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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1haiHa-0004d0-PW; Tue, 11 Jun 2019 15:01:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1haiHC-0003zY-3U for linux-arm-kernel@lists.infradead.org; Tue, 11 Jun 2019 15:01:31 +0000 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 AFDBE346; Tue, 11 Jun 2019 08:01:29 -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 103473F246; Tue, 11 Jun 2019 08:01:24 -0700 (PDT) Date: Tue, 11 Jun 2019 16:01:22 +0100 From: Catalin Marinas To: Andrey Konovalov Subject: Re: [PATCH v16 16/16] selftests, arm64: add a selftest for passing tagged pointers to kernel Message-ID: <20190611150122.GB63588@arrakis.emea.arm.com> References: <9e1b5998a28f82b16076fc85ab4f88af5381cf74.1559580831.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <9e1b5998a28f82b16076fc85ab4f88af5381cf74.1559580831.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190611_080130_239405_BE4AABE5 X-CRM114-Status: GOOD ( 14.73 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , kvm@vger.kernel.org, Szabolcs Nagy , Will Deacon , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Khalid Aziz , linux-kselftest@vger.kernel.org, Felix Kuehling , Vincenzo Frascino , Jacob Bramley , Leon Romanovsky , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, Christoph Hellwig , Jason Gunthorpe , Dmitry Vyukov , Dave Martin , Evgeniy Stepanov , linux-media@vger.kernel.org, Kevin Brodsky , Kees Cook , Ruben Ayrapetyan , Ramana Radhakrishnan , Alex Williamson , Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, Kostya Serebryany , Greg Kroah-Hartman , Yishai Hadas , linux-kernel@vger.kernel.org, Jens Wiklander , Lee Smith , Alexander Deucher , Andrew Morton , enh , Robin Murphy , Christian Koenig , Luc Van Oostenryck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jun 03, 2019 at 06:55:18PM +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. > > Signed-off-by: Andrey Konovalov BTW, you could add Co-developed-by: Catalin Marinas since I wrote the malloc() etc. hooks. > +static void *tag_ptr(void *ptr) > +{ > + unsigned long tag = rand() & 0xff; > + if (!ptr) > + return ptr; > + return (void *)((unsigned long)ptr | (tag << TAG_SHIFT)); > +} With the prctl() option, this function becomes (if you have a better idea, fine by me): ----------8<--------------- #include #include #define TAG_SHIFT (56) #define TAG_MASK (0xffUL << TAG_SHIFT) #define PR_SET_TAGGED_ADDR_CTRL 55 #define PR_GET_TAGGED_ADDR_CTRL 56 # define PR_TAGGED_ADDR_ENABLE (1UL << 0) 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) { static int tagged_addr_err = 1; unsigned long tag = 0; if (tagged_addr_err == 1) tagged_addr_err = prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0); if (!ptr) return ptr; if (!tagged_addr_err) tag = rand() & 0xff; return (void *)((unsigned long)ptr | (tag << TAG_SHIFT)); } -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel