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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 463BEC43461 for ; Wed, 16 Sep 2020 21:01:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6A49206BE for ; Wed, 16 Sep 2020 21:01:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="WFTrHxF7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726497AbgIPVB2 (ORCPT ); Wed, 16 Sep 2020 17:01:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726447AbgIPQaY (ORCPT ); Wed, 16 Sep 2020 12:30:24 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37E2DC0698D5 for ; Wed, 16 Sep 2020 04:39:59 -0700 (PDT) Received: from zn.tnic (p200300ec2f0c3e000ee699b54c433a91.dip0.t-ipconnect.de [IPv6:2003:ec:2f0c:3e00:ee6:99b5:4c43:3a91]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 892AD1EC0136; Wed, 16 Sep 2020 13:34:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1600256096; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4PTEjwjWCxnifqmay2schcOj42jghOVREf92+55yeao=; b=WFTrHxF7aRz7y3HdsqQHlVAeb4hm08P7tXBq736IBvFvIZOjHWA9xn9q1riewV2WbR9icz iiN5tWrJ/meR4p+KaiHlSbPKh+I+6uPtGCgPevihelODO0dFz3FambZKKFAwUEYD1CEt6H 4NDo7BaAFj0otmUOpYlM3d6k3MEDils= Date: Wed, 16 Sep 2020 13:34:49 +0200 From: Borislav Petkov To: Arvind Sankar Cc: Nick Desaulniers , Josh Poimboeuf , Rong Chen , kernel test robot , "Li, Philip" , x86-ml , LKML , clang-built-linux , Marco Elver Subject: Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e Message-ID: <20200916113449.GH2643@zn.tnic> References: <5f60c4e0.Ru0MTgSE9A7mqhpG%lkp@intel.com> <20200915135519.GJ14436@zn.tnic> <20200915141816.GC28738@shao2-debian> <20200915160554.GN14436@zn.tnic> <20200915170248.gcv54pvyckteyhk3@treble> <20200915204912.GA14436@zn.tnic> <20200915215054.GA1104608@rani.riverdale.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200915215054.GA1104608@rani.riverdale.lan> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 15, 2020 at 05:50:54PM -0400, Arvind Sankar wrote: > On Tue, Sep 15, 2020 at 10:49:12PM +0200, Borislav Petkov wrote: > > > > (Btw, clang doesn't need to add that "xor %eax,%eax" - panic() should not be > > returning, ever. :-)) > > > > I think this is because panic() is varargs, and clang doesn't support > gcc's -mskip-rax-setup. The normal ABI requires the caller to set RAX to > the number of arguments in vector registers. > > https://patchwork.ozlabs.org/project/gcc/patch/20141218131150.GA32638@intel.com/ Ah, good point. Found this in the ABI doc: "For calls that may call functions that use varargs or stdargs (prototype-less calls or calls to functions containing ellipsis (...) in the declaration) %al is used as hidden argument to specify the number of vector registers used. The contents of %al do not need to match exactly the number of registers, but must be an upper bound on the number of vector registers used and is in the range 0–8 inclusive." Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette