From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH] [RFC] Taint the kernel for unsafe module options Date: Thu, 6 Mar 2014 08:58:35 +0100 Message-ID: <20140306075835.GC17001@phenom.ffwll.local> References: <1394011994-30604-1-git-send-email-daniel.vetter@ffwll.ch> <87r46gywul.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ee0-f41.google.com (mail-ee0-f41.google.com [74.125.83.41]) by gabe.freedesktop.org (Postfix) with ESMTP id 865A2FAB20 for ; Wed, 5 Mar 2014 23:58:40 -0800 (PST) Received: by mail-ee0-f41.google.com with SMTP id t10so946439eei.0 for ; Wed, 05 Mar 2014 23:58:39 -0800 (PST) Content-Disposition: inline In-Reply-To: <87r46gywul.fsf@rustcorp.com.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Rusty Russell Cc: Li Zhong , Daniel Vetter , Intel Graphics Development , linux-kernel@vger.kernel.org, Jean Delvare , Andrew Morton , Jon Mason List-Id: intel-gfx@lists.freedesktop.org On Thu, Mar 06, 2014 at 11:19:54AM +1030, Rusty Russell wrote: > Daniel Vetter writes: > > Users just love to set random piles of options since surely enabling > > all the experimental stuff helps. Later on we get bug reports because > > it all fell apart. > > > > Even more fun when it's labelled a regression when some change only > > just made the feature possible (e.g. stolen memory fixes suddenly > > making fbc possible). > > > > Make it clear that users are playing with fire here. In drm/i915 all > > these options follow the same pattern of using -1 as the per-machine > > default, and any other value being used for force the parameter. > > > > Adding a pile of cc's to solicit input and figure out whether this > > would be generally useful - this quick rfc is just for drm/i915. > > If this is a good idea, you can write a macro module_param_unsafe_named > which is a general wrapper. For this to work I need to somehow store the safe default value somewhere. since with bools or strings there really isn't such a thing, even less than with integers where my fairly abitrary -1 choice is already restricting. But I don't have a good idea how to do that, since creating a local static struct in the macro to store the default + the pointer to the storage location feels a bit ugly. > > -module_param_named(modeset, i915.modeset, int, 0400); > > Wait, WTF? Why do you prefix i915 here manually? That means that > the commandline parameter would be "i915.i915.modeset=" and the > module parameter would be "i915.modeset="... Nope, this is the named macro. The name of the param is the first parameter to the macro "modeset", "i915.modeset" is just the variable it'll get stored in. We've specifically switched to the _named version to avoid ugly i915.i915* paramters ;-) -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch