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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE3E0C433F5 for ; Sat, 8 Oct 2022 07:33:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0FDDE6B0072; Sat, 8 Oct 2022 03:33:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AECE6B0073; Sat, 8 Oct 2022 03:33:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E91926B0074; Sat, 8 Oct 2022 03:33:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id D71376B0072 for ; Sat, 8 Oct 2022 03:33:14 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 8978B16046B for ; Sat, 8 Oct 2022 07:33:14 +0000 (UTC) X-FDA: 79996966308.20.17228AF Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by imf13.hostedemail.com (Postfix) with ESMTP id B64C320022 for ; Sat, 8 Oct 2022 07:33:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=inria.fr; s=dc; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=zZQ88pPgtouR86lBpg+x1aw/csf1v9uxp8peXKk1cb0=; b=j3ST7SGnTYT/Y5wi6lWHZVyoTN6fTohW3n4oD0o9maLZmdhUccDAwXNB CrIK4oBY5dqegOsWJRE3rrwkzrofbuFPsdX2RZ0LPGmouitc76P+QhHmS HaFrH+aHq9cCtdo04t374NKt8+gA8QS7/hDJOozImMV5dxKm1CxmPsJ2W U=; X-IronPort-AV: E=Sophos;i="5.95,169,1661810400"; d="scan'208";a="56593050" Received: from 51.123.68.85.rev.sfr.net (HELO hadrien) ([85.68.123.51]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Oct 2022 09:33:09 +0200 Date: Sat, 8 Oct 2022 09:33:08 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: Kees Cook cc: "Jason A. Donenfeld" , linux-kernel@vger.kernel.org, patches@lists.linux.dev, Andreas Noever , Andrew Morton , Andy Shevchenko , Borislav Petkov , Catalin Marinas , =?ISO-8859-15?Q?Christoph_B=F6hmwalder?= , Christoph Hellwig , Christophe Leroy , Daniel Borkmann , Dave Airlie , Dave Hansen , "David S. Miller" , Eric Dumazet , Florian Westphal , Greg Kroah-Hartman , "H. Peter Anvin" , Heiko Carstens , Helge Deller , Herbert Xu , Huacai Chen , Hugh Dickins , Jakub Kicinski , "James E. J. Bottomley" , Jan Kara , Jason Gunthorpe , Jens Axboe , Johannes Berg , Jonathan Corbet , Jozsef Kadlecsik , KP Singh , Marco Elver , Mauro Carvalho Chehab , Michael Ellerman , Pablo Neira Ayuso , Paolo Abeni , Peter Zijlstra , Richard Weinberger , Russell King , Theodore Ts'o , Thomas Bogendoerfer , Thomas Gleixner , Thomas Graf , Ulf Hansson , Vignesh Raghavendra , WANG Xuerui , Will Deacon , Yury Norov , dri-devel@lists.freedesktop.org, kasan-dev@googlegroups.com, kernel-janitors@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-mmc@vger.kernel.org, linux-mtd@lists.infradead.org, linux-nvme@lists.infradead.org, linux-parisc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, linux-um@lists.infradead.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, netdev@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, Jan Kara Subject: Re: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible In-Reply-To: <53DD0148-ED15-4294-8496-9E4B4C7AD061@chromium.org> Message-ID: References: <53DD0148-ED15-4294-8496-9E4B4C7AD061@chromium.org> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1665214394; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=zZQ88pPgtouR86lBpg+x1aw/csf1v9uxp8peXKk1cb0=; b=2gyXfd0UHJnURjYLOJodw+w7WS5TxQxJ8trV2IV28E/g/dR7JRywnPusOfXZF5aKxayObS Ck+yO2vZNiDrQa/F9P8JUi3937+HYYt4v96lGC4fxFGOrNWKfH3VfGRYxLr9yVBfqjSAXn 2/e8XZTWI4yBaCFmn9BTa0UDUDDL7k0= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=inria.fr header.s=dc header.b=j3ST7SGn; spf=pass (imf13.hostedemail.com: domain of julia.lawall@inria.fr designates 192.134.164.83 as permitted sender) smtp.mailfrom=julia.lawall@inria.fr; dmarc=pass (policy=none) header.from=inria.fr ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665214394; a=rsa-sha256; cv=none; b=KwsFKHVvhvFe62dmQzvNWCl2Tlj3PfRw3GTV/R4rNoT/bpvtDABBcRHR6Ey65w5jUWb3he VOfKDGzI/3Rmr0yHpZzhgXPRK/6kOBU6/06joxAmSH5b0MlwJAZoW/YIBorD9J7mmDD4OW vEY0BN739wGIK+GSN7ji+A84mESbcs8= X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B64C320022 X-Stat-Signature: odwyh4fjtjfy9bxobm687m3aruupd7ak Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=inria.fr header.s=dc header.b=j3ST7SGn; spf=pass (imf13.hostedemail.com: domain of julia.lawall@inria.fr designates 192.134.164.83 as permitted sender) smtp.mailfrom=julia.lawall@inria.fr; dmarc=pass (policy=none) header.from=inria.fr X-HE-Tag: 1665214393-508438 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > >> @minus_one@ > >> expression FULL; > >> @@ > >> > >> - (get_random_int() & ((FULL) - 1) > >> + prandom_u32_max(FULL) > > > >Ahh, well, okay, this is the example I mentioned above. Only works if > >FULL is saturated. Any clever way to get coccinelle to prove that? Can > >it look at the value of constants? > > I'm not sure if Cocci will do that without a lot of work. The literals trick I used below would need a lot of fanciness. :) If FULL is an arbitrary expression, it would not be easy to automate. If it is a constant then you can use python/ocaml to analyze its value. But if it's a #define constant then you would need a previous rule to match the #define and find that value. For LITERAL, I think you could just do constant int LITERAL; for the metavariable declaration. julia