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[23.128.96.18]) by mx.google.com with ESMTP id t22si4436985edr.571.2020.07.01.13.51.35; Wed, 01 Jul 2020 13:51:58 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b="iT/B790I"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726255AbgGAUvR (ORCPT + 99 others); Wed, 1 Jul 2020 16:51:17 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:57629 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725535AbgGAUvR (ORCPT ); Wed, 1 Jul 2020 16:51:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593636676; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NbYjpD75KSjMkRrn1WEH75w+FOpZgxrMTEmZVf5CAxw=; b=iT/B790I1C+Q2wQ2k9gjmTjUtaXdeFFNYXs3i2sQ8DQH7cg8VkhVfQObSQdrfxwFBby0Af J0wizowoDryIk/Uup0PVaGxp0wk1hCKvbrjqLr2xpEd0Zv9xp2WjRXj5Jmu40rvoqHAbHE fEwBNwQndjAjQIqqb5s1r6Zpc7GM3oU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-319-pboVzBC7OOSn7T4XBAcKlw-1; Wed, 01 Jul 2020 16:51:12 -0400 X-MC-Unique: pboVzBC7OOSn7T4XBAcKlw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 39BFF1083E80; Wed, 1 Jul 2020 20:51:11 +0000 (UTC) Received: from treble (ovpn-117-134.rdu2.redhat.com [10.10.117.134]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 868255C557; Wed, 1 Jul 2020 20:51:10 +0000 (UTC) Date: Wed, 1 Jul 2020 15:51:08 -0500 From: Josh Poimboeuf To: Andy Lutomirski Cc: Linus Torvalds , Andy Lutomirski , Peter Zijlstra , the arch/x86 maintainers , Linux Kernel Mailing List Subject: Re: objtool clac/stac handling change.. Message-ID: <20200701205108.wtgfnijav7lgfiqe@treble> References: <5F1767D0-416A-4BA4-9DFF-E82D1EA3F5EE@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5F1767D0-416A-4BA4-9DFF-E82D1EA3F5EE@amacapital.net> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 01, 2020 at 01:36:22PM -0700, Andy Lutomirski wrote: > If we do this extable change, we end up with a different mess: some > exception handlers will clear AC and some won’t. I’m sure objtool can > deal with this with some effort, but I’m not convinced it’s worth it. Yeah. Peter's more of the expert here, but I think we'd at least need to annotate the code which expects an implicit CLAC so objtool knows what to expect. It's not trivial, but it might be doable. -- Josh