From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE80418F2C1; Tue, 20 Aug 2024 17:30:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724175016; cv=none; b=XsMwLth9KwmTj36+uvEzsFwsrdjvLpAhNtOt/6bVggxQdemGCccHgNxSdhoTaVz9QoGuwz6G/klm1rNqaFEtE1VFaIGJ09fuYMNsxjttEShOgllez0jD5ikfAKyFTf4tzbMAYAKruKUPSRm0nsUeiV5Km/LJmC1hI/Kke9uR2YM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724175016; c=relaxed/simple; bh=EKv/6g0B787M/ao79ZkDIikg1jmgFTajJr+aTG8aYbA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oc6D3FPVwEqiiUqge9ArIjdh+BegmWJwxO9+mR/xm+Ya5hYzbyGbLI/O/HEDnwVTnMBhyITeAA8VLsZtrFvfWHrw/1wZMWmCjFmrMT4Ju2Bnw8KRO67++9Y7pmE+mGsF552aqad75pxEY0FSwLjb10YeuxDm1VfpuPPdG1J8qVA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id EFB55C4AF52; Tue, 20 Aug 2024 17:30:09 +0000 (UTC) Date: Tue, 20 Aug 2024 18:30:07 +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 , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , Kees Cook , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , Thiago Jung Bauermann , Ross Burton , 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 v10 13/40] arm64/mm: Map pages for guarded control stack Message-ID: References: <20240801-arm64-gcs-v10-0-699e2bd2190b@kernel.org> <20240801-arm64-gcs-v10-13-699e2bd2190b@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Aug 20, 2024 at 04:28:21PM +0100, Mark Brown wrote: > On Tue, Aug 20, 2024 at 03:59:21PM +0100, Catalin Marinas wrote: > > On Mon, Aug 19, 2024 at 05:33:24PM +0100, Mark Brown wrote: > > > On Mon, Aug 19, 2024 at 10:10:36AM +0100, Catalin Marinas wrote: > > > > Is there any arch restriction with setting BTI and GCS? It doesn't make > > > > sense but curious if it matters. We block the exec permission anyway > > > > (unless the BTI pages moved to PIE as well, I don't remember). > > > > As you say BTI should be meaningless for a non-executable page like GCS, > > > I'm not aware of any way in which it matters. BTI is separate to PIE. > > > My thoughts were whether we can get rid of this hunk entirely by > > handling it in the core code. We'd allow BTI if one wants such useless > > combination but clear VM_MAYEXEC in the core code (and ignore VM_SHARED > > since you can't set it anyway). > > I have to admit that the BTI because I was shoving _EXEC in there rather > than because it specifically needed to be blocked. So change the check > for VM_SHARED to a VM_WARN_ON(), and leave the _EXEC check for now > pending the above core change? Yes, sounds good. -- Catalin