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[217.140.110.172]) by mx.google.com with ESMTP id g24si1150134eda.131.2019.06.11.08.01.30 for ; Tue, 11 Jun 2019 08:01:30 -0700 (PDT) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com 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 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 , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Kevin Brodsky , Szabolcs Nagy 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9e1b5998a28f82b16076fc85ab4f88af5381cf74.1559580831.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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