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=-3.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 D535DC2D0DB for ; Thu, 30 Jan 2020 20:06:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7E652082E for ; Thu, 30 Jan 2020 20:06:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SCOXsrrQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727650AbgA3UGo (ORCPT ); Thu, 30 Jan 2020 15:06:44 -0500 Received: from mail-ot1-f68.google.com ([209.85.210.68]:35936 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726267AbgA3UGo (ORCPT ); Thu, 30 Jan 2020 15:06:44 -0500 Received: by mail-ot1-f68.google.com with SMTP id g15so4332435otp.3 for ; Thu, 30 Jan 2020 12:06:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=rzmr0rCxGWcUXC+WtCSYHcwAxAhm1rZi8aLPGy+zipE=; b=SCOXsrrQ2ObFfZaBtqJq0DweOFAu4+39JIJl85RMqvCtoyXm+/S4/HPnc7EFZDh+cW eiOqMdPlJG/h6uiagKDOPeyA5N4tOc1XMHpHvFWUHC3QzIvVee2baYUUgtGO6PaqW2rF uc8apzSUGKYutdy4d9u9G9Y4FMwp1RtcGzS2uPVxukfjbm1JY87CoaNNQNKgykYV/g94 O4JgzX5WL9e8fhQpF0wWH1y/+rkyfZc+D0FQXmeu8dvq1/gETW8rLoPRAIZ8SDOgv1GZ AhbAwRyNDnYT4HdKQWXG195myoT2MfBqYJXKgUjDD3Q91C1ib+5syKysxHx+P8Y6zDNV lkOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rzmr0rCxGWcUXC+WtCSYHcwAxAhm1rZi8aLPGy+zipE=; b=gdmq2Je4XPKnJsu7KrP9o/UJ4w+zkwBQYz5kMnRfZQk0X1cqdEdswFzzo2deLg3sG+ D9GBnv0MavlRuqY5u2SnWobVhYdDln37zrejOCy9z+b/mzL3oP6+7RvUcVXnCSD3aJDV YXpbRWWdYISU1Dqp9lrnHORcgpzSseHIwWTTt9ib8yPnkTHIoX0wMsmwegrjMEfHcUDz GnHwkA9aDh5JCOh/1VBR9YhLu0kH0NDoGDHVuT/hBHRjAhj8kng+Xj4FzxDBazuyNH+2 UiWO4oEi7Zp0RAnm6D9VS8kBZELd0Y5jMjcMUvdLL3W+cvZleuaQrOWKz39nngeCRBpZ jkqQ== X-Gm-Message-State: APjAAAW1htVwxAtJt2nhd7k+ou1g/jEtdyJSD8BvRd7UDRUOot2Abm7y 3ISdpVDRclZ/KmM3oOUXaduwXzKvZoP09ua7JK0= X-Google-Smtp-Source: APXvYqwDOXbQ7i2RXELeFvJBGmrWClW+wJQ/ItCOwsSrDcfc14orMFQIqzZvtLfp6JIvIHnB8qauCPnoyidEz6YYb3o= X-Received: by 2002:a05:6830:1e30:: with SMTP id t16mr5021001otr.220.1580414801839; Thu, 30 Jan 2020 12:06:41 -0800 (PST) MIME-Version: 1.0 References: <20200130180048.2901-1-hjl.tools@gmail.com> <202001301139.F8859A4@keescook> <202001301152.DF108B6CC@keescook> In-Reply-To: <202001301152.DF108B6CC@keescook> From: "H.J. Lu" Date: Thu, 30 Jan 2020 12:06:06 -0800 Message-ID: Subject: Re: [PATCH] x86: Don't discard .exit.text and .exit.data at link-time To: Kees Cook Cc: LKML , Andy Lutomirski , Thomas Gleixner , Thomas Lendacky , Sami Tolvanen , Heiko Carstens , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , "the arch/x86 maintainers" , Yu-cheng Yu Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 30, 2020 at 11:58 AM Kees Cook wrote: > > On Thu, Jan 30, 2020 at 11:45:15AM -0800, H.J. Lu wrote: > > On Thu, Jan 30, 2020 at 11:40 AM Kees Cook wrote: > > > > > > On Thu, Jan 30, 2020 at 10:00:48AM -0800, H.J. Lu wrote: > > > > Since .exit.text and .exit.data sections are discarded at runtime, we > > > > should undefine EXIT_TEXT and EXIT_DATA to exclude .exit.text and > > > > .exit.data sections from default discarded sections. > > > > > > This is just a correctness fix, yes? The EXIT_TEXT and EXIT_DATA were > > > already included before the /DISCARD/ section here, so there's no > > > behavioral change with this patch, correct? > > > > That is correct. I was confused by EXIT_TEXT and EXIT_DATA in generic > > DISCARDS. My patch just makes it more explicit. > > Okay, so to that end and because this isn't arch-specific, I'd like to > see this be a behavioral flag, and then the generic DISCARDS macro can > be adjusted. This lets all architectures implement this without having > to scatter undef/define lines in each arch. > > Something like this: > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index e00f41aa8ec4..f242d3b4814d 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -894,11 +894,17 @@ > * section definitions so that such archs put those in earlier section > * definitions. > */ > -#define DISCARDS \ > - /DISCARD/ : { \ > +#ifdef RUNTIME_DISCARD_EXIT > +#define EXIT_DISCARDS > +#else > +#define EXIT_DISCARDS \ > EXIT_TEXT \ > EXIT_DATA \ > - EXIT_CALL \ > + EXIT_CALL > +#endif > +#define DISCARDS \ > + /DISCARD/ : { \ > + EXIT_DISCARDS \ > *(.discard) \ > *(.discard.*) \ > *(.modinfo) \ > > Then x86 and all other architectures that do this can just use > #define RUNTIME_DISCARD_EXIT > at the top (like EMITS_PT_NOTE, etc). > It should work. Thanks. -- H.J.