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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 84FEDC3DA41 for ; Tue, 9 Jul 2024 16:53:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gcy3fHo5vBcXrbdA86NHRYB58PzZwZB6GgkjeWq9i2A=; b=MFfYLjrkNBYtfmND3MisGMdA8E xpBKgxIzbvm0rs6wAp3TJMyF+BS1DcTlsI4C0ebaWvCOQSY1twTFVYqcFeuPSxvRC7qKpPXJ6VuSz D6YUh4v9oMqxLEG9LBc4gKhty0W62UaXj3p/RJf9LGQq0M7y7a+tnAzNr6CHeI7tGOh4+ySm2W5qv eDXXEiWOWfNLLHpS1flO1//uDSET48q+0RR8es0krT10KUUgn7IjLBH8UAe3FwombK4iS5fwUHtIe 7YrGqNA42dHH22q/K4kVSDMC8xaYkcEiO4NI5cUKoo1VWBP2nRmIipoZphN18hpJLPQPg7sVixojE N4SHXn7w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRE5D-000000083fm-4AND; Tue, 09 Jul 2024 16:52:51 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRE4x-000000083dm-3Psu for linux-arm-kernel@lists.infradead.org; Tue, 09 Jul 2024 16:52:37 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 2DD47614B0; Tue, 9 Jul 2024 16:52:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27920C3277B; Tue, 9 Jul 2024 16:52:34 +0000 (UTC) Date: Tue, 9 Jul 2024 17:52:31 +0100 From: Catalin Marinas To: Linus Torvalds Cc: Mark Rutland , Linux ARM Subject: Re: arm64 uaccess series Message-ID: References: <20240709161022.1035500-1-torvalds@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240709161022.1035500-1-torvalds@linux-foundation.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240709_095235_921316_9D8BD773 X-CRM114-Status: GOOD ( 18.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jul 09, 2024 at 09:01:58AM -0700, Linus Torvalds wrote: > This is also available at > > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git arm64-uaccess > > and is three patches, although I expect that I'll only merge the first > two in the 6.11 merge window because that final one is still a bit > special. > > I've been running variations of this on my Altra machine for the last > month or more, but admittedly my loads are trivial and uninteresting (ie > mostly kernel builds). So my test coevrage is not very wide. I can temporarily pull this branch and 'runtime-constants' into arm64 'for-kernelci'. It's an unstable branch, it doesn't end up in -next. It's just pointed at by various CI systems to get some wider testing. I can even pull all four branches if you think it's useful. > I like the bit 55 checks in that access_ok() rewrite - and they are > actually simpler than worrying about 64-bit overflow - but they are also > admittedly quite different from what the code does elsewhere, and > there's the whole discussion about how the top byte ignore should really > work. We are still debating this. I don't think the ABI change is that bad but, OTOH, user programs with MTE enabled (which would relax the access_ok()) haven't been tested much. As a kind of precaution, we could enforce the current behaviour via the sysctl abi.tagged_addr_disabled and wire it up via a static key. Currently this sysctl only prevents setting of the TIF_TAGGED_ADDR flag (and implicitly enforces stricter checks in access_ok()). -- Catalin