Re: [PATCH] powerpc/32: indirect function call use bctrl rather than blrl in ret_from_kernel_thread

From: Segher Boessenkool
Date: Fri Aug 20 2021 - 14:17:17 EST


On Fri, Aug 20, 2021 at 12:18:45PM -0500, Segher Boessenkool wrote:
> On Fri, Aug 20, 2021 at 10:15:11PM +1000, Michael Ellerman wrote:
> > Christophe Leroy <christophe.leroy@xxxxxxxxxx> writes:
> > > Copied from commit 89bbe4c798bc ("powerpc/64: indirect function call
> > > use bctrl rather than blrl in ret_from_kernel_thread")
> > >
> > > blrl is not recommended to use as an indirect function call, as it may
> > > corrupt the link stack predictor.
> >
> > Do we know if any 32-bit CPUs have a link stack predictor or similar?
>
> 74xx do.

7450 and later, that is. Will I ever get that right, sigh.


Segher