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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28E72EE4996 for ; Tue, 22 Aug 2023 16:50:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8C48E28004B; Tue, 22 Aug 2023 12:50:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 84E85280046; Tue, 22 Aug 2023 12:50:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7162428004B; Tue, 22 Aug 2023 12:50:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 61B8F280046 for ; Tue, 22 Aug 2023 12:50:13 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 2E73E8033D for ; Tue, 22 Aug 2023 16:50:13 +0000 (UTC) X-FDA: 81152328306.29.EF9769A Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf08.hostedemail.com (Postfix) with ESMTP id 46761160006 for ; Tue, 22 Aug 2023 16:50:11 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf08.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1692723011; h=from:from:sender: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: in-reply-to:in-reply-to:references:references; bh=8vl3Nr8O11qLMz2NpoD9NYX+RYzFC1PH909tLnYL/sk=; b=Cp6EmLYjUaa8zAE1t0lpJ4Ia03OcVWJslnivRVC/5OdHtDBmLR7vwmWtM9DLr8j8mLUoY7 PqSy1sR1Olaux45mEE8Aru1zIB/eo/IAm9vi6UHBFjaALEtVVVYzHixdL/6fIuXJz75wQL idtZxW/E5Qg6LnUafSpC1zYNK5Ayi1s= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf08.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1692723011; a=rsa-sha256; cv=none; b=jYYK0T8BSL91k4H/DV5HEuDPOAnxplOTcunYTiBDM9aLlI5Yp+AjGFzM7xSF4/hTIRoSDu BceF3lcGLgmcqLeL0gkGjOQFahc3OHN4LtrSIolePO6M2gGvB76Rbs0bs3yC1xIrKUjmLn V4ctjq1ampABJ11ZkYJ8+HHeLM4uZgg= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 488DF65A73; Tue, 22 Aug 2023 16:50:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21995C433C8; Tue, 22 Aug 2023 16:49:55 +0000 (UTC) Date: Tue, 22 Aug 2023 17:49:51 +0100 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 03/36] arm64/gcs: Document the ABI for Guarded Control Stacks Message-ID: References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-3-68cfa37f9069@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 46761160006 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: zpdnhs3uzx7q9jjbmu7tkt7u6bznsipd X-HE-Tag: 1692723011-375933 X-HE-Meta: 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 z+Ea/q7g HLJOJfd54PuWQISxhxU0BZxaU7TgTzIZjMj0+oxI3ESjfQCmn1cbvLjQs9ScnzMXdi2jFaPmsJtHYgcRlmj7QMIRXksEBrwn4VF1meSCGb4nigVCet3tgqh8QtOK/ATsCU7bdDDA0MOn+2+of/gBHJB8BhoXddJJ9p0P1IT1pLSYofdUOp7JnLmWjzXlLzrSM/97wwXdgRgU05l2FggJfvnRDGceNTmvfcW5RNgq84YldmhvmNyVljGFl6AnNeEQQHxiT/vfxEH6/4fMmAmBeagd/sL2M9GGaFsDa8HRtvMpTrVkt4Rcqz+rQpQB7k+vvZbMJ7huYZ73kz+dgopR5bFrHfRPQlLVCz/VXVITmXX0BTHF0ZC+X0D4Mtsf/PzUUmvKiRnNcIjEOhS9T/vAgheQeksR1NHc/9mT7v0Jd44oNIJ0ksm6ay5enzNajEndYdXU5AR4lCaU+hzHoKe2FXLagsdbXxfe1iEynD58pgH5kDYw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 18, 2023 at 08:38:02PM +0100, Mark Brown wrote: > On Fri, Aug 18, 2023 at 06:29:54PM +0100, Catalin Marinas wrote: > > A related question - it may have been discussed intensively on the x86 > > thread (I may read it sometime) - why not have the libc map the shadow > > Your assumption that this is a single thread feels optimistic there. Yeah and I unfortunately ignored all of them. > > stack and pass the pointer/size to clone3()? It saves us from having to > > guess what the right size we'd need. struct clone_args is extensible. > > I can't recall or locate the specific reasoning there right now, perhaps > Rick or someone else can? I'd guess there would be compat concerns for > things that don't go via libc which would complicate the story with > identifying and marking things as GCS/SS safe, it's going to be more > robust to just supply a GCS if the process is using it. That said > having a default doesn't preclude us using the extensibility to allow > userspace directly to control the GCS size, I would certainly be in > favour of adding support for that. It would be good if someone provided a summary of the x86 decision (I'll get to those thread but most likely in September). I think we concluded that we can't deploy GCS entirely transparently, so we need a libc change (apart from the ELF annotations). Since libc is opting in to GCS, we could also update the pthread_create() etc. to allocate the shadow together with the standard stack. Anyway, that's my preference but maybe there were good reasons not to do this. -- Catalin