On Thu, 2016-04-14 at 14:01 +0200, Miroslav Benes wrote:
> On Wed, 13 Apr 2016, Michael Ellerman wrote:
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index d68fbf63b083..b0476bb30f92 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -298,6 +298,19 @@ unlock:
> > rcu_read_unlock();
> > }
> >
> > +/*
> > + * Convert a function address into the appropriate ftrace location.
> > + *
> > + * Usually this is just the address of the function, but on some architectures
> > + * it's more complicated so allow them to provide a custom behaviour.
> > + */
> > +#ifndef klp_get_ftrace_location
> > +static unsigned long klp_get_ftrace_location(unsigned long faddr)
> > +{
> > + return faddr;
> > +}
> > +#endif
>
> Whoah, what an ugly hack :)
Hey it's a "cool trick" ;)
> Note to my future self - This is what you want to do if you need a weak
> static inline function.
>
> static inline is probably unnecessary here so __weak function would be
> enough. It would introduce powerpc-specific livepatch.c though because of
> it and this is not worth it.
Yeah that was my logic, at least for now. We can always change it in future
to be weak if anyone cares deeply.
> > static void klp_disable_func(struct klp_func *func)
> > {
> > struct klp_ops *ops;
> > @@ -312,8 +325,14 @@ static void klp_disable_func(struct klp_func *func)
> > return;
> >
> > if (list_is_singular(&ops->func_stack)) {
> > + unsigned long ftrace_loc;
>
> This is a nit, but could you move the definition up to have them all in
> one place to be consistent with the rest of the code? The same applies to
> klp_enable_func() below.
Hmm, actually I moved it in there because you pointed out we only needed it
inside the if:
http://lkml.kernel.org/r/alpine.LNX.2.00.1603151113020.20252@xxxxxxxxxxxxx
Thinking about it, we need ftrace_loc only in cases where we call
ftrace_set_filter_ip() right? So we can move klp_get_ftrace_location()
call to appropriate if branch both in klp_disable_func() and
klp_enable_func().
But I guess you meant the function call, not the variable declaration.
Personally I think it's better this way, as the variable is in scope for the
shortest possible amount of time, but I can change it if you want me to.
cheers
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