[PATCH] arm64: ftrace: add missing BTIs

[Mark Brown]

On Mon, Nov 29, 2021 at 05:37:51PM +0000, Mark Rutland wrote:
> On Mon, Nov 29, 2021 at 04:50:39PM +0000, Mark Brown wrote:

> > > +#ifdef BTI_C
> > > +	BTI_C
> > > +#endif

> > The ifdefs here feel ugly enough that it might be worth doing that right
> > now TBH.  I'm trying to think of any cases where we might also need a
> > BTI J but nothing springs to mind right now.

> Agreed on the ugliness -- I'd like to revisit that with some related
> cleanup/improvement to our existing SYM_*() macros. I just didn't want to do
> that as a prerequisite for the fix as it'd make backports painful, e.g. by
> creating a dependency on commit:

>   1cbdf60bd1b74e39 ("kasan: arm64: support specialized outlined tag mismatch checks")

> ... which uses the ifdef pattern above.

Ugh, that's not great.  But yes, backporting was why I did the Reviwed-by.
If we knew the names we were going for it'd be easy enough to add a new
SYM_CODE_ varaint without introducing dependencies but that might be
getting ahead of things.

> I'm also not sure what naming/structure we'd like, or whether it's simpler to
> unconditionally define BTI_C.

The unconditional definition seems like it might be neater as a
minimally intrusive thing for backporting, we can always refactor later.
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