From patchwork Mon May 27 09:43:19 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jani Nikula X-Patchwork-Id: 13674965 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2D312C25B7C for ; Mon, 27 May 2024 09:43:37 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7FE7810F9DB; Mon, 27 May 2024 09:43:35 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="NTd9Ovw7"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0339510F9DA; Mon, 27 May 2024 09:43:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1716803012; x=1748339012; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=V7W+PZvSNN60O9e3tJb1hk9bjQ3NW3P32Xw/JTV/pUQ=; b=NTd9Ovw7NLmfLq1ecFQNsFE/0AtFsx2+RCxV8ry2nU+D2e9fNiZl0ilX kzxnI673QTMZ9sChTpU0oElTDYiqaHCa1H1RCitDonYo2tIQWFhVZ1hUN UjVQ5ZXSB52tmcr1dFfknp+qTgoHfNv+SalOM4ehIy6Ctz8M2/oagYmou DHnGXKInJgiu5YktXSZWmB/cdCKJL81JxAP0T8bU/DWvZprZyvgi+mb4M 4JT0WYDUD6ozZjWYYZ7m/80Ifww9DzFht2U3PizrBje6kpO2o693PN7iG GYpGrktKDEoujiWknNTMi526Ow81+PrIywLex+Ibq4AJmUI7TT7eAN3r0 g==; X-CSE-ConnectionGUID: gu+GO2FdQY6CoX53UeLXFw== X-CSE-MsgGUID: ggc55xGlQx2VGFrfuragOg== X-IronPort-AV: E=McAfee;i="6600,9927,11084"; a="30621981" X-IronPort-AV: E=Sophos;i="6.08,192,1712646000"; d="scan'208";a="30621981" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2024 02:43:31 -0700 X-CSE-ConnectionGUID: AwnyfvCXQgWn9JMdt8o7SA== X-CSE-MsgGUID: YJPCK6WAQ8a7+D1XJxu9CA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,192,1712646000"; d="scan'208";a="35187606" Received: from lfiedoro-mobl.ger.corp.intel.com (HELO localhost) ([10.245.246.200]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 May 2024 02:43:28 -0700 From: Jani Nikula To: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Cc: intel-gfx@lists.freedesktop.org, jani.nikula@intel.com, Kees Cook , Andy Shevchenko Subject: [PATCH 1/2] string: add mem_is_zero() helper to check if memory area is all zeros Date: Mon, 27 May 2024 12:43:19 +0300 Message-Id: <20240527094320.2653177-1-jani.nikula@intel.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Almost two thirds of the memchr_inv() usages check if the memory area is all zeros, with no interest in where in the buffer the first non-zero byte is located. Checking for !memchr_inv(s, 0, n) is also not very intuitive or discoverable. Add an explicit mem_is_zero() helper for this use case. Signed-off-by: Jani Nikula --- Cc: Kees Cook Cc: Andy Shevchenko --- include/linux/string.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index 60168aa2af07..3da305dab927 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -279,6 +279,18 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt) void *memchr_inv(const void *s, int c, size_t n); char *strreplace(char *str, char old, char new); +/** + * mem_is_zero - Check if an area of memory is all 0's. + * @s: The memory area + * @n: The size of the area + * + * Return: True if the area of memory is all 0's. + */ +static inline bool mem_is_zero(const void *s, size_t n) +{ + return !memchr_inv(s, 0, n); +} + extern void kfree_const(const void *x); extern char *kstrdup(const char *s, gfp_t gfp) __malloc;