Hi Everyone,
On Wed, Feb 05, 2025 at 09:43:12AM +0100, Rasmus Villemoes wrote:
> On Mon, Feb 03 2025, Shyam Saini <shyamsaini@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > Move the following to module.h to allow common usages:
> > - lookup_or_create_module_kobject()
> > - to_module_attr
> > - to_module_kobject
> >
> > This makes lookup_or_create_module_kobject() as inline.
> >
> > Signed-off-by: Shyam Saini <shyamsaini@xxxxxxxxxxxxxxxxxxx>
> > ---
> > include/linux/module.h | 39 +++++++++++++++++++++++++++++++++++++++
> > kernel/params.c | 39 ---------------------------------------
> > 2 files changed, 39 insertions(+), 39 deletions(-)
> >
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index 12f8a7d4fc1c..ba5f5e6c3927 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -894,8 +894,47 @@ static inline void *module_writable_address(struct module *mod, void *loc)
> > #endif /* CONFIG_MODULES */
> >
> > #ifdef CONFIG_SYSFS
> > +/* sysfs output in /sys/modules/XYZ/parameters/ */
> > +#define to_module_attr(n) container_of_const(n, struct module_attribute, attr)
> > +#define to_module_kobject(n) container_of(n, struct module_kobject, kobj)
> > extern struct kset *module_kset;
> > extern const struct kobj_type module_ktype;
> > +
> > +static inline struct module_kobject * __init lookup_or_create_module_kobject(const char *name)
>
> As others have said, this is way too big for an inline. Also, __init is
> at best harmless (if it is indeed inlined into all callers), but if for
> whatever reason the compiler decides to emit an OOL version, we
> definitely do not want that in .init.text as we are now calling it from
> non-init code.
>
> > +{
> > + struct module_kobject *mk;
> > + struct kobject *kobj;
> > + int err;
> > +
> > + kobj = kset_find_obj(module_kset, name);
> > + if (kobj) {
> > + mk = to_module_kobject(kobj);
> > + } else {
> > + mk = kzalloc(sizeof(struct module_kobject), GFP_KERNEL);
> > + BUG_ON(!mk);
> > +
>
> And while the BUG_ON() is borderline acceptable in the current,
> only-used-during-init, state, that definitely must go away once the
> function can be called from non-init code.
>
> This is what I alluded to when I said that the function might need some
> refactoring before module_add_driver can start using it.
>
> I'd say that the BUG_ON can simply be removed and replaced by a return
> NULL; an "impossible" error case that can already be hit by some of the
> code below, so callers have to be prepared for it anyway. If the
> allocation fails (during early boot or later), the allocator already
> makes a lot of noise, so there's no reason to even do a WARN_ON, and
> since it "only" affects certain /sys objects, it's probably better to
> let the machine try to complete boot instead of killing it.
>
> Also, I agree with the suggestion to drop/outdent the whole else{} branch by
> changing the if() to do "return to_module_kobject(kobj);".
>
> To summarize:
>
> - refactor to do an early return
>
> - drop BUG_ON, replace by return NULL.
>
> - drop static and __init, perhaps change __init to __modinit (which is a
> pre-existing #define in params.c, so the function remains __init if
> !CONFIG_MODULES), add an appropriate declaration somewhere, and if you
> like, also do the rename
>
> - make use of it from module_add_driver()
I have addressed these feedback in v2, thank you for the reviews.
Thanks,
Shyam
