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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS 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 47CB7C43381 for ; Wed, 20 Feb 2019 11:18:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22B6D205F4 for ; Wed, 20 Feb 2019 11:18:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727947AbfBTLSu (ORCPT ); Wed, 20 Feb 2019 06:18:50 -0500 Received: from ozlabs.org ([203.11.71.1]:36755 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727157AbfBTLSp (ORCPT ); Wed, 20 Feb 2019 06:18:45 -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 444FTs4sxKz9s71; Wed, 20 Feb 2019 22:18:41 +1100 (AEDT) From: Michael Ellerman To: Segher Boessenkool Cc: Balbir Singh , 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: <20190219201539.GT14180@gate.crashing.org> References: <20190214062339.7139-1-mpe@ellerman.id.au> <20190216105511.GA31125@350D> <20190216142206.GE14180@gate.crashing.org> <20190217062333.GC31125@350D> <87ef86dd9v.fsf@concordia.ellerman.id.au> <20190217215556.GH31125@350D> <87imxhrkdt.fsf@concordia.ellerman.id.au> <20190219201539.GT14180@gate.crashing.org> Date: Wed, 20 Feb 2019 22:18:38 +1100 Message-ID: <87sgwi7lo1.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: > On Mon, Feb 18, 2019 at 11:49:18AM +1100, Michael Ellerman wrote: >> Balbir Singh writes: >> > Fair enough, my point was that the compiler can help out. I'll see what >> > -Wconversion finds on my local build :) >> >> I get about 43MB of warnings here :) > > Yes, -Wconversion complains about a lot of things that are idiomatic C. > There is a reason -Wconversion is not in -Wall or -Wextra. Actually a lot of those go away when I add -Wno-sign-conversion. And what's left seems mostly reasonable, they all indicate the possibility of a bug I think. In fact this works and would have caught the bug: diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index d8c8d7c9df15..3114e3f368e2 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -904,7 +904,12 @@ static inline int pud_none(pud_t pud) static inline int pud_present(pud_t pud) { + __diag_push(); + __diag_warn(GCC, 8, "-Wconversion", "ulong -> int"); + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT)); + + __diag_pop(); } extern struct page *pud_page(pud_t pud); Obviously we're not going to instrument every function like that. But we could start instrumenting particular files. cheers