From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 0F8226B05A3 for ; Sat, 29 Jul 2017 20:39:48 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id 125so317864638pgi.2 for ; Sat, 29 Jul 2017 17:39:48 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id z185si1569317pgb.54.2017.07.29.17.39.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 29 Jul 2017 17:39:47 -0700 (PDT) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6U0clRQ039341 for ; Sat, 29 Jul 2017 20:39:46 -0400 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0a-001b2d01.pphosted.com with ESMTP id 2c0np48hpk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sat, 29 Jul 2017 20:39:46 -0400 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 29 Jul 2017 20:39:45 -0400 Date: Sat, 29 Jul 2017 17:39:24 -0700 From: Ram Pai Subject: Re: [RFC v6 27/62] powerpc: helper to validate key-access permissions of a pte Reply-To: Ram Pai References: <1500177424-13695-1-git-send-email-linuxram@us.ibm.com> <1500177424-13695-28-git-send-email-linuxram@us.ibm.com> <87tw1we0q5.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87tw1we0q5.fsf@linux.vnet.ibm.com> Message-Id: <20170730003924.GJ5664@ram.oc3035372033.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Thiago Jung Bauermann Cc: 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, mhocko@kernel.org, dave.hansen@intel.com, mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, akpm@linux-foundation.org, khandual@linux.vnet.ibm.com On Fri, Jul 28, 2017 at 06:00:02PM -0300, Thiago Jung Bauermann wrote: > > Ram Pai writes: > > --- a/arch/powerpc/mm/pkeys.c > > +++ b/arch/powerpc/mm/pkeys.c > > @@ -201,3 +201,36 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, > > */ > > return vma_pkey(vma); > > } > > + > > +static bool pkey_access_permitted(int pkey, bool write, bool execute) > > +{ > > + int pkey_shift; > > + u64 amr; > > + > > + if (!pkey) > > + return true; > > + > > + pkey_shift = pkeyshift(pkey); > > + if (!(read_uamor() & (0x3UL << pkey_shift))) > > + return true; > > + > > + if (execute && !(read_iamr() & (IAMR_EX_BIT << pkey_shift))) > > + return true; > > + > > + if (!write) { > > + amr = read_amr(); > > + if (!(amr & (AMR_RD_BIT << pkey_shift))) > > + return true; > > + } > > + > > + amr = read_amr(); /* delay reading amr uptil absolutely needed */ > > Actually, this is causing amr to be read twice in case control enters > the "if (!write)" block above but doesn't enter the other if block nested > in it. > > read_amr should be called only once, right before "if (!write)". the code can be simplified without having to read amr twice. will fix it. thanks, RP > > -- > Thiago Jung Bauermann > IBM Linux Technology Center -- 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