Re: [RFC PATCH] Allow optional module parameters
From: Rusty Russell
Date: Mon Jul 01 2013 - 04:53:13 EST
Rusty Russell <rusty@xxxxxxxxxxxxxxx> writes:
>
Lucas De Marchi <lucas.demarchi@xxxxxxxxxxxxxx> writes:
>
> Hi Rusty,
>
>
>
> On Mon, Mar 18, 2013 at 11:32 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
>
>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:
>
>>> On Sun, Mar 17, 2013 at 7:24 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
>
>>>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:
>
>>>>> On Thu, Mar 14, 2013 at 10:03 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> 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 <luto@xxxxxxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
More majordomo info at
http://vger.kernel.org/majordomo-info.html
Please read the FAQ at
http://www.tux.org/lkml/