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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 80D2AC43381 for ; Sun, 17 Feb 2019 08:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58C262075C for ; Sun, 17 Feb 2019 08:34:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726501AbfBQIej (ORCPT ); Sun, 17 Feb 2019 03:34:39 -0500 Received: from ozlabs.org ([203.11.71.1]:40759 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725768AbfBQIej (ORCPT ); Sun, 17 Feb 2019 03:34:39 -0500 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 442Kzx30D5z9sLw; Sun, 17 Feb 2019 19:34:37 +1100 (AEDT) From: Michael Ellerman To: Segher Boessenkool , Balbir Singh Cc: erhard_f@mailbox.org, jack@suse.cz, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, aneesh.kumar@linux.vnet.ibm.com Subject: Re: [PATCH] powerpc/64s: Fix possible corruption on big endian due to pgd/pud_present() In-Reply-To: <20190216142206.GE14180@gate.crashing.org> References: <20190214062339.7139-1-mpe@ellerman.id.au> <20190216105511.GA31125@350D> <20190216142206.GE14180@gate.crashing.org> Date: Sun, 17 Feb 2019 19:34:36 +1100 Message-ID: <87bm3add9f.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Segher Boessenkool writes: > Hi all, > > On Sat, Feb 16, 2019 at 09:55:11PM +1100, Balbir Singh wrote: >> On Thu, Feb 14, 2019 at 05:23:39PM +1100, Michael Ellerman wrote: >> > In v4.20 we changed our pgd/pud_present() to check for _PAGE_PRESENT >> > rather than just checking that the value is non-zero, e.g.: >> > >> > static inline int pgd_present(pgd_t pgd) >> > { >> > - return !pgd_none(pgd); >> > + return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); >> > } >> > >> > Unfortunately this is broken on big endian, as the result of the >> > bitwise && is truncated to int, which is always zero because > > (Bitwise "&" of course). Thanks, I fixed that up. cheers