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 E58D0C55191 for ; Sat, 25 Apr 2020 17:31:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C468D20728 for ; Sat, 25 Apr 2020 17:31:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="BTmQGxPN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726349AbgDYRbu (ORCPT ); Sat, 25 Apr 2020 13:31:50 -0400 Received: from mail.skyhub.de ([5.9.137.197]:37688 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbgDYRbu (ORCPT ); Sat, 25 Apr 2020 13:31:50 -0400 Received: from zn.tnic (p200300EC2F2A1100992835E22F06EF88.dip0.t-ipconnect.de [IPv6:2003:ec:2f2a:1100:9928:35e2:2f06:ef88]) (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 E661D1EC0CD6; Sat, 25 Apr 2020 19:31:48 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1587835909; 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=uFkXHVwwFH85jEcy4ns2EHqg9WJsW4QYuQw8r9bQI2U=; b=BTmQGxPNkg4Aex6qccxM+7l3usJmduwct1PjS327BGPnactFewmsBn0SUUBJN/bLHJm8uS bH1n7RXre+Ch0s1AD3P0KBwk5St68VwI+8uFYYn10XCufU/CWkI+iRdM03E3fujigj8wt4 mpPVdtWb+IP77M7zyMU6HTk4NzaAazQ= Date: Sat, 25 Apr 2020 19:31:40 +0200 From: Borislav Petkov To: Arvind Sankar Cc: Nick Desaulniers , Michael Matz , Jakub Jelinek , Sergei Trofimovich , LKML , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , x86@kernel.org, clang-built-linux , Kees Cook , Martin =?utf-8?B?TGnFoWth?= , =?utf-8?Q?Fr=C3=A9d=C3=A9ric_Pierret_=28fepitre=29?= , boris.ostrovsky@oracle.com, jgross@suse.com, linuxppc-dev@lists.ozlabs.org, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras Subject: Re: [PATCH] x86: Fix early boot crash on gcc-10, next try Message-ID: <20200425173140.GB24294@zn.tnic> References: <20200422192113.GG26846@zn.tnic> <20200422212605.GI26846@zn.tnic> <20200423125300.GC26021@zn.tnic> <20200423161126.GD26021@zn.tnic> <20200425014657.GA2191784@rani.riverdale.lan> <20200425085759.GA24294@zn.tnic> <20200425150440.GA470719@rani.riverdale.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200425150440.GA470719@rani.riverdale.lan> 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 11:04:40AM -0400, Arvind Sankar wrote: > I'd put the clause about stack protector being disabled and the > tail-call one together, to make clear that you still need the never > return and always inline bits. Done. > Also, this function is implemented by multiple arch's and they all > have similar comments -- might be better to consolidate the comment in > the generic (dummy) one in include/linux/stackprotector.h laying out > the restrictions that arch implementations should follow? I'm not sure gcc-10 does the same thing on other arches - I'd let gcc guys chime in here and other arch maintainers to decide what to do. > There's also the one in init/main.c which is used by multiple > architectures. On x86 at least, the call to arch_call_rest_init at the > end of start_kernel does not get tail-call optimized by gcc-10, but I > don't see anything that actually prevents that from happening. We should > add the asm("") there as well I think, unless the compiler guys see > something about this function that will always prevent the optimization? Hmm, that's what I was afraid of - having to sprinkle this around. Yah, let's wait for compiler guys to have a look here and then maybe I'll convert that thing to a macro called compiler_prevent_tail_call_opt() or so, so that it can be sprinkled around. ;-\ -- 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 BED0CC54FCB for ; Sat, 25 Apr 2020 17:33:47 +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 3399720700 for ; Sat, 25 Apr 2020 17:33:46 +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="BTmQGxPN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3399720700 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 498dS82G1PzDqkK for ; Sun, 26 Apr 2020 03:33:44 +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=BTmQGxPN; 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 498dQK3W3wzDqMK for ; Sun, 26 Apr 2020 03:32:09 +1000 (AEST) Received: from zn.tnic (p200300EC2F2A1100992835E22F06EF88.dip0.t-ipconnect.de [IPv6:2003:ec:2f2a:1100:9928:35e2:2f06:ef88]) (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 E661D1EC0CD6; Sat, 25 Apr 2020 19:31:48 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1587835909; 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=uFkXHVwwFH85jEcy4ns2EHqg9WJsW4QYuQw8r9bQI2U=; b=BTmQGxPNkg4Aex6qccxM+7l3usJmduwct1PjS327BGPnactFewmsBn0SUUBJN/bLHJm8uS bH1n7RXre+Ch0s1AD3P0KBwk5St68VwI+8uFYYn10XCufU/CWkI+iRdM03E3fujigj8wt4 mpPVdtWb+IP77M7zyMU6HTk4NzaAazQ= Date: Sat, 25 Apr 2020 19:31:40 +0200 From: Borislav Petkov To: Arvind Sankar Subject: Re: [PATCH] x86: Fix early boot crash on gcc-10, next try Message-ID: <20200425173140.GB24294@zn.tnic> References: <20200422192113.GG26846@zn.tnic> <20200422212605.GI26846@zn.tnic> <20200423125300.GC26021@zn.tnic> <20200423161126.GD26021@zn.tnic> <20200425014657.GA2191784@rani.riverdale.lan> <20200425085759.GA24294@zn.tnic> <20200425150440.GA470719@rani.riverdale.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200425150440.GA470719@rani.riverdale.lan> 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, 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 Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sat, Apr 25, 2020 at 11:04:40AM -0400, Arvind Sankar wrote: > I'd put the clause about stack protector being disabled and the > tail-call one together, to make clear that you still need the never > return and always inline bits. Done. > Also, this function is implemented by multiple arch's and they all > have similar comments -- might be better to consolidate the comment in > the generic (dummy) one in include/linux/stackprotector.h laying out > the restrictions that arch implementations should follow? I'm not sure gcc-10 does the same thing on other arches - I'd let gcc guys chime in here and other arch maintainers to decide what to do. > There's also the one in init/main.c which is used by multiple > architectures. On x86 at least, the call to arch_call_rest_init at the > end of start_kernel does not get tail-call optimized by gcc-10, but I > don't see anything that actually prevents that from happening. We should > add the asm("") there as well I think, unless the compiler guys see > something about this function that will always prevent the optimization? Hmm, that's what I was afraid of - having to sprinkle this around. Yah, let's wait for compiler guys to have a look here and then maybe I'll convert that thing to a macro called compiler_prevent_tail_call_opt() or so, so that it can be sprinkled around. ;-\ -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette