepak R Varma To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v3 3/3] perf/x86/intel: Use sysfs_emit() in show() callback function Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As per C99 standard, snprintf() returns the number of bytes that would be encoded in the destination buffer when it is sufficiently large. This return value may be different from what the caller is expecting and hence may lead to potential errors in the program. Kernel release 2.6.2 introduced scnprintf() & vscnprintf() which precisely return the actual bytes encoded into the destination buffer. For the sysfs attribute show() callback functions, which returns the number of bytes to the user space, a more recent recommendation is to use sysfs_emit() or sysfs_emit_at() instead of sprintf() family of functions. This is recorded in the Documentation/filesystems/sysfs.rst Kernel documentation file. Issue identified using the coccinelle device_attr_show.cocci script. Signed-off-by: Deepak R Varma --- Changes in v3: - None. Changes in v2: - Revise patch log message to include details on the potential issues wi= th current implementation and how the proposal is a better solution. Feedback provided by Peter Zijlstra arch/x86/events/intel/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 9fce2d1247a7..75ab89ff3a0f 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -5387,7 +5387,7 @@ static ssize_t show_sysctl_tfa(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, 40, "%d\n", allow_tsx_force_abort); + return sysfs_emit(buf, "%d\n", allow_tsx_force_abort); } =20 static ssize_t set_sysctl_tfa(struct device *cdev, @@ -5421,7 +5421,7 @@ static ssize_t branches_show(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, PAGE_SIZE, "%d\n", x86_pmu.lbr_nr); + return sysfs_emit(buf, "%d\n", x86_pmu.lbr_nr); } =20 static DEVICE_ATTR_RO(branches); @@ -5437,7 +5437,7 @@ static ssize_t pmu_name_show(struct device *cdev, struct device_attribute *attr, char *buf) { - return snprintf(buf, PAGE_SIZE, "%s\n", pmu_name_str); + return sysfs_emit(buf, "%s\n", pmu_name_str); } =20 static DEVICE_ATTR_RO(pmu_name); --=20 2.34.1