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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 868D5C55189 for ; Wed, 22 Apr 2020 11:40:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F6052082E for ; Wed, 22 Apr 2020 11:40:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="b5QyaoAh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727005AbgDVLkr (ORCPT ); Wed, 22 Apr 2020 07:40:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47574 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726261AbgDVLkq (ORCPT ); Wed, 22 Apr 2020 07:40:46 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7AC3DC03C1A8 for ; Wed, 22 Apr 2020 04:40:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=FMnNnD/g5k61t/UJVaLjWLk7lqOWCoUUvUZPwgeC4zI=; b=b5QyaoAhKw9dLQtOhIkFBippwO ii9AFrlgzCqp3ycOgyREkrZdoZhL+40vlAgzyNwsd8lC2nuitaPrw5xF8icyyx/CR5AuVAHPlCPin JABZZykr0nnT1/U1J+mFhWj0wE/pepgsfB0AxLv0tlcMSoKT1oe34v111Q5G//IZjlGMA685Kujzr of6ciJX2NC4TQ8udJogzxzqw5Bh0dNb26Ky/+xSDnaLWhsmLCFS4HubOtmRjyAsM5SbDt0mG/zd2w 9jDZhknxlTk7QODtO8M5F4usKWLsQ3QUu1/Kh6IJDX/C+QYk2NDB/c7wKFw+zfCpE915DqOzoQDvz C3rBOJcw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jRDjd-00075p-DO; Wed, 22 Apr 2020 11:40:09 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 03655300739; Wed, 22 Apr 2020 13:40:08 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E4EA2203AA838; Wed, 22 Apr 2020 13:40:07 +0200 (CEST) Date: Wed, 22 Apr 2020 13:40:07 +0200 From: Peter Zijlstra To: Borislav Petkov Cc: Nick Desaulniers , Michael Matz , Jakub Jelinek , Sergei Trofimovich , LKML , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski , "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: <20200422114007.GC20730@hirez.programming.kicks-ass.net> References: <20200417080726.GS2424@tucnak> <20200417084224.GB7322@zn.tnic> <20200417085859.GU2424@tucnak> <20200417090909.GC7322@zn.tnic> <20200417190607.GY2424@tucnak> <20200422102309.GA26846@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200422102309.GA26846@zn.tnic> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 22, 2020 at 12:23:09PM +0200, Borislav Petkov wrote: > 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 (""); > } You haz a whitespace issue there. Also, can we get this in writing, signed in blood, from the various compiler teams ;-)