From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx125.postini.com [74.125.245.125]) by kanga.kvack.org (Postfix) with SMTP id 633E46B00B7 for ; Wed, 22 May 2013 09:42:44 -0400 (EDT) Date: Wed, 22 May 2013 14:41:24 +0100 From: Russell King - ARM Linux Subject: Re: [PATCH v2 00/10] uaccess: better might_sleep/might_fault behavior Message-ID: <20130522134124.GD18614@n2100.arm.linux.org.uk> References: <201305221125.36284.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201305221125.36284.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Arnd Bergmann Cc: "Michael S. Tsirkin" , linux-m32r-ja@ml.linux-m32r.org, kvm@vger.kernel.org, Peter Zijlstra , Catalin Marinas , Will Deacon , David Howells , linux-mm@kvack.org, Paul Mackerras , "H. Peter Anvin" , linux-arch@vger.kernel.org, linux-am33-list@redhat.com, Hirokazu Takata , x86@kernel.org, Ingo Molnar , Benjamin Herrenschmidt , microblaze-uclinux@itee.uq.edu.au, Chris Metcalf , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Michal Simek , linux-m32r@ml.linux-m32r.org, linux-kernel@vger.kernel.org, Koichi Yasutake , linuxppc-dev@lists.ozlabs.org On Wed, May 22, 2013 at 11:25:36AM +0200, Arnd Bergmann wrote: > Given the most commonly used functions and a couple of architectures > I'm familiar with, these are the ones that currently call might_fault() > > x86-32 x86-64 arm arm64 powerpc s390 generic > copy_to_user - x - - - x x > copy_from_user - x - - - x x > put_user x x x x x x x > get_user x x x x x x x > __copy_to_user x x - - x - - > __copy_from_user x x - - x - - > __put_user - - x - x - - > __get_user - - x - x - - > > WTF? I think your table is rather screwed - especially on ARM. Tell me - how can __copy_to_user() use might_fault() but copy_to_user() not when copy_to_user() is implemented using __copy_to_user() ? Same for copy_from_user() but the reverse argument - there's nothing special in our copy_from_user() which would make it do might_fault() when __copy_from_user() wouldn't. The correct position for ARM is: our (__)?(pu|ge)t_user all use might_fault(), but (__)?copy_(to|from)_user do not. Neither does (__)?clear_user. We might want to fix those to use might_fault(). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org