Path: csiph.com!news.mixmin.net!aioe.org!news.servidellagleba.it!bofh.it!news.nic.it!robomod From: Anshuman Khandual Newsgroups: linux.kernel Subject: Re: [RFC v2 00/12] powerpc: Memory Protection Keys Date: Tue, 20 Jun 2017 08:10:02 +0200 Message-ID: References: User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Tm-As-Mml: disable X-Cbid: 17062006-0044-0000-0000-0000027068AD X-Ibm-Av-Detection: SAVI=unused REMOTE=unused XFE=unused X-Cbparentid: 17062006-0045-0000-0000-000007000C70 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-20_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1706200113 Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 40 Organization: linux.* mail to news gateway X-Original-Cc: dave.hansen@intel.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com X-Original-Date: Tue, 20 Jun 2017 11:35:00 +0530 X-Original-Message-ID: <09886a82-872d-8a43-fd61-549cf006ce6e@linux.vnet.ibm.com> X-Original-References: <1497671564-20030-1-git-send-email-linuxram@us.ibm.com> <1497935415.2255.1.camel@gmail.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1670312 On 06/20/2017 10:40 AM, Balbir Singh wrote: > On Fri, 2017-06-16 at 20:52 -0700, Ram Pai wrote: >> Memory protection keys enable applications to protect its >> address space from inadvertent access or corruption from >> itself. > > I presume by itself you mean protection between threads? Between threads due to race conditions or from the same thread because of programming error. > >> >> The overall idea: >> >> A process allocates a key and associates it with >> a address range within its address space. > > OK, so this is per VMA? Yeah but the same key can be given to multiple VMAs. Any change will effect every VMA who got tagged by it. > >> The process than can dynamically set read/write >> permissions on the key without involving the >> kernel. > > This bit is not clear, how can the key be set without > involving the kernel? I presume you mean the key is set With pkey_mprotect() system call, all the effected PTEs get tagged for once. Switching the permission happens just by writing into the register on the fly. > in the PTE's and the access protection values can be > set without involving the kernel? PTE setting happens once, access protection values can be changed on the fly through register.