Messages in this thread | | | Subject | Re: [PATCH 2/5] livepatch: Allow architectures to specify an alternate ftrace location | From | Michael Ellerman <> | Date | Thu, 14 Apr 2016 23:06:18 +1000 |
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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@pobox.suse.cz
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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