From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.7 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 5E79C7D2EF for ; Wed, 12 Jun 2019 14:21:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2409272AbfFLOV1 (ORCPT ); Wed, 12 Jun 2019 10:21:27 -0400 Received: from foss.arm.com ([217.140.110.172]:53910 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409269AbfFLOV0 (ORCPT ); Wed, 12 Jun 2019 10:21:26 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D86152B; Wed, 12 Jun 2019 07:21:25 -0700 (PDT) Received: from e119884-lin.cambridge.arm.com (e119884-lin.cambridge.arm.com [10.1.196.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7D4B33F557; Wed, 12 Jun 2019 07:21:24 -0700 (PDT) From: Vincenzo Frascino To: linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Andrey Konovalov , Alexander Viro Subject: [PATCH v4 0/2] arm64 relaxed ABI Date: Wed, 12 Jun 2019 15:21:09 +0100 Message-Id: <20190612142111.28161-1-vincenzo.frascino@arm.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On arm64 the TCR_EL1.TBI0 bit has been always enabled on the arm64 kernel, hence the userspace (EL0) is allowed to set a non-zero value in the top byte but the resulting pointers are not allowed at the user-kernel syscall ABI boundary. This patchset proposes a relaxation of the ABI with which it is possible to pass tagged tagged pointers to the syscalls, when these pointers are in memory ranges obtained as described in tagged-address-abi.txt contained in this patch series. Since it is not desirable to relax the ABI to allow tagged user addresses into the kernel indiscriminately, this patchset documents a new sysctl interface (/proc/sys/abi/tagged_addr) that is used to prevent the applications from enabling the relaxed ABI and a new prctl() interface that can be used to enable or disable the relaxed ABI. This patchset should be merged together with [1]. [1] https://patchwork.kernel.org/cover/10674351/ Cc: Catalin Marinas Cc: Will Deacon CC: Andrey Konovalov CC: Alexander Viro Signed-off-by: Vincenzo Frascino Vincenzo Frascino (2): arm64: Define Documentation/arm64/tagged-address-abi.txt arm64: Relax Documentation/arm64/tagged-pointers.txt Documentation/arm64/tagged-address-abi.txt | 111 +++++++++++++++++++++ Documentation/arm64/tagged-pointers.txt | 23 +++-- 2 files changed, 127 insertions(+), 7 deletions(-) create mode 100644 Documentation/arm64/tagged-address-abi.txt -- 2.21.0