Re: [RFC PATCH] Allow optional module parameters
From: Jonathan Masters
Date: Mon Jul 01 2013 - 12:33:25 EST
One caveat. Sometimes we have manufactured parameters intentionally to cause a module to fail. We should standardize that piece.
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On Jul 1, 2013, at 4:53, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
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Rusty Russell <rusty@xxxxxxxxxxxxxxx> writes:
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> Lucas De Marchi <lucas.demarchi@xxxxxxxxxxxxxx> writes:
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>> Hi Rusty,
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>>
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>> On Mon, Mar 18, 2013 at 11:32 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
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>>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:
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>>>> On Sun, Mar 17, 2013 at 7:24 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
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>>>>> Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes:
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>>>>>> On Thu, Mar 14, 2013 at 10:03 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
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>>>>>>> Err, yes. Don't remove module parameters, they're part of the API. Do
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>>>>>>> you have a particular example?
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>>>>>>
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>>>>>> So things like i915.i915_enable_ppgtt, which is there to enable
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>>>>>> something experimental, needs to stay forever once the relevant
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>>>>>> feature becomes non-experimental and non-optional? This seems silly.
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>>> ...
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>>>>>> Having the module parameter go away while still allowing the module to
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>>>>>> load seems like a good solution (possibly with a warning in the logs
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>>>>>> so the user can eventually delete the parameter).
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>>>>>
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>>>>> Why not do that for *every* missing parameter then? Why have this weird
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>>>>> notation where the user must know that the parameter might one day go
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>>>>> away?
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>>>>
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>>>> Fair enough. What about the other approach, then? Always warn if an
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>>>> option doesn't match (built-in or otherwise) but load the module
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>>>> anyways.
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>>>
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>>> What does everyone think of this? Jon, Lucas, does this match your
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>>> experience?
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>>>
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>>> Thanks,
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>>> Rusty.
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>>>
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>>> Subject: modules: don't fail to load on unknown parameters.
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>>>
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>>> Although parameters are supposed to be part of the kernel API, experimental
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>>> parameters are often removed. In addition, downgrading a kernel might cause
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>>> previously-working modules to fail to load.
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>>
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>> I agree with this reasoning
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>>
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>>>
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>>> On balance, it's probably better to warn, and load the module anyway.
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>>
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>> However loading the module anyway would bring at least one drawback:
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>> if the user made a typo when passing the option the module would load
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>> anyway and he will probably not even look in the log, since there's
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>> was no errors from modprobe.
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>
OK, so I've had this patch on the backburner, but noone has come up with
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anything better so I'll queue it into modules-next now.
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>
Thanks,
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Rusty.
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>
modules: don't fail to load on unknown parameters.
>
>
Although parameters are supposed to be part of the kernel API, experimental
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parameters are often removed. In addition, downgrading a kernel might cause
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previously-working modules to fail to load.
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>
On balance, it's probably better to warn, and load the module anyway.
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This may let through a typo, but at least the logs will show it.
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>
Reported-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
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Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
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diff --git a/kernel/module.c b/kernel/module.c
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index 3c2c72d..46db10a 100644
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--- a/kernel/module.c
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+++ b/kernel/module.c
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@@ -3206,6 +3206,17 @@ out:
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return err;
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}
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+static int unknown_module_param_cb(char *param, char *val, const char *modname)
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+{
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+ /* Check for magic 'dyndbg' arg */
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+ int ret = ddebug_dyndbg_module_param_cb(param, val, modname);
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+ if (ret != 0) {
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+ printk(KERN_WARNING "%s: unknown parameter '%s' ignored\n",
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+ modname, param);
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+ }
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+ return 0;
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+}
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+
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/* Allocate and load the module: note that size of section 0 is always
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zero, and we rely on this for optional sections. */
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static int load_module(struct load_info *info, const char __user *uargs,
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@@ -3292,7 +3303,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
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/* Module is ready to execute: parsing args may do that. */
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err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
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- -32768, 32767, &ddebug_dyndbg_module_param_cb);
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+ -32768, 32767, unknown_module_param_cb);
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if (err < 0)
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goto bug_cleanup;
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>
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