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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 D3A6DC54FCB for ; Sat, 25 Apr 2020 22:17:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D67C20706 for ; Sat, 25 Apr 2020 22:17:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="TblBEYYV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726338AbgDYWRl (ORCPT ); Sat, 25 Apr 2020 18:17:41 -0400 Received: from mail.skyhub.de ([5.9.137.197]:54894 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbgDYWRl (ORCPT ); Sat, 25 Apr 2020 18:17:41 -0400 Received: from zn.tnic (p200300EC2F2A110011AF566E608DBC7E.dip0.t-ipconnect.de [IPv6:2003:ec:2f2a:1100:11af:566e:608d:bc7e]) (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 882CE1EC0CFA; Sun, 26 Apr 2020 00:17:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1587853059; 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:in-reply-to:in-reply-to: references:references; bh=dL/4+F/i9p4Rl9Mx/xjx1nvt6QzxFIox9qHe7WXmyFs=; b=TblBEYYVBE117oRluNpJNENnYeOMCXqC/PfzHUdL+2vSRmqMvQy+meocoqlRkiQ6dm3Iwc L2W0F0ifdIT+uqXVrfbz3xnhSFDCv99NuSUY4gzMe4QZkhhdVsZeF9dp1iEu+D0o330Nwx iTAQdlLBKNKi+8JkcWTj55M/pDBeSUs= Date: Sun, 26 Apr 2020 00:17:28 +0200 From: Borislav Petkov To: Segher Boessenkool Cc: Arvind Sankar , Jakub Jelinek , jgross@suse.com, x86@kernel.org, Kees Cook , Peter Zijlstra , linuxppc-dev@lists.ozlabs.org, Michael Matz , Nick Desaulniers , LKML , Sergei Trofimovich , clang-built-linux , Ingo Molnar , Paul Mackerras , Andy Lutomirski , "H. Peter Anvin" , =?utf-8?Q?Fr=C3=A9d=C3=A9ric_Pierret_=28fepitre=29?= , Thomas Gleixner , Martin =?utf-8?B?TGnFoWth?= , boris.ostrovsky@oracle.com Subject: Re: [PATCH] x86: Fix early boot crash on gcc-10, next try Message-ID: <20200425221728.GE24294@zn.tnic> References: <20200423125300.GC26021@zn.tnic> <20200423161126.GD26021@zn.tnic> <20200425014657.GA2191784@rani.riverdale.lan> <20200425085759.GA24294@zn.tnic> <20200425150440.GA470719@rani.riverdale.lan> <20200425173140.GB24294@zn.tnic> <20200425183701.GE17645@gate.crashing.org> <20200425185313.GD24294@zn.tnic> <20200425191549.GF17645@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200425191549.GF17645@gate.crashing.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 25, 2020 at 02:15:49PM -0500, Segher Boessenkool wrote: > My point is that you should explain at *every use* of this why you cannot > have tail calls *there*. This is very unusual, after all. > > There are *very* few places where you want to prevent tail calls, that's > why there is no attribute for it. Well, there is only one reason *why* so far - to prevent the stack canary cookie from being checked before returning from the function which set it. That could be explained once over the macro definition so that it can be looked up. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette 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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 6D0A4C54FCB for ; Sat, 25 Apr 2020 22:20:15 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D5B502076C for ; Sat, 25 Apr 2020 22:20:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="TblBEYYV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D5B502076C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 498lpg5Jd8zDqCs for ; Sun, 26 Apr 2020 08:20:11 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=alien8.de (client-ip=2a01:4f8:190:11c2::b:1457; helo=mail.skyhub.de; envelope-from=bp@alien8.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=alien8.de Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=alien8.de header.i=@alien8.de header.a=rsa-sha256 header.s=dkim header.b=TblBEYYV; dkim-atps=neutral Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 498llz0KwPzDqbl for ; Sun, 26 Apr 2020 08:17:50 +1000 (AEST) Received: from zn.tnic (p200300EC2F2A110011AF566E608DBC7E.dip0.t-ipconnect.de [IPv6:2003:ec:2f2a:1100:11af:566e:608d:bc7e]) (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 882CE1EC0CFA; Sun, 26 Apr 2020 00:17:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1587853059; 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:in-reply-to:in-reply-to: references:references; bh=dL/4+F/i9p4Rl9Mx/xjx1nvt6QzxFIox9qHe7WXmyFs=; b=TblBEYYVBE117oRluNpJNENnYeOMCXqC/PfzHUdL+2vSRmqMvQy+meocoqlRkiQ6dm3Iwc L2W0F0ifdIT+uqXVrfbz3xnhSFDCv99NuSUY4gzMe4QZkhhdVsZeF9dp1iEu+D0o330Nwx iTAQdlLBKNKi+8JkcWTj55M/pDBeSUs= Date: Sun, 26 Apr 2020 00:17:28 +0200 From: Borislav Petkov To: Segher Boessenkool Subject: Re: [PATCH] x86: Fix early boot crash on gcc-10, next try Message-ID: <20200425221728.GE24294@zn.tnic> References: <20200423125300.GC26021@zn.tnic> <20200423161126.GD26021@zn.tnic> <20200425014657.GA2191784@rani.riverdale.lan> <20200425085759.GA24294@zn.tnic> <20200425150440.GA470719@rani.riverdale.lan> <20200425173140.GB24294@zn.tnic> <20200425183701.GE17645@gate.crashing.org> <20200425185313.GD24294@zn.tnic> <20200425191549.GF17645@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200425191549.GF17645@gate.crashing.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jakub Jelinek , jgross@suse.com, Michael Matz , Kees Cook , Peter Zijlstra , Martin =?utf-8?B?TGnFoWth?= , x86@kernel.org, Nick Desaulniers , LKML , Sergei Trofimovich , clang-built-linux , Arvind Sankar , Ingo Molnar , Paul Mackerras , Andy Lutomirski , "H. Peter Anvin" , =?utf-8?Q?Fr=C3=A9d=C3=A9ric_Pierret_=28fepitre=29?= , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, boris.ostrovsky@oracle.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sat, Apr 25, 2020 at 02:15:49PM -0500, Segher Boessenkool wrote: > My point is that you should explain at *every use* of this why you cannot > have tail calls *there*. This is very unusual, after all. > > There are *very* few places where you want to prevent tail calls, that's > why there is no attribute for it. Well, there is only one reason *why* so far - to prevent the stack canary cookie from being checked before returning from the function which set it. That could be explained once over the macro definition so that it can be looked up. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette