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=-11.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 9CB24C433E2 for ; Wed, 16 Sep 2020 18:33:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65D70206B5 for ; Wed, 16 Sep 2020 18:33:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="UJn3OxXs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727999AbgIPSdw (ORCPT ); Wed, 16 Sep 2020 14:33:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728006AbgIPS3r (ORCPT ); Wed, 16 Sep 2020 14:29:47 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BECB8C061756 for ; Wed, 16 Sep 2020 11:28:38 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id g29so4406973pgl.2 for ; Wed, 16 Sep 2020 11:28:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=+hNBdZ8eBcNPHlpjzcCHTGcOrY0T16QrOvnANJBRf5g=; b=UJn3OxXsgeR+LsCuSfNvXya9vhUOiyVdyMak20SRdAJqfk4AROUrO28wc/DqxY8j7R CD4QVJWEtv/kXlII7emMwzIFLCimmiU/Bapwbn+Y0W+d6n4ErcWsunM0nJESM9l5QcOZ ZB0pT/qSF4Jq4eNKZGM2L3Q3Sk6E57zTnnlsciK2u2iCT5eOIqhuhvEvFnJjavicYMRa eMy3Z/w+8uL8SXMPdBkmVcwGekPw16ASzESxcOzCWKvYctse2wso8g/x5vAuDfm2O5r9 jEHE5+FtbNdSCayMdpS9h7lg0eboE2dQWDFev3WbXUyTMwAuyoMk3X7V9m09RabM4Gl/ dUNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=+hNBdZ8eBcNPHlpjzcCHTGcOrY0T16QrOvnANJBRf5g=; b=p4Xq2FQaPad015qsBr1YfvgsA2rdYejFT/tUFCXPdRLfbYyMTEKj2a53PX+sAIeJ8Q 7bMNrPjteQKfaQeFGqZcPOJpFB6JrPuQsdJawhGbcvJhiZkLC7qNv9KlivqqY65wsv2u fCg0xlxmeml2WFF9AhE7anVT7ows9841hvAyQDk2DNTGXWcOz50gcdVz0HGZtRasQ9lY /3tmxzGYtCQJpO1Lv5mSR54mJDFv01Dvegfxv1PuJ0RLdk3+6ZWloR+BUgkjywtzTWxo 4TK8wB0ZGHvtL3pW7agfLCWkDDpqzW3TtOvu6i6HPPAuRtF192sJVBNcbPVr2Hz/HY8D ehsA== X-Gm-Message-State: AOAM532SDE0If+UIX13z6hnUEbLMxLErtNcDhghbK965azXmn17poStN CTbFahQ+naXE4G1MXM+XLMW93jKUU76CRnc8OC5u9g== X-Google-Smtp-Source: ABdhPJzT0dEfcc/QV2EgegMA+KZ3+WWSPKOX0k0yoo8D1el0gfNIR0iFf5qhJmmlBD59oyTGhPuueUT9fSR1EVV0R6A= X-Received: by 2002:a63:5d57:: with SMTP id o23mr3347261pgm.263.1600280918024; Wed, 16 Sep 2020 11:28:38 -0700 (PDT) MIME-Version: 1.0 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> <20200916113449.GH2643@zn.tnic> In-Reply-To: <20200916113449.GH2643@zn.tnic> From: Nick Desaulniers Date: Wed, 16 Sep 2020 11:28:26 -0700 Message-ID: Subject: Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e To: Borislav Petkov Cc: Arvind Sankar , Josh Poimboeuf , Rong Chen , kernel test robot , "Li, Philip" , x86-ml , LKML , clang-built-linux , Marco Elver Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 16, 2020 at 4:34 AM Borislav Petkov wrote: > > 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 t= o > > the number of arguments in vector registers. > > > > https://patchwork.ozlabs.org/project/gcc/patch/20141218131150.GA32638@i= ntel.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=E2=80=938 inclusive." pt. 3 https://nickdesaulniers.github.io/blog/2014/04/18/lets-write-some-x86= -64/ ...2014, jesus... "But you never can tell exactly what the compiler is doing. It doesn=E2=80= =99t always come out the way you want. Like a dusty pane or warped mirror." Seems I'd learn more about that than I'd could have ever envisioned... --=20 Thanks, ~Nick Desaulniers