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=-5.5 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no 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 765A8C07E94 for ; Fri, 4 Jun 2021 08:25:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A39861411 for ; Fri, 4 Jun 2021 08:25:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230050AbhFDI1X convert rfc822-to-8bit (ORCPT ); Fri, 4 Jun 2021 04:27:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:60020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230044AbhFDI1W (ORCPT ); Fri, 4 Jun 2021 04:27:22 -0400 Received: from jic23-huawei (cpc108967-cmbg20-2-0-cust86.5-4.cable.virginm.net [81.101.6.87]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AFBB96140F; Fri, 4 Jun 2021 08:25:34 +0000 (UTC) Date: Fri, 4 Jun 2021 09:27:20 +0100 From: Jonathan Cameron To: Joe Perches Cc: linux-iio@vger.kernel.org, Andrew Morton , Arnd Bergmann , Andy Shevchenko , Jonathan Cameron , LKML Subject: Re: General kernel misuse of vsnprintf SPECIAL %# (was: Re: [PATCH v2 0/4] iio: Drop use of %hhx and %hx format strings) Message-ID: <20210604092720.5b59319b@jic23-huawei> In-Reply-To: <7a7e5cf61177b168f465f2502fde7a1e04293063.camel@perches.com> References: <20210603180612.3635250-1-jic23@kernel.org> <9499203f1e993872b384aabdec59ac223a8ab931.camel@perches.com> <20210603202546.0d12e7ad@jic23-huawei> <7a7e5cf61177b168f465f2502fde7a1e04293063.camel@perches.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Thu, 03 Jun 2021 12:34:28 -0700 Joe Perches wrote: > On Thu, 2021-06-03 at 20:25 +0100, Jonathan Cameron wrote: > > On Thu, 03 Jun 2021 11:58:15 -0700 Joe Perches wrote: > > > It looks to me as though %# is relatively commonly misused in the kernel. > > > > > > Pehaps for the decimal portion of the format, checkpatch could have some > > > test for use of non-standard lengths. > > > > > > Given the use is generally meant for a u8, u16, u32, or u64, perhaps > > > checkpatch should emit a warning whenever the length is not 4, 6, 10, or 18. > > > > Would have saved me some trouble, so I'm definitely in favour of checkpatch > > catching this. > > > > I wonder if a better option is to match on 1, 2, 4, 8, 16 as likely to be > > caused by people getting the usage wrong rather than a deliberate attempt > > to pretty print something a little unusual? > > Dunno. %#0x and %x[123] seems pretty silly as it'll always emit the number > of digits in the value. Good point for those two cases - definitely want to catch them. > > There aren't too many other odd uses other than those. Perhaps you are right - after all anyone who is deliberately doing something unusual will know they are doing it and can ignore the checkpatch warning. Not as though it's going to happen very often from your stats below - looks like maybe 17 of those cases 'might' be deliberate. Jonathan > > > > $ git grep -P -h -o '%#\d+\w+' | sort | uniq -c | sort -rn > > 8 and 16 are perhaps commonly misused. > > >     392 %#08x > > >      17 %#08lx > > >       9 %#08zx > > >       6 %#8x > > >       4 %#08llx > > >       1 %#8lx > > >       1 %#08 > > > >       7 %#16llx > > >       5 %#16 > > >       4 %#016Lx > > >       1 %#16x > > >       1 %#16lx > > These are the odd ones: > > > >     144 %#02x > > >      27 %#0x > > >      23 %#2x > > >      17 %#3lx > > >      15 %#3x > > >      14 %#03x > > >       6 %#012llx > > >       4 %#05x > > >       4 %#02X > > >       3 %#01x > > >       2 %#09x > > >       2 %#05lx > > >       1 %#5x > > >       1 %#5lx > > >       1 %#2Lx > > >       1 %#2llx > > >       1 %#12x > > >       1 %#0lx > > >       1 %#05llx > > >       1 %#03X > >