From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751673AbeCNVD7 (ORCPT ); Wed, 14 Mar 2018 17:03:59 -0400 Received: from mail-qt0-f195.google.com ([209.85.216.195]:33256 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405AbeCNVDz (ORCPT ); Wed, 14 Mar 2018 17:03:55 -0400 X-Google-Smtp-Source: AG47ELuDr939fQ4V9DJdebnx9a7h2q722SN6jy71DSf3hbMi47M6jL2WptK5p2bmJd25ZGSEGp+VYA== From: Ram Pai To: mpe@ellerman.id.au Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, akpm@linux-foundation.org, dave.hansen@intel.com, benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, ebiederm@xmission.com, linuxram@us.ibm.com, corbet@lwn.net, arnd@arndb.de, fweimer@redhat.com, msuchanek@suse.com, Ulrich.Weigand@de.ibm.com Subject: [PATCH v3] powerpc: treat pkey-0 special Date: Wed, 14 Mar 2018 14:01:35 -0700 Message-Id: <1521061295-22605-1-git-send-email-linuxram@us.ibm.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Applications need the ability to associate an address-range with some key and latter revert to its initial default key. Pkey-0 comes close to providing this function but falls short, because the current implementation disallows applications to explicitly associate pkey-0 to the address range. This patch clarifies the semantics of pkey-0 and provides the corresponding implementation on powerpc. Pkey-0 is special with the following semantics. (a) it is implicitly allocated and can never be freed. It always exists. (b) it is the default key assigned to any address-range. (c) it can be explicitly associated with any address-range. Tested on powerpc. History: v3 : added clarification of the semantics of pkey0. -- suggested by Dave Hansen v2 : split the patch into two, one for x86 and one for powerpc -- suggested by Michael Ellermen cc: Dave Hansen cc: Michael Ellermen cc: Ingo Molnar Signed-off-by: Ram Pai --- arch/powerpc/include/asm/pkeys.h | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h index 0409c80..3c1deec 100644 --- a/arch/powerpc/include/asm/pkeys.h +++ b/arch/powerpc/include/asm/pkeys.h @@ -101,10 +101,18 @@ static inline u16 pte_to_pkey_bits(u64 pteflags) static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) { - /* A reserved key is never considered as 'explicitly allocated' */ - return ((pkey < arch_max_pkey()) && - !__mm_pkey_is_reserved(pkey) && - __mm_pkey_is_allocated(mm, pkey)); + /* pkey 0 is allocated by default. */ + if (!pkey) + return true; + + if (pkey < 0 || pkey >= arch_max_pkey()) + return false; + + /* Reserved keys are never allocated. */ + if (__mm_pkey_is_reserved(pkey)) + return false; + + return __mm_pkey_is_allocated(mm, pkey); } extern void __arch_activate_pkey(int pkey); @@ -150,7 +158,8 @@ static inline int mm_pkey_free(struct mm_struct *mm, int pkey) if (static_branch_likely(&pkey_disabled)) return -1; - if (!mm_pkey_is_allocated(mm, pkey)) + /* pkey 0 cannot be freed */ + if (!pkey || !mm_pkey_is_allocated(mm, pkey)) return -EINVAL; /* -- 1.8.3.1