Re: [PATCH v13 0/2] arm64: Enable BTI for the executable as well as the interpreter

Mark Brown
2022-04-20T11:57:39Z

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On Wed, Apr 20, 2022 at 10:57:30AM +0100, Catalin Marinas wrote:
> On Wed, Apr 20, 2022 at 10:36:13AM +0100, Will Deacon wrote:

> > Kees, please can you drop this series while Catalin's alternative solution
> > is under discussion (his Reviewed-by preceded the other patches)?

> > https://lore.kernel.org/r/20220413134946.2732468-1-catalin.marinas@arm.com

> > Both series expose new behaviours to userspace and we don't need both.

> I agree. Even though the patches have my reviewed-by, I think we should
> postpone them until we figure out a better W^X solution that does not
> affect BTI (and if we can't, we revisit these patches).

Indeed. I had been expecting this to follow the pattern of the previous
nine months or so and be mostly ignored for the time being while
Catalin's new series goes forward. Now that it's applied it might be
worth keeping the first patch still in case someone else needs it but
the second patch can probably wait.

> Arguably, the two approaches are complementary but the way this series
> turned out is for the BTI on main executable to be default off. I have a
> worry that the feature won't get used, so we just carry unnecessary code
> in the kernel. Jeremy also found this approach less than ideal:

> https://lore.kernel.org/r/59fc8a58-5013-606b-f544-8277cda18e50@arm.com

I'm not sure there was a fundamental concern with the approach there but
rather some pushback on the instance on turning it off by default.

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