Re: [PATCH] objtool,static_call: Don't emit static_call_site for .exit.text

From: Peter Zijlstra
Date: Thu Mar 18 2021 - 04:31:21 EST

On Thu, Mar 18, 2021 at 08:59:45AM +0100, Peter Zijlstra wrote:
> On Wed, Mar 17, 2021 at 07:02:12PM -0500, Josh Poimboeuf wrote:
> > On Wed, Mar 17, 2021 at 01:45:57PM +0100, Peter Zijlstra wrote:
> > > arguably it simply isn't a good idea to use static_call() in __exit
> > > code anyway, since module unload is never a performance critical path.
> >
> > Couldn't you make the same argument about __init functions, which are
> > allowed to do static calls?
> I suppose we could indeed make that argument. Much of that code was
> copied from jump_label without much consideration. And I now I suppose
> I'll have to consider jump_label in __exit too :/
> > We might consider a STATIC_CALL_SITE_EXIT flag, but I suppose we've run
> > out of flag space.
> Yeah, we're definitely short on flags. Let me try and figure out when
> exactly it's all discarded.

Ha!, x86 stuffs .exit.text in [__init_begin, __init_end) and it is
discarded right along with initmem.

But that means it should match init and be tagged init and all *should*
work, but somehow it doesn't... clearly I'm missing something again