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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 65FFBC64EBC for ; Thu, 4 Oct 2018 18:45:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E7672084D for ; Thu, 4 Oct 2018 18:45:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="vgOrKxK/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E7672084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727871AbeJEBkR (ORCPT ); Thu, 4 Oct 2018 21:40:17 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:35274 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727663AbeJEBkR (ORCPT ); Thu, 4 Oct 2018 21:40:17 -0400 Received: by mail-wr1-f67.google.com with SMTP id w5-v6so11035960wrt.2; Thu, 04 Oct 2018 11:45:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=L6Y9Y1jCXQH7QQjG9calOBdWeNbOMMFYVQu/Ox98vB8=; b=vgOrKxK/q2tJ7F/UCKQRnmLRUAucoC0SvgMKiHYTVchGyXsRZh1ed+VJBar9p32AKa 38tYmKFFHGFnwxapelde/IfBfLhVaLg2+FejLCn8t/jIdb7bfVN5bIKuocJzwFn4Wj/w xPbZw9yk6KCbSsYXJJgSBmfWWboelNUVlFm1VsK634/ZS8r/7VFbIYw6kd+icA4hIlIE Oyz2/jzEN9HWVnpJts4rW3i8SUAneZidarOQujBMncFEn1u1RjDI5QIUgZNCf45EHYYD r5dp5HR9LFrj3PBlWlOSrFRkaFmf7ka4q7vtCb6Db5sYoKKQq2EqfIpaj1HcG3frOoaN GZwQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=L6Y9Y1jCXQH7QQjG9calOBdWeNbOMMFYVQu/Ox98vB8=; b=AgPKjnUAzSQGLjj0tg/OU2xAATQmWbRwUmpVsc1SKLWKubq/LKpjvSOsZdc19zW4bZ gvKkRR66pr+d914PAqkntRAXGmPkVWcBwUU4I8pmup/Ned4EGZD0jWkSXWKpoKC5FnZ8 IlVz5wJlmOpAhBjmU8v7sqg+OOQuYcQl5N5XpnLGTbXUl+1hf7qu4UboGMe+DiwoXIwC Q36zO73Rk77J1ptqcXKvvx+bG1r6IKjIHdulgrKkOe/Ns8vonwMWVpdJVUsMkKB50XR8 ywlSSuFY/OcKaVolRPZU9c+26z6ciVq5DnR5npBO+QInkMcUW6WkOi/XUtJJIUBstMcL +yOg== X-Gm-Message-State: ABuFfohY+CiutVyDLy3lVl9Ihyfde4HTl7KJWS9nHSm1TyOMBV83T1Rq 0u2ilR+OQbuY/3NvUskpwW6dSNKvA0AUmw== X-Google-Smtp-Source: ACcGV61hOdwqNSBvlJajxj/pdEOmynGkdMNjQB6Zleujc4lafi4r4UuhHNvKmRJ8PZTfaArEArTI5g== X-Received: by 2002:adf:ecc9:: with SMTP id s9-v6mr5426983wro.142.1538678743514; Thu, 04 Oct 2018 11:45:43 -0700 (PDT) Received: from flashbox ([2a01:4f8:10b:24a5::2]) by smtp.gmail.com with ESMTPSA id u191-v6sm7000307wmd.31.2018.10.04.11.45.42 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Oct 2018 11:45:42 -0700 (PDT) Date: Thu, 4 Oct 2018 11:45:40 -0700 From: Nathan Chancellor To: Bart Van Assche Cc: "James E.J. Bottomley" , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Nick Desaulniers Subject: Re: -Wswitch Clang warnings in drivers/scsi Message-ID: <20181004184540.GA17513@flashbox> References: <20181004183047.GA1885@flashbox> <1538678069.230807.6.camel@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1538678069.230807.6.camel@acm.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 04, 2018 at 11:34:29AM -0700, Bart Van Assche wrote: > On Thu, 2018-10-04 at 11:30 -0700, Nathan Chancellor wrote: > > Hi SCSI folks, > > > > In an effort to get the kernel building warning free with Clang, we've > > come across an interesting occurrence in a few scsi drivers: > > > > drivers/scsi/hpsa.c:6533:7: warning: overflow converting case value to switch condition type (2148024833 to 18446744071562609153) [-Wswitch] > > case CCISS_GETPCIINFO: > > ^ > > ./include/uapi/linux/cciss_ioctl.h:65:26: note: expanded from macro 'CCISS_GETPCIINFO' > > #define CCISS_GETPCIINFO _IOR(CCISS_IOC_MAGIC, 1, cciss_pci_info_struct) > > ^ > > ./include/uapi/asm-generic/ioctl.h:86:28: note: expanded from macro '_IOR' > > #define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size))) > > ^ > > ./include/uapi/asm-generic/ioctl.h:70:2: note: expanded from macro '_IOC' > > (((dir) << _IOC_DIRSHIFT) | \ > > ^ > > > > I see this warning in drivers/scsi/hpsa.c and drivers/scsi/smartpqi/smartpqi_init.c > > on an arm64 allyesconfig build and it has also been reported in a couple of files in > > drivers/scsi/cxlflash. > > > > As the warning states, there is an overflow because the switch statement's value is of > > type int but the switch value is greater than INT_MAX. I did a brief sweep of the tree > > and it seems that all uses of _IOC in switch statement values either are small enough > > to fit into size int or the value is of size unsigned int. > > > > I am unsure of the implications of using a smaller _IOC value or converting all ioctls > > to expect a cmd of type unsigned int (especially since that has userspace implications) > > but I didn't see any negative ioctl commands. Some clarity and insight would be > > appreciated. > > Have you verified how gcc compiles these switch statements? Maybe gcc supports > switch / case statements on integral types that are larger than an int? > > Bart. Hi Bart, That is entirely possible, I will do some research. I did build with GCC to see if there was any warning and there isn't so I'll be curious to see what is happening at a lower level. Thanks for the comment! Nathan