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=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID 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 06403C43142 for ; Mon, 25 Jun 2018 23:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB6B2262B1 for ; Mon, 25 Jun 2018 23:25:17 +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="GgtYaecb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB6B2262B1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932883AbeFYXZP (ORCPT ); Mon, 25 Jun 2018 19:25:15 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:44080 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754207AbeFYXZM (ORCPT ); Mon, 25 Jun 2018 19:25:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=PeMZQUvfUzbFmDayzJrOYU1TpyvbJicBz6oQIbqgi4A=; b=GgtYaecbs8SRAh5BSKMVgNh5m o8QfHfZvSQvLmiZATjOq/M7Rok2/0tTXfjFwaPesAGQfFLe9+gF95VKMKmA63y/7yDKOi5n0WDys+ GrVSuZTNxr22g26RLKtMoasjx69a3Bysnyq7zopJsaLxEHKX33z0AviX6VhcneSV+leJToay2dV2p urxN6809l5RpGA28qvnd124UxT6LSDVlLO/SA6TNHXVAMZYRn6ltmHXhCM25e16WzNB9Zu/HUIHNf yKGMAAkS9knirlCtmGbJ8ku0ocprNMZ+ceRAtws9n0uBv+i9zSN/X08AON5bDeACsf4vurEEPRmxN pOF/+Xlsg==; Received: from static-50-53-52-16.bvtn.or.frontiernet.net ([50.53.52.16] helo=dragon.dunlab) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fXar5-0006XG-8M; Mon, 25 Jun 2018 23:25:07 +0000 Subject: Re: [PATCH v5 15/27] compiler: Option to default to hidden symbols To: Thomas Garnier , kernel-hardening@lists.openwall.com Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Borislav Petkov , "Luis R. Rodriguez" , Greg Kroah-Hartman , Arnd Bergmann , Christopher Li , Steven Rostedt , Jason Baron , "Rafael J. Wysocki" , Kate Stewart , Mika Westerberg , Philippe Ombredanne , Lukas Wunner , Kees Cook , Masahiro Yamada , "Peter Zijlstra (Intel)" , Mathieu Desnoyers , Sergey Senozhatsky , Petr Mladek , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org References: <20180625224014.134829-1-thgarnie@google.com> <20180625224014.134829-16-thgarnie@google.com> From: Randy Dunlap Message-ID: <8486eb8b-e233-4e2f-e976-da7b4cefc673@infradead.org> Date: Mon, 25 Jun 2018 16:25:03 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180625224014.134829-16-thgarnie@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/25/18 15:39, Thomas Garnier wrote: > Provide an option to default visibility to hidden except for key > symbols. This option is disabled by default and will be used by x86_64 > PIE support to remove errors between compilation units. > > The default visibility is also enabled for external symbols that are > compared as they maybe equals (start/end of sections). In this case, > older versions of GCC will remove the comparison if the symbols are > hidden. This issue exists at least on gcc 4.9 and before. > > Signed-off-by: Thomas Garnier > --- > diff --git a/init/Kconfig b/init/Kconfig > index 24b60536e26b..d4f90cc38ede 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1718,6 +1718,13 @@ config PROFILING > config TRACEPOINTS > bool > > +# > +# Default to hidden visibility for all symbols. > +# Useful for Position Independent Code to reduce global references. > +# > +config DEFAULT_HIDDEN > + bool > + I certainly would appreciate a better/more descriptive kconfig symbol name here. > source "arch/Kconfig" > > endmenu # General setup thanks, -- ~Randy