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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C33CFC433F5 for ; Mon, 28 Mar 2022 20:21:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344476AbiC1UXY (ORCPT ); Mon, 28 Mar 2022 16:23:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241225AbiC1UXT (ORCPT ); Mon, 28 Mar 2022 16:23:19 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1E8796661F for ; Mon, 28 Mar 2022 13:21:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1648498897; 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: in-reply-to:in-reply-to:references:references; bh=3p40tNFk+gHnhhZuqFavI/fEyZfK9XcFxgpC8+00PDQ=; b=Y4auQ0hn1yFrGRjlqtgBhF8t4ymheWBy8wt0cEUNIdPtF76Lb+m9rIzW/uqKyfiWsPWm8L sPAXxT06tMJQFMZUA/qws8p+W6Gw+USjg2iJ2I4N7YaeZUl3NeZtRfoiC+qd1HgXUbam6h WOdsOwLteN6uj42F63dDGzbWUlxE3n0= Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-292-vGSgA54GN4W0sIsGlhcIDQ-1; Mon, 28 Mar 2022 16:21:35 -0400 X-MC-Unique: vGSgA54GN4W0sIsGlhcIDQ-1 Received: by mail-qv1-f70.google.com with SMTP id g1-20020ad446c1000000b00440c9327221so12188512qvw.6 for ; Mon, 28 Mar 2022 13:21:35 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=3p40tNFk+gHnhhZuqFavI/fEyZfK9XcFxgpC8+00PDQ=; b=vjQKUKkMPcDHBU986aj83z6ZNf+j4CPcGjqfLLPZMYnsmdnp372EJpBFJztcMVpfkY qqJ3ytojcIMkvUi1xDxPF2SUuAnDikgK9iA81Za6a/0NgBtwT+OzNg1+Nh79jf9mQWHk m2T1ATpl2qepUT4AZ7aTN3x5hvcyL1mp5uTNmqTcSe71KlhtecIqKtYdkLh3g7/6UJBz psTWd1Cz0M+9NLG40MGAIqTQlINQjnuK1aXZveMbKhasTLlupNETsl/73o3i8spNwMoS I/YMlCZ5e2anq9yoM+nxwoGz89k0rwghD5uC0iuNIsvI6RVpRR2bGhhpgqXKNl0YGIfO QfoA== X-Gm-Message-State: AOAM532MmUSPNyG9uKildtpGOuPAEuUoVllr/nO/ELCwcK7RePTJ5lsg pyKPs7BwnH61JdUytEY15yZ+tZ2H0Vc8ZDcgFqooRXOnerTud8TxhAa3GohWpoipi5fECp259+y u4O5vfXrddVgn75LgrkN7GyTH X-Received: by 2002:a05:6214:29c7:b0:441:3f11:9315 with SMTP id gh7-20020a05621429c700b004413f119315mr22667899qvb.87.1648498895152; Mon, 28 Mar 2022 13:21:35 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwNM++ZxHApL6PNdttJ/yUMPNMmzlV+WiT8X4Xf2ogElGi09uECpKMGDIcr2ELe1JrOd+5kdg== X-Received: by 2002:a05:6214:29c7:b0:441:3f11:9315 with SMTP id gh7-20020a05621429c700b004413f119315mr22667879qvb.87.1648498894940; Mon, 28 Mar 2022 13:21:34 -0700 (PDT) Received: from treble ([2600:1700:6e32:6c00::35]) by smtp.gmail.com with ESMTPSA id g9-20020a05620a108900b0067b13036bd5sm8275335qkk.52.2022.03.28.13.21.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Mar 2022 13:21:34 -0700 (PDT) Date: Mon, 28 Mar 2022 13:21:31 -0700 From: Josh Poimboeuf To: Peter Zijlstra Cc: Christophe Leroy , "aik@ozlabs.ru" , "linux-kernel@vger.kernel.org" , "rostedt@goodmis.org" , "naveen.n.rao@linux.vnet.ibm.com" , "linuxppc-dev@lists.ozlabs.org" , Sathvika Vasireddy , Will Deacon , Mark Rutland , ardb@kernel.org Subject: Re: [RFC PATCH 3/3] objtool/mcount: Add powerpc specific functions Message-ID: <20220328202131.jis7swqswm7chn6k@treble> References: <20220318105140.43914-1-sv@linux.ibm.com> <20220318105140.43914-4-sv@linux.ibm.com> <0b55f122-4760-c1ba-840a-0911cefec2ad@csgroup.eu> <20220328195920.dqlfra3lcardko6r@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 28, 2022 at 10:14:38PM +0200, Peter Zijlstra wrote: > > FWIW, there have been some objtool patches for arm64 stack validation, > > but the arm64 maintainers have been hesitant to get on board with > > objtool, as it brings a certain maintenance burden. Especially for the > > full stack validation and ORC unwinder. But if you only want inline > > static calls and/or mcount then it'd probably be much easier to > > maintain. > > IIRC the major stumbling block for arm64 is the whole jump-table thing. > Either they need to rely on compiler plugins to provide objtool that > data (yuck, since we support at least 2 different compilers), disable > jump-tables (yuck, for that limits code-gen just to please a tool) or > use DWARF (yuck, because build times). Well yeah, that was indeed the main technical issue but I seem to remember some arm64 maintainers not really being sold on the value of objtool regardless. > There was a little talk about an impromptu 'abi' to communicate > jump-table details to objtool without going full on DWARF, but that > seems to have hit a dead end again. Probably my fault, not enough hours in the day... -- Josh