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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, 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 4FE7EC10F03 for ; Fri, 22 Mar 2019 14:05:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A20421874 for ; Fri, 22 Mar 2019 14:05:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728093AbfCVOFQ (ORCPT ); Fri, 22 Mar 2019 10:05:16 -0400 Received: from mout.kundenserver.de ([217.72.192.75]:55721 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727487AbfCVOFQ (ORCPT ); Fri, 22 Mar 2019 10:05:16 -0400 Received: from wuerfel.lan ([149.172.19.189]) by mrelayeu.kundenserver.de (mreue106 [212.227.15.145]) with ESMTPA (Nemesis) id 1Mlejs-1ghJNm2mf4-00igkg; Fri, 22 Mar 2019 15:05:08 +0100 From: Arnd Bergmann To: Andrew Morton Cc: clang-built-linux@googlegroups.com, Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , Zhao Qiang , Yalin Wang , stable@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] bitrev: fix constant bitrev Date: Fri, 22 Mar 2019 15:04:55 +0100 Message-Id: <20190322140503.123580-1-arnd@arndb.de> X-Mailer: git-send-email 2.20.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:DjxO67pqGSmp/6OXn3JSRwKihmVX3Z6HQD8rsXRcR2QgYIGheUs 1A/SGunzMjAjCuL9pk10yL/joHa/RBrzqiF8gFGRG+pqe6MsayQLHLFPiTPyQ5I0q+W7Kct 0BLMvLUSMD89AgV7l6z5dIMS0ObsvhWlWK8KaPxLGoRboVGFxEmwsDABe/ullalPP/YAd3Z EhuYoUJN+mpe1qDOzLKgQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:Z//SUnpAaVw=:RMLFOHxNBAN5wj1JB7NMYh EAAYYml6kukoFQkDrnPEWxcmm56Xwzcs810TaF/STKKS4rBLLM7DSxpar8OIzSjg0wePPRvUF n9j8bO96nTBReKb4QAphhU/Ms/2HDNRzNrdOcRDGaVW94IkE8ik0Q0qTguICzx6Li4uqNoG1H WiDu0vCMxoBWR6vEGj8Z0Hxjnp3jhQnKJ4BTvLk2xxlA1PyWNmoj6El0G2ZX+jULukRkQ38Ez +f81FanxuYYGT9KljND87Zgvq1JiFciFW0QmSLFARXeNK9YYPyO6nLEwhTcG4f70XbHDpYs9y 99HljQsq1C6fnKJJdd14+XTz4zu0gMtSWZ6jrsXXoliCi/4+fE2xgH1rkPF1QGvPVFdzaiyRS yx6KS60m3z1M1JqYElpFCIj4kaX0vm46l4adjIaFnhi0S9EiSNeejBQM06d5oVtMmuPUjMrwp NI3G1Zl8VhRscEYalsfvCLRm3vNGb7hsBfEM+9wVk/0LN4ZL8xRnu33u7XNARnRLCgyUgHttV /F1M7A8RENahjyQd0kc8aWwU+7L8VuCNfqGPEJgveIe556dMRP0RmOSb3eDKINcSm6sDS1MDl ikTwlYy8OnaO8KkRyr4i8CmxvsQdjbPJAyN/naOV8Xo91MFizgQ0xKyGvDHBXnhPSwdMwPT6t lnQvp7bwCbE13pJIAypceEXbOogX8wn4OvIl7qMihUUbDuCuZgGlyDn3sN/USamu9R3ZVB7A6 gWwi9FrxgIxIKhTsNI+uQ2/EZ0mBvKk1xoneqg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org clang points out with hundreds of warnings that the bitrev macros have a problem with constant input: drivers/hwmon/sht15.c:187:11: error: variable '__x' is uninitialized when used within its own initialization [-Werror,-Wuninitialized] u8 crc = bitrev8(data->val_status & 0x0F); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/bitrev.h:102:21: note: expanded from macro 'bitrev8' __constant_bitrev8(__x) : \ ~~~~~~~~~~~~~~~~~~~^~~~ include/linux/bitrev.h:67:11: note: expanded from macro '__constant_bitrev8' u8 __x = x; \ ~~~ ^ Both the bitrev and the __constant_bitrev macros use an internal variable named __x, which goes horribly wrong when passing one to the other. The obvious fix is to rename one of the variables, so this adds an extra '_'. It seems we got away with this because - there are only a few drivers using bitrev macros - usually there are no constant arguments to those - when they are constant, they tend to be either 0 or (unsigned)-1 (drivers/isdn/i4l/isdnhdlc.o, drivers/iio/amplifiers/ad8366.c) and give the correct result by pure chance. In fact, the only driver that I could find that gets different results with this is drivers/net/wan/slic_ds26522.c, which in turn is a driver for fairly rare hardware (adding the maintainer to Cc for testing). Cc: Zhao Qiang Cc: Yalin Wang Cc: stable@vger.kernel.org Fixes: 556d2f055bf6 ("ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction") Signed-off-by: Arnd Bergmann --- include/linux/bitrev.h | 46 +++++++++++++++++++++--------------------- 1 file changed, 23 insertions(+), 23 deletions(-) diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h index 50fb0dee23e8..d35b8ec1c485 100644 --- a/include/linux/bitrev.h +++ b/include/linux/bitrev.h @@ -34,41 +34,41 @@ static inline u32 __bitrev32(u32 x) #define __constant_bitrev32(x) \ ({ \ - u32 __x = x; \ - __x = (__x >> 16) | (__x << 16); \ - __x = ((__x & (u32)0xFF00FF00UL) >> 8) | ((__x & (u32)0x00FF00FFUL) << 8); \ - __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4); \ - __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2); \ - __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1); \ - __x; \ + u32 ___x = x; \ + ___x = (___x >> 16) | (___x << 16); \ + ___x = ((___x & (u32)0xFF00FF00UL) >> 8) | ((___x & (u32)0x00FF00FFUL) << 8); \ + ___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4); \ + ___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2); \ + ___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1); \ + ___x; \ }) #define __constant_bitrev16(x) \ ({ \ - u16 __x = x; \ - __x = (__x >> 8) | (__x << 8); \ - __x = ((__x & (u16)0xF0F0U) >> 4) | ((__x & (u16)0x0F0FU) << 4); \ - __x = ((__x & (u16)0xCCCCU) >> 2) | ((__x & (u16)0x3333U) << 2); \ - __x = ((__x & (u16)0xAAAAU) >> 1) | ((__x & (u16)0x5555U) << 1); \ - __x; \ + u16 ___x = x; \ + ___x = (___x >> 8) | (___x << 8); \ + ___x = ((___x & (u16)0xF0F0U) >> 4) | ((___x & (u16)0x0F0FU) << 4); \ + ___x = ((___x & (u16)0xCCCCU) >> 2) | ((___x & (u16)0x3333U) << 2); \ + ___x = ((___x & (u16)0xAAAAU) >> 1) | ((___x & (u16)0x5555U) << 1); \ + ___x; \ }) #define __constant_bitrev8x4(x) \ ({ \ - u32 __x = x; \ - __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4); \ - __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2); \ - __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1); \ - __x; \ + u32 ___x = x; \ + ___x = ((___x & (u32)0xF0F0F0F0UL) >> 4) | ((___x & (u32)0x0F0F0F0FUL) << 4); \ + ___x = ((___x & (u32)0xCCCCCCCCUL) >> 2) | ((___x & (u32)0x33333333UL) << 2); \ + ___x = ((___x & (u32)0xAAAAAAAAUL) >> 1) | ((___x & (u32)0x55555555UL) << 1); \ + ___x; \ }) #define __constant_bitrev8(x) \ ({ \ - u8 __x = x; \ - __x = (__x >> 4) | (__x << 4); \ - __x = ((__x & (u8)0xCCU) >> 2) | ((__x & (u8)0x33U) << 2); \ - __x = ((__x & (u8)0xAAU) >> 1) | ((__x & (u8)0x55U) << 1); \ - __x; \ + u8 ___x = x; \ + ___x = (___x >> 4) | (___x << 4); \ + ___x = ((___x & (u8)0xCCU) >> 2) | ((___x & (u8)0x33U) << 2); \ + ___x = ((___x & (u8)0xAAU) >> 1) | ((___x & (u8)0x55U) << 1); \ + ___x; \ }) #define bitrev32(x) \ -- 2.20.0