From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75DC9C282CE for ; Wed, 22 May 2019 14:16:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55F672173E for ; Wed, 22 May 2019 14:16:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729003AbfEVOQW (ORCPT ); Wed, 22 May 2019 10:16:22 -0400 Received: from foss.arm.com ([217.140.101.70]:52330 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727284AbfEVOQV (ORCPT ); Wed, 22 May 2019 10:16:21 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E408280D; Wed, 22 May 2019 07:16:20 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 57C233F718; Wed, 22 May 2019 07:16:15 -0700 (PDT) Date: Wed, 22 May 2019 15:16:12 +0100 From: Catalin Marinas To: Andrey Konovalov Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Luc Van Oostenryck , Dave Martin , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v15 17/17] selftests, arm64: add a selftest for passing tagged pointers to kernel Message-ID: <20190522141612.GA28122@arrakis.emea.arm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Mon, May 06, 2019 at 06:31:03PM +0200, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > This patch adds a simple test, that calls the uname syscall with a > tagged user pointer as an argument. Without the kernel accepting tagged > user pointers the test fails with EFAULT. That's probably sufficient for a simple example. Something we could add to Documentation maybe is a small library that can be LD_PRELOAD'ed so that you can run a lot more tests like LTP. We could add this to selftests but I think it's too glibc specific. --------------------8<------------------------------------ #include #define TAG_SHIFT (56) #define TAG_MASK (0xffUL << TAG_SHIFT) void *__libc_malloc(size_t size); void __libc_free(void *ptr); void *__libc_realloc(void *ptr, size_t size); void *__libc_calloc(size_t nmemb, size_t size); static void *tag_ptr(void *ptr) { unsigned long tag = rand() & 0xff; if (!ptr) return ptr; return (void *)((unsigned long)ptr | (tag << TAG_SHIFT)); } static void *untag_ptr(void *ptr) { return (void *)((unsigned long)ptr & ~TAG_MASK); } void *malloc(size_t size) { return tag_ptr(__libc_malloc(size)); } void free(void *ptr) { __libc_free(untag_ptr(ptr)); } void *realloc(void *ptr, size_t size) { return tag_ptr(__libc_realloc(untag_ptr(ptr), size)); } void *calloc(size_t nmemb, size_t size) { return tag_ptr(__libc_calloc(nmemb, size)); }