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 42C46C3DA6F for ; Thu, 24 Aug 2023 15:43:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7F9AE28007A; Thu, 24 Aug 2023 11:43:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A9918E0011; Thu, 24 Aug 2023 11:43:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 698AE28007A; Thu, 24 Aug 2023 11:43:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 5B00A8E0011 for ; Thu, 24 Aug 2023 11:43:40 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 2F4781603B8 for ; Thu, 24 Aug 2023 15:43:40 +0000 (UTC) X-FDA: 81159418200.11.023852F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf29.hostedemail.com (Postfix) with ESMTP id 73EB212002B for ; Thu, 24 Aug 2023 15:43:38 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=none; spf=pass (imf29.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1692891818; a=rsa-sha256; cv=none; b=3hBM2z86453p3Qh/4xTxMWlfNTmf+6vsAxrun1+mWw/8+hbe+e2VtylHmRleWuS7TG1DwB xUN0kh8tK48MBYfnah2J9Tz0VzF/sMh6RUVqp/2r6ZlWB+sluMtQZLVmhXes8n4zUv1gjx wwMXnzkU7EUOhv+QsKVjZAngHuPdWd8= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=none; spf=pass (imf29.hostedemail.com: domain of cmarinas@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1692891818; 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=W7V+hcmGnathMjkCclop8V3dR1xONmnxVMUFtVfFJhA=; b=NMnOBqSCiYlc4nOVJZdJ5gnXUOPdYfP+cHt0LIFzDxyVTLLrYjwPBLVhaa7lSgQi0MkVPm yL7oBAPceMkPZLi7Qbqz/cThPrud0v4Ch2jT0s5gnM1wVjHdLIiE/HnMDgES036oXWCv6+ 9J+WqjGhDeln1BhzrIG/eHUC59qowW0= 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 87C5867110; Thu, 24 Aug 2023 15:43:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D722EC433C8; Thu, 24 Aug 2023 15:43:23 +0000 (UTC) Date: Thu, 24 Aug 2023 16:43:19 +0100 From: Catalin Marinas To: Mark Brown Cc: Szabolcs Nagy , 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 , "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: <43ec219d-bf20-47b8-a5f8-32bc3b64d487@sirena.org.uk> <227e6552-353c-40a9-86c1-280587a40e3c@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 73EB212002B X-Stat-Signature: 4nj8rk6npgg1xw6msrs3txmdohps7s4q X-HE-Tag: 1692891818-243465 X-HE-Meta: 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 saAPjcnl XmYI/WDkvSSysCU6UazoQfOFTSGc6JioAQD3mU/M9zH01waJO5shFGvdmyJvdMeVsz8VIbiijv9l71My15SIu03vIHzBKyL2CRZFBxBsCNRMKFTAOQJoVio3ZzRpvUHMcBin5IHc5usbGdC1Y+hkz0frrN8yR4NH1lzl0NtBfZBfQvEiR/1Xc6s6koHbhhR57WchnpQbGarFlY1KOx7OdeyIRdlMvKFgQKgUPBNQlqKaPCQ1pGgEqS67uawZJ+bzdzPgwua2d02fjDbSRmJPEVuQ4qRsWnWMtJRgN05r4Xk8EXGGfI3nFKQsbZsLrjn7XzBmz1c4gYSFHeoXIksWMv8Qooz/ZrPMl/U3dFKjpHszC44cBgpPrNUE7MMAoCq0CY3VQsIZM6xxpDRTcpz+bn4OvS48dIu9T4Y16t9winF3pTUatnL9/EKYDgx74hM4yQ/kZ02nIwZj6eQkPIJMb8aiRtxJefrTCOTqSUeH0L8MOWMM= 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 Wed, Aug 23, 2023 at 07:16:52PM +0100, Mark Brown wrote: > On Wed, Aug 23, 2023 at 06:40:40PM +0100, Szabolcs Nagy wrote: > > i don't know if we can allow disabled gcs thread creation with locked > > gcs state. (i can see arguments both ways, so further prctl flag may > > be needed which may be another divergence from x86) > > I think that if we do add a new flag that'd just be new functionality, > the divergence would be in allowing configuration via clone3() rather > than the flag. TBH I'm not sure I see a use case for locking but > providing a mechanism for getting out of the lock, that seems very > questionable. You are right, once the configuration is locked a plain clone() or clone3() without a GCS pointer should be rejected. Is there a use-case for the unlocked configuration to allow disabling the GCS implicitly via a clone syscall? If we go for extending clone3, I wonder whether we should also introduce a sigaltstack2/3 ;). I haven't checked what the current patches do and won't have time until early September (on holiday from the end of today). -- Catalin