Re: [PATCH 06/15] arm64: kvm: Move __smccc_workaround_1_smc to .rodata

Will Deacon
2020-05-11T10:29:31Z

On Mon, May 11, 2020 at 11:04:59AM +0100, Marc Zyngier wrote:
> On Thu, 30 Apr 2020 15:48:22 +0100
> David Brazdil <dbrazdil@google.com> wrote:
>
> > This snippet of assembly is used by cpu_errata.c to overwrite parts of KVM hyp
> > vector. It is never directly executed, so move it from .text to .rodata.
> >
> > Signed-off-by: David Brazdil <dbrazdil@google.com>
> > ---
> > arch/arm64/kvm/hyp/hyp-entry.S | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
> > index 5986e1d78d3f..7e5f386c5c2d 100644
> > --- a/arch/arm64/kvm/hyp/hyp-entry.S
> > +++ b/arch/arm64/kvm/hyp/hyp-entry.S
> > @@ -364,6 +364,11 @@ SYM_CODE_END(__bp_harden_hyp_vecs)
> > .popsection
> >
> > #ifndef __HYPERVISOR__
> > + /*
> > + * This is not executed directly and is instead copied into the vectors
> > + * by install_bp_hardening_cb().
> > + */
> > + .pushsection .rodata
> > SYM_CODE_START(__smccc_workaround_1_smc)
>
> I wonder whether we should keep the SYM_CODE_START() annotation or not.
> It feels weird to say "code" in a rodata section, and the alignment
> doesn't matter as we copy it in place, as you noticed.

The BTI patches hook these, but I don't see that being relevant for a
vector entry as PSTATE.BTYPE is zapped to 0.

Will