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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 87F75C55186 for ; Wed, 22 Apr 2020 10:35:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 686C520656 for ; Wed, 22 Apr 2020 10:35:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="VMGpvZXL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730356AbgDVKXh (ORCPT ); Wed, 22 Apr 2020 06:23:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730298AbgDVKXQ (ORCPT ); Wed, 22 Apr 2020 06:23:16 -0400 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AFBFC03C1A8 for ; Wed, 22 Apr 2020 03:23:16 -0700 (PDT) Received: from zn.tnic (p200300EC2F0DC100B57FB20533079C8E.dip0.t-ipconnect.de [IPv6:2003:ec:2f0d:c100:b57f:b205:3307:9c8e]) (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 62BE41EC0D3A; Wed, 22 Apr 2020 12:23:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1587550994; 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=HDuUABhmmUgyzWxWyDZN0U/l9ljHbsLtT1vuHABexv8=; b=VMGpvZXLrSuGmV7jBbvq6prp0sGWkwub9bVK9v+hBWVzuN3uZLatR/bWbn4DIlfGT5phAV nB5cmO0sy1MEES5H2XDEWMrDgQ5Plz5VVrG6Y8Wru9Fbv+SF6kb66ffM0KULxdBT/QupyU smykpf8zpVCgU+9dum7H9GzuokZvXuo= Date: Wed, 22 Apr 2020 12:23:09 +0200 From: Borislav Petkov To: Nick Desaulniers Cc: Michael Matz , Jakub Jelinek , Sergei Trofimovich , LKML , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , clang-built-linux Subject: Re: [PATCH v2] x86: fix early boot crash on gcc-10 Message-ID: <20200422102309.GA26846@zn.tnic> References: <20200417075739.GA7322@zn.tnic> <20200417080726.GS2424@tucnak> <20200417084224.GB7322@zn.tnic> <20200417085859.GU2424@tucnak> <20200417090909.GC7322@zn.tnic> <20200417190607.GY2424@tucnak> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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 Ok, let's try the simple and clean fix first. Nick, would that work on LLVM too? And I hope this will remain working and the compiler won't jump over an inline asm and go nuts. Thx. --- diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 3b9bf8c7e29d..06d2e16bedbb 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -266,6 +266,13 @@ static void notrace start_secondary(void *unused) wmb(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); + + /* + * Prevent tail call to cpu_startup_entry() because the stack protector + * guard has been changed in the middle of this function and must not be + * checked before tail calling another function. + */ + asm (""); } /** -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette