From: Thiago Jung Bauermann Subject: Re: [RFC v6 27/62] powerpc: helper to validate key-access permissions of a pte Date: Fri, 28 Jul 2017 18:00:02 -0300 Message-ID: <87tw1we0q5.fsf@linux.vnet.ibm.com> References: <1500177424-13695-1-git-send-email-linuxram@us.ibm.com> <1500177424-13695-28-git-send-email-linuxram@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-reply-to: <1500177424-13695-28-git-send-email-linuxram@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: Ram Pai 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 List-Id: linux-arch.vger.kernel.org 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)". -- Thiago Jung Bauermann IBM Linux Technology Center