From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03B4CC2D0BF for ; Tue, 10 Dec 2019 21:12:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C38432077B for ; Tue, 10 Dec 2019 21:12:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576012327; bh=itWihxWxovXnJNR9Dz5lHXRgZXTfMWzOkcG76mDc7sE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=R2sxBhq21p/uh+5GOQrVq5d96WCfJGGaLF9SJGHZz+lkWYUpB/EIGMdbKVtloShs2 uMZBtDEfIF9HWIuGbZl85XVoLOQgHGbwAbAYBV6PEu9Ow/EMkp6ujEqchZtJRQt/T5 FCPPUrFE1Zq3ojsAYZa41Slv1ZBon+iJ7xKAfOck= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728648AbfLJVMH (ORCPT ); Tue, 10 Dec 2019 16:12:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:35174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728868AbfLJVLz (ORCPT ); Tue, 10 Dec 2019 16:11:55 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1344B246BE; Tue, 10 Dec 2019 21:11:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576012314; bh=itWihxWxovXnJNR9Dz5lHXRgZXTfMWzOkcG76mDc7sE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P4jT5g1qRANmitOcSYsmGKF27/NlC+UmMoW+G6KxdsD/nH7h0wQK6GiJyCCYcY+wU vq1JKysx4EBDKoyjFnriHRmBNWZOZFzZewdstAKrlhtXELvRmsT/g/J1/fa8QF9VnQ lJa20wDIJMG/31pTHyL+UAQeVRm6Poi//12+DJpU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Andrew Jeffery , Joel Stanley , Greg Kroah-Hartman , Sasha Levin , linux-fsi@lists.ozlabs.org Subject: [PATCH AUTOSEL 5.4 249/350] fsi: core: Fix small accesses and unaligned offsets via sysfs Date: Tue, 10 Dec 2019 16:05:54 -0500 Message-Id: <20191210210735.9077-210-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191210210735.9077-1-sashal@kernel.org> References: <20191210210735.9077-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrew Jeffery [ Upstream commit 9f4c2b516b4f031e3cd0e45957f4150b3c1a083d ] Subtracting the offset delta from four-byte alignment lead to wrapping of the requested length where `count` is less than `off`. Generalise the length handling to enable and optimise aligned access sizes for all offset and size combinations. The new formula produces the following results for given offset and count values: offset count | length --------------+------- 0 1 | 1 0 2 | 2 0 3 | 2 0 4 | 4 0 5 | 4 1 1 | 1 1 2 | 1 1 3 | 1 1 4 | 1 1 5 | 1 2 1 | 1 2 2 | 2 2 3 | 2 2 4 | 2 2 5 | 2 3 1 | 1 3 2 | 1 3 3 | 1 3 4 | 1 3 5 | 1 We might need something like this for the cfam chardevs as well, for example we don't currently implement any alignment restrictions / handling in the hardware master driver. Signed-off-by: Andrew Jeffery Signed-off-by: Joel Stanley Link: https://lore.kernel.org/r/20191108051945.7109-6-joel@jms.id.au Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/fsi/fsi-core.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index 1f76740f33b6f..9282239b4d959 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -544,6 +544,31 @@ static int fsi_slave_scan(struct fsi_slave *slave) return 0; } +static unsigned long aligned_access_size(size_t offset, size_t count) +{ + unsigned long offset_unit, count_unit; + + /* Criteria: + * + * 1. Access size must be less than or equal to the maximum access + * width or the highest power-of-two factor of offset + * 2. Access size must be less than or equal to the amount specified by + * count + * + * The access width is optimal if we can calculate 1 to be strictly + * equal while still satisfying 2. + */ + + /* Find 1 by the bottom bit of offset (with a 4 byte access cap) */ + offset_unit = BIT(__builtin_ctzl(offset | 4)); + + /* Find 2 by the top bit of count */ + count_unit = BIT(8 * sizeof(unsigned long) - 1 - __builtin_clzl(count)); + + /* Constrain the maximum access width to the minimum of both criteria */ + return BIT(__builtin_ctzl(offset_unit | count_unit)); +} + static ssize_t fsi_slave_sysfs_raw_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) @@ -559,8 +584,7 @@ static ssize_t fsi_slave_sysfs_raw_read(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += read_len) { - read_len = min_t(size_t, count, 4); - read_len -= off & 0x3; + read_len = aligned_access_size(off, count - total_len); rc = fsi_slave_read(slave, off, buf + total_len, read_len); if (rc) @@ -587,8 +611,7 @@ static ssize_t fsi_slave_sysfs_raw_write(struct file *file, return -EINVAL; for (total_len = 0; total_len < count; total_len += write_len) { - write_len = min_t(size_t, count, 4); - write_len -= off & 0x3; + write_len = aligned_access_size(off, count - total_len); rc = fsi_slave_write(slave, off, buf + total_len, write_len); if (rc) -- 2.20.1