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=-7.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 6A366C433DB for ; Fri, 19 Mar 2021 12:31:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2720C64F75 for ; Fri, 19 Mar 2021 12:31:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229927AbhCSMa5 (ORCPT ); Fri, 19 Mar 2021 08:30:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:36586 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229634AbhCSMa2 (ORCPT ); Fri, 19 Mar 2021 08:30:28 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 25C2E64E09; Fri, 19 Mar 2021 12:30:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616157027; bh=STuc4t7Ex+kxKPe6umFc1+qm6aDEDEQvBbxhw2YlGvY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OEqj7olBLe9tvO/HUo8ZkhlvM7YIVwA4mQbLGLJOYiN7bYkggTOI+iNfMK/gFmE1a A9itO1s+Z7s5DKzwKe9TNmdbwqmfy7oEhtohrurO/N5BPvx3toX+dGH9/8CIhIByPP 4bz+Za+WCbyzcHVkPlO4lja5iNfkp0FpZ1l5KiGhfS2sgmvC2gz5MqOzs6yhzuVNWP +1nEv30LHt5BALndrYJHE4qOFPxHawirlyafcTNJZp6kjpnGllZLt01+7P1sS6iFe6 cEGO3hL0pB82BBQPD6v3MM5jIBA9Ww6io3dQFU8jvheSp+cYTcPJvwGK9Q6gkhkCnq J2TaDnvcHlcnQ== Date: Fri, 19 Mar 2021 12:30:23 +0000 From: Mark Brown To: "Madhavan T. Venkataraman" Cc: mark.rutland@arm.com, jpoimboe@redhat.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 1/8] arm64: Implement stack trace termination record Message-ID: <20210319123023.GC5619@sirena.org.uk> References: <5997dfe8d261a3a543667b83c902883c1e4bd270> <20210315165800.5948-1-madvenka@linux.microsoft.com> <20210315165800.5948-2-madvenka@linux.microsoft.com> <20210318150905.GL5469@sirena.org.uk> <8591e34a-c181-f3ff-e691-a6350225e5b4@linux.microsoft.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="S1BNGpv0yoYahz37" Content-Disposition: inline In-Reply-To: <8591e34a-c181-f3ff-e691-a6350225e5b4@linux.microsoft.com> X-Cookie: No purchase necessary. User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --S1BNGpv0yoYahz37 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Mar 18, 2021 at 03:26:13PM -0500, Madhavan T. Venkataraman wrote: > On 3/18/21 10:09 AM, Mark Brown wrote: > > If we are going to add the extra record there would probably be less > > potential for confusion if we pointed it at some sensibly named dummy > > function so anything or anyone that does see it on the stack doesn't get > > confused by a NULL. > I agree. I will think about this some more. If no other solution presents > itself, I will add the dummy function. After discussing this with Mark Rutland offlist he convinced me that so long as we ensure the kernel doesn't print the NULL record we're probably OK here, the effort setting the function pointer up correctly in all circumstances (especially when we're not in the normal memory map) is probably not worth it for the limited impact it's likely to have to see the NULL pointer (probably mainly a person working with some external debugger). It should be noted in the changelog though, and/or merged in with the relevant change to the unwinder. --S1BNGpv0yoYahz37 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmBUmV8ACgkQJNaLcl1U h9ABJwgAgN92saU1Ljsz55wJhiKxyalqRT9vs3rxeTR2So6rrXGyFb8YKrZacIrG tARHk3LFN8JU5kHE0iEHvLkqkmVxgGwxppsyKRSy9tL44fURVTS4ZA0+Flhm8wdf yCqxgPwKgN4viY1sDH4HL1jOpa3AdK/x93O0qelxHYw4UZsruna6jmxVRle4gwj3 U2qv7muAQiTigUJluJ5KZLRzs4ca1c0bfldwvfM3ruTwmiE/sggqMC+3LWi0aPlc PUMp0wqWkCkoqNXHS1qIiU/lp0ZhW+qdhBe0SrSsYHpAUSZw/iDb475VjlKRKdCD DY84czq9IA2dQnZ1LQTL9TyU6bMRwg== =ouYL -----END PGP SIGNATURE----- --S1BNGpv0yoYahz37--