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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4B350C43381 for ; Fri, 22 Mar 2019 05:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22C8B218E2 for ; Fri, 22 Mar 2019 05:23:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727802AbfCVFX2 (ORCPT ); Fri, 22 Mar 2019 01:23:28 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45666 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727516AbfCVFXQ (ORCPT ); Fri, 22 Mar 2019 01:23:16 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1h7Ce9-000161-PH; Fri, 22 Mar 2019 05:23:13 +0000 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1h7Ce9-0001or-Jn; Fri, 22 Mar 2019 05:23:13 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Jiri Kosina" , "Rasmus Villemoes" Date: Fri, 22 Mar 2019 05:20:18 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 09/16] HID: debug: improve hid_debug_event() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.64-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Rasmus Villemoes commit 92529623d242cea4440958d7bcebdf291f4ab15e upstream. The code in hid_debug_event() causes horrible code generation. First, we do a strlen() call for every byte we copy (we're doing a store to global memory, so gcc has no way of proving that strlen(buf) doesn't change). Second, since both i, list->tail and HID_DEBUG_BUFSIZE have signed type, the modulo computation has to take into account the possibility that list->tail+i is negative, so it's not just a simple and. Fix the former by simply not doing strlen() at all (we have to load buf[i] anyway, so testing it is almost free) and the latter by changing i to unsigned. This cuts 29% (69 bytes) of the size of the function. Signed-off-by: Rasmus Villemoes Signed-off-by: Jiri Kosina Signed-off-by: Ben Hutchings --- drivers/hid/hid-debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -658,13 +658,13 @@ EXPORT_SYMBOL_GPL(hid_dump_device); /* enqueue string to 'events' ring buffer */ void hid_debug_event(struct hid_device *hdev, char *buf) { - int i; + unsigned i; struct hid_debug_list *list; unsigned long flags; spin_lock_irqsave(&hdev->debug_list_lock, flags); list_for_each_entry(list, &hdev->debug_list, node) { - for (i = 0; i < strlen(buf); i++) + for (i = 0; buf[i]; i++) list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] = buf[i]; list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;