Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754487Ab3GAQdV (ORCPT ); Mon, 1 Jul 2013 12:33:21 -0400 Received: from mx4-phx2.redhat.com ([209.132.183.25]:57778 "EHLO mx4-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751386Ab3GAQdT convert rfc822-to-8bit (ORCPT ); Mon, 1 Jul 2013 12:33:19 -0400 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Subject: Re: [RFC PATCH] Allow optional module parameters References: <87ehfhtftn.fsf@rustcorp.com.au> <87sj3tsawh.fsf@rustcorp.com.au> <87hak8qfu5.fsf@rustcorp.com.au> <87sj3qpwdz.fsf@rustcorp.com.au> <87a9m6sri3.fsf@rustcorp.com.au> From: Jonathan Masters MIME-Version: 1.0 In-Reply-To: <87a9m6sri3.fsf@rustcorp.com.au> Message-Id: <9F26321B-7088-4D16-80D5-72EB388F8E49@redhat.com> Date: Mon, 1 Jul 2013 12:33:11 -0400 (EDT) To: Rusty Russell Cc: Lucas De Marchi , Andy Lutomirski , "linux-kernel@vger.kernel.org" , Ben Hutchings , "linux-kbuild@vger.kernel.org" X-Mailer: Zimbra 8.0.3_GA_5664 (MobileSync - Apple-iPad2C5/1002.329) Thread-Topic: Allow optional module parameters Thread-Index: lVvC5sUGXGoG5aIWIYn4o9qRXo5EpQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4502 Lines: 112 One caveat. Sometimes we have manufactured parameters intentionally to cause a module to fail. We should standardize that piece. -- Sent from my iPad On Jul 1, 2013, at 4:53, Rusty Russell wrote: > Rusty Russell writes: >> Lucas De Marchi writes: >>> Hi Rusty, >>> >>> On Mon, Mar 18, 2013 at 11:32 PM, Rusty Russell wrote: >>>> Andy Lutomirski writes: >>>>> On Sun, Mar 17, 2013 at 7:24 PM, Rusty Russell wrote: >>>>>> Andy Lutomirski writes: >>>>>>> On Thu, Mar 14, 2013 at 10:03 PM, Rusty Russell wrote: >>>>>>>> Err, yes. Don't remove module parameters, they're part of the API. Do >>>>>>>> you have a particular example? >>>>>>> >>>>>>> So things like i915.i915_enable_ppgtt, which is there to enable >>>>>>> something experimental, needs to stay forever once the relevant >>>>>>> feature becomes non-experimental and non-optional? This seems silly. >>>> ... >>>>>>> Having the module parameter go away while still allowing the module to >>>>>>> load seems like a good solution (possibly with a warning in the logs >>>>>>> so the user can eventually delete the parameter). >>>>>> >>>>>> Why not do that for *every* missing parameter then? Why have this weird >>>>>> notation where the user must know that the parameter might one day go >>>>>> away? >>>>> >>>>> Fair enough. What about the other approach, then? Always warn if an >>>>> option doesn't match (built-in or otherwise) but load the module >>>>> anyways. >>>> >>>> What does everyone think of this? Jon, Lucas, does this match your >>>> experience? >>>> >>>> Thanks, >>>> Rusty. >>>> >>>> Subject: modules: don't fail to load on unknown parameters. >>>> >>>> Although parameters are supposed to be part of the kernel API, experimental >>>> parameters are often removed. In addition, downgrading a kernel might cause >>>> previously-working modules to fail to load. >>> >>> I agree with this reasoning >>> >>>> >>>> On balance, it's probably better to warn, and load the module anyway. >>> >>> However loading the module anyway would bring at least one drawback: >>> if the user made a typo when passing the option the module would load >>> anyway and he will probably not even look in the log, since there's >>> was no errors from modprobe. > > OK, so I've had this patch on the backburner, but noone has come up with > anything better so I'll queue it into modules-next now. > > Thanks, > Rusty. > > modules: don't fail to load on unknown parameters. > > Although parameters are supposed to be part of the kernel API, experimental > parameters are often removed. In addition, downgrading a kernel might cause > previously-working modules to fail to load. > > On balance, it's probably better to warn, and load the module anyway. > This may let through a typo, but at least the logs will show it. > > Reported-by: Andy Lutomirski > Signed-off-by: Rusty Russell > > diff --git a/kernel/module.c b/kernel/module.c > index 3c2c72d..46db10a 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3206,6 +3206,17 @@ out: > return err; > } > > +static int unknown_module_param_cb(char *param, char *val, const char *modname) > +{ > + /* Check for magic 'dyndbg' arg */ > + int ret = ddebug_dyndbg_module_param_cb(param, val, modname); > + if (ret != 0) { > + printk(KERN_WARNING "%s: unknown parameter '%s' ignored\n", > + modname, param); > + } > + return 0; > +} > + > /* Allocate and load the module: note that size of section 0 is always > zero, and we rely on this for optional sections. */ > static int load_module(struct load_info *info, const char __user *uargs, > @@ -3292,7 +3303,7 @@ static int load_module(struct load_info *info, const char __user *uargs, > > /* Module is ready to execute: parsing args may do that. */ > err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, > - -32768, 32767, &ddebug_dyndbg_module_param_cb); > + -32768, 32767, unknown_module_param_cb); > if (err < 0) > goto bug_cleanup; > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/