Re: [PATCH v11 19/39] arm64/mm: Handle GCS data aborts

Mark Brown
2024-08-22T17:30:59Z

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On Thu, Aug 22, 2024 at 06:19:38PM +0100, Catalin Marinas wrote:
> On Thu, Aug 22, 2024 at 05:44:19PM +0100, Mark Brown wrote:
> > On Thu, Aug 22, 2024 at 05:12:30PM +0100, Catalin Marinas wrote:
> > > On Thu, Aug 22, 2024 at 02:15:22AM +0100, Mark Brown wrote:
> >
> > > > +static bool is_invalid_gcs_access(struct vm_area_struct *vma, u64 esr)
> >
> > > > + } else if (unlikely(vma->vm_flags & VM_SHADOW_STACK)) {
> > > > + /* Only GCS operations can write to a GCS page */
> > > > + return is_write_abort(esr);
> > > > + }

> > Yes, that should check for a data abort. I think I'd formed the
> > impression that is_write_abort() included that check somehow. As you
> > say it's to avoid spinning trying to resolve a permission fault for a
> > write (non-GCS reads to a GCS page are valid), I do think we need the
> > is_write_abort() since non-GCS reads are valid so something like:
> >
> > if (!esr_is_data_abort(esr))
> > return false;
> >
> > return is_write_abort(esr);
>
> We do need the write abort check but not unconditionally, only if to a
> GCS page (you can have other genuine write aborts).

tThat was to replace the checks in the above case, not the function as a
whole.

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