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[217.140.101.70]) by mx.google.com with ESMTP id 26si3252056ejn.294.2019.05.22.07.16.21 for ; Wed, 22 May 2019 07:16:22 -0700 (PDT) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com 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) 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, 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)); }