From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ram Pai Subject: Re: [RFC v5 12/38] mm: ability to disable execute permission on a key at creation Date: Tue, 11 Jul 2017 14:51:05 -0700 Message-ID: <20170711215105.GA5542@ram.oc3035372033.ibm.com> References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <1499289735-14220-13-git-send-email-linuxram@us.ibm.com> <3bd2ffd4-33ad-ce23-3db1-d1292e69ca9b@intel.com> <1499808577.2865.30.camel@kernel.crashing.org> Reply-To: Ram Pai Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1499808577.2865.30.camel@kernel.crashing.org> Sender: owner-linux-mm@kvack.org To: Benjamin Herrenschmidt Cc: Dave Hansen , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, arnd@arndb.de, corbet@lwn.net, mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, khandual@linux.vnet.ibm.com List-Id: linux-arch.vger.kernel.org On Wed, Jul 12, 2017 at 07:29:37AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-07-11 at 11:11 -0700, Dave Hansen wrote: > > On 07/05/2017 02:21 PM, Ram Pai wrote: > > > Currently sys_pkey_create() provides the ability to disable read > > > and write permission on the key, at creation. powerpc has the > > > hardware support to disable execute on a pkey as well.This patch > > > enhances the interface to let disable execute at key creation > > > time. x86 does not allow this. Hence the next patch will add > > > ability in x86 to return error if PKEY_DISABLE_EXECUTE is > > > specified. > > That leads to the question... How do you tell userspace. > > (apologies if I missed that in an existing patch in the series) > > How do we inform userspace of the key capabilities ? There are at least > two things userspace may want to know already: > > - What protection bits are supported for a key the userspace is the one which allocates the keys and enables/disables the protection bits on the key. the kernel is just a facilitator. Now if the use space wants to know the current permissions on a given key, it can just read the AMR/PKRU register on powerpc/intel respectively. > > - How many keys exist There is no standard way of finding this other than trying to allocate as many till you fail. A procfs or sysfs file can be added to expose this information. > > - Which keys are available for use by userspace. On PowerPC, the > kernel can reserve some keys for itself, so can the hypervisor. In > fact, they do. this information can be exposed through /proc or /sysfs I am sure there will be more demands and requirements as applications start leveraging these feature. RP > > Cheers, > Ben. -- Ram Pai -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33465 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933178AbdGKVvQ (ORCPT ); Tue, 11 Jul 2017 17:51:16 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6BLnGGF090414 for ; Tue, 11 Jul 2017 17:51:15 -0400 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bn0mv6hba-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 11 Jul 2017 17:51:15 -0400 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Jul 2017 17:51:15 -0400 Date: Tue, 11 Jul 2017 14:51:05 -0700 From: Ram Pai Subject: Re: [RFC v5 12/38] mm: ability to disable execute permission on a key at creation Reply-To: Ram Pai References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <1499289735-14220-13-git-send-email-linuxram@us.ibm.com> <3bd2ffd4-33ad-ce23-3db1-d1292e69ca9b@intel.com> <1499808577.2865.30.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1499808577.2865.30.camel@kernel.crashing.org> Message-ID: <20170711215105.GA5542@ram.oc3035372033.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Benjamin Herrenschmidt Cc: Dave Hansen , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, arnd@arndb.de, corbet@lwn.net, mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, khandual@linux.vnet.ibm.com Message-ID: <20170711215105.QN-lO2gCVn9zbZWlrw3qMXaUQMeo_2fQgqOcuI5zvdU@z> On Wed, Jul 12, 2017 at 07:29:37AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-07-11 at 11:11 -0700, Dave Hansen wrote: > > On 07/05/2017 02:21 PM, Ram Pai wrote: > > > Currently sys_pkey_create() provides the ability to disable read > > > and write permission on the key, at creation. powerpc has the > > > hardware support to disable execute on a pkey as well.This patch > > > enhances the interface to let disable execute at key creation > > > time. x86 does not allow this. Hence the next patch will add > > > ability in x86 to return error if PKEY_DISABLE_EXECUTE is > > > specified. > > That leads to the question... How do you tell userspace. > > (apologies if I missed that in an existing patch in the series) > > How do we inform userspace of the key capabilities ? There are at least > two things userspace may want to know already: > > - What protection bits are supported for a key the userspace is the one which allocates the keys and enables/disables the protection bits on the key. the kernel is just a facilitator. Now if the use space wants to know the current permissions on a given key, it can just read the AMR/PKRU register on powerpc/intel respectively. > > - How many keys exist There is no standard way of finding this other than trying to allocate as many till you fail. A procfs or sysfs file can be added to expose this information. > > - Which keys are available for use by userspace. On PowerPC, the > kernel can reserve some keys for itself, so can the hypervisor. In > fact, they do. this information can be exposed through /proc or /sysfs I am sure there will be more demands and requirements as applications start leveraging these feature. RP > > Cheers, > Ben. -- Ram Pai